Displacement Issue

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Old 01 January 2013   #1
Displacement Issue

Hello Everyone,

This is the first time i ever post a question on this forum, but i have acquired a great deal of knowledge by reading all of the helpful tips. However, i have a serious problem that has vexed me for weeks now.

I just started incorporating displacement maps into my workflow. Everything seems to be working just fine, except for one problem.

When i apply my displacement map in Maya then render, my texture map renders dark and muddy. The displacement map looks fine but for some reason i causes my color channel to darken in the final render.

When i remove the displacement from the network, however, the color channel returns to its original brightness.

I've been trying to find solutions for this and have spent many hours reading the forums. It is driving me up the wall and through the roof!!!

If anyone has any suggestions, i would love to hear from you.

BTW, i am using mental ray for the render.
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Old 01 January 2013   #2
Can you post an example image? This way we can see more clearly what's going on.
 
Old 01 January 2013   #3
This is pretty much an exercise i did on my own to play with displacements from zbrush into maya. Its a simple planet with some hastily sculpted terrain. I threw it together on the fly.

W/o the displacement map, the color map renders fine. Enter displacement, it comes out much darker in the render. I have my light (sun) set to 1.5 int.

Even stranger, i added another sphere to act as the atmosphere and it comes out looking a bit better. I have a glow (set to 5) applied to the mat for the atmosphere. Light still set at 1.5 int.

In any case, the fact that my color map was darkened after applying the displacement still bothers me. Any thoughts?
Attached Images
File Type: jpg Planet_w_disp.jpg (10.5 KB, 15 views)
File Type: jpg Planet_w_atmo.jpg (15.3 KB, 17 views)
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Old 01 January 2013   #4
What Maya version are you using? Any chance you could upload your scene and texture for us to take a look?
 
Old 01 January 2013   #5
I'm using Maya 2010

Hmm, can't seem to upload my scene but i can provide some stats and screenshots of the scene if it helps.

I also forgot to point out that i am still pretty green when it comes to rendering with Mental Ray.

So i have two lights, one acting as a key (Sunlight) the other acting as filler (moonlight). See Ex_01 below. Also displays my grid so you can see the scaling, which might also be a problem?

Ex_01.jpg

Sunlight:
Int = 1.3
Raytrace shadows: on
Shadow Rays = 1
Ray Depth Limit = 1

Moonlight
Int = .7
no shadows

It could also be my displacement map, here are some stats for it; also uploaded a JPG if it helps:

Ex_02.jpg

Displacement Map:
Format = TIFF
Res = 2048x2048
8 bit
RGB mode

Note: I have watched the Scott Spencer tutorial, good stuff, but my problem persists.

If any more info would help I will do my best to provide it. Still playing with this at the moment; I have many other models to move on to but i would like to figure this out before i go willy-nilly making displacement maps for them and have this problem continue to nag me.
Attached Images
File Type: jpg Ex_01.jpg (64.2 KB, 5 views)
File Type: jpg Ex_02.jpg (67.5 KB, 4 views)
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Old 01 January 2013   #6
I kinda agree with you that the problem should be your displacement. Is there anywhere you can upload at least your original displacement maps and post your displacement values? The one you attached here turned into JPEG.
 
Old 01 January 2013   #7
I had to upload my displacement as a jpg. The site wont let me upload the TIFF for viewing on the forum.

What exactly should i do to my displacement to prevent this from happening?
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Old 01 January 2013   #8
Yet another note: I am using a Blinn shader for the planet. Only the surface, which contains the displacement, is giving me problems. The geometry acting as the atmosphere and cloud layers seem to render without any issues.

I hope someone can help. I'm just about ready to claw my face off and go "Hulk Smash" on everything in my room.

If worse comes to worse i'll start over, something must have gone wrong in my process. If it continues, i swear i will turn my room upside down in a blind rage.

I just want to make pretty displacement maps for my models and this issue is the only thing standing in my way =(.......for now.
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Old 01 January 2013   #9
*long drawn out sigh*

In all my infinite wisdom and knuckle-headedness, i just discovered that i somehow set the Diffuse in my shader to below .3?

I have no idea how that happened. I must have accidentally clicked on that part of the attr editor at some point.

Cranked it up to 1 and got a much better result.

Ex_03.jpg

Now i get this error message....

// Warning: (Mayatomr.Geometry) : World_crustShape: subdivision surface does not support separate displace approximation, ignored. Tune primary tessellation / approximation for displacement. //

If it isn't one thing, it is another.
Attached Images
File Type: jpg Ex_03.jpg (14.8 KB, 8 views)
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Old 01 January 2013   #10
Sidenote: 8-bit displacement does not provide enough precision for displacement.

You should use a 32-bit map for that.
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Old 01 January 2013   #11
Smile

Thanks for the input Bitter. I'm just beginning to explore displacement, rendering, and texturing; so any input helps.

Thanks to Panupat and Ralph for trying to help, it is greatly appreciated.

Strangely enough that error message doesn't pop up anymore and now i feel comfortable enough to move on to my other models.
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Old 01 January 2013   #12
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