Is there ever a time when you need a back-facing triangle? Or to switch what direction they face?
imm
Is the counterclockwise orientation of halfedges inside a face standard for being considered a front-facing triangle?
tbell
@imm In my (limited) experience it is more standard than the reverse (sort of follows the right hand rule, if you want an outward-pointing normal vector), but I also think many graphics frameworks (and file types) just let you specify which winding direction means what.
InfinityAxiom
One interesting property of a Moebius strip is that cutting it along the center line with a pair of scissors creates a geometry that is very different than if you cut the strip about a third of the way in from the edge. Cutting a Möbius strip along the center line with a pair of scissors yields one long strip with two full twists in it, rather than two separate strips; the result is not a Möbius strip. If the strip is cut along about a third of the way in from the edge, it creates two strips: One is a thinner Möbius strip. The other is a longer but thin strip with two full twists in it – this is a neighborhood of the edge of the original strip, and it comprises one-third of the width and twice the length of the original strip. (Source: https://en.wikipedia.org/wiki/Möbius_strip)
Is there ever a time when you need a back-facing triangle? Or to switch what direction they face?
Is the counterclockwise orientation of halfedges inside a face standard for being considered a front-facing triangle?
@imm In my (limited) experience it is more standard than the reverse (sort of follows the right hand rule, if you want an outward-pointing normal vector), but I also think many graphics frameworks (and file types) just let you specify which winding direction means what.
One interesting property of a Moebius strip is that cutting it along the center line with a pair of scissors creates a geometry that is very different than if you cut the strip about a third of the way in from the edge. Cutting a Möbius strip along the center line with a pair of scissors yields one long strip with two full twists in it, rather than two separate strips; the result is not a Möbius strip. If the strip is cut along about a third of the way in from the edge, it creates two strips: One is a thinner Möbius strip. The other is a longer but thin strip with two full twists in it – this is a neighborhood of the edge of the original strip, and it comprises one-third of the width and twice the length of the original strip. (Source: https://en.wikipedia.org/wiki/Möbius_strip)