1) i think yes, the main reason is what i told you. there isn't much use of vertexprocessing at all for shading and all that. transforming takes 4 instructions. the most of the shading capabilities now relie in the pixelshader, wich makes much more sence. the whole lightingequation now works in the pixelshader, no vertexshader needed anymore.
the only use for the vertexfunction now is transforming. (mainfunction). and with this transforming i mean skinning, blending etc. for animation of the mesh. that needs real branching, but with branching and looping it doesn't need much instructions (again, 4 instructions for the actual transformation
)
2) for what you need the 1024 in vertexshading? the rest, see 1)
3) again, i don't really understand your formulation (just english problems
). i'll try to answer anyways to what i think i understand: programs like 3dsmax, languages like renderman all are great in one thing: realistic materials. and how are they done? procedural, to 99%. they use noise, complex math functions, etc to shade their stuff to make it look like brick walls, wood, water surfaces, metall, glass etc. these are REALLY complex but are needed for realistic, stunning visuals. and for implementing them, you need much instructions. they provide that much instructions to make even offline rendering attractive on the gpu. i dont think looking up 1024 textures with anysotropic trilinear filtering on a 512x512x512 3d texture does work yet with 100fps, but simply the possibility to use that power gives renderers like for example for 3dsmax the possibility to expose ANY shader they want.
and if its not enough, most real materials are actually 2, or more.
take wood. most wood has a thin lack over it, wich happens to act like glass. take a pc screen. actually you have 2 or 3 glasses in front of the actual image. cars have twolayered materials, skin does have it even. exposing them takes much instructions, as you need to do complex lighting equations, complex material equations and combinations of them..
oh, and then you want those materials even animated?.. even more instructions
other posibilities: you can supersample, gives you the possibility to scatter trhough clouds to do the whole lightingequation of full3d clouds on a simple 2d texture, so you update that texture, and bind this then for the actual image (you don't need to update that often..). you can render real 3dtextures volumetric with the supersampling..
