[rlgl] Create function `rlUpdateMeshAt` (#1010)

* [rlgl] Create function `rlUpdateMeshAt`

* [rlgl] Update function `rlUpdateMeshAt`

1 files changed, 33 insertions, 15 deletions

diff --git a/src/rlgl.h b/src/rlgl.h
index 61a29518..5c71c478 100644
--- a/src/rlgl.h
+++ b/src/rlgl.h
@@ -505,6 +505,7 @@ RLAPI bool rlRenderTextureComplete(RenderTexture target);                 // Ver
 // Vertex data management
 RLAPI void rlLoadMesh(Mesh *mesh, bool dynamic);                          // Upload vertex data into GPU and provided VAO/VBO ids
 RLAPI void rlUpdateMesh(Mesh mesh, int buffer, int num);                  // Update vertex or index data on GPU (upload new data to one buffer)
+RLAPI void rlUpdateMeshAt(Mesh mesh, int buffer, int num, int index);     // Update vertex or index data on GPU, at index
 RLAPI void rlDrawMesh(Mesh mesh, Material material, Matrix transform);    // Draw a 3d mesh with material and transform
 RLAPI void rlUnloadMesh(Mesh mesh);                                       // Unload mesh data from CPU and GPU
 
@@ -2512,6 +2513,14 @@ unsigned int rlLoadAttribBuffer(unsigned int vaoId, int shaderLoc, void *buffer,
 // Update vertex or index data on GPU (upload new data to one buffer)
 void rlUpdateMesh(Mesh mesh, int buffer, int num)
 {
+    rlUpdateMeshAt(mesh, buffer, num, 0);
+}
+
+// Update vertex or index data on GPU, at index
+// WARNING: error checking is in place that will cause the data to not be
+//          updated if offset + size exceeds what the buffer can hold
+void rlUpdateMeshAt(Mesh mesh, int buffer, int num, int index)
+{
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     // Activate mesh VAO
     if (vaoSupported) glBindVertexArray(mesh.vaoId);
@@ -2521,51 +2530,60 @@ void rlUpdateMesh(Mesh mesh, int buffer, int num)
         case 0:     // Update vertices (vertex position)
         {
             glBindBuffer(GL_ARRAY_BUFFER, mesh.vboId[0]);
-            if (num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*3*num, mesh.vertices, GL_DYNAMIC_DRAW);
-            else glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float)*3*num, mesh.vertices);
+            if (index == 0 && num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*3*num, mesh.vertices, GL_DYNAMIC_DRAW);
+            else if (index + num >= mesh.vertexCount) break;
+            else glBufferSubData(GL_ARRAY_BUFFER, sizeof(float)*3*index, sizeof(float)*3*num, mesh.vertices);
 
         } break;
         case 1:     // Update texcoords (vertex texture coordinates)
         {
             glBindBuffer(GL_ARRAY_BUFFER, mesh.vboId[1]);
-            if (num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*2*num, mesh.texcoords, GL_DYNAMIC_DRAW);
-            else glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float)*2*num, mesh.texcoords);
+            if (index == 0 && num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*2*num, mesh.texcoords, GL_DYNAMIC_DRAW);
+            else if (index + num >= mesh.vertexCount) break;
+            else glBufferSubData(GL_ARRAY_BUFFER, sizeof(float)*2*index, sizeof(float)*2*num, mesh.texcoords);
 
         } break;
         case 2:     // Update normals (vertex normals)
         {
             glBindBuffer(GL_ARRAY_BUFFER, mesh.vboId[2]);
-            if (num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*3*num, mesh.normals, GL_DYNAMIC_DRAW);
-            else glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float)*3*num, mesh.normals);
+            if (index == 0 && num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*3*num, mesh.normals, GL_DYNAMIC_DRAW);
+            else if (index + num >= mesh.vertexCount) break;
+            else glBufferSubData(GL_ARRAY_BUFFER, sizeof(float)*3*index, sizeof(float)*3*num, mesh.normals);
 
         } break;
         case 3:     // Update colors (vertex colors)
         {
             glBindBuffer(GL_ARRAY_BUFFER, mesh.vboId[3]);
-            if (num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*4*num, mesh.colors, GL_DYNAMIC_DRAW);
-            else glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(unsigned char)*4*num, mesh.colors);
+            if (index == 0 && num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*4*num, mesh.colors, GL_DYNAMIC_DRAW);
+            else if (index + num >= mesh.vertexCount) break;
+            else glBufferSubData(GL_ARRAY_BUFFER, sizeof(unsigned char)*4*index, sizeof(unsigned char)*4*num, mesh.colors);
 
         } break;
         case 4:     // Update tangents (vertex tangents)
         {
             glBindBuffer(GL_ARRAY_BUFFER, mesh.vboId[4]);
-            if (num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*4*num, mesh.tangents, GL_DYNAMIC_DRAW);
-            else glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float)*4*num, mesh.tangents);
+            if (index == 0 && num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*4*num, mesh.tangents, GL_DYNAMIC_DRAW);
+            else if (index + num >= mesh.vertexCount) break;
+            else glBufferSubData(GL_ARRAY_BUFFER, sizeof(float)*4*index, sizeof(float)*4*num, mesh.tangents);
         } break;
         case 5:     // Update texcoords2 (vertex second texture coordinates)
         {
             glBindBuffer(GL_ARRAY_BUFFER, mesh.vboId[5]);
-            if (num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*2*num, mesh.texcoords2, GL_DYNAMIC_DRAW);
-            else glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(float)*2*num, mesh.texcoords2);
+            if (index == 0 && num >= mesh.vertexCount) glBufferData(GL_ARRAY_BUFFER, sizeof(float)*2*num, mesh.texcoords2, GL_DYNAMIC_DRAW);
+            else if (index + num >= mesh.vertexCount) break;
+            else glBufferSubData(GL_ARRAY_BUFFER, sizeof(float)*2*index, sizeof(float)*2*num, mesh.texcoords2);
         } break;
         case 6:     // Update indices (triangle index buffer)
         {
+            // the * 3 is because each triangle has 3 indices
             unsigned short *indices = mesh.indices;
             glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mesh.vboId[6]);
-            if (num >= mesh.triangleCount*3) // 3 indices per triangle
-                glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(*indices)*num, indices, GL_DYNAMIC_DRAW);
+            if (index == 0 && num >= mesh.triangleCount)
+                glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(*indices)*num*3, indices, GL_DYNAMIC_DRAW);
+            else if (index + num >= mesh.triangleCount)
+                break;
             else
-                glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, sizeof(*indices)*num, indices);
+                glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, sizeof(*indices)*index*3, sizeof(*indices)*num*3, indices);
         } break;
         default: break;
     }