Ambient lights and bump mapping

[joojaa]

In reply to:
light seems to emit from the point of the ambient light, and not from all directions. then, theoretically, you would have areas to brighten and darken to make bump maps. (not a flat color.) Why doesn't ambient light pick up the bump information then?

Because its still ambient lightning even if it does originate from a certain point. The idea behind this seems a bit obscure (hey its cg not realworld physics), but its actualy quite usefull for some effects (also its a kind of a remaint from early maya days before you could say that a light dont affect specular etc).
But why on earth cant you just use point lights then...

[djsmackmackey]

Well, because I actually have the ambient shade set to 0, not 1. I was just using that as an example. Like I said, I'll just stick with the way I have it working for now.

[jeffd]

Okay, this whole thread confused me enough that I just had to go up to the article on CGW.com to try and figure out what DJ was going for. And I think I get it now.

It looks to me like the lighting is being done with pseudo-HDRI/sky.mll methods where the surface normal is doing a lookup into a skybox texture. Which I guess is sort of an ambient lighting with direction. Am I on the right track here?

--JeffD

[djsmackmackey]

more or less I think you've got it. ILM developed this technique as a kind of modification of HDRI almost. They call it ambient occlusion I believe. But I want to know how they get bump mapping to show up. Unless they used displacement, but that doesn't make much sense for all those rivots in the planes. but they do say they "baked" it, so perhaps that means they just apply it as a texture. I have a very easy but slightly time consuming way of matching real light for compositing CG elements into live action backgrounds. The problem is, right now , they way I do it is to apply it to the ambient channel of every material in the scene. Then I have to reroute the bump map for each material, in order to make the bumps show. Now, I can make the lighting work with a single ambient light, but then bump mapping get's screwed up. That's why I originated the post, was to find a way to make bump maps and ambient lights get along.

[jeffd]

Have you followed the lengthy HDRI/sky.mll thread?

I haven't followed it that closely, but I wonder if it works with bump-mapping...

--JeffD

[djsmackmackey]

I've read a few of the posts on that thread. It gets about as confusing as this one though. It's not that bad if I can't use the ambient light and just use the ambient channel of the materials. It just would have been a bit of a time saver. but I guess if I just get in the habit of making the connections while I'm making materials, it should be fine. Thanks for the help though everyone!