I do not know whether to write about this already but still ask.
How to create a material that emits light without geo light
or how to install geo light for groups?

A constant material will ‘emit’ light if you crank up the colour values enough (and make sure you are using PBR).

Ok, constants material is really works, but it is too weak. Is there no material in Houdini that really emits light, which would be displayed on other objects? Is it possible to create such material in surface shader builder or in light shader builder?
I saw demo video Houdini in which spheres were kicked downstairs and broke. Splinters were shone from within, how to achieve such effect?

I think it's geometry lights.

To have a surface emit light from the shader, you need to have an export parameter vector “Ce” for Color emission. You can set this Ce export to any pattern created by your shader but you need to know how to work with VOPs in surface shaders.

You can author a surface shader that can use a geometry (point, vertex or primitive if you wish) attribute that is set per group that multiplies the value feeding Ce inside the surface shader. Say float “emission_intensity”. Set it to 0 for those surfaces that you wish to emit no light and above 0 for those surfaces that you do wish to emit light.

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A few shaders have an export parameter variable called Ce that peform a simple single color emission:
- Mantra Surface has an emission tab and a color that you can set for emission. The intensity of the value determines the amount of light cast
- Constant Surface shader as you know

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The problem with using Ce as surface light emission is that it is quite noisy in PBR at this time (as of H12.1 that is).
As well, this is calculated as surface emission and not light emission. PBR casts two types of rays (at a minimum) when computing secondary illumination: surface and light rays. You really want to separate these surface emitters as actual light (specular) reflections but using Ce directly lumps surface illumination in to surface (diffuse) reflection rays and not the light reflection rays.

Geometry Lights in H12.1 are somewhat limited and again don't properly allow you to separate light (specular) reflections for comp later on.


This may all change very soon.

Wow, thanks for the detailed answer.

I guess you're right

A viable alternative depending on your scene might be to instance lights over SOME of the points on the geometry. This works nicely because the instanced lights can draw their color from those points, and depending on your shot you could get aways with a small fraction of the points on the geometry.

This is also light emission, not surface emission.

I just thought I would mention it as an option for some shots.

Ok, thank you Netvudu))

OK, not sure if this helps... I'm a newbie so this might not be the best way... please correct me if things have changed since this post...

Create a Texture Map and apply the texture you want to Emit colour.

Create a Principle Shader.

Set Surface > white

Textures > Emission > Use Texture > Locate texture file and load it in

Push the Intensity right up - I used 10 (it goes higher than the slider)

You should now see some results if you render...

In my situation I was using a single colour logo (red)on a TV and managed to get more of a emission if I added the colour red to the Emission section in the Surface Tab...

Give it try... hope it helps...