Indigo Renderer Forum

Hello Everyone,

A few questions on emitting materials. I am using Blender, and I noticed when exporting that although most material types can be an emitting material.

With respect to lighting, is there any advantage to one type over the other? What is the difference in the emitted light for each material type?

Also, can a mesh that is assigned an emitting material be a single plane? If so, would I be correct in assuming that the plane normal is the light direction?

Thanks in advance!

If im understanding your question correctly, black body lights are good when you don't want to change the color of the lighting. Conversely, rgb emitters are useful when you want colored lighting.

I think mesh emitters have to have thickness..

neo0.,

Thanks for the response! According to the documentation, "Mes light is deprecated, use emitting materials instead". While I have not tried each of the material types as an emitting material, I was wondering if there was any material that points tothe difference between a diffuse emitting material and a phong emitting material, and whether or not the materials can be applied to a plane.

Thanks again

neo0.
Wrong, wrong and wrong

Right is: RGB emiters have whatever color you assign to them, blackbody lights can only have light colors from the blackbody scale (see http://en.wikipedia.org/wiki/Color_temperature)
Stop spreading your "knowledge" in the forums, first learn the stuff you are talking about before telling others "how to"

OBI_Ron
The mats of course can be applied to a plane without no thickness and the normal is the light direction, thats right!
You can change the strength of your light in your material and light normalization settings (ignore this if it sounds over the top) so you can still see the other materials properties like phong or diffuse.
If your light, however, is strong enough you wont see no difference between them two

One thing to add:
Blackbody emitters have a continuing spectrum - as lightsource, they're more realistic.
I'm not sure wether RGB gets extrapolated to a full spectrum or it's rather like a triple-peak-emitter............
It's probably easier to use RGB if you have a certain colour in mind but if you want to do something in that Red->white->blue_with_violet_touch range of blackbody, you should use them. (Just about any standard lightsource from candle-flame to halogen-spotlight gives a colour from the blackbody-curve.
If you want to simulate unicolor-LEDS, you should stick with RGB)

Thanks everyone for the information! If I may, I'd like to tag on another question that is closely related.

Scale for an object that has an emitting material applied:

From a Blender perspective, I can scale the object, or I can scale the mesh (tab into edit mode, select all and scale). If I understand correctly from what I have read, scaling down an object with an emitting material applied makes it act more like a point light with sharper shadows.

Does it make a difference how I scale the object? Should I scale the object or the mesh. My reason for asking is that in Blender, if I have several objects that are referencing the same mesh (instancing, if you will), then I am limited to scaling the object, because scaling the mesh would scale all instances.

Thanks again!

it won't make a difference in the way the light creates shadows, if that's what you mean. the softness or sharpness of your shadows depends on the geometry of your light source and its relative size and distance from the other objects in your scene.

About performance of one material over the other for emission, it depends if you are looking for some glowing material (and in this case you need the material parameters to be set accordingly) or as a light source. In the later case I would suggest to use a diifuse material with full black as albedo, because you usually don't want light interacting with the emitter (ie want no caustics and such).

Not sure I understand the blender concern, but the smaller a light source relatively to the lighten geometries, the sharper the shadows.

Thanks again everyone,

As far as Blender goes, if I am instancing, using the same mesh for several objects, I cannot apply the scaling. Meaning, if I scale an object that is using a shared mesh, I cannot apply the scale (ctrl a) such that the object would now have a scale factor of 1,1,1. If the object is not using a shared mesh, then I can apply the scaling.

However, given that either way I scale in Blender, Indigo will treat it the same - relative to other geometry in the scene, it really doesn't matter.

Thanks again!