Simple Questions

1. It depends on the graphics card. Generally, the more triangles, the slower it will be. But larger triangles with complicated shaders may be slower if you become fill rate limited.

2. no idea, not that fimiliar with OpenGL.

3. ditto

4. Yes. All state changes will affect how long it takes to render a scene. Usually it won't be much of a problem until you have very large scenes and you are changing the texture hundreds of times per frame. In those cases, you need to look into state sorting to reduce how many times you change a texture.

5. There is a very long process that goes on with GPU. I will try to find a good link to the rendering pipeline. There are several steps that occur for each vertex/pixel on the way to the screen.

Edit: Here is a link that gives a decent summary of the pipeline.

2.0 How big will be the impact of automatic texture coordinate generation(OpenGl) on the FPS? Why ?

minimal. It's a cheap operation.

3.0 Is automatic texture coordinate generation supported on even low-level GPU's? Has the GeForceII support for texture coordinate generation?

Every openGL compliant graphics card can generate tex coords - even those without GPU's...