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Home Jeff's Blog Displacement and broken edges
Displacement and broken edges PDF Print E-mail
Written by Jeff Patton   
Wednesday, 22 April 2009 16:49

displacement thumbnailI was working on a project where I needed to use some displacement maps on a material.  So, I was setting up the material in the matlab for use in my scene when I noticed the tearing edge effect my material was having on the test object.

To make a long story short, I didn't notice that I had set the Max. Displace value too high for our 3dsmax material lab test object.  It's currently configured for 4" and that's too high for this particular mesh.  So, if you're finding the edges tearing on your meshes when using displaced materials, keep an eye on your max. displace setting to make sure that's not the culprit.

Here are some images to help illustrate this issue.  The first image shows what happens if the current values are used.  NOTE:  I also decreased the Max. Subdivisions to 256.  I did this because the mesh is so heavy mental ray shouldn't need to subdivide much.  That being said, I had it originally configured at 1k in case anyone tried to displace hair/grass and needed the extra details.

(click image to enlarge)

Small displacement image1

In the second render I've adjusted the max. displace value down to a more reasonable value (1") and doing so helps remove the edge tearing.

(click image to enlarge)

I could have reduced the max. displace value further for this particular material, but I figured I'd mention to set it at 1" to cover some extreme displacement scenarios.  If you're just midly displacing something like I am here, .25" or .5" would probably work fine.

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Daniel Fleming wrote on April 24, 2009
 
Title: ...
thats the global setting though correct? so what happens if you want to displace more than one thing in a scene?
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Jeff Patton wrote on April 24, 2009
 
Title: ...
Then you'd use the local settings.

Select object in your scene > right click to bring up the menu and select object properties > mental ray tab > Uncheck "Use Global Settings" and specify whatever values you need for that particular mesh.
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Ivar wrote on May 04, 2009
 
Title: Trying to bevel the corners
Hi there, I in the past trying to solve that problem of broken edges, solved that problem including some kind of "bevel" on the corners, worked well.
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ethan janssens wrote on May 19, 2009
 
Title: geomerty
what about the importance of the geometry build-up you're displacing?

a geo with

______________
______________
______________

lines in it

will not displace a

| | | | | | | | | | | | map very good, even at high detail levels..

sure, the geo-orb for material testing is a very thick geometry-object, can't imagine a scene with all objects like this :(
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kieran wrote on September 16, 2009
 
Title: the maps seem?
out of interest have you looked at the pixels either side of the break? Color wise for the displacement map they could be out, (ie one pixel is (255 255 250) and the pixel next to it could be (255 255 251)...if that makes sense. I've found previously this does the same effect of a broken edge.
if i'm not making sense, just say and i'll make an example :D
Cheers!
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Kentzin Netrevalli wrote on March 05, 2010
 
Title: doesn't work for me
Hello, I did the same.. lowering the values.. but I got a flat displaced mesh too...
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Matt McIver wrote on February 25, 2012
 
Title: ...
3dsmax has default only positive displacement. To solve this go to the Output panel of the displacement map and set the output curve to -1...1. (You can also use -0.5 ... 0.5).
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