For non-transparent models, to a degree it gets done by the depth buffer. For transparent models, depth buffer is not helpful. But even when using the depth bu

For non-transparent models, to a degree it gets done by the depth buffer. For transparent models, depth buffer is not helpful. But even when using the depth buffer, drawing in front-to-back order will drastically improve performance as fragment shaders don't have to run for occluded fragments that get depth culled.