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Visual Reality: Tutorials: Hexagon |
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Using the Orient Normals ToolNothing can be quite so perplexing as diligently working on a model to get it just the way you envision it in your mind, exporting it as an OBJ, and then importing it into a different program like Carrara or Poser -- only to find that some facets are invisible. What's up with that? Odds are that the normals for the problematic facets are reversed. Polygons, or facets, in a 3D model have two sides, a frontface and a backface. The frontface is the one that you -- and your rendering program -- expect to see. The backface is the one that the program expects to face away from the camera; not all rendering programs display backfaces, or display them correctly. Poser, for example, seems to have a real problem with backfacing polygons.
It's not so much that you or the program don't see the backfacing polygons but that you're seeing through them. You can think of a facet in a 3D model as a one-way mirror (or, as some people refer to it, a two-way mirror). If you're a fan of Law and Order, CSI, NCIS, or any other lawyers/cops/procedural show, then you've seen one-way mirrors. That's where the bad guys are in one room and the good guys -- and the eyewitness -- are in an adjoining one. The good guys can see through the one-way mirror to look at the bad guys, but the bad guys just see their reflections. A backfacing polygon is like looking at the mirror with the good guys -- you can see through it to what's on the other side. When you look at the polygon from the other side, though, the frontface, you see the texture that's been applied to it, whether that's a mirror texture, grass, skin, lava, you name it. Although some 3D programs can display backfaces, and some can reverse normals to correct backfacing polygons in models, it's a good habit to correct these problems in Hexagon before exporting the model. The Hexagon Orient Normals tool enables you to unify normals so all facets for a model face the same direction. You can also reverse normals on all or individual facets, whether to correct a problem with just a few facets or to create a cool effect with a model. The following tutorials explain how to use Hexagon's Orient Normals tool when reversing normals for individual facets that you haven't pre-selected, for a group of facets that you've pre-selected, for all facets on the object, and for unifying and reversing all facets on a model. An exercise illustrating these processes is also included to get you really comfortable with this tool.
Reverse Individual Facets that Aren't Pre-Selected |
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