[AlexP]

I wanted to add backplate with emitter. But it seems hide to gi/refl-refr doesn't seem to work, it's just clamped a litte. Please take a look (small and noisy from fire but same with production):

without hide:


with:


I use newest 3.1.1.

[F. Tella]

Hi Alex,

What I see in your images looks ok to me. What were you expecting?

Fernando

[AlexP]

I was expecting emitter visible to camera only which emits no light.

[eric nixon]

You need to put the HDRI into the background channel only, then it wont emit any light.

As a side note, 'hide to gi' is currently broken in mw3.1.1, it works in Fire but not in production mode.

[AlexP]

When has it been broken? Have you noticed last working version?

[eric nixon]

MW 2.7.23 probably. (by broken I mean that it doesn't function as expected, but it still does some weird effect)

[F. Tella]

Hi Alex,

If you hide an object to reflections/refractions, that object won't be seen in reflections (in a mirror) or refractions (through a real glass)

If you hide an object to GI its geometry won't generate shadows on the surrounding objects and won't be taken into account for light bounces. It will still produce shadows over itself, you will see the geometry behind it refracted and it will still emit light if it's an emitter, but light will travel straight through it.

All these settings does not affect the way the light is emitted by the object by any mean (I think that's what you are trying to do). If you are trying to achieve the effect of self-illumination, that's not a feature we have.

I usually make a plane, apply a texture emitter with low power and adjust in multilight.

Regarding if Hide to GI is working or not, I would say it mainly works although it may have some glitches.

[AlexP]

It was possible earlier with hide to gi and I achieved transparent effect by adding "vacuum" BSDF. Now it seems only possibility is to use blocked emitters as Dario suggested. But it's really hard to block all objects from multiple emitter and remember to check it when adding new objects...

[F. Tella]

You can still make invisible emitters by hiding them to camera, reflections and refractions and adding a ghost BSDF to the material. But non-emitting emitters are not possible yet.

[tom]

I was expecting emitter visible to camera only which emits no light.

This is ridiculously easy. So, all you need to do is enclosing your emitter in another geometry (this could be a cube) and hiding cube from the camera. The cube material could be pure black, rough0 with nd=1 for an efficient computation. I've presented this method titled Tom's Light Trap back in Oct 2006 under the Think! blog. Wow, it's been so long.

[eric nixon]

EDIT; Thanks for the reminder I'd forgotten this idea...

I am concerned that these 'non-emitters' could slow down the render, esp if multilight is enabled?

I would probably want these emitters to show up in sharp reflections but remain hidden to gi, and was wondering how much of an impact they would have on render times, perhaps a hard-coded 'non-emitter' would be more efficient?

Also why does nd1, rough0 matter if its pure black, my habit is just to leave the default; lambert nd3. Is there really a difference in speed?

[F. Tella]

I was expecting emitter visible to camera only which emits no light.

This is ridiculously easy. So, all you need to do is enclosing your emitter in another geometry (this could be a cube) and hiding cube from the camera. The cube material could be pure black, rough0 with nd=1 for an efficient computation. I've presented this method titled Tom's Light Trap back in Oct 2006 under the Think! blog. Wow, it's been so long.

Great, master! Thinking out of the box!

Works perfect.

We should rescue all those tricks/hacks and put them in the blog. I remember they were funny and instructive at the same time.

Cheers!

Fernando