diff options
author | Chris Blackbourn <chrisbblend@gmail.com> | 2022-09-12 03:58:14 +0300 |
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committer | Chris Blackbourn <chrisbblend@gmail.com> | 2022-09-12 05:23:22 +0300 |
commit | 94e211ced914faff7c1f8d0f68209038afa974bf (patch) | |
tree | 5b43ecb8471fa941ff484e8aa02f54b8cd35abc9 /source/blender/geometry/intern/uv_parametrizer.cc | |
parent | c9a8380426462686e3281ed5ee504a4a8f553d6b (diff) |
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
Diffstat (limited to 'source/blender/geometry/intern/uv_parametrizer.cc')
-rw-r--r-- | source/blender/geometry/intern/uv_parametrizer.cc | 83 |
1 files changed, 59 insertions, 24 deletions
diff --git a/source/blender/geometry/intern/uv_parametrizer.cc b/source/blender/geometry/intern/uv_parametrizer.cc index 4f763b09bef..f074febe23a 100644 --- a/source/blender/geometry/intern/uv_parametrizer.cc +++ b/source/blender/geometry/intern/uv_parametrizer.cc @@ -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; |