| clearDepth | Whether to clear both the depth buffer and the stencil buffer. | 
| clearColor | Should clear color buffer? | 
| clearFlags | Which render targets to clear, defined using a bitwise OR combination of RTClearFlags values. | 
| backgroundColor | Color to clear with. | 
| depth | Depth to clear with (default is 1.0). | 
| stencil | Stencil to clear with (default is 0). | 
Adds a "clear render target" command.