[Bf-committers] unwrapping on subsurfed meshes

Nick Winters nwinters3000 at gmail.com
Mon Oct 3 20:44:03 CEST 2005

this is not a problem with lscm

uv coordinates are interpolated the same way using and not using
subsurf and simple subdivision

however, subdivision surfaces will warp faces in strange ways. 
particularly if verticies don't have edges coming out at regular
angles.  For example, a quad with two edges forming a line will be
stretched back somewhat into a quad.  If you texture it as if it were
a triangle [lscm or from window projection will] then the distortion
will be noticable.

notice the distortion of the aqua quad [right is subsurfed]

but the distortion will be noticable whatever you do.  Your remaining
option is to build your mesh so that subsurf doesn't distort faces
like that.  The names are abundant, but the primary idea is to have as
much of your mesh as possible use entirely quads in a grid
arrangement.  For example, details such as the mouth of a character
should have a ring of quads going around them.  Put the verticies with
more [or fewer] than 4 edges in a place that doesn't move a lot, like
the center of the cheeck.  This technique tends to have the edges
coming off of a vert go in regular directions.  Like off a 4-edged
vert going at approximately right angles.  This minimizes distortion

the only way I can see to cram the problems into the texture mapping
instead of the modeling is to let the artist define how the texture
coordinates are interoplated across the face.  Like have a bicubic
patch [with control points editable by the artist] for uv coordinates
of a quad instead of just 4 points interpolated lineraly...

I think having a proper mesh is better

[if the masochist in you wants to get out, suburfing a mesh produces
something which warps less than the original mesh [it is all quads and
the only non-4 edgd verts are at non-4 sided polygon centers or at
non-4 edged verticies you made].  if you uv map that version [you'll
have to re-rig it too]  your results will be better.  ]

rant mode off

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