Gamma Correction Problem with Bitmaps

V-Ray V-Ray for 3ds Max Issues
1

Dear Group,

I am using LWF for my renderings. I have read numerous tutorials in this forum about the process. In particular, I have read through the tutorial for LWF on the following site:

http://www.gijsdezwart.nl/tutorials.php

Since I use Viz 2005, I use the the Viz gamma correction function in Preferences → Gamma for gamma correcting my bitmaps and ColorCorrect for gamma correcting colors. When gamma correcting bitmaps, I set the input and output gamma to 2.2 (I use HSV Exponential Color Mapping).

I have noticed something very peculiar. For starters, some of my renders have looked washed out. But more than this, I have noticed that the diffuse maps in my renders also look washed out. For example, observe the following (Please excuse the poor quality; these were only crude tests):

In this rendering, I noticed that the floor map and stone map for the hearth looked washed out:

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The following is a clip of the two maps in question:

600×600 48.2 KB

As you can see, the maps as they are rendered in the scene are washed out. What I decided to do is use ColorCorrect for the diffuse maps. In ColorCorrect, I set the Source to the respective bitmaps and I set the gamma at 2.2. I rendered the scene and here is the result:

600×450 30.9 KB

As you can see, the stone hearth and the wood floor have far more fidelity to the tone of their respective bitmaps. This leads me to believe that there may be a bug in VRay for gamma correcting bitmaps. Or it could be that I do not know what I am doing :? Has anyone else experienced the same issue?

2

V-Ray itself does not do anything to bitmaps; the gamma settings are supposed to be handled internally by 3dsmax/VIZ, so I’m not sure what may be wrong there…

Best regards,
Vlado

3

Just a guess, but could it be the HSV Exponential Color Mapping you’re using? Try using linear color mapping with no multipliers.

4

Typically I use HSV Exponential but the above renders were rendered using Linear Mapping.

5

what gamma options did you pick, when impoting ypur bitmaps to your material?

6

Any bright or dark multipliers other than ‘1’? Can you post a scene?

BTW: I’ve used Viz 2005 w/ LWF for a couple of years with no problems.

7

Vlado,

There is something definitely wrong. I have manually set the gamma setting for the bitmap to 2.2. I did not experience this problem when I tried a scanline render of the scene (see below):

600×450 30.3 KB

8

The scanline renders with Linear color mapping at 1/1 multipliers always, so you need to use that in V-Ray too, for any comparisons between them. If you wish, you can send me just the floor of your scene along with its bitmap so that I can take a look at it.

Best regards,
Vlado