Vray lights block light?!

[Alex_M]

It seems that Vray lights block light. How can I avoid this? I have a pool which has spotlights in it and it creates light that shines on the ceiling above. When I add another light above the pool shining towards that ceiling, it blocks the light that the pool creates.

[LudvikKoutny]

You can check invisible checkbox. Light will cease to cast shadows but also disappear. If you need it to be visible, then you can just create VrayMTL with self illumination of same intensity, then apply it on a geometry matching light source shape, and make sure this geometry does not affect GI, nor does it cast shadows. If it's visible for reflections and refraction depends on if your VrayLight is. You don't want both VrayLight and a stand in geometry to be visible twice for any ray type.

[Alex_M]

The light is invisible but still blocks light.

[vlado]

The light is invisible but still blocks light.

I don't know how that would happen. Can you post an image or a part of the scene?

Best regards,
Vlado

[Alex_M]

Sure, please see attached part of the scene. When the light "VRayLight Pool Ambiance" is turned off, you can see the light from the pool falls freely on the ceiling as it should. When the same light is turned on however, the light from the pool no longer reaches the ceiling.

Thanks a lot for the help!

[Svetlozar Draganov]

Thank you very much for the scene. This is a bug, the direct light is not blocked but the GI illumination is.
It seams that the invisible option is not taken into account for the GI calculation.
We'll make a note about it and will fix it.

[vlado]

It's not a bug really; the light is an actual emitting object that is physically in the scene; some hacks are used to allow it to pass camera rays or shadow rays from other lights through, but it does block GI and reflection rays.

To do what you want, you could try plugging a white VRayColor texture into the light texture slot and making the alpha of the VRayColor texture 0.0.

Best regards,
Vlado

[Alex_M]

Ha, never knew that lights block other light. This suggestion does the trick, thanks. Although I see this to be a pain to set up for each light. Could this be changed in future versions so it works without workarounds? Or is this on purpose?

By the way, what if I wanted to use an image texture in the texture slot of the lights? How can I make their alpha 0.0 so they let light through?

It's not a bug really; the light is an actual emitting object that is physically in the scene; some hacks are used to allow it to pass camera rays or shadow rays from other lights through, but it does block GI and reflection rays.

To do what you want, you could try plugging a white VRayColor texture into the light texture slot and making the alpha of the VRayColor texture 0.0.

Best regards,
Vlado

[vlado]

Could this be changed in future versions so it works without workarounds?

Nope It's on purpose; like I said normally the light is a physical surface in the scene.

By the way, what if I wanted to use an image texture in the texture slot of the lights? How can I make their alpha 0.0 so they let light through?

You could use f.e. a ColorCorrection texture where the "Alpha=" parameter is set to "Zero"

Best regards,
Vlado

[Alex_M]

I knew it must have been on purpose. You guys know what you're doing. Alright, thanks again for the help and valuable tips!

[Morne]

I have a similar situation. I have a dome light with HDRI lighting an object on ground plane. I add a plane vraylight above my object to boost the lighting/reflection on some areas of it, however this light blocks the light cast from the dome light. Would be nice if we could right click the light object (like any other object) and in it's max object properties untick cast shadows (even though in it own vray properties it still CAST shadows from its own emitted light)

[vlado]

You can use the solution mentioned earlier in the thread.

Best regards,
Vlado

[Morne]

But then as mentioned, what do you do if you already have a texture in the light?

[Zdravko.Keremidchiev]

As Vlado mentioned

You could use f.e. a ColorCorrection texture where the "Alpha=" parameter is set to "Zero"