Drongle asked in the Content UG meeting about what I’ll call the breakeven point when using normal maps. When does a normal map cost more or less than the number of triangles it replaces?
This question comes from considering the cost added by downloading and rendering another texture, the normal map. As GPU’s render triangles faster every day, there is a moving point at which it may be cheaper to add some number of triangles and skip the normal map. But, where is that point?
The answer is: it is different on each computer. The only way to know is to test. But, that only tells you for the specific hardware you are using.
It would be good to have a rules of thumb that works for the majority of people. Nyx Linden says, “It depends on how overloaded the GPU is in terms of computing and at which stage of the pipeline, the overall memory usage, which depends on the scene and the available hardware, etc. turning on normal maps for a surface is going to increase the load on the GPU computationally, regardless of what texture detail the normal map is. Adding a more detailed normal map will increase memory needs and the stress of managing all the extra texture data. That being said, if you can get away with significantly simpler geometry for a little bit of texture data, that would speed things up greatly for any users that are geometry bound.
