Beyond3D heeft weer een erg diep artikel over de voordelen en nadelen van T&L / geometrie acceleratie in elkaar gedraaid. Eén van de problemen is overdraw: het renderen van onzichtbare pixels, die een groot deel van de beschikbare fillrate voor zich op eisen:
In our previous article, talking about the problem of fill-rate limits, one of the issues we forgot to address is that of depth complexity, otherwise known as overdraw. Depth complexity is the problem of triangles overlapping to form additional triangles and pixels. This means that you create extra triangles to be rendered as well as extra pixels.
Now typically a game such as Quake II will have a depth complexity of about 3x, resulting in a 3x fill-rate hit. Now with T&L the problem is that you'll be dealing with a great deal more triangles that are a lot smaller. With that, you're going to be experiencing a great deal more overlapping of the triangles and in turn more depth complexity. To illustrate this, here is a picture of NVIDIA's tree demo running in wire frame. Looking at the screenshot below you can really see how much depth complexity there is. Now of course it should be considered that just technology demo. The purpose was to show the highest quality that an object could reach and still maintain a high level of performance. Now because of this, not only does this object look better than it would within any actual game, but depth complexity is also greater. The purpose of us showing this though is that just while T&L will make objects look better, it will also cause a great fill-rate hit and triangle rate hit because of overdraw