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Fix T84078: improve UV unwrapping for quads with an internal reflex angle 

When triangulating meshes, the UV unwrapper was previously using a
heuristic to split quads into triangles. If one of the internal angles
is greater than 180degrees, a so-called "reflex angle", the heuristic
was giving a poor choice of split.

Instead of using a special case for quads, this change routes everything
through the generic n-gon `BLI_polyfill_beautify` method instead.

Reviewed By: Brecht Van Lommel

Differential Revision: https://developer.blender.org/D16505
This commit is contained in:
Chris Blackbourn 2022-12-06 13:48:23 +13:00
parent 644afda7eb
commit f450d39ada
Notes: blender-bot 2023-02-14 04:24:05 +01:00 
Referenced by issue #84078, Wrong UV unwrapping some faces with reflex angle. (Was obtuse angle)
1 changed files with 1 additions and 22 deletions
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23
source/blender/geometry/intern/uv_parametrizer.cc
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@ -1124,16 +1124,6 @@ static PFace *p_face_add_fill(ParamHandle *handle, PChart *chart, PVert *v1, PVe
return f;
}
static bool p_quad_split_direction(ParamHandle *handle, const float **co, const ParamKey *vkeys)
{
/* Slight bias to prefer one edge over the other in case they are equal, so
* that in symmetric models we choose the same split direction instead of
* depending on floating point errors to decide. */
float bias = 1.0f + 1e-6f;
float fac = len_v3v3(co[0], co[2]) * bias - len_v3v3(co[1], co[3]);
return fac <= 0.0f;
}
/* Construction: boundary filling */
static void p_chart_boundaries(PChart *chart, PEdge **r_outer)
@ -3946,21 +3936,10 @@ void GEO_uv_parametrizer_face_add(ParamHandle *phandle,
}
/* No "ears" have previously been inserted. Continue as normal. */
}
if (nverts > 4) {
if (nverts > 3) {
/* ngon */
p_add_ngon(phandle, key, nverts, vkeys, co, uv, pin, select);
}
else if (nverts == 4) {
/* quad */
if (p_quad_split_direction(phandle, co, vkeys)) {
p_face_add_construct(phandle, key, vkeys, co, uv, 0, 1, 2, pin, select);
p_face_add_construct(phandle, key, vkeys, co, uv, 0, 2, 3, pin, select);
}
else {
p_face_add_construct(phandle, key, vkeys, co, uv, 0, 1, 3, pin, select);
p_face_add_construct(phandle, key, vkeys, co, uv, 1, 2, 3, pin, select);
}
}
else if (!p_face_exists(phandle, vkeys, 0, 1, 2)) {
/* triangle */
p_face_add_construct(phandle, key, vkeys, co, uv, 0, 1, 2, pin, select);