Problem with "Secondary Matte Environment"

[JulianT_CD]

Hi,

the option "Secondary Matte Environment" is not working as I expected. Not sure if this is a bug or working as designed.

I just made a quick test scene with a camera, a chrome sphere and large planes as matte objects around the sphere to catch the background and offscreen reflection rays. These extend well beyond the viewing frustum of the camera:



I want to render over black for compositing, so I am setting the 3ds Max Environment to black and copy the backplate into the Secondary Matte Environment:



However, the offscreen reflection rays don't return the Secondary Matte environment, but the black 3ds Max background. I expected the backplate to appear in the offscreen reflections:



I can't imagine why it should be useful to return black reflection rays when rendering over a black BG for compositing...
I only get the behaviour I want when I set the 3ds Max background to be the backplate, which for compositing is not what I want.

Is this a bug? If not, how else could I make offscreen reflection rays return the backplate?

Thanks!

[tashko.zashev]

Hi,

It would be better to see the entire setup, but from what I see in the screenshots attached, the black part of that sphere are reflection rays hit the environment color. Nothing unusual here. In the places where you have matte surfaces all reflections rays are set to use the color/map set for the Secondary matte environment. For all additional reflection rays the environment map/color will be used instead. This information can be overridden by mapping the Reflection/refraction environment slot. Then you will be able to get all reflections on the sphere and black background.

[JulianT_CD]

Hallo Tashko,

no, the black reflected parts in the sphere are matte objects. They extend outside the cameras viewing frustum. Since these matte objects are set to "Matte for refl/refr" I expected to see the "Secondary Matte Environment" to show here, even for rays that escaped the viewing frustum of the camera. But I guess "Secondary Matte Environment" doesn't work for offscreen rays?

Basically what I wanted to do is use the backplate for providing most of the reflections visible on the sphere (even though these would be LDR then), because the HDRI I use in the Dome Light is not a close enough match to the backplate. That's why I built these planes around the sphere and set them to be Matte objects.

I attached the scene.

[JulianT_CD]

Using the "Reflection/refraction environment" for offscreen rays (as you suggested), doesn't yield the same projection of the backplate compared to putting it into the 3ds Max environment. The Mapping of the backplate is set to "Screen" everywhere.

Have a look pls...

Backplate in 3ds Max Environment:



3ds Max Environment black, but backplate in "Reflection/refraction environment":



That whole Matte object thing is still a bit of a black box for me :-/

[tashko.zashev]

Thank you for attaching the file for this issue.
I'm getting identical results when mapping the Environment and Reflection/refraction slots on that area. I don't have the original texture files and maps so I had to recreate some of them.

Is it possible to send me the entire project in archived file to support@chaosgroup.com ?

[JulianT_CD]

Sorry, I accidently set the Max Environment to "Spherical" and didn't see it. It's now rendering the same.

However, back to post #3 in this thread. Doesn't "Matte for refl/ref" work for offscreen reflection and refraction rays? For me offscreen reflection rays that hit matte objects render the black background color instead of the "Secondary Matte environment". Is this how it's designed to work?

[tashko.zashev]

Sorry, I accidently set the Max Environment to "Spherical" and didn't see it. It's now rendering the same.

However, back to post #3 in this thread. Doesn't "Matte for refl/ref" work for offscreen reflection and refraction rays? For me offscreen reflection rays that hit matte objects render the black background color instead of the "Secondary Matte environment". Is this how it's designed to work?

Actually I'm not sure if this is a bug or expected behavior. Probably this is how the reflection rays of matte objects are projected onto the sphere. Let me check this issue with our developers in order to give you more precise information.
Thanks.

[tashko.zashev]

Ok, it's not a bug. Due to the projection mapping we use to derive the secondary mate reflections this is an expected result. I see that we have an option in our V-Ray for Maya plugin to disable it and force the engine to use environment map instead.
If this is will help to your workflow I can make a feature request to add the same functionality in our V-Ray for Max plugin?
I found a discussion about similar issue : http://forums.chaosgroup.com/showthr...than-vray-2-40

[LudvikKoutny]

I think it's desirable and expected that matte objects return environment for off-screen rays, as if they had 0 opacity. That should be the default behavior.

[JulianT_CD]

I see that we have an option in our V-Ray for Maya plugin to disable it and force the engine to use environment map instead.

You mean the Secondary Matte environment?

If this is will help to your workflow I can make a feature request to add the same functionality in our V-Ray for Max plugin?
I found a discussion about similar issue : http://forums.chaosgroup.com/showthr...than-vray-2-40[/QUOTE]

Yes thanks, please add that as a feature request.

[JulianT_CD]

I think it's desirable and expected that matte objects return environment for off-screen rays, as if they had 0 opacity. That should be the default behavior.

Most of the time, yes. In my case, however, my environment HDRI was too different from the backplate and I couldn't find one that matched more closely. So I wanted to use the backplate for many of the offscreen reflection rays as well in order to provide a reflection environment that was visually a little bit more coherent than just using the HDRI environment for all offscreen reflections. Does that make sense?

[LudvikKoutny]

Most of the time, yes. In my case, however, my environment HDRI was too different from the backplate and I couldn't find one that matched more closely. So I wanted to use the backplate for many of the offscreen reflection rays as well in order to provide a reflection environment that was visually a little bit more coherent than just using the HDRI environment for all offscreen reflections. Does that make sense?

Absolutely.

[tashko.zashev]

A new feature request is added in our system.

[JulianT_CD]

Thank you, Tashko!

[busseynova]

Bumping this old discussion rather than creating a new one as I think this might be the old issue as discussed above.

This is a screen grab of a section of a 360x180 cylindrical render of a test scene consisting of 3 objects: a Vray plane with mirror material, paving object, and a matte shadow catcher object which extends from the paving. A vray sun lights the scene but is the other side of the vray plane so the latter two objects are in shadow here.

Black 3DS environment, vray sky in vray environment, with a 360 equirectangular image set to spherical mapping in the reflection override and secondary matte override.
The result I was hoping for was to get the same reflection as from the reflection override, on the reflection of the matte object, but as you can see, the projection is distorted.
I would then copy the map and tune it to look like shadows of the object (Vray plane in this case) in its own reflections.

Is this the same situation as described above and if so has any fix been implemented as yet?

RGB on left alpha in right