muralist opened this issue on Jun 03, 2008 · 38 posts
bagginsbill posted Wed, 04 June 2008 at 6:10 AM
Quote - Displacement works in the normal direction (perpendicular to the surface). If two surfaces meet at, say, 90 degrees, and displacement is carried to the edges of the surfaces, they will appear to separate.
This is true for un-welded polygons - not true if they're welded.
When two polygons appear to share an edge, but they each have their own pair of vertices forming the edge, it only looks like they are joined. Any displacement works as John describes, moving the polygon in the direction of its normal.
However, when the two polygons actually share an edge, the normal is smoothly interpolated across the edge. Any displacement will do the right thing. Were this not the case, then displacement would never work on a Poser sphere or cylinder, yet it works perfectly.
Also, are you actually trying to displace (expand) the cylinder here? Or did you do that by mistake. Particularly, is it your intention that the smooth parts of this cylinder remain in their original positions? If so, you may be dealing with an issue I've written about a jillion times.
In Poser, displacement is based on the numerical value of the displacement source (image or math nodes.) Black = 0 = no displacement. White = 1 = 100% displacement. Mid gray = .5 = half displacement!
Many applications other than Poser use a convention that the displacement map is offset by 50%, so that mid gray is intended to mean no displacement (.5 - .5 = 0), black is negative half inward displacement (0 - .5 = -.5) and white is half outward displacement (1 - .5 = .5).
This is the style of map produced by ZBrush, for example.
If you've got a displacement map that is encoded this way, you're getting displacement from the mid-gray when you intended that you have none. The solution is to use a math node and subtract .5 from your displacement, and plug that into the displacement input.
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