Whats the difference between Vray Light Material and Vray Mesh Light

[Robert]

Sorry to ask in such a way, I know there a differences, but I really would like to know what are the down points of using either of them and how to adjust your render settings to make both work well.

For example: When I use Self Illumination right from Modos base Mesh, Vray tend to produce a very noise image. So Mesh Lights do that better, but I can't really do everything with Mesh light. For example the scree of a TV. Better as Mesh Light or Vray Light Material.. or leave it Modo shading?

[vladimir.nedev]

Right now the V-Ray light material is just the same as using the Luminosity in MODO's material or the Self-Illumination in V-Ray's main material.
Might be a tiny bit faster as it's a simpler material, less code to execute.

Eventually, the V-Ray light material needs to have a "Direct illumination" option, which basically turns the mesh it's applied to into a mesh light.
Right now the V-Ray core for the mesh light doesn't support applying it to only some mesh polygons, so I have to either complicate the export a lot or have it be less useful than people would expect.

The mesh light is sampled directly and is most useful when you have it applied to a relatively small object.
In your case a mesh light will probably be better as well.

Greetings,
Vladimir Nedev

[Robert]

Thanks for that explanation. In some cases its just much more difficult to use mesh lights then just give some polygons a shader.
If I currently light a scene with self illuminated polygons, like I do often with Modo render, Vray rendering turns to be very noisy and with lot GI spots. That vanish if I use Mesh Light of course.
So at the moment I turn all larger surfaces and the ones with more then 1.0 value into mesh lights and leave the rest to be Modo ones. I haven't seen a big different between Modos self illumination and Vrays Light shader as well. Good to know that its right now of little use.