blender
/
blender
134
400
Fork 583
Code Issues 6.3k Pull Requests 758 Projects 19 Wiki Activity

Fix T100874: improve uv unwrap of degenerate geometry 

Provide reasonable defaults for UV unwrap for triangles with zero area:

* Three vertices are arranged in a line.
* Two vertices are at the same 3D location.
* All three vertices are at the same 3D location.

Change fixes quads / ngons which have triangulations with zero area.

Change fixes both "Angle Based" method and "Conformal" method.

Differential Revision: https://developer.blender.org/D15922
This commit is contained in:
Chris Blackbourn 2022-09-12 12:58:14 +12:00
parent c9a8380426
commit 94e211ced9
Notes: blender-bot 2023-02-14 00:06:52 +01:00 
Referenced by issue #100874, **UW unwrap** unwraps UVs incorrectly
1 changed files with 59 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

83
source/blender/geometry/intern/uv_parametrizer.cc
View File

@ -307,12 +307,70 @@ static float p_vec2_angle(const float v1[2], const float v2[2], const float v3[2
{
return angle_v2v2v2(v1, v2, v3);
}
/* Angles close to 0 or 180 degrees cause rows filled with zeros in the linear_solver.
* The matrix will then be rank deficient and / or have poor conditioning.
* => Reduce the maximum angle to 179 degrees, and spread the remainder to the other angles.
*/
static void fix_large_angle(const float v_fix[3],
const float v1[3],
const float v2[3],
float *r_fix,
float *r_a1,
float *r_a2)
{
const float max_angle = (float)M_PI * (179.0f / 180.0f);
const float fix_amount = *r_fix - max_angle;
if (fix_amount < 0.0f) {
return; /* angle is reasonable, i.e. less than 179 degrees. */
}
/* The triangle is probably degenerate, or close to it.
* Without loss of generality, transform the triangle such that
* v_fix == { 0, s}, *r_fix = 180 degrees
* v1 == {-x1, 0}, *r_a1 = 0
* v2 == { x2, 0}, *r_a2 = 0
*
* With `s = 0`, `x1 > 0`, `x2 > 0`
*
* Now make `s` a small number and do some math:
* tan(*r_a1) = s / x1
* tan(*r_a2) = s / x2
*
* Remember that `tan = sin / cos`, `sin(s) ~= s` and `cos(s) = 1`
*
* Rearrange to obtain:
* *r_a1 = fix_amount * x2 / (x1 + x2)
* *r_a2 = fix_amount * x1 / (x1 + x2)
*/
const float dist_v1 = len_v3v3(v_fix, v1);
const float dist_v2 = len_v3v3(v_fix, v2);
const float sum = dist_v1 + dist_v2;
const float weight = (sum > 1e-20f) ? dist_v2 / sum : 0.5f;
/* Ensure sum of angles in triangle is unchanged. */
*r_fix -= fix_amount;
*r_a1 += fix_amount * weight;
*r_a2 += fix_amount * (1.0f - weight);
}
static void p_triangle_angles(
const float v1[3], const float v2[3], const float v3[3], float *r_a1, float *r_a2, float *r_a3)
{
*r_a1 = p_vec_angle(v3, v1, v2);
*r_a2 = p_vec_angle(v1, v2, v3);
*r_a3 = (float)M_PI - *r_a2 - *r_a1;
*r_a3 = p_vec_angle(v2, v3, v1);
/* Fix for degenerate geometry e.g. v1 = sum(v2 + v3). See T100874 */
fix_large_angle(v1, v2, v3, r_a1, r_a2, r_a3);
fix_large_angle(v2, v3, v1, r_a2, r_a3, r_a1);
fix_large_angle(v3, v1, v2, r_a3, r_a1, r_a2);
/* Workaround for degenerate geometry, e.g. v1 == v2 == v3. */
*r_a1 = max_ff(*r_a1, 0.001f);
*r_a2 = max_ff(*r_a2, 0.001f);
*r_a3 = max_ff(*r_a3, 0.001f);
}
static void p_face_angles(PFace *f, float *r_a1, float *r_a2, float *r_a3)
@ -2266,7 +2324,6 @@ using PAbfSystem = struct PAbfSystem {
float *bAlpha, *bTriangle, *bInterior;
float *lambdaTriangle, *lambdaPlanar, *lambdaLength;
float (*J2dt)[3], *bstar, *dstar;
float minangle, maxangle;
};
static void p_abf_setup_system(PAbfSystem *sys)
@ -2294,9 +2351,6 @@ static void p_abf_setup_system(PAbfSystem *sys)
for (i = 0; i < sys->ninterior; i++) {
sys->lambdaLength[i] = 1.0;
}
sys->minangle = 1.0 * M_PI / 180.0;
sys->maxangle = (float)M_PI - sys->minangle;
}
static void p_abf_free_system(PAbfSystem *sys)
@ -2707,25 +2761,6 @@ static bool p_chart_abf_solve(PChart *chart)
e3 = e2->next;
p_face_angles(f, &a1, &a2, &a3);
if (a1 < sys.minangle) {
a1 = sys.minangle;
}
else if (a1 > sys.maxangle) {
a1 = sys.maxangle;
}
if (a2 < sys.minangle) {
a2 = sys.minangle;
}
else if (a2 > sys.maxangle) {
a2 = sys.maxangle;
}
if (a3 < sys.minangle) {
a3 = sys.minangle;
}
else if (a3 > sys.maxangle) {
a3 = sys.maxangle;
}
sys.alpha[e1->u.id] = sys.beta[e1->u.id] = a1;
sys.alpha[e2->u.id] = sys.beta[e2->u.id] = a2;
sys.alpha[e3->u.id] = sys.beta[e3->u.id] = a3;