Creating a matte window texture

rares

Hy guys ! i'm trying to create a matte glass texture for the windows of a car. I've never done this before , so the first thing i tried was using an hdri enviroment and baking the reflections to get a base for the glass look, the problem with that is that there is no way , as far as i can tell, to bake reflections independent of a camera ( i'm using batch bake in mental ray)...granted i could bake separate maps from a view that favourises each window and then cut and paste the good bits in a final map, but i wonder if there isn't an easier way.
How do you guys make textures for matte glass ?

Ben Apuna

Cube map? maybe...

rares

That's the kinda thing i had in mind, except that instead of using a cube to extract my reflection i want to be able to use the meshes for the windows to do that.
I don't think that chopping up a cube map would give a good result because the windows are slanted and convex, and they'd reflect the enviroemnt differentely than the straight faces of a cube

Ben Apuna

No, you don't want to chop up the cube map and apply it as a mapped texture. You need to find a way to hook it up in your shader to give off proper real time reflections.

I might be totally misunderstanding what you are trying to do here.

If you want a render of these windows with reflections. Then the other way to handle it is to turn on raytracing and actually have something in your scene for the windows to reflect. A good cheat is too just have a environment image mapped to a cylinder or half sphere which surrounds your object.

Sorry for the short reply earlier, I was heading off to sleep and figured the info on the wiki page would be self explanitory.

rares

I don't have to do any shader work, no realtime reflection required, the car itself will only have a color map, so i just need the windows to look like they're made of glass, but not actually be reflective, the way i wanted to achieve this was to mix the color fo the glass with a bit of the baked reflection....the only problem i had was getting a baked reflection that was independent of the viewport camera, but in the end i think i'll just bake reflection on each window from a view that gives good results, and combine the pieces in the color map.
Thanks for your help Ben Apuna

low odor

hmmm..I not sure if I understand 100% either..but one way you could do it, would be to aply the evnviroment map to the object. In the(bitmap) coordinates rollout of your material , switch it from texture to environment. Then switch your mapping to spherical or screen(whatever fits). Once you RTT it should have the enviroment map baaked into the texture

rares

that's a great ideea low odor, i'm not sure i understood the entire process too well tho, so i'm just gonna say what i did :
1) i mapped an eviroment texture to the color slot of the shader using a spehrical projection, like this :



2) i used convert to file texture with default options
what i got didn't look much like a reflection tho
here's the comparison : enviroment converted to texture left, baked relfection right



if i didn't understand the process please correct me

Eric Chadwick

Reflection angle is always relative to the viewing angle. In the case of baking a texture, the "viewing" angle is both isometric and dead-on to each polygon, which means each polygon's baked reflection will get something close to a single pixel of the reflection map (with some averaging from the vertex normals).

In other words, you can't use a render-to-texture to bake a decent reflection.

If you want to bake in a reflection (which always looks crap IMO, better to go with gray windows) then you should just layer it on in Photoshop.

rares

the baked reflection alone wouldn't have been the final texture, i do plan to layer it in photoshop.

MoP

Personally I wouldn't bother baking any reflection at all, it will most likely always look weird, since it would be specific but un-moving. If you absolutely can't use a dynamic environment map for whatever reason (ancient engine? Handheld?), it's probably better to go with a simple gradient with a non-specific highlight or two painted on top.

rares

i'll probably do a mixture of what you suggested and baked reflections from apropriate angles, because a gradient alone doesn't have much variation. I just wanted some different aproaches to experiment with .
Thanks guys