by amuzen » 12 Feb 2013, 18:21
This still isn't fully accurate because the batch count (number of different material+texture+shader combinations) of the model can have a much bigger impact on the performance than the vertex count, especially on modern GPUs and certain graphics engines. This is the case because every batch requires the CPU to bind different material properties/textures/shaders and issue a separate drawing call to the GPU.
Hence, the rendering time of a model can sometimes be decreased without touching the geometry at all. For example, if you have a model that uses 10 different diffuse textures, 3 different shaders, and 5 different specularity and shininess values (at least 10 batches), it will render slower than one in which the diffuse textures have been baked into 1 texture, the shader count has been reduced to 1 and the materials have been reduced to 1 by using a specular+shininess texture (1 batch total).