Problem with enviroment textures applied in render setting to get Background layer

[Witt3D]

Hi, some strange things happen if i use enviroment texture in render setting.

I cannot use camera image plane, cause vray doesnt handle it like a background, so camera mapping is applied. Also i cannot get in render element the backgroyund layer for post.

So my workaround is to put my background image in render settings like enviroment, and in my placeenviroment texture set to "Screen".

With these settings, i get my background without camera mapping aplied, and i get it as background layer in render element. Eveything fine, since vray starts to do strnge things with this workaround.

Refraction gets dark like image attached.

Other example, just solid ground gets semitransparent, dont know why.

[vlado]

Can you post some example scene?

Best regards,
Vlado

[Witt3D]

[Witt3D]

I guess the best way to share scene i could find.

If you hit render as you open the scene you get this image, both things happen. Transparent material really dark, and opaque material ges semitransparent in some areas.

[Witt3D]

Just notice, if you render with render region, also if you uncheck it, when you save on exr you only get the render region. With png or jpg you get the whole image.

[Zdravko.Keremidchiev]

You need to enable Affect background option in the Color mapping roll-out to match the background intensity of the reflection and refraction one. Also, The region exr issue is on our To do list.

[Witt3D]

Hi Zdravko, thank you for the answer.

But just too quick. In fact, as i mentioned before, my whole workaround is just to get the background out of the camera mapping. If i check this option, my background gets camera mapping applied and has no sense. Is just simple, i have a background where i dont need to get anything, no GI, no light, no depth, no camera mapping applied, nothing, just be visible and affect reflections and refractions. As you can see in the new image, the background now is dark.

Also as you can notice the semitransparent issue in the opaque material keep also "Affect Background" is checked.

[Zdravko.Keremidchiev]

The issue comes from the fact that you need to match the background to the refl and refraction, where you have applied color correction and you don't want to apply this correction to the background image. Any particular reason you don't want to check Affect background option. If you want to increase the brightness of the image you can change its color gain value or use HDRI image instead.
Also, you can still see the trees through that object because it has reflections and you have overridden the reflections with that image set to screen projection. To work around that you can set separate PlaceEnvTex node with spherical mapping for the reflection and refraction override slot.

[Witt3D]

Hi, Zdravko, any other workaround to have what we want?

I understand what you are telling, but we work lots of times with photographer, and we get background images, no HDRI. We want to be as accurate as possible, so i get a profesional photo with really good balance. We dont want to touch it, and we want to have the same aspect on the final render. What you say about color gain is not correct for us, we dont get the same feeling (if you really want to be accurate) and also we dont have the feedback to know if our lighthing is matching the one of the photo. In fact there are houndreds of cases, where we dont have the HDRI and we just want to have a good photo as background as it is, without aplying for example a 0.2 burn of reinhard color mapping, where for our render can work, but for the backgorund photo we get a washed out look.

I understand the thing about reflections and screen projection (we are also programmers). So the best workaround would be a virtual plane (just like camera image plane) where we have a texture or image without getting color mapping applied, and where the reflection and refraction has color mapping applied but with the negative correction if needed.

I dont know if you understand what im trying to say. Do you?

Thank you.

[Zdravko.Keremidchiev]

I understand, but in case that you want to keep the background image as it is: you either should not use any color correction or keep the same workflow and color correct the reflection and refraction alone to match the background image brightness.

[Witt3D]

ufff.... let me suggest for the next update to include a virtual camera plane where no camera mapping is applied, and in background, the render engine takes the same image with the negative color mapping applied to match just reflections and refractions.

That would be a really GREAT step forward. I know "Next" is coming, but i usually hear about render times, and so on. Rarely i hear one big improvement for artist (not technissians). We speak about physical accurate render engines, but we have to spend hours and hours in post to solve and fake things that are real and physical render engines don?t achieve on the render.

And you know what? I dont care if my render takes 6 hours at night or 4 hours and 30 minutes. For me, it would be great just to avoid any post. That would be a GREAT update or render engine and time saving, much more than getting a 20% speed on the new version.

I could post houndreds of examples where it is so, with light, with camera balances, with light propagation, with complex materials, ... tons of example where we hear "physical render" and where we need to do hard post to mimic real world. This is the reason i tell you, if you want to hear an artist and thechnissian advice or tip, just to work on an upgrade that make our life easier, not just in speed up the render time.

And one MUST is this one we are speaking about. I cannot think in any render i took in more tahn 15 years with any render engine, where i didnt need to touch skies or backgrounds once is rendered. And the main reason is cause camera mapping is applied. And you cannot imagine the time saving it would be when we have to introduce a 3D element in a photo. This way we would have real time feedback with photo insertions.

Sorry for the pleading, but the 3D part and lighting, and texturing and shader takes so much time, that once is render, you still have to work on the image for reasons like this one.

Thanks in advance.
Cheers.