RTT renders OK but saves 3 stops overexposed

[michaelbreathes]

I am doing some texture baking and having an issue with the image being saved incorrectly.

Max 2012 with VRay 2.0

Rendering out to a VRayCompleteMap, using the VRay frame buffer, "rendered frame window" is unchecked in the RTT dialogue.

The VRay frame buffer looks correct when it renders, the buffer disappears after rendering and the resultant saved file is way blown out. Tried with png, jpg, tga for good measure.

 

If I save as an EXR, I find in PShop if I adjust the exposure by 3 stops it looks perfect.

If, in addition to saving from the RTT dialogue, I save in the Render Settings Vray FRame Buffer rollout, Save Separate Render Channels and save the RGB, that save will be correctly exposed.

 

Both of these are a pain. I don't want to have to adjust exposure for every bake, and I don't want to save multiple versions of the same image and have to delete the garbage saves, then replace the correct map in the material.

 

For the fun of it, I tried turning off the VRay framebuffer to see if Max will save it correctly, but no dice.

 

Attached image showing an example with the Max buffer (since Vray's disappears)

 

Has anyone had this happen?

I don't understand why it renders just fine in the buffer but saves so far off the mark.

[Tommy L]

What are your Max gamma settings and your Vray color mapping settings? Probably a max gamma setting is awry if its saving incorrectly out of both buffers.

[michaelbreathes]

No Gamma correction. I'm not 100% sure offhand about the VRay Color Mapping. I'll need to check in the morning when I'm back at the office.

When I render through a VRay camera, or through a Perspective view, it saves out OK though. As well as when saving via the Split Render Channels. Exposure Control is set to Photographic in the Environment and Effects dialogue.

I'm not sure I see how Gamma or Color Mapping settings could goof it up this much, since the goof is only happening when the buffer is being saved down to an image. I'll post those settings in the morning, but they should be Reinhard with default settings.

[Tommy L]

VRay disappearing can probably be rectified by turning off the progressive quality option for the viewport.

I havent used VRayCompleteMap, but maybe thats the culprit.

VRay Color Mapping can be responsible for huge swings in tone, but not at Reinhard default.

Youre texture baking? Try turning on Gamma correction in Max options and setting it to input 1 and output 2.2

Cant remember if VRay 2.0 had the same gamma control options as 2.4.... I think you may be able to just hit Linear workflow and it will solve it. Sure looks like a gamma handling issue to me.

[michaelbreathes]

Thanks. I'll give these a shot in the morning, but I'm not getting my hopes up. My experience with Gamma hasn't shown this drastic of a difference, and again, the rendering is fine in all buffers, only the saved image is off. Except when saved via Split Render Channels. In that case it is saved correctly.

I'll give it a shot though. Also, in the Save File dialogue, I'll try the Gamma output override rather than using the "system default" setting.

[michaelbreathes]

Ok, so gamma made no major difference.

However it seems I was wrong in my initial assumption on what was happening...while rendering, checking the channel dropdown in the buffer indeed shows the VRayCompleteMap and was showing it as blown out. So it was being saved correctly from there, rather than the rgb channel.

It seems that VrayTotalLighting gives me what I need.

 

I went with the VRayCompleteMap because that is what is shown as example in the official VRay documentation. In that case, it saves correctly as the rgb from the buffer.

Has anyone with texture baking experience seen anything like this happen? Do you bake to CompleteMap or TotalLighting?

[Scott Schroeder]

It's your exposure control. RTT in older versions of max cannot process it.

 

Of the standard max exposure controls, Vray only fully supports Logarithmic exposure control. The rest are half or unsupported.

Edited October 9, 2013 by VelvetElvis