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SyllogismSlap
11-18-2009, 07:45 AM
Hi All

I'm sure there is a simple answer to this but I've been unable to find a solution. Basically I'm using a displacement map to create a river in some terrain, I'm doing this using a displacement map(not the space warp modifier which makes max crash when I try apply it)

Anyway what I'd like to do is instead of the surface raising up where there is white I'd like it to sink down into the mesh. At the moment black seems to be no displacement at all. What I want is to make it sink into the mesh not grow the entire mesh. The reason for this is if I apply an displacement map to the entire mesh then everything gets raised up except for the darker regions. What I want is for say white not raise the mesh at all and for black to sink into the mesh.

Is this possible?

thanks

Syllogism
SyllogismSlap
11-18-2009, 08:07 AM
ok I figured it out. You just need to make the area transparent instead of white
SyllogismSlap
11-18-2009, 09:09 AM
actually I was wrong... I still have the problem, I've attached a pic to illustrate it.

I've managed to solve it using vraydisplacementMOD and changing the shift value. Is it possible to do without vray?
bonestructure
11-21-2009, 03:03 PM
Instead of using pure black and white, for areas you don't want to raise or lower, you have to use a median gray. I think it's called a 15% gray by photographers, but I can't be sure of that as I'm on my laptop at the moment and my gray reference is on my working computer. Once you find the right gray, you have a shade that will neither raise or lower in displacement, then any combination of shaded above or below that level can be carefully controlled.
soulburn3d
11-21-2009, 04:38 PM
In general, I find the best way to do this is as follows... White areas of your map pushes up, black areas push down, and 50% grey does nothing. As you've discovered though, the displacement map is setup so that black does nothing and white pushes up. To modify this behavior, go into the bitmap map and go into the "Output" rollup. And change the parameter called RGB Offset to a value of -0.5. Now it will react like the situation I outline above. The RGB Offset basically does the same thing as that vray shift value you mentionned. Hope that helps.

- Neil
phix314
11-21-2009, 07:22 PM
Instead of using pure black and white, for areas you don't want to raise or lower, you have to use a median gray. I think it's called a 15% gray by photographers, but I can't be sure of that as I'm on my laptop at the moment and my gray reference is on my working computer. Once you find the right gray, you have a shade that will neither raise or lower in displacement, then any combination of shaded above or below that level can be carefully controlled.

18% ;)

That value of gray doesn't apply to cg, it's a logarithmic middle ground within light meters.
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