Complete model transparent after lit up background because it was too dark

[3d-laboratory]

This is related to the old threads where the issue of too dark rendered background images was mentioned:
5 years ago; https://forums.chaos.com/forum/chaos...image-too-dark
2 years ago; https://forums.chaos.com/forum/chaos...image-too-dark 2 years ago

In a new project I also lit up the background with the method suggested by hermit.crab with "increase either the "Render multiplier" or the "Overall multiplier" in the VRayBitmap". The result is now, that my background image has the brightness I wanted, but the whole model in the foreground is now transparent. See image below. There is a white roof structure and you can see the background is coming trough. I did set up the scene new and again had the same problem. And Murphys law: the error
occurs on Sunday evening, deadline monday morning....Can you help me?

[fixeighted]

One option is to make a plane the same aspect as the plate your using and apply a Vray light material to it, using the plate as the source.
Align the plate to the camera so it matches the framing you have.
You can then set it to not cast/receive shadows/GI and control its brightness as you wish.

[3d-laboratory]

Thank you, that also was my thought, in this case it would work, but it´ isn´t as comfortable as the way it should work. I experimented also with "GI environment" in the render setup-->VRay-->Environment as suggested in another topic with no success.
My biggest question is how it could be that a raytracing renderer makes a model transparent when the background is brighter. This doesn´t fit in my brain . Or is it the beginning of stealth technology for houses? Always look twice when you run over the field, watch your nose...

[^Lele^]

It's looking like wrong scene setup, but without a scene there's no way of knowing for sure.

[Joelaff]

Like a screen space environment perhaps ?

[3d-laboratory]

May be that it is due to my method of setting up the background for rendering. I make a material with the "Environment-->Screen" setting and drag it to the Environment Map slot in "Rendering-->Environment". As I need it very rare to view through a glass building it can be possible that it is old "knowledge" from mental ray times. As I saw in the VRay help there is also a "Background render element" which I never used. I will explore it, but it seems to be more useful for interior renderings. Additional there was a thread from 2015 who says to add the background in the VFB (https://forums.chaos.com/forum/v-ray...ough-materials), but I didn´t find that "background slot" in the "VFB rollout" which is mentioned there. May be outdated...

[Margarita.Stoeva]

Screen space environment has been causing this transparency issue for quite some time now. We have it already logged in our internal bug tracking system under VMAX-9605. I updated it with link to this thread.
As a workaround, you could try assigning additional environment maps in the Environment rollout of Render Setup for both GI and Reflection/Refraction environment. You can place there the same bitmap but with spherical mapping instead or simply set some appropriate solid color for override. This should make things work while still using screen space background environment map.

Regarding the other mentioned approach with VFB Background in the thread from 2015, I would instead interpret the content in it to using VFB2 Background layer: https://docs.chaos.com/display/VMAX/...ers-Background
(Basically, just set your background environment map with a mapping that is not screen and then load the image in VFB Background layer to show up instead.)

I hope this helps and it's not too late to do for your project.

Best regards,
Margarita

[3d-laboratory]

Dear Margarita, thank you very much. This works for me, the only difference according to your suggestion was, that I had to set the Maps to screen, not to spherical in the GI environment and the Reflection/refraction environment of the Render setup-->Vray-->Environment tab. Sadly I had to finish this morning, so I used two renderings, one with glas for the reflections, one without glas for getting a alpha map. The rest was up to the "compositing". Next time I have the solution

[Joelaff]

I did the exact same thing first time I used vray. Seems logical that it should work.