Lights Diffuse & Specular question

[mitchino]

For the life of me, I still don't get it in c4d. I can have a light affect only the diffuse, but I can't have them affect only the reflection. I've tried a light on it's own, I've tried a light with a light material, and I've tried a light with an ordinary material with self illumination enabled.

Can anyone look at this file, and get the light on the left to affect only diffuse, and the light on the right to only affect specular?

[TomG]

I'll take a look - I am not 100% sure that the LightMtl Advanced features are working as expected based on some of my earlier tests, as I was getting different results in C4D compared to a similar set up in Max. I will let you know shortly what I find with your scene too! Thanks!

[TomG]

Yes, it's not working as expected.

In your scene btw:

You have lights with the Corona Light Mtl applied. You should just have regular geometric objects, not lights :) In this instance, two planes, with the CoronaLightMtl applied. Using a Light Material turns that geometric object into a light source. It should be one or the other - a Corona Light, or geometry with a Light Material applied.

Then the Specular only light material should have Emit Light unchecked in the Emission tab (as you don't want it contributing to GI). This should stop it casting light into the scene, with the Advanced tab keeping it showing in reflections and refractions. However, unchecking Emit light does not stop it emitting light at the moment.

The Diffuse only would keep Emit light checked, and have the other options in advanced unchecked. Again however, unchecking Visible in reflections for this material is not making it invisible in reflections like it should.

So at present, this is not working as expected, even with a correct scene setup. Attaching the scene as I'd set it up (just used spheres for the geometry rather than planes, but could do it on any object - there's no performance penalty for using geometry with LightMtl applied vs an actual CoronaLight), even though the scene is not working as expected at present.

PS - C4D R19, Oct 13th build of Corona.

[TomG]

Here's the result of the similar set up in Max, I left the light materials visible directly. The one on the left casts GI, but no reflections, the one on the right reflections but no GI.

EDIT For those who don't want to download the C4D scene, attaching the result - both light materials continue to cast GI and show in reflections, even with the relevant checkboxes unchecked.

[mitchino]

I don't have r19, but had another go with my file, using planes with light materials, and yes it doesn't work. I also notice if you switch emit light off, the render gets extremely noisy.

[TomG]

Ty for testing! At present the answer is that there will be a way to do this, set up like in the scene I shared, but that during development this is not working in the current build.

[burnin]

Yes, in cinema it only works with Ray Switcher for now.
Done tests with all the possibilities (scene posted previously). 

[mitchino]

It does work - as a convoluted workaround. The same functionality takes less than 5 seconds to set up in other engines.

For now I got where I wanted to using multipass. I look forward to a future build where this is a trivial task in Corona.

Thanks to everyone who pondered this problem, and to the devs who continue to make Corona so awesome.