Emit, Radiosity, and UV Textures

I recently started getting into using UV-mapped textures and radiosity. I’m making a model of a room, and it’s looking pretty good. One of the walls has two windows on it, so, after applying separate color and normal maps, I added a map that masks the window portion to white, the rest black, and then set that texutre to affect the Emit value. It looks nice, but I don’t think it’s actually emitting in the sense the Radiosity needs.

For example, I added a mesh to the room as an overhead light, and set it’s material Emit value to 0.2. When I render, I see that the radiosity is being calculated. But when I turn it off on that “light” and just stick with the emit that’s coming from the window, nothing seems to get processed. The windows look brighter, as if light would be shining from them, but it doesn’t have an effect on the room.

Like I wrote above, I’m really new at radiosity, so let me know if I’m missing something incredibly obvious.

Maybe the normal vector of the window points in the wrong direction.

I’m not 100% sure, but I’m pretty certain that radiosity works only off the emit value on the material, not the emit value in the texture (as your test shows!)

So I think you need a separate mesh for your window emitter. You could try this: create an emitter mesh just in front of your windows - if you turn the alpha on the new material to 0.001 (as low as it will go but NOT zero) and click z-transparent the new mesh will be invisible but should still emit light for the radiosity calculation.

Okay, I’ll give that a shot. I did find that my normals were pointing in the wrong direction, but changing them to point the right way didn’t affect anything. So, I’ll try the mesh trick and report back.

By the way, can anyone else confirm this behavior (or lack of) with emit and textures? There’s really no interaction between texture emits and radiosity? Seems a shame, but, then again, I’m not the hacker having to deal with the guts of something like that.

Okay, that sort of worked. I was able to get emit to happen from the mesh, BUT none of the textures showed up when I pulled all the lights off the scene. I only saw the raw cubes I used to make the scene.

Do textures just not react to texture-based emits? Do texture emits do anything beyond brightening the color texture benath them? It’s not a big deal–I can place lights to compensate–but I’d like to know for future reference.

BTW, here’s the movie of the room I’ve been modelling, fading in and out between the current and planned room (we’re remodelling in real life :wink: ):

Not sure exactly what the texture emits do: but sadly it is true that you can only see material textures via normal blender lights, not with the radiosity calculated lighting… So if you want textures, you need some sort of normal lighting as well - however the light can be a lot dimmer that it would normally be, so experiment a bit (I found low power hemilights gave the best results)

Hopefully this is something that will be fixed in the future though!

EDIT: Nice movie! You might also be interested in Quicktime VR’s which you can produce with Blender quite easily. Do a search for “gocubic” on this forum for a tutorial. There’s a sample I made with Yafray here