1. override
void renderTextureMesh(RenderState renderState, RenderTexture renderTexture, Int16List ixList, Float32List vxList)

Source 

@override
void renderTextureMesh(
    RenderState renderState, RenderTexture renderTexture,
    Int16List ixList, Float32List vxList) {

  activateRenderProgram(renderProgramSimple);
  activateBlendMode(renderState.globalBlendMode);
  activateRenderTexture(renderTexture);
  renderProgramSimple.renderTextureMesh(renderState, ixList, vxList);
}