From c2f74d62435a25dc52d1a640db1c417ad7ec75d3 Mon Sep 17 00:00:00 2001
From: Bastien Montagne <bastien@blender.org>
Date: Mon, 14 Jun 2021 11:06:35 +0200
Subject: BLI_math: Fix several division-by-zero cases.

Those were caused by various tools used on degenerate geometry, see
T79775.

Note that fixes are as low-level as possible, to ensure they cover as
much as possible of unreported issues too.

We still probably have many more of those hidden in BLI_math though.
---
 source/blender/blenlib/BLI_math_vector.h           |  6 +++++-
 source/blender/blenlib/intern/math_geom.c          |  9 ++++++++-
 source/blender/blenlib/intern/math_vector.c        | 15 +++++++++++++++
 source/blender/blenlib/intern/math_vector_inline.c | 15 +++++++++++++++
 4 files changed, 43 insertions(+), 2 deletions(-)

(limited to 'source')

diff --git a/source/blender/blenlib/BLI_math_vector.h b/source/blender/blenlib/BLI_math_vector.h
index bb1e1a1c38d..7e734a18e8c 100644
--- a/source/blender/blenlib/BLI_math_vector.h
+++ b/source/blender/blenlib/BLI_math_vector.h
@@ -327,7 +327,11 @@ MINLINE bool is_zero_v2(const float a[3]) ATTR_WARN_UNUSED_RESULT;
 MINLINE bool is_zero_v3(const float a[3]) ATTR_WARN_UNUSED_RESULT;
 MINLINE bool is_zero_v4(const float a[4]) ATTR_WARN_UNUSED_RESULT;
 
-bool is_finite_v2(const float a[3]) ATTR_WARN_UNUSED_RESULT;
+MINLINE bool is_zero_v2_db(const double a[2]) ATTR_WARN_UNUSED_RESULT;
+MINLINE bool is_zero_v3_db(const double a[3]) ATTR_WARN_UNUSED_RESULT;
+MINLINE bool is_zero_v4_db(const double a[4]) ATTR_WARN_UNUSED_RESULT;
+
+bool is_finite_v2(const float a[2]) ATTR_WARN_UNUSED_RESULT;
 bool is_finite_v3(const float a[3]) ATTR_WARN_UNUSED_RESULT;
 bool is_finite_v4(const float a[4]) ATTR_WARN_UNUSED_RESULT;
 
diff --git a/source/blender/blenlib/intern/math_geom.c b/source/blender/blenlib/intern/math_geom.c
index 01cda6c9e4a..897c18adba5 100644
--- a/source/blender/blenlib/intern/math_geom.c
+++ b/source/blender/blenlib/intern/math_geom.c
@@ -3344,6 +3344,13 @@ float closest_to_ray_v3(float r_close[3],
                         const float ray_dir[3])
 {
   float h[3], lambda;
+
+  if (UNLIKELY(is_zero_v3(ray_dir))) {
+    lambda = 0.0f;
+    copy_v3_v3(r_close, ray_orig);
+    return lambda;
+  }
+
   sub_v3_v3v3(h, p, ray_orig);
   lambda = dot_v3v3(ray_dir, h) / dot_v3v3(ray_dir, ray_dir);
   madd_v3_v3v3fl(r_close, ray_orig, ray_dir, lambda);
@@ -4467,7 +4474,7 @@ void interp_weights_poly_v2(float *w, float v[][2], const int n, const float co[
     d_curr = d_next;
     DIR_V2_SET(&d_next, v_next, co);
     ht = mean_value_half_tan_v2_db(&d_curr, &d_next);
-    w[i_curr] = (float)((ht_prev + ht) / d_curr.len);
+    w[i_curr] = (d_curr.len == 0.0) ? 0.0f : (float)((ht_prev + ht) / d_curr.len);
     totweight += w[i_curr];
 
     /* step */
diff --git a/source/blender/blenlib/intern/math_vector.c b/source/blender/blenlib/intern/math_vector.c
index a21e0c8f092..521171cda95 100644
--- a/source/blender/blenlib/intern/math_vector.c
+++ b/source/blender/blenlib/intern/math_vector.c
@@ -657,6 +657,11 @@ void angle_poly_v3(float *angles, const float *verts[3], int len)
  */
 void project_v2_v2v2(float out[2], const float p[2], const float v_proj[2])
 {
+  if (UNLIKELY(is_zero_v2(v_proj))) {
+    zero_v2(out);
+    return;
+  }
+
   const float mul = dot_v2v2(p, v_proj) / dot_v2v2(v_proj, v_proj);
 
   out[0] = mul * v_proj[0];
@@ -668,6 +673,11 @@ void project_v2_v2v2(float out[2], const float p[2], const float v_proj[2])
  */
 void project_v3_v3v3(float out[3], const float p[3], const float v_proj[3])
 {
+  if (UNLIKELY(is_zero_v3(v_proj))) {
+    zero_v3(out);
+    return;
+  }
+
   const float mul = dot_v3v3(p, v_proj) / dot_v3v3(v_proj, v_proj);
 
   out[0] = mul * v_proj[0];
@@ -677,6 +687,11 @@ void project_v3_v3v3(float out[3], const float p[3], const float v_proj[3])
 
 void project_v3_v3v3_db(double out[3], const double p[3], const double v_proj[3])
 {
+  if (UNLIKELY(is_zero_v3_db(v_proj))) {
+    zero_v3_db(out);
+    return;
+  }
+
   const double mul = dot_v3v3_db(p, v_proj) / dot_v3v3_db(v_proj, v_proj);
 
   out[0] = mul * v_proj[0];
diff --git a/source/blender/blenlib/intern/math_vector_inline.c b/source/blender/blenlib/intern/math_vector_inline.c
index ead354c2d87..e0df9665a7e 100644
--- a/source/blender/blenlib/intern/math_vector_inline.c
+++ b/source/blender/blenlib/intern/math_vector_inline.c
@@ -1282,6 +1282,21 @@ MINLINE bool is_zero_v4(const float v[4])
   return (v[0] == 0.0f && v[1] == 0.0f && v[2] == 0.0f && v[3] == 0.0f);
 }
 
+MINLINE bool is_zero_v2_db(const double v[2])
+{
+  return (v[0] == 0.0 && v[1] == 0.0);
+}
+
+MINLINE bool is_zero_v3_db(const double v[3])
+{
+  return (v[0] == 0.0 && v[1] == 0.0 && v[2] == 0.0);
+}
+
+MINLINE bool is_zero_v4_db(const double v[4])
+{
+  return (v[0] == 0.0 && v[1] == 0.0 && v[2] == 0.0 && v[3] == 0.0);
+}
+
 MINLINE bool is_one_v3(const float v[3])
 {
   return (v[0] == 1.0f && v[1] == 1.0f && v[2] == 1.0f);
-- 
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