Does Face direction really matter?
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What are the reasons face direction is important?
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Jim:
If you have tried/used -BTM's sculpt script, you will see quickly, upon activating the tool, that the "polarity" of the faces determines which direction the mesh is moved. Even if you use it on a TIN. This is at least in my direct experience.
I thought that it had an effect on some renderers, however, that is still not an area I have experience in. And the reason for this is aversion to "tediosity" -
Jim,
nuclearmoose recently had issues with front/back faces while modelling a component...
http://forums.sketchucation.com/viewtopic.php?p=205673#p205673
And again in this topic...
http://forums.sketchucation.com/viewtopic.php?f=79&t=25006
This is my understanding of how face direction matters, and Gaieus gives a very detailed and informative advice on this in the second link
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It makes a difference if you plan on rendering as well, some render engines/exporters wont give proper results if the normals are not correct.
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In my head this is directly related to Jim's question I promise:
Are thie file formats that store vertex normals? Do most formats store that?
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.obj can store normals, although i dont know how commonly its used.
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Sorry for the beginners question, but can someone tell me how the first vertex in a face is determined? Is it the point of insertion? Guess the direction of the face is then related to the sequence in the array?
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@honoluludesktop said:
Sorry for the beginners question, but can someone tell me how the first vertex in a face is determined? Is it the point of insertion? Guess the direction of the face is then related to the sequence in the array?
1) Front or back visible when drawing a rectangle is determined by the direction the diagonal is going.
Not by first and second click.2)It also depends in which axes plane you are drawing.
Just 1) and 2) determine front and back for new rectangles not touching other rectangles. Otherwise they tend to inherite their orientations.
(Circles and polygons follow different rules)See attached file Face_orient.skp with the diagram. Try it to see what happens when.
http://sketchup.google.com/3dwarehouse/details?mid=509c2a6868ab3855b2dd3120ca5e0662
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