impressive 3d tech : VolumetricBillboards

[ghoulsblade]

stumbled across this gem recently and wanted to share, see video at bottom : http://www.antisphere.com/Research/Volu ... boards.php

[charlie]

That is very nice looking and seemingly very cheap as well.

[alapshin]

May be I've read not so carefully, but I am not sure at all that these billboards are cheap.. Storing mipmapped 3D textures is very expensive GPU memory usage. One object - one 3D texture... Assuming that 3D texture size is rounded up to the nearest power of two, for object 129x129x129 (actually for 256 x 256 x 256) we need 2^24 * 4 = 64Mb).. Not a practical approach if I understand it correctly..

And rendering technique is CPU-based (or it is not obvious how to made it GPU-based).. Slices, computing intersections.. That's not good, I suppose. The main question I got reading this article: Is it really useful for rendering simple objects like trees? I think that no. Only area I see where it may be applied - fluids rendering.. but again, because of 3D volume textures only the small areas may be rendered..

Some benchmarking is needed for such works... Interesting question arised for me: Is it faster, for example, than "Smoke" demo by nVidia (from nVidia DX10 SDK)?

P.S. Sorry for grumbling in this thread

[alapshin]

No chances to render fluids.. Rendering algorithm works only with static geometry because of need in offline preprocessing. So, it is only for small static objects rendering..

[Sauer2]

What about this technology made by unlimited detail?
http://unlimiteddetailtechnology.com/
Does it have the same problem?
I guess, animations in general are rather hard to make that way, because you'd need to move thousands of points. Well, maybe if it was all written in assembly..

[charlie]

Sauer2: I'm not so sure it would be that hard... I'm mean, towards the end of the video for the volumetric billboards, they show a tree swaying in the wind that is composed of multiple volumetric billboards. Since these billboards are 3d objects, and can be viewed from any angle, what's to stop having them moved around in an animation?

[Sindwiller]

The result is indeed impressive if compared with normal 2D billboards. I can remember Guild Wars having 2D billboards for far away objects additionally to several LOD levels for example. It would be even more effective if done with 3D billboards. But as alapshin said, it's not memory efficient at all. It's still wiser to use low detail props and LOD levels for that, it seems. It strikes me as a good technique for the future though.

[alapshin]

@charlie: I mean animation of the model that is inside billboard, not the animation of the model by rotating several billboards of the same model. The second approach is for rare cases and it is not able to look like simulation.. It will be only the emulation.

I still do not understand why usual tree model rendering is worth than proposed method.. Can anyone point me to the advantage of the method?

P.S. Agreed with Sindwiller's opinion

[charlie]

I think the point is that it's computationally a lot, lot cheaper than intersecting rays with the equivalent 3d model.

Essentially it is pre-rendered. Shadows etc have been done off-line. You skip out on a whole lot of work, and it all fits comfortably on the GPU.

[alapshin]

Hmm.. Prerendered shadows.. It means that this approach is only for static lighting.. and if I understood you correctly shadows are wrong after billboard rotation, cause orientation is changed without change of light position..

And yes, it is much cheaper to use this technique instead of computing rays intersection, I agree with that..

[ghoulsblade]

about 3d texture in vram : dds can use compression for 2d textures, maybe that is possible for 3d as well ?
even if not, using it for very few highly repetitive elements like grass would still be very interesting.

[alapshin]

Sauer2: I have looked at the link you posted, but have found nothing about details of the technology.. tbh, I do not believe in their technology, at least in the things they described. Processing billions of points in a high quality and without GPU (as they said) is doubtful for me. But may be I am wrong.. I have downloaded video clips from their site, but they were left at my work.. I'll look them on Monday