Idea: Control Light Via Diffusion ?

Is it possible to shoot light as in rays that are only received by an objects diffuse maps or surface diffuse shaders? I was just thinking about an application via scripts that could speed up render times. What if we could paint on diffuse-light only maps in a 2d app or with Blenders 3d painting tools. Then later we could have a node or material channel in which to input these diffuse-light only maps. Maybe these materials or nodes could distribute levels of light based on the scale of white to black in a map. Pure Black could mean no light. Pure White could mean full light power. If noisy strokes are painted on the map composed of complex tones then the light distribution would be more complex. Is it even possible to control light with painterly detail via scripts? Or is this something that is better left up to hard coded features?

As we advance forward with Blenders rendering features we could look at many options. We could work on ways to give 3d artist more artistic control during the rendering process. Machine driven computer GI solutions are great. But after a while the pure GI “look” levels off or is too slow for some task. Artist will tire on common GI for every render. Any ideas?

I have no idea what you’re trying to achive

yes, you can paint textures that are projected by lamps

yes, you have some control over which lamps light what objects… but not in the way you asked. You can use the layer property of lamps to have the lamp only light objects [dunno what it does about shadows] on the same layer as the lamp. [both lamps and any other object can be on any number of layers, so if both the object and the lamp share a single layer then the lamp will light that object]

With one twist - if you need multiple layers active to render the scene, and the light(s) in question will end up being inside an object, regardless of what layer it’s on, it will occlude the lamp’s light. The lamp will only illuminate stuff on it’s own layer, this part is true, but objects on other layers can certainly block the light… be it bug or feature, that’s the way it is.

Duplicating the scene and doing the compositing in Sequence is the way around it.

In CVS and upcoming 2.42 you can also use groups (per material) to define what lamps can affect it. This offers a much better level of control than layers (especially when you’re also trying to use them to organise your scene, which is what they should really be kept for…)

Sounds good, although I would still like a diffusion map. Its odd to be able to have a spec map and not a diffusion map. They are kind of opposites.

Map a black&white texture to Col and set its blending mode to Multiply.

I usually just map a Cloud texture or a black and white 8bit map to “Ref”. The I play with the blending modes to get it right. :wink:

UV maps give your even more precise control.:smiley:

Sounds great!

Maybe my idea for controlling light via an object surface has nothing to do with diffusion. The more that I think about it’s controlling the measured “visibility” of light on a objects surface I’m concerned with here. This is more that just assigning a light to an single object. The light controls the objects visibility still in this case. I want the object to determine how visible it is to a lights rays via a map or texture.