Don't allocate a full-sized array when creating a VertexBuffer.

We can allocate a much smaller zeroed buffer and copy that multiple times in order to zero the memory. When creating large VertexBuffers, this caps our temporary allocation size significantly.

OpenRA.Platforms.Default/VertexBuffer.cs

@@ -27,20 +27,32 @@ namespace OpenRA.Platforms.Default
 			OpenGL.CheckGLError();
 			Bind();
 
-			var ptr = GCHandle.Alloc(new T[size], GCHandleType.Pinned);
+			// Generates a buffer with uninitialized memory.
-			try
-			{
 			OpenGL.glBufferData(OpenGL.GL_ARRAY_BUFFER,
 					new IntPtr(VertexSize * size),
-					ptr.AddrOfPinnedObject(),
+					IntPtr.Zero,
 					OpenGL.GL_DYNAMIC_DRAW);
+			OpenGL.CheckGLError();
+
+			// We need to zero all the memory. Let's generate a smallish array and copy that over the whole buffer.
+			var zeroedArrayElementSize = Math.Min(size, 2048);
+			var ptr = GCHandle.Alloc(new T[zeroedArrayElementSize], GCHandleType.Pinned);
+			try
+			{
+				for (var offset = 0; offset < size; offset += zeroedArrayElementSize)
+				{
+					var length = Math.Min(zeroedArrayElementSize, size - offset);
+					OpenGL.glBufferSubData(OpenGL.GL_ARRAY_BUFFER,
+						new IntPtr(VertexSize * offset),
+						new IntPtr(VertexSize * length),
+						ptr.AddrOfPinnedObject());
+					OpenGL.CheckGLError();
+				}
 			}
 			finally
 			{
 				ptr.Free();
 			}
-
-			OpenGL.CheckGLError();
 		}
 
 		public void SetData(T[] data, int length)
@@ -108,6 +120,7 @@ namespace OpenRA.Platforms.Default
 				return;
 			disposed = true;
 			OpenGL.glDeleteBuffers(1, ref buffer);
+			OpenGL.CheckGLError();
 		}
 	}
 }