Images rendered in Backburner in 3ds Max are brighter or darker than expected

Autodesk Support

Sep 16, 2024

Products and versions covered

Issue:

Images rendered with mental ray or V-Ray with Backburner in 3ds Max are brighter or darker than normal, or have incorrect Gamma. Rendering with OCIO through backburner is not supported

mental ray Correct Gamma from 3ds Max
Correct gamma rendered from 3ds Max

Incorrect gamma from mental ray in 3ds Max -- too bright
Incorrect gamma from rendered from 3ds Max (Override; too bright.)

Incorrect gamma from mental ray in 3ds Max - too dark
Incorrect gamma from 3ds Max (underexposed).
 

Causes:

  • Bitmap textures or rendered images may have Gamma Override set, instead of Automatic settings checked.
  • Corrupted 3ds Max preferences.
  • Scenes may be dependent upon Environment backgrounds or self-illuminated surrounding geometry to light them instead of actual lights.

Solution:

To address this issue, check the following:

 

Check scene geometry is responding properly to light sources

  1. Select the problem objects.
  2. From the Command Panel, choose the Modify Panel.
  3. In the Modifiers list, apply an Edit Normals modifier to the affected objects that are selected. This will help to check if the face or polygon normals are facing "outward."
Note: Blue lines indicate "outward" facing object normals, green lines indicate "inward"  or reversed object normals.
  1. If the faces are not pointing outward, apply a Normal modifier.
  2. Set the Normal modifier to Flip and/or Unify to fix the face normals.

 

Check Gamma settings

  1. In the 3ds Max Customize menu, choose Preferences.
  2. Select Gamma and LUT. 
  3. Set the 3ds Max Display Gamma to be On and at the default of 2.2.
Note: Input Gamma for all bitmaps loaded into the Material Editor should be set to Automatic. JPG images will be loaded at 2.2 Gamma. Do not override them with another 2.2 setting when picking and loading the images.

Output Gamma for renders should be set to Automatic. For 16-bit linear workflow, we recommend rendering to 16-bit half-float EXR files, not the legacy RLA or RPF formats. The EXR images will be saved with an embedded gamma of 1.0, but you can change their exposure (with no loss in quality) in programs such as Adobe After Effects. (For Adobe After Effects, make sure any composition using EXR files are set to 16-bit color space in the Preferences -- not the default of 8-bit.)

 

Check Exposure Controls

  1. Open the 3ds Max Rendering menu.
  2. Choose Exposure Control.
  3. If using a Physical Camera, Exposure should be set to On. This will ensure that renders look bright when displayed in the 3ds Max Virtual Frame Buffer window (again, the Display Gamma in Max should be set to 2.2).

 

Scene Settings for Backburner rendering

  • If using V-Ray, use V-Ray Physical cameras instead of the native 3ds Max Physical cameras.
  • If using Arnold or ART, make sure Exposure settings are turned on as per the preceding steps.
  • Finally, for all jobs submitted through Backburner, ensure the Input and Output Gamma settings for the job are set to 1.0, not 2.2.
To do this:
  1. Click on the job in the Backburner Queue Monitor.
  2. Select Edit.
  3. Change the settings from the Job parameters menu for the Gamma.

 

Reset the 3ds Max Preferences

Test resetting the preferences on the workstation submitting the render job, as the preferences may be corrupted causing incorrect Gamma output. See: How to reset 3ds Max user preference settings back to default.

 

Save output files as EXRs

Should the issue persist, try saving any output files as 16 or 32-bit EXR files. Currently PNG files don't have separate alpha channels -- they only have transparency, which can cause Gamma-related issues when saving.

For production rendering, try rendering to 16-bit (Half-Float) EXR files. (Rendering to 32-bit EXR format can produce very large files for compositing, so make sure your systems has adequate drive storage and RAM to handle these.)

Products:

3ds Max;

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