exclude from whitebalance in bitmaps/texutures

[themaxxer]

I have wished this before, because I think it's a useful feature and I would use it every day for archviz renderings.
so, that's because I don't understand why this was not wished before...

it's a daily problem if you put a background photo (white balanced from camera) as outlook or background for your rendering and the physical camera in max is also white balanced then you get a doubled white balance on the bitmap...
so, it would be great if you have an exclude button in the white balance tab of the physical camera to exclude objects from the white balance...

another question is how do you guys avoid this? is this not a problem for you?
I have images where blue sky get's really ugly yellowish in the rendering...

best regards
themaxxer

[andy51]

I would do any background, in post and frankly while Auto Exposure is a very handy addition to Vray, I'm not so sure about Auto White balance, as you say, many background images and the vast majority of textures, are photos, which already have (should have) correct white balance

[OPEN_RANGE]

the problem I think with doing backgrounds in post is in interior scenes. I want th ebackgound seen thru the windows to show up in all of th ereflections on counters, floors etc. That doesn't happen if you add the background in post. Maybe there is some work around I am unaware of.

I'm working on a scene like this now. I have a background photo mapped to a plane and it is seen thru a large wall of windows. I have vray properties for the plane set to do not receive or generate GI. I have one max omni light set to include the plane only and control it's brightness form there. The white balance of the vray camera does indeed seem to affect the appearance of this background photo.

[andy51]

the problem I think with doing backgrounds in post is in interior scenes. I want th ebackgound seen thru the windows to show up in all of th ereflections on counters, floors etc. That doesn't happen if you add the background in post. Maybe there is some work around I am unaware of.

I'm working on a scene like this now. I have a background photo mapped to a plane and it is seen thru a large wall of windows. I have vray properties for the plane set to do not receive or generate GI. I have one max omni light set to include the plane only and control it's brightness form there. The white balance of the vray camera does indeed seem to affect the appearance of this background photo.

Instead of using a plane, with an image texture applied, and lighting it with a max omni light, try using the plane, then applying a VRayLightMtl to it and using the image texture, as a texture for theVRayLightMtl. That way you can control the brightness of the image and have no need to exclude it from GI (you may need to have "Compensate camera exposure" checked).

Oh and when you say "I want the background seen thru the windows to show up in all of the reflections on counters, floors etc" you render the image with the correct background", then render a mask, which doesn't include the background image and possibly excludes the glass as well, unless you set it up correctly so it is black in the alpha... and use that to correct any white balance issues you have with the background

[OPEN_RANGE]

Those are good tips Andy. Thanks, I will try the light material. So far I don’t feel the white balance issue is a big enough problem for me to justify rendering twice to get the mask and etc. Good to know how to do that when it becomes needed.