1. override
void renderTriangle(RenderState renderState, num x1, num y1, num x2, num y2, num x3, num y3, int color)

Source 

@override
void renderTriangle(
  RenderState renderState,
  num x1, num y1, num x2, num y2, num x3, num y3, int color) {

  activateRenderProgram(renderProgramTriangle);
  activateBlendMode(renderState.globalBlendMode);
  renderProgramTriangle.renderTriangle(
      renderState, x1, y1, x2, y2, x3, y3, color);
}