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View Full Version : Displacement Maps are not linear relative to RGB... ??? Help please.

BxHBxH
04-11-2003, 06:36 PM
Hey there CGTalker's... bit of an issue here that I could use some help on. I'm trying to accurately displace a ground model based on a grayscale map that I am painting. Anyway, after some experimentation it appears that the Displace modifier in max is not displacing the mesh linearly relative to the RGB value of the grayscale map. It appears the regions close to white are displacing more than those in the black region.

I've got an example of the problem here:

www.bxhdesigns.com/bugs/DisplacementProblem.zip (http://www.bxhdesigns.com/bugs/DisplacementProblem.zip)

Starting in the lower right corner the green surface should be displaced vertically evenly for each region of the displacement map. Note that the regions on the displacement map are each separated by 50:

Region 1: 0,0,0
Region 2: 50,50,50
Region 3: 100,100,100
Region 4: 150,150,150
Region 5: 200,200,200
Region 6: 255,255,255

Thus I would expect the vertical displacement to be even for each step in the displacement map.

Any ideas? Please help. this would be a great way to get the exact displacement I need for this ground model.

Thanks!

-brian
www.bxhdesigns.com
EricChadwick
04-11-2003, 06:47 PM
Can't see what the problem is. The green guy matches the red guys perfectly, as far as I can see, in 3ds max 5.1.
BxHBxH
04-11-2003, 07:12 PM
Whoah... we're on 3dsmax 4.26 here... bugger. If this is fixed in max 5 maybe I can finally convince the "powers-that-be" that we need to upgrade... :)
EricChadwick
04-11-2003, 07:18 PM
Hmm. Out of curiousity I just loaded it in 4.26, and it displays just fine for me. Same as 5.1.

Although you said it was a 50-unit difference between all steps, the last one is technically 55... (255 - 200 = 55)
BxHBxH
04-11-2003, 07:27 PM
Hmmm... interesting... this is what my viewport shows in max 4.26:

http://www.bxhdesigns.com/bugs/displace_bad.gif
EricChadwick
04-11-2003, 07:29 PM
Weird. Don't see that at all.

Maybe you loaded the JPG via a material and you're accidentally grabbing some blur values? Try re-loading it via the modifier as a straight bitmap?
BxHBxH
04-11-2003, 07:44 PM
Posm... very odd. I just installed the max5 demo version and it appears correct in there - but still bad in max 4.26. I tried recreating the displace with a straight link to the image, rather than through a map - same problem. Odd. Could you send me your version of the file in 4.26 so I could try and compare them and see what's up?

thank so much for your quick help...
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