I have a few questions about GPU's Vs CPU's.


I am a user of Blender and I am fairly new to 3D.
My understanding is that GPU's are more powerful that CPU's in many ways. Especially when it comes to Graphics.

So why is it that the CPU of the computer does the actual rendering and the GPU is only used for the model creation process? Doesn't that waste the power of the GPU?

Now with Blender being open source it should be possible to shift the pipeline to the GPU, correct? Or is that just too much work, or not possible?

Because from my point of view I should be able to take the new Nvidia Quado series video cards with their CUDA interface and with some changes to Blender use the Quadro to render the image. Would that not work?

Say for instance I had a system that took advantage of 2 Nvidia Quadro 2200 S4 series video cards connected with SLI. That would give me 1920 processor cores and around 12 gigs of video ram. Would that not be enough power to render the final image? Instead of using a set of RenderBoxx 10300 clustered together?

It really seems like a waste of money for me to buy a 20-30 thousand dollar 3D graphics machine with that much video power and then have to buy a rendering farm for another 20-100 thousand dollars.

So could someone please explain to me the reason that the cpu must do that work. Because it seems to me that the CPU micro-code controllers and code processing pipelines are not really built for that kind of work.

So why not use the GPU for all of the work? or use the cpu to handle to overflow?
Call me dumb, but that just makes more sense to me.

Thanks

I thought I had logged in when I wrote this post, but obviously not. thanks if you can help explain this to me

I think that GPUs are too specialised and have a limited number of shaders and it limits the number of ways they can calculate the final image. That's why the processor is doing all the rendering. But I may be wrong.
I know there are renderers that use the GPU to render fast but I don't know what is the quality of those renders.
_________________
Andyba, 3d artist
skills: 3d modeling, texturing, rendering, 3d character animation, compositing
3d software experience: 3ds max, Maya, Softimage XSI, Deep Paint 3d, Body Paint 3D, Wings 3D, Z Brush
2d software experience: Adobe Photoshop, Adobe After effects, Macromedia Flash, Freehand

May be in the future the GPUs will be used for rendering...
But right now people are using huge render farms.
Silly people... Why would they do it?
_________________
Andyba, 3d artist
skills: 3d modeling, texturing, rendering, 3d character animation, compositing
3d software experience: 3ds max, Maya, Softimage XSI, Deep Paint 3d, Body Paint 3D, Wings 3D, Z Brush
2d software experience: Adobe Photoshop, Adobe After effects, Macromedia Flash, Freehand

As anydba wrote it is possible to render with GPU on special render engines.

Here is an example of gpu rendering in Autodesk Maya with the FurryBall renderer.


Pretty impressive, eh?

Ooh, this renderer might be very useful to me. I found another example where it calculates ambient occlusion which is really amazing.

Here's the deal. A GPU is very powerful for processing graphics information, but when you are rendering something or modeling something, you are actually running a program that is then creating the models and such. So a GPU rendering models would be the same thing as your GPU running firefox, or windows, or internet explorer. It comes down tot he way the program is written as to how rendering will be carried out. multi-processor programming is very difficult, so I wouldn't count on the GPU's being used to render in any great deal anytime soon.

Just as you said, GPU's deal with streams of very specific information.

About rendering with GPU:
Here is a very interesting video showing some new technology renderer that uses the GPU and compares it to some GI Vray renders. The anti aliasing is not that good but the global illumination is pretty amazing.


_________________
Andyba, 3d artist
skills: 3d modeling, texturing, rendering, 3d character animation, compositing
3d software experience: 3ds max, Maya, Softimage XSI, Deep Paint 3d, Body Paint 3D, Wings 3D, Z Brush
2d software experience: Adobe Photoshop, Adobe After effects, Macromedia Flash, Freehand

Wow these are pretty damn fast GI renders.
It is strange that the guy in the video tells that the quality is identical to vray while on the video itself I can see that it is not.

I cannot see the videos ... can you post links?