Streamline backplate integration workflow

[^Lele^]

set the GI environment to black.

[kosso_olli]

Yeah, right. I mean the whole process, with all tricks and checkboxes. Matte for refl/refr on/off and so on...

[kosso_olli]

Waiting, because it still doesn't work here.

[kosso_olli]

Okay guys, what the heck am I doing wrong? It doesn't work here, and never did. What exactly is the reason I get these seams? Scene file attached, please help me.

matte_proj.zip

[LudvikKoutny]

Well, this one actually is correct I am afraid. My best guess is that matte object gets clipped right outside of the camera frame. It's the only reasonable thing that can be done. V-Ray can't just make up information that's outside of the backplate, so right where camera view ends, backplate should be cut and it's opacity should be 0. The thing is it's usually lot less obvious if you have matching HDRI and backplate, and that HDRI is properly oriented to the backplate, Then in reflection, road on the plate would end, and it would start showing road on the HDRI, which would still be noticeable, but a lot less than road ending in a grass.

[LudvikKoutny]

So I am necromancing this thread because unfortunately HDRI/backplate workflow is still not working correctly.

I've been using Lele's suggestion to enable GI override and set it to black, but I've still been getting screen mapped backplates in environment slot ghosting through my scene geometry, and I think I've nailed down what causes it... And it's the pesky DomeLight again

Basically, when I enable GI override ghosting disappears from diffuse GI component of the material, but remains in reflection component:


So i tried to enable Reflection environment override too, and now I got black hole in my reflection:


So what's most likely happening there, is that matte ground geometry correctly passes rays, that intersect it outside of camera frustum through, but it passes them straight to environment. And environment is max's bitmap set to screen mode, so all values are returned in screen space, causing ghosting. What should happen instead is that matte object should pass those rays through, but it should pass them to hit the DomeLight, not the environment. That will A: give correct result and B: eliminate the ghosting.

[kosso_olli]

I just tried it, same here. That is very annoying, because even if the object has glossy reflections, the ghosting in the reflection pass remains sharp.

[vlado]

The "secondary matte environment" slot in the render settings enables you define what kind of environment is used for matte objects visible in reflections, you'll have to put something meaningful there, like a spherical map or something.

Best regards,
Vlado

[vlado]

Also if you want me to notice a post related to mattes please post in a different thread I'm not looking at this thread anymore as the original subject on the streamlining is more or less exhausted (where I agreed that yes, it needs streamlining).

Best regards,
Vlado

[kosso_olli]

The "secondary matte environment" slot in the render settings enables you define what kind of environment is used for matte objects visible in reflections, you'll have to put something meaningful there, like a spherical map or something.

Best regards,
Vlado

There is a spherical HDRI both in the domelight and in the secondary ray environment slot. Will send a scene for investigation.

[vlado]

There is a spherical HDRI both in the domelight and in the secondary ray environment slot. Will send a scene for investigation.

The slot is empty in the screenshot above (the last slot in the Environment section).

Best regards,
Vlado

[LudvikKoutny]

The thing is that even when spherical map is put in those slot, it's not MIS sampled. If there is for example strong highlight on HDRI map in that particular direction, it will be sampled via environment, not domelight, so instead of correct illumination, it will be just dark and noisy.

[kosso_olli]

Scene was sent for investigation.