Env reflections not working with refraction

[sharktacos]

Simple scene: a plane in front of sphere. The sphere is set to be reflective metal, the plane is set to be glass. Both vrayMtl. GI is off.

If the reflections are coming from an HDR in a dome light, it works fine. (affect diffuse is off so we just get the reflections)

If the reflections are instead coming from the same HDR in the reflection texture slot in the render settings environment tab, then the HDR reflections are not visible through the glass.

Is there something I am doing wrong?

[Dariusz Makowski (Dadal)]

Did you put the HDR texture in to refraction slot of the envi slot as well? Is the glass plane thick ?

[sharktacos]

Thanks, that's helpful. No I did not have the HDR in the refraction slot. When I put it there too, I can see the reflections through it which is great.

Only problem now is that I see the HDR not only reflecting off of the sphere, but also in the "sky" behind it in the glass. In contrast, if I have the dome light set to invisible it will only show me the relfections on the sphere through the glass. This is significant in comp. Is there a way to get the same behavior from the environment slots that I can get from a dome?

[Dariusz Makowski (Dadal)]

I'm lost. can you post some screenshots or something? It works on my end or at least I did not notice the issues.

[Svetlozar Draganov]

Thanks, that's helpful. No I did not have the HDR in the refraction slot. When I put it there too, I can see the reflections through it which is great.

Only problem now is that I see the HDR not only reflecting off of the sphere, but also in the "sky" behind it in the glass. In contrast, if I have the dome light set to invisible it will only show me the relfections on the sphere through the glass. This is significant in comp. Is there a way to get the same behavior from the environment slots that I can get from a dome?

It would be better to use custom-object-environment-override instead of global ones.
You could get the reflection of the sphere through the plane as you have with domelight if you add vray-material-override-node to sphere material and then apply the hdr-map into Environment Override node.
Please follow the image bellow and let us know if you have any questions about it.

[sharktacos]

Here's a pic illustrating the problem:



As you can see above, the global environment overrides give a result that will be problematic in comp (what I described above as seeing the HDR through the glass in the "sky"). The dome light does not have this issue.

Svetlozar, the method you outlined works too (i.e. it give a result like we get with the dome light) however since it is a material override I would need to apply this to every material in the scene. What I want is a global approach that I apply once universally. So I was hoping there was a way to get the same behavior from the global environment override. Is this a feature request, or is there a way to get it to do that currently?

[Svetlozar Draganov]

Is there any particular reason to avoid DomeLight approach ?
Another similar approach like the one I mentioned earlier would be to wrap the entire scene into a sphere and attach the texture into self-illumination-slot of that sphere. Then if you create a local-override and replace reflection material with a pure black material you will have the same behavior as with the dome-light. With this method you won't have to override every single material, only sphere-material should be overwritten.
Example Scene=>684_dome-light-override.zip

[sharktacos]

"Is there any particular reason to avoid DomeLight approach ?"

The only reason would be speed (since the dome light is quite slow), but it is possible to turn off "affect diffuse" and "affect specular" on the dome.
I believe that this would then be the same speed as the environment override approach, yes?

Out of curiosity, is there a reason the override has a different behavior than the dome here?

[Dariusz Makowski (Dadal)]

"Is there any particular reason to avoid DomeLight approach ?"

The only reason would be speed (since the dome light is quite slow), but it is possible to turn off "affect diffuse" and "affect specular" on the dome.
I believe that this would then be the same speed as the environment override approach, yes?

Out of curiosity, is there a reason the override has a different behavior than the dome here?

You cant cut the render times by not using dome light affect diffuse+spec

If you dont have dome light affect diffuse affect specular then you dont have light in ur scene. U only have reflections. Unless you can live with only reflections you need light. You also need specular in order for the reflections to be accurate.

[Svetlozar Draganov]

Out of curiosity, is there a reason the override has a different behavior than the dome here?

Both tools actually are completely different and I am not quite sure whether they should have the same behavior.

[sharktacos]

You cant cut the render times by not using dome light affect diffuse+spec. If you dont have dome light affect diffuse affect specular then you dont have light in ur scene.

Right, that's the idea. The enviroment override reflection/refraction also does not provide light.

The way we commonly use this is in combination with a directional light (simulating the sun). So the dome would provide the HDR reflections, and the directional light would provide the diffuse and spec.

You also need specular in order for the reflections to be accurate.

I don't think that's actually true. First of all, I'm pretty sure a dome light does not produce spec at all, since it does not have a point of origin. Second, spec simulates the reflection of a light source. HDR images contain those light sources as part of the image (the sun in the sky or the lightbulbs in a room) which would be more physically accurate than a spec dot is.

At any rate, the only intent here is to use the dome light to get HDRI reflections on the objects. Spec can come from the other lights in the scene.

[sharktacos]

Both tools actually are completely different and I am not quite sure whether they should have the same behavior.

Can you elaborate? What would be reason for them to have different behaviors?

[Dariusz Makowski (Dadal)]

Right, that's the idea. The enviroment override reflection/refraction also does not provide light.

The way we commonly use this is in combination with a directional light (simulating the sun). So the dome would provide the HDR reflections, and the directional light would provide the diffuse and spec.



I don't think that's actually true. First of all, I'm pretty sure a dome light does not produce spec at all, since it does not have a point of origin. Second, spec simulates the reflection of a light source. HDR images contain those light sources as part of the image (the sun in the sky or the lightbulbs in a room) which would be more physically accurate than a spec dot is.

At any rate, the only intent here is to use the dome light to get HDRI reflections on the objects. Spec can come from the other lights in the scene.

Umh....

1. Dome light is producing specular.
2. In vray you actually do need specular+reflection for matte/brushed objects in order to get accurate result.
3. You cant really reproduce specular coming from IBL using point/direct/area lights as its very complex and 360 degree... So you will not get nice looking matte reflections from multiple light sources in IBL. For example night shots with many lights etc etc.
4. Instead of using dome light for reflections u might as well just use self illumination material + sphere to get reflections or environment overrides.

I know what you are doing more or less. And it do can work to the certain point and works very well in certain cases. You also need ur lights in ur scene to be properly setup to account for the missing IBL. Still in some cases u might just need to spend the time

The reason why they have different behavior is the way they are being sampled I believe. Dome Interpolates and MIS + more to the texture it uses. Then based on that match it generates light/specular. Environment overrides dont do any of that. It just creates invisible sphere around your scene and then just use that to reflect/refract/cast gi - then again I might be wrong to all of it

[sharktacos]

Umh....
1. Dome light is producing specular.

I did a test and you are correct. It looks like it is deriving it from the hotspots on the HDRI. Interesting.

As to the other points, it is certainly true that the dome light is capable of doing a lot of cool stuff that goes beyond what the reflection/refraction slots in the env override does. No doubt about that. However in this case I am not trying to do that. I am simply wanting get environment reflections from an HDRI on materials. Not as a complete lighting solution, but rather as one piece of it.

[Dariusz Makowski (Dadal)]

I did a test and you are correct. It looks like it is deriving it from the hotspots on the HDRI. Interesting.

As to the other points, it is certainly true that the dome light is capable of doing a lot of cool stuff that goes beyond what the reflection/refraction slots in the env override does. No doubt about that. However in this case I am not trying to do that. I am simply wanting get environment reflections from an HDRI on materials. Not as a complete lighting solution, but rather as one piece of it.

Then simply do not use IBL and just put a texture in to your env refl/refr overrides and that should do it.

Or just create a big sphere, set pri vis off cast/recieve shadow off and apply vraylightmrl with texture in it.

I'm not sure but wsnt that explained early in topic?