hello all
I'm trying to have a volumic object that would be visible only when lit by a light.ie totally transparent when there is no light.is there a shader that could achieve that ?
thanks
luc

Applying a Mantra Surface Shader to your object:

Zero diffuse.
No object reflections.
Only light reflections (referred to as Specular by older users).

If you want zero alpha as well, dive in to the Mantra Surface Shader and find the node with the label “surfaceOutput” and create an input parameter for Af and set it to 0.

Note that if you don't wire a parameter in to the output Af (Alpha final), the average vector component of the Opacity is used as the alpha. The way the Mantra Surface Shader is constructed, the light and object reflections are multiplied by the opacity of the surface. By supplying a specific input to Af allows you to set the final rendered alpha to whatever you want.

Is that what you are after?