Displacement maps create the effect of making certain parts of the geometry appear to protrude.

Is there a way to use something like a displacement map to cause the geometry to appear to indent instead of protrude?

I am specifically dealing with a brick wall of a house, and I want to show a little bit of depth between the bricks and the mortar.  A regular displacement map looks mostly good, except in places where there are the square holes for windows.  The shading is off on the edges and the bricks are trying to overlap with the window frames.  I think it would come off better if I could indent the mortar and not protrude the bricks.

I should add that I am using grayscale displacement maps in Poser 10.  I don't have much experience with normal maps- is a normal map the answer?

Try using negative values in the displacement. Instead of .001 try -.001, you will also need to reverse your light and dark areas.

Try using negative values in the displacement. Instead of .001 try -.001, you will also need to reverse your light and dark areas.

You're welcome.

Actually, I use displacement a lot. A lot, a lot. So hear me out.

Displacement can raise or indent from the same map. Grey is the middle value, or flat. White raises the mesh. Black indents. Numerical value does matter, but try inverting the white in your map in an image editor. It will work

I've been hesitant to throw my hat into this discussion, but figured I should comment before things swing wildly into the realm of confusion.

Black is zero displacement in Poser Firefly Micropolygonal Displacement. It always has been.

In order to utilize middle grey as zero displacement, and utilize "black" values as negative (black representing varying values not perceptible to the eye), such as the type of maps produced by various sculpting softwares, you need to run the maps through a subtract. Otherwise nasty ballooning and seam cracks will occur. This is long running common knowledge about Poser Displacement, which any old timer hereabouts will confirm. Thus...

And the resulting displacements, negative and positive. Forgive the render/mats it was done years ago in Poser 8. I created the maps in Zbrush. The figure is also my creation... 

Please read this thread, as explained by Bagginsbill.

https://www.renderosity.com/forums/threads/2741587/why-is-displacement-breaking-this-model#msg3245284