Redesigned physics module (IN PROGRESS)

physac modules is being redesigned. Physics base behaviour is done and
it is composed by three steps: apply physics, resolve collisions and fix
overlapping.

A basic example is currently in progress. The next steps are try to add
torque and unoriented physic collisions and implement physics basic
functions to add forces. Rigidbody grounding state is automatically
calculated and has a perfect result. Rigidbodies interacts well with
each others.

To achieve physics accuracy, UpdatePhysics() is called a number of times
per frame. In a future, it should be changed to another thread and call
it without any target frame restriction.

Basic physics example has been redone (not finished) using the new
module functions. Forces examples will be redone so I removed it from
branch.

3 files changed, 325 insertions, 314 deletions

diff --git a/src/physac.c b/src/physac.c
index 4c50dd41..13247117 100644
--- a/src/physac.c
+++ b/src/physac.c
@@ -1,6 +1,6 @@
 /**********************************************************************************************
 *
-*   [physac] raylib physics engine module - Basic functions to apply physics to 2D objects
+*   [physac] raylib physics module - Basic functions to apply physics to 2D objects
 *
 *   Copyright (c) 2015 Victor Fisac and Ramon Santamaria
 *
@@ -29,329 +29,343 @@
     #include "raylib.h"
 #endif
 
-#include <math.h>
-#include <stdlib.h>             // Required for: malloc(), free()
+#include <stdlib.h>         // Declares malloc() and free() for memory management
+#include <math.h>           // abs() and fminf()
 
 //----------------------------------------------------------------------------------
 // Defines and Macros
 //----------------------------------------------------------------------------------
-#define DECIMAL_FIX     0.26f       // Decimal margin for collision checks (avoid rigidbodies shake)
+#define MAX_PHYSIC_OBJECTS      256
+#define PHYSICS_GRAVITY         -9.81f/2
+#define PHYSICS_STEPS           450
+#define PHYSICS_ACCURACY        0.0001f     // Velocity subtract operations round filter (friction)
+#define PHYSICS_ERRORPERCENT    0.001f        // Collision resolve position fix
 
 //----------------------------------------------------------------------------------
 // Types and Structures Definition
+// NOTE: Below types are required for PHYSAC_STANDALONE usage
 //----------------------------------------------------------------------------------
 // ...
 
 //----------------------------------------------------------------------------------
 // Global Variables Definition
 //----------------------------------------------------------------------------------
-static Collider *colliders;         // Colliders array, dynamically allocated at runtime
-static Rigidbody *rigidbodies;      // Rigitbody array, dynamically allocated at runtime
-static bool collisionChecker;
-
-static int maxElements;             // Max physic elements to compute
-static bool enabled;                // Physics enabled? (true by default)
-static Vector2 gravity;             // Gravity value used for physic calculations
+static PhysicObject *physicObjects[MAX_PHYSIC_OBJECTS];             // Physic objects pool
+static int physicObjectsCount;                                      // Counts current enabled physic objects
 
 //----------------------------------------------------------------------------------
-// Module specific Functions Declarations
+// Module specific Functions Declaration
 //----------------------------------------------------------------------------------
-static float Vector2Length(Vector2 vector);
-static float Vector2Distance(Vector2 a, Vector2 b);
-static void Vector2Normalize(Vector2 *vector);
+static float Vector2DotProduct(Vector2 v1, Vector2 v2);             // Returns the dot product of two Vector2
 
 //----------------------------------------------------------------------------------
-// Module Functions Definitions
+// Module Functions Definition
 //----------------------------------------------------------------------------------
-void InitPhysics(int maxPhysicElements)
-{
-    maxElements = maxPhysicElements;
-    
-    colliders = (Collider *)malloc(maxElements*sizeof(Collider));
-    rigidbodies = (Rigidbody *)malloc(maxElements*sizeof(Rigidbody));
-    
-    for (int i = 0; i < maxElements; i++)
-    {
-        colliders[i].enabled = false;
-        colliders[i].bounds = (Rectangle){ 0, 0, 0, 0 };
-        colliders[i].radius = 0;
-        
-        rigidbodies[i].enabled = false;
-        rigidbodies[i].mass = 0.0f;
-        rigidbodies[i].velocity = (Vector2){ 0.0f, 0.0f };
-        rigidbodies[i].acceleration = (Vector2){ 0.0f, 0.0f };
-        rigidbodies[i].isGrounded = false;
-        rigidbodies[i].isContact = false;
-        rigidbodies[i].friction = 0.0f;
-    }
-    
-    collisionChecker = false;
-    enabled = true;
-    
-    // NOTE: To get better results, gravity needs to be 1:10 from original parameter
-    gravity = (Vector2){ 0.0f, -9.81f/10.0f };     // By default, standard gravity
-}
-
-void UnloadPhysics()
-{
-    free(colliders);
-    free(rigidbodies);
-}
-
-void AddCollider(int index, Collider collider)
-{
-    colliders[index] = collider;
-}
 
-void AddRigidbody(int index, Rigidbody rigidbody)
+// Initializes pointers array (just pointers, fixed size)
+void InitPhysics()
 {
-    rigidbodies[index] = rigidbody;
+    // Initialize physics variables
+    physicObjectsCount = 0;
 }
 
-void ApplyPhysics(int index, Vector2 *position)
+// Update physic objects, calculating physic behaviours and collisions detection
+void UpdatePhysics()
 {
-    if (rigidbodies[index].enabled)
+    // Reset all physic objects is grounded state
+    for(int i = 0; i < physicObjectsCount; i++)
     {
-        // Apply friction to acceleration
-        if (rigidbodies[index].acceleration.x > DECIMAL_FIX)
-        {
-            rigidbodies[index].acceleration.x -= rigidbodies[index].friction;
-        }
-        else if (rigidbodies[index].acceleration.x < -DECIMAL_FIX)
-        {
-            rigidbodies[index].acceleration.x += rigidbodies[index].friction;
-        }
-        else
-        {
-            rigidbodies[index].acceleration.x = 0;
-        }
-        
-        if (rigidbodies[index].acceleration.y > DECIMAL_FIX / 2)
-        {
-            rigidbodies[index].acceleration.y -= rigidbodies[index].friction;
-        }
-        else if (rigidbodies[index].acceleration.y < -DECIMAL_FIX / 2)
-        {
-            rigidbodies[index].acceleration.y += rigidbodies[index].friction;
-        }
-        else
-        {
-            rigidbodies[index].acceleration.y = 0;
-        }
-        
-        // Apply friction to velocity
-        if (rigidbodies[index].isGrounded)
-        {
-            if (rigidbodies[index].velocity.x > DECIMAL_FIX)
-            {
-                rigidbodies[index].velocity.x -= rigidbodies[index].friction;
-            }
-            else if (rigidbodies[index].velocity.x < -DECIMAL_FIX)
-            {
-                rigidbodies[index].velocity.x += rigidbodies[index].friction;
-            }
-            else
-            {
-                rigidbodies[index].velocity.x = 0;
-            }
-        }
-        
-        if (rigidbodies[index].velocity.y > DECIMAL_FIX / 2)
-        {
-            rigidbodies[index].velocity.y -= rigidbodies[index].friction;
-        }
-        else if (rigidbodies[index].velocity.y < -DECIMAL_FIX / 2)
-        {
-            rigidbodies[index].velocity.y += rigidbodies[index].friction;
-        }
-        else
-        {
-            rigidbodies[index].velocity.y = 0;
-        }
-        
-        // Apply gravity
-        rigidbodies[index].velocity.y += gravity.y;
-        rigidbodies[index].velocity.x += gravity.x;
-        
-        // Apply acceleration
-        rigidbodies[index].velocity.y += rigidbodies[index].acceleration.y;
-        rigidbodies[index].velocity.x += rigidbodies[index].acceleration.x;
-        
-        // Update position vector
-        position->x += rigidbodies[index].velocity.x;        
-        position->y -= rigidbodies[index].velocity.y;
-        
-        // Update collider bounds
-        colliders[index].bounds.x = position->x;
-        colliders[index].bounds.y = position->y;
-        
-        // Check collision with other colliders
-        collisionChecker = false;
-        rigidbodies[index].isContact = false;
-        for (int j = 0; j < maxElements; j++)
+        if(physicObjects[i]->rigidbody.enabled) physicObjects[i]->rigidbody.isGrounded = false;
+    }
+    
+    for(int steps = 0; steps < PHYSICS_STEPS; steps++)
+    {
+        for(int i = 0; i < physicObjectsCount; i++)
         {
-            if (index != j)
+            if(physicObjects[i]->enabled)
             {
-                if (colliders[index].enabled && colliders[j].enabled)
+                // Update physic behaviour
+                if(physicObjects[i]->rigidbody.enabled)
                 {
-                    if (colliders[index].type == COLLIDER_RECTANGLE)
+                    // Apply friction to acceleration in X axis
+                    if (physicObjects[i]->rigidbody.acceleration.x > PHYSICS_ACCURACY) physicObjects[i]->rigidbody.acceleration.x -= physicObjects[i]->rigidbody.friction/PHYSICS_STEPS;
+                    else if (physicObjects[i]->rigidbody.acceleration.x < PHYSICS_ACCURACY) physicObjects[i]->rigidbody.acceleration.x += physicObjects[i]->rigidbody.friction/PHYSICS_STEPS;
+                    else physicObjects[i]->rigidbody.acceleration.x = 0.0f;
+                    
+                    // Apply friction to velocity in X axis
+                    if (physicObjects[i]->rigidbody.velocity.x > PHYSICS_ACCURACY) physicObjects[i]->rigidbody.velocity.x -= physicObjects[i]->rigidbody.friction/PHYSICS_STEPS;
+                    else if (physicObjects[i]->rigidbody.velocity.x < PHYSICS_ACCURACY) physicObjects[i]->rigidbody.velocity.x += physicObjects[i]->rigidbody.friction/PHYSICS_STEPS;
+                    else physicObjects[i]->rigidbody.velocity.x = 0.0f;
+                    
+                    // Apply gravity to velocity
+                    if (physicObjects[i]->rigidbody.applyGravity) physicObjects[i]->rigidbody.velocity.y += PHYSICS_GRAVITY/PHYSICS_STEPS;
+                    
+                    // Apply acceleration to velocity
+                    physicObjects[i]->rigidbody.velocity.x += physicObjects[i]->rigidbody.acceleration.x/PHYSICS_STEPS;
+                    physicObjects[i]->rigidbody.velocity.y += physicObjects[i]->rigidbody.acceleration.y/PHYSICS_STEPS;
+                    
+                    // Apply velocity to position
+                    physicObjects[i]->transform.position.x += physicObjects[i]->rigidbody.velocity.x/PHYSICS_STEPS;
+                    physicObjects[i]->transform.position.y -= physicObjects[i]->rigidbody.velocity.y/PHYSICS_STEPS;
+                }
+                
+                // Update collision detection
+                if (physicObjects[i]->collider.enabled)
+                {
+                    // Update collider bounds
+                    physicObjects[i]->collider.bounds = TransformToRectangle(physicObjects[i]->transform);
+                    
+                    // Check collision with other colliders
+                    for (int k = 0; k < physicObjectsCount; k++)
                     {
-                        if (colliders[j].type == COLLIDER_RECTANGLE)
+                        if (physicObjects[k]->collider.enabled && i != k)
                         {
-                            if (CheckCollisionRecs(colliders[index].bounds, colliders[j].bounds))
+                            // Check if colliders are overlapped
+                            if (CheckCollisionRecs(physicObjects[i]->collider.bounds, physicObjects[k]->collider.bounds))
                             {
-                                collisionChecker = true;
+                                // Resolve physic collision
+                                // NOTE: collision resolve is generic for all directions and conditions (no axis separated cases behaviours)
+                                // and it is separated in rigidbody attributes resolve (velocity changes by impulse) and position correction (position overlap)
+                                
+                                // 1. Calculate collision normal
+                                // -------------------------------------------------------------------------------------------------------------------------------------
+                                
+                                // Define collision ontact normal
+                                Vector2 contactNormal = { 0.0f, 0.0f };
+                                
+                                // Calculate direction vector from i to k
+                                Vector2 direction;
+                                direction.x = (physicObjects[k]->transform.position.x + physicObjects[k]->transform.scale.x/2) - (physicObjects[i]->transform.position.x + physicObjects[i]->transform.scale.x/2);
+                                direction.y = (physicObjects[k]->transform.position.y + physicObjects[k]->transform.scale.y/2) - (physicObjects[i]->transform.position.y + physicObjects[i]->transform.scale.y/2);
+                                
+                                // Define overlapping and penetration attributes
+                                Vector2 overlap;
+                                float penetrationDepth = 0.0f;
                                 
-                                if ((colliders[index].bounds.y + colliders[index].bounds.height <= colliders[j].bounds.y) == false)
+                                // Calculate overlap on X axis
+                                overlap.x = (physicObjects[i]->transform.scale.x + physicObjects[k]->transform.scale.x)/2 - abs(direction.x);
+                                
+                                // SAT test on X axis
+                                if (overlap.x > 0.0f)
                                 {
-                                    rigidbodies[index].isContact = true;
+                                    // Calculate overlap on Y axis
+                                    overlap.y = (physicObjects[i]->transform.scale.y + physicObjects[k]->transform.scale.y)/2 - abs(direction.y);
+                                    
+                                    // SAT test on Y axis
+                                    if (overlap.y > 0.0f)
+                                    {
+                                        // Find out which axis is axis of least penetration
+                                        if (overlap.y > overlap.x)
+                                        {
+                                            // Point towards k knowing that direction points from i to k
+                                            if (direction.x < 0.0f) contactNormal = (Vector2){ -1.0f, 0.0f };
+                                            else contactNormal = (Vector2){ 1.0f, 0.0f };
+                                            
+                                            // Update penetration depth for position correction
+                                            penetrationDepth = overlap.x;
+                                        }
+                                        else
+                                        {
+                                            // Point towards k knowing that direction points from i to k
+                                            if (direction.y < 0.0f) contactNormal = (Vector2){ 0.0f, 1.0f };
+                                            else contactNormal = (Vector2){ 0.0f, -1.0f };
+                                            
+                                            // Update penetration depth for position correction
+                                            penetrationDepth = overlap.y;
+                                        }
+                                    }
+                                }
+                                
+                                // Update rigidbody grounded state
+                                if (physicObjects[i]->rigidbody.enabled)
+                                {
+                                    if (contactNormal.y < 0.0f) physicObjects[i]->rigidbody.isGrounded = true;
+                                }
+                                
+                                // 2. Calculate collision impulse
+                                // -------------------------------------------------------------------------------------------------------------------------------------
+                                
+                                // Calculate relative velocity
+                                Vector2 relVelocity = { physicObjects[k]->rigidbody.velocity.x - physicObjects[i]->rigidbody.velocity.x, physicObjects[k]->rigidbody.velocity.y - physicObjects[i]->rigidbody.velocity.y };
+
+                                // Calculate relative velocity in terms of the normal direction
+                                float velAlongNormal = Vector2DotProduct(relVelocity, contactNormal);
+                            
+                                // Dot not resolve if velocities are separating
+                                if (velAlongNormal <= 0.0f)
+                                {
+                                    // Calculate minimum bounciness value from both objects
+                                    float e = fminf(physicObjects[i]->rigidbody.bounciness, physicObjects[k]->rigidbody.bounciness);
+                                    
+                                    // Calculate impulse scalar value
+                                    float j = -(1.0f + e) * velAlongNormal;
+                                    j /= 1.0f/physicObjects[i]->rigidbody.mass + 1.0f/physicObjects[k]->rigidbody.mass;
+                                    
+                                    // Calculate final impulse vector
+                                    Vector2 impulse = { j*contactNormal.x, j*contactNormal.y };
+                                    
+                                    // Calculate collision mass ration
+                                    float massSum = physicObjects[i]->rigidbody.mass + physicObjects[k]->rigidbody.mass;
+                                    float ratio = 0.0f;
+                                    
+                                    // Apply impulse to current rigidbodies velocities if they are enabled
+                                    if (physicObjects[i]->rigidbody.enabled) 
+                                    {
+                                        // Calculate inverted mass ration
+                                        ratio = physicObjects[i]->rigidbody.mass/massSum;
+                                        
+                                        // Apply impulse direction to velocity
+                                        physicObjects[i]->rigidbody.velocity.x -= impulse.x*ratio;
+                                        physicObjects[i]->rigidbody.velocity.y -= impulse.y*ratio;
+                                    }
+                                    
+                                    if (physicObjects[k]->rigidbody.enabled) 
+                                    {
+                                        // Calculate inverted mass ration
+                                        ratio = physicObjects[k]->rigidbody.mass/massSum;
+                                        
+                                        // Apply impulse direction to velocity
+                                        physicObjects[k]->rigidbody.velocity.x += impulse.x*ratio;
+                                        physicObjects[k]->rigidbody.velocity.y += impulse.y*ratio;
+                                    }
+                                    
+                                    // 3. Correct colliders overlaping (transform position)
+                                    // ---------------------------------------------------------------------------------------------------------------------------------
+                                    
+                                    // Calculate transform position penetration correction
+                                    Vector2 posCorrection;
+                                    posCorrection.x = penetrationDepth/((1.0f/physicObjects[i]->rigidbody.mass) + (1.0f/physicObjects[k]->rigidbody.mass))*PHYSICS_ERRORPERCENT*contactNormal.x;
+                                    posCorrection.y = penetrationDepth/((1.0f/physicObjects[i]->rigidbody.mass) + (1.0f/physicObjects[k]->rigidbody.mass))*PHYSICS_ERRORPERCENT*contactNormal.y;
+                                    
+                                    // Fix transform positions
+                                    if (physicObjects[i]->rigidbody.enabled)
+                                    {                                        
+                                        // Fix physic objects transform position
+                                        physicObjects[i]->transform.position.x -= 1.0f/physicObjects[i]->rigidbody.mass*posCorrection.x;
+                                        physicObjects[i]->transform.position.y += 1.0f/physicObjects[i]->rigidbody.mass*posCorrection.y;
+                                        
+                                        // Update collider bounds
+                                        physicObjects[i]->collider.bounds = TransformToRectangle(physicObjects[i]->transform);
+                                        
+                                        if (physicObjects[k]->rigidbody.enabled)
+                                        {
+                                            // Fix physic objects transform position
+                                            physicObjects[k]->transform.position.x += 1.0f/physicObjects[k]->rigidbody.mass*posCorrection.x;
+                                            physicObjects[k]->transform.position.y -= 1.0f/physicObjects[k]->rigidbody.mass*posCorrection.y;
+                                            
+                                            // Update collider bounds
+                                            physicObjects[k]->collider.bounds = TransformToRectangle(physicObjects[k]->transform);
+                                        }
+                                    }
                                 }
-                            }
-                        }
-                        else
-                        {
-                            if (CheckCollisionCircleRec((Vector2){colliders[j].bounds.x, colliders[j].bounds.y}, colliders[j].radius, colliders[index].bounds))
-                            {
-                                collisionChecker = true;
-                            }
-                        }
-                    }
-                    else
-                    {
-                        if (colliders[j].type == COLLIDER_RECTANGLE)
-                        {
-                            if (CheckCollisionCircleRec((Vector2){colliders[index].bounds.x, colliders[index].bounds.y}, colliders[index].radius, colliders[j].bounds))
-                            {
-                                collisionChecker = true;
-                            }
-                        }
-                        else
-                        {
-                            if (CheckCollisionCircles((Vector2){colliders[j].bounds.x, colliders[j].bounds.y}, colliders[j].radius, (Vector2){colliders[index].bounds.x, colliders[index].bounds.y}, colliders[index].radius))
-                            {
-                                collisionChecker = true;
                             }
                         }
                     }
                 }
             }
         }
-        
-        // Update grounded rigidbody state
-        rigidbodies[index].isGrounded = collisionChecker;
-        
-        // Set grounded state if needed (fix overlap and set y velocity)
-        if (collisionChecker && rigidbodies[index].velocity.y != 0)
-        {
-            position->y += rigidbodies[index].velocity.y;
-            rigidbodies[index].velocity.y = -rigidbodies[index].velocity.y * rigidbodies[index].bounciness;
-        }
-        
-        if (rigidbodies[index].isContact)
-        {
-            position->x -= rigidbodies[index].velocity.x;
-            rigidbodies[index].velocity.x = rigidbodies[index].velocity.x;
-        }
     }
 }
 
-void SetRigidbodyEnabled(int index, bool state)
-{
-    rigidbodies[index].enabled = state;
-}
-
-void SetRigidbodyVelocity(int index, Vector2 velocity)
-{
-    rigidbodies[index].velocity.x = velocity.x;
-    rigidbodies[index].velocity.y = velocity.y;
-}
-
-void SetRigidbodyAcceleration(int index, Vector2 acceleration)
+// Unitialize all physic objects and empty the objects pool
+void ClosePhysics()
 {
-    rigidbodies[index].acceleration.x = acceleration.x;
-    rigidbodies[index].acceleration.y = acceleration.y;
+    // Free all dynamic memory allocations
+    for (int i = 0; i < physicObjectsCount; i++) free(physicObjects[i]);
+    
+    // Reset enabled physic objects count
+    physicObjectsCount = 0;
 }
 
-void AddRigidbodyForce(int index, Vector2 force)
+// Create a new physic object dinamically, initialize it and add to pool
+PhysicObject *CreatePhysicObject(Vector2 position, float rotation, Vector2 scale)
 {
-    rigidbodies[index].acceleration.x = force.x / rigidbodies[index].mass;
-    rigidbodies[index].acceleration.y = force.y / rigidbodies[index].mass;
+    // Allocate dynamic memory
+    PhysicObject *obj = (PhysicObject *)malloc(sizeof(PhysicObject));
+    
+    // Initialize physic object values with generic values
+    obj->id = physicObjectsCount;
+    obj->enabled = true;
+    
+    obj->transform = (Transform){ (Vector2){ position.x - scale.x/2, position.y - scale.y/2 }, rotation, scale };
+    
+    obj->rigidbody.enabled = false;
+    obj->rigidbody.mass = 1.0f;
+    obj->rigidbody.acceleration = (Vector2){ 0.0f, 0.0f };
+    obj->rigidbody.velocity = (Vector2){ 0.0f, 0.0f };
+    obj->rigidbody.applyGravity = false;
+    obj->rigidbody.isGrounded = false;
+    obj->rigidbody.friction = 0.0f;
+    obj->rigidbody.bounciness = 0.0f;
+    
+    obj->collider.enabled = false;
+    obj->collider.type = COLLIDER_RECTANGLE;
+    obj->collider.bounds = TransformToRectangle(obj->transform);
+    obj->collider.radius = 0.0f;
+    
+    // Add new physic object to the pointers array
+    physicObjects[physicObjectsCount] = obj;
+    
+    // Increase enabled physic objects count
+    physicObjectsCount++;
+    
+    return obj;
 }
 
-void AddForceAtPosition(Vector2 position, float intensity, float radius)
+// Destroy a specific physic object and take it out of the list
+void DestroyPhysicObject(PhysicObject *pObj)
 {
-    for(int i = 0; i < maxElements; i++)
+    // Free dynamic memory allocation
+    free(physicObjects[pObj->id]);
+    
+    // Remove *obj from the pointers array
+    for (int i = pObj->id; i < physicObjectsCount; i++)
     {
-        if(rigidbodies[i].enabled)
+        // Resort all the following pointers of the array
+        if ((i + 1) < physicObjectsCount)
         {
-            // Get position from its collider
-            Vector2 pos = {colliders[i].bounds.x, colliders[i].bounds.y};
-            
-            // Get distance between rigidbody position and target position
-            float distance = Vector2Distance(position, pos);
-            
-            if(distance <= radius)
-            {
-                // Calculate force based on direction
-                Vector2 force = {colliders[i].bounds.x - position.x, colliders[i].bounds.y - position.y};
-                
-                // Normalize the direction vector
-                Vector2Normalize(&force);
-                
-                // Invert y value
-                force.y *= -1;
-                
-                // Apply intensity and distance
-                force = (Vector2){force.x * intensity / distance, force.y * intensity / distance};
-                
-                // Add calculated force to the rigidbodies
-                AddRigidbodyForce(i, force);
-            }
+            physicObjects[i] = physicObjects[i + 1];
+            physicObjects[i]->id = physicObjects[i + 1]->id;
         }
+        else free(physicObjects[i]);
     }
+    
+    // Decrease enabled physic objects count
+    physicObjectsCount--;
 }
 
-void SetColliderEnabled(int index, bool state)
-{
-    colliders[index].enabled = state;
-}
-
-Collider GetCollider(int index)
+// Convert Transform data type to Rectangle (position and scale)
+Rectangle TransformToRectangle(Transform transform)
 {
-    return colliders[index];
+    return (Rectangle){transform.position.x, transform.position.y, transform.scale.x, transform.scale.y};
 }
 
-Rigidbody GetRigidbody(int index)
+// Draw physic object information at screen position
+void DrawPhysicObjectInfo(PhysicObject *pObj, Vector2 position, int fontSize)
 {
-    return rigidbodies[index];
+    // Draw physic object ID
+    DrawText(FormatText("PhysicObject ID: %i - Enabled: %i", pObj->id, pObj->enabled), position.x, position.y, fontSize, BLACK);
+    
+    // Draw physic object transform values
+    DrawText(FormatText("\nTRANSFORM\nPosition: %f, %f\nRotation: %f\nScale: %f, %f", pObj->transform.position.x, pObj->transform.position.y, pObj->transform.rotation, pObj->transform.scale.x, pObj->transform.scale.y), position.x, position.y, fontSize, BLACK);
+    
+    // Draw physic object rigidbody values
+    DrawText(FormatText("\n\n\n\n\n\nRIGIDBODY\nEnabled: %i\nMass: %f\nAcceleration: %f, %f\nVelocity: %f, %f\nApplyGravity: %i\nIsGrounded: %i\nFriction: %f\nBounciness: %f", pObj->rigidbody.enabled, pObj->rigidbody.mass, pObj->rigidbody.acceleration.x, pObj->rigidbody.acceleration.y, 
+    pObj->rigidbody.velocity.x, pObj->rigidbody.velocity.y, pObj->rigidbody.applyGravity, pObj->rigidbody.isGrounded, pObj->rigidbody.friction, pObj->rigidbody.bounciness), position.x, position.y, fontSize, BLACK);
+    
+    DrawText(FormatText("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nCOLLIDER\nEnabled: %i\nBounds: %i, %i, %i, %i\nRadius: %i", pObj->collider.enabled, pObj->collider.bounds.x, pObj->collider.bounds.y, pObj->collider.bounds.width, pObj->collider.bounds.height, pObj->collider.radius), position.x, position.y, fontSize, BLACK);
 }
 
 //----------------------------------------------------------------------------------
-// Module specific Functions Definitions
+// Module specific Functions Definition
 //----------------------------------------------------------------------------------
-static float Vector2Length(Vector2 vector)
-{
-    return sqrt((vector.x * vector.x) + (vector.y * vector.y));
-}
 
-static float Vector2Distance(Vector2 a, Vector2 b)
+// Returns the dot product of two Vector2
+static float Vector2DotProduct(Vector2 v1, Vector2 v2)
 {
-    Vector2 vector = {b.x - a.x, b.y - a.y};
-    return sqrt((vector.x * vector.x) + (vector.y * vector.y));
-}
+    float result;
 
-static void Vector2Normalize(Vector2 *vector)
-{
-    float length = Vector2Length(*vector);
-    
-    if (length != 0.0f)
-    {
-        vector->x /= length;
-        vector->y /= length;
-    }
-    else 
-    {
-        vector->x = 0.0f;
-        vector->y = 0.0f;
-    }
+    result = v1.x*v2.x + v1.y*v2.y;
+
+    return result;
 }
diff --git a/src/physac.h b/src/physac.h
index 9e1b0b88..b948e4ce 100644
--- a/src/physac.h
+++ b/src/physac.h
@@ -1,6 +1,6 @@
 /**********************************************************************************************
 *
-*   [physac] raylib physics engine module - Basic functions to apply physics to 2D objects
+*   [physac] raylib physics module - Basic functions to apply physics to 2D objects
 *
 *   Copyright (c) 2015 Victor Fisac and Ramon Santamaria
 *
@@ -31,62 +31,64 @@
 
 //----------------------------------------------------------------------------------
 // Types and Structures Definition
+// NOTE: Below types are required for PHYSAC_STANDALONE usage
 //----------------------------------------------------------------------------------
-// Collider types
+
+// Vector2 type
+typedef struct Vector2 {
+    float x;
+    float y;
+} Vector2;
+
 typedef enum { COLLIDER_CIRCLE, COLLIDER_RECTANGLE, COLLIDER_CAPSULE } ColliderType;
 
-// Transform struct
 typedef struct Transform {
     Vector2 position;
     float rotation;
     Vector2 scale;
 } Transform;
 
-// Rigidbody struct
 typedef struct Rigidbody {
-    bool enabled;
+    bool enabled;           // Acts as kinematic state (collisions are calculated anyway)
     float mass;
     Vector2 acceleration;
     Vector2 velocity;
-    bool isGrounded;
-    bool isContact;     // Avoid freeze player when touching floor
     bool applyGravity;
-    float friction;     // 0.0f to 1.0f
-    float bounciness;   // 0.0f to 1.0f
+    bool isGrounded;
+    float friction;         // Normalized value
+    float bounciness;       // Normalized value
 } Rigidbody;
 
-// Collider struct
 typedef struct Collider {
     bool enabled;
     ColliderType type;
-    Rectangle bounds;   // Used for COLLIDER_RECTANGLE and COLLIDER_CAPSULE
-    int radius;         // Used for COLLIDER_CIRCLE and COLLIDER_CAPSULE
+    Rectangle bounds;       // Used for COLLIDER_RECTANGLE and COLLIDER_CAPSULE
+    int radius;             // Used for COLLIDER_CIRCLE and COLLIDER_CAPSULE
 } Collider;
 
+typedef struct PhysicObject {
+    unsigned int id;
+    Transform transform;
+    Rigidbody rigidbody;
+    Collider collider;
+    bool enabled;
+} PhysicObject;
+
 #ifdef __cplusplus
 extern "C" {            // Prevents name mangling of functions
 #endif
 
 //----------------------------------------------------------------------------------
-// Module Functions Declarations
+// Module Functions Declaration
 //----------------------------------------------------------------------------------
-void InitPhysics(int maxPhysicElements);                                    // Initialize all internal physics values
-void UnloadPhysics();                                                       // Unload physic elements arrays
-
-void AddRigidbody(int index, Rigidbody rigidbody);                          // Initialize a new rigidbody with parameters to internal index slot
-void AddCollider(int index, Collider collider);                             // Initialize a new Collider with parameters to internal index slot
-
-void ApplyPhysics(int index, Vector2 *position);                            // Apply physics to internal rigidbody, physics calculations are applied to position pointer parameter
-void SetRigidbodyEnabled(int index, bool state);                            // Set enabled state to a defined rigidbody
-void SetRigidbodyVelocity(int index, Vector2 velocity);                     // Set velocity of rigidbody (without considering of mass value)
-void SetRigidbodyAcceleration(int index, Vector2 acceleration);             // Set acceleration of rigidbody (without considering of mass value)
-void AddRigidbodyForce(int index, Vector2 force);                           // Set rigidbody force (considering mass value)
-void AddForceAtPosition(Vector2 position, float intensity, float radius);   // Add a force to all enabled rigidbodies at a position
+void UpdatePhysics();                                                                   // Update physic objects, calculating physic behaviours and collisions detection
+void ClosePhysics();                                                                    // Unitialize all physic objects and empty the objects pool
 
-void SetColliderEnabled(int index, bool state);                             // Set enabled state to a defined collider
+PhysicObject *CreatePhysicObject(Vector2 position, float rotation, Vector2 scale);      // Create a new physic object dinamically, initialize it and add to pool
+void DestroyPhysicObject(PhysicObject *pObj);                                           // Destroy a specific physic object and take it out of the list
 
-Rigidbody GetRigidbody(int index);                                          // Returns the internal rigidbody data defined by index parameter
-Collider GetCollider(int index);                                            // Returns the internal collider data defined by index parameter
+Rectangle TransformToRectangle(Transform transform);                                    // Convert Transform data type to Rectangle (position and scale)
+void DrawPhysicObjectInfo(PhysicObject *pObj, Vector2 position, int fontSize);          // Draw physic object information at screen position
 
 #ifdef __cplusplus
 }
diff --git a/src/raylib.h b/src/raylib.h
index c598ec30..b9cf05a4 100644
--- a/src/raylib.h
+++ b/src/raylib.h
@@ -465,37 +465,40 @@ typedef struct {
 // Camera system modes
 typedef enum { CAMERA_CUSTOM = 0, CAMERA_FREE, CAMERA_ORBITAL, CAMERA_FIRST_PERSON, CAMERA_THIRD_PERSON } CameraMode;
 
-// Collider types
 typedef enum { COLLIDER_CIRCLE, COLLIDER_RECTANGLE, COLLIDER_CAPSULE } ColliderType;
 
-// Transform struct
 typedef struct Transform {
     Vector2 position;
     float rotation;
     Vector2 scale;
 } Transform;
 
-// Rigidbody struct
 typedef struct Rigidbody {
-    bool enabled;
+    bool enabled;           // Acts as kinematic state (collisions are calculated anyway)
     float mass;
     Vector2 acceleration;
     Vector2 velocity;
-    bool isGrounded;
-    bool isContact;     // Avoid freeze player when touching floor
     bool applyGravity;
-    float friction;     // 0.0f to 1.0f
-    float bounciness;   // 0.0f to 1.0f
+    bool isGrounded;
+    float friction;         // Normalized value
+    float bounciness;       // Normalized value
 } Rigidbody;
 
-// Collider struct
 typedef struct Collider {
     bool enabled;
     ColliderType type;
-    Rectangle bounds;   // Used for COLLIDER_RECTANGLE and COLLIDER_CAPSULE
-    int radius;         // Used for COLLIDER_CIRCLE and COLLIDER_CAPSULE
+    Rectangle bounds;       // Used for COLLIDER_RECTANGLE and COLLIDER_CAPSULE
+    int radius;             // Used for COLLIDER_CIRCLE and COLLIDER_CAPSULE
 } Collider;
 
+typedef struct PhysicObject {
+    unsigned int id;
+    Transform transform;
+    Rigidbody rigidbody;
+    Collider collider;
+    bool enabled;
+} PhysicObject;
+
 #ifdef __cplusplus
 extern "C" {            // Prevents name mangling of functions
 #endif
@@ -800,25 +803,17 @@ void SetShaderMap(Shader *shader, int mapLocation, Texture2D texture, int textur
 void SetBlendMode(int mode);                                        // Set blending mode (alpha, additive, multiplied)
 
 //----------------------------------------------------------------------------------
-// Physics System Functions (engine-module: physac)
+// Physics System Functions (Module: physac)
 //----------------------------------------------------------------------------------
-void InitPhysics(int maxPhysicElements);                                    // Initialize all internal physics values
-void UnloadPhysics();                                                       // Unload physic elements arrays
-
-void AddRigidbody(int index, Rigidbody rigidbody);                          // Initialize a new rigidbody with parameters to internal index slot
-void AddCollider(int index, Collider collider);                             // Initialize a new Collider with parameters to internal index slot
-
-void ApplyPhysics(int index, Vector2 *position);                            // Apply physics to internal rigidbody, physics calculations are applied to position pointer parameter
-void SetRigidbodyEnabled(int index, bool state);                            // Set enabled state to a defined rigidbody
-void SetRigidbodyVelocity(int index, Vector2 velocity);                     // Set velocity of rigidbody (without considering of mass value)
-void SetRigidbodyAcceleration(int index, Vector2 acceleration);             // Set acceleration of rigidbody (without considering of mass value)
-void AddRigidbodyForce(int index, Vector2 force);                           // Set rigidbody force (considering mass value)
-void AddForceAtPosition(Vector2 position, float intensity, float radius);   // Add a force to all enabled rigidbodies at a position
+void InitPhysics();                                                                     // Initializes pointers array (just pointers, fixed size)
+void UpdatePhysics();                                                                   // Update physic objects, calculating physic behaviours and collisions detection
+void ClosePhysics();                                                                    // Unitialize all physic objects and empty the objects pool
 
-void SetColliderEnabled(int index, bool state);                             // Set enabled state to a defined collider
+PhysicObject *CreatePhysicObject(Vector2 position, float rotation, Vector2 scale);      // Create a new physic object dinamically, initialize it and add to pool
+void DestroyPhysicObject(PhysicObject *pObj);                                           // Destroy a specific physic object and take it out of the list
 
-Rigidbody GetRigidbody(int index);                                          // Returns the internal rigidbody data defined by index parameter
-Collider GetCollider(int index);                                            // Returns the internal collider data defined by index parameter
+Rectangle TransformToRectangle(Transform transform);                                    // Convert Transform data type to Rectangle (position and scale)
+void DrawPhysicObjectInfo(PhysicObject *pObj, Vector2 position, int fontSize);          // Draw physic object information at screen position
 
 //------------------------------------------------------------------------------------
 // Audio Loading and Playing Functions (Module: audio)