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MartinK
10-21-2005, 06:51 AM
Hi

I'm working on a project that I will render in several passes and I was wondering:
Do you usually render a separate bump-map pass and if not, which passes do include the bump in?

I'm planning to renderer the following passes: Ambient, Contour/Shaded, Specular, Shadow, Reflection and Ambient Occlusion.

Thanks for any advices.

Martin K

Splin
10-21-2005, 02:02 PM
I would do for everything else with bump. Only for shadows pass not, but that also depends on the scene basis. Basically..if it looks ok..noone cares how it was made :)

Sharky0815
10-21-2005, 03:56 PM
If you try to imagine what a "bump pass" would look like you will come to the conclusion that a bump map will influence the look of all of the passes you mentioned. So, you can't render a "bump pass" per se. I think the closest you could come to that would be bent normals. Also, it sounds like you want to rendern in passes but dont know why. First think about what you want to be able to do in post, then decide what kind of pass you need.

Think about it like drawing a painting on a lot of transparent layers. There is no rule what to paint on which layer. It is your decision, based on how flexible you want to be.

MartinK
10-21-2005, 07:30 PM
Thanks for your reply, splin.

Sharky0815, Im wondering how you came to that conclusion? There are several reasons why I want to render in passes, and none of them is just because it sounds fun..

Anyway, after some research Ill found that bump in the ambient/contour or diffuse pass as well as in the specular-pass will give a nice result. All the other passes can do without a bump-map.

Any tips & tricks are welcome.

Thanks
Martin K

lazzhar
10-21-2005, 08:36 PM
Try this:
http://www.3drender.com/light/compositing/index.html

And as Sharky0815 said, the bump is supposed to perturb surface of one of layers contributing to make the final look. On of the passes that seems getting subtle bumpiness is the specular pass. You can use it also to add some special effect such as glow that give a very nice look to the final render.
Good luck.

jeremybirn
10-22-2005, 01:29 AM
Anyway, after some research Ill found that bump in the ambient/contour or diffuse pass as well as in the specular-pass will give a nice result. All the other passes can do without a bump-map.

The other pass that bump would have a big influence on is the reflection pass - it distorts the reflections.

If you render a specular pass with a bump map and a reflection pass without a bump map, you can still comp them together, it just gives you something that would only be realistic if you thought of it as a multi-layer surface. Sometimes you might even render two specular passes, one with a bump map, and the other without, if you wanted layered highlights where some were broad and soft, but there were others broken up by the bump map into smaller sparkles. This really all depends on what you want. (Being able to layer together bump and non-bump passes is perhaps the only quality advantage to using bump mapping instead of displacement mapping.)

-jeremy

MartinK
10-22-2005, 04:55 AM
Thanks for your replys guys. It's helped a lot

Martin K

Sharky0815
10-22-2005, 09:18 AM
I didnt mean to offend, its just that I seem to see a lot of people hellbent on rendering as many passes as they can so I tend to overreact. I see now what it is you wanted to get at. Hope to have helped anyway and good luck with your project!

MartinK
10-22-2005, 09:22 AM
Thats okay, Sharky0815. The rest of your reply was constructive and helpful. Sorry for just reacting to those two lines :)

Martin K

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