[Bf-blender-cvs] [9df476ecaac] blender2.8: BLI_math: add `isect_seg_seg_v3` function and use in the cloth collision algorith.

[mano-wii]

Commit: 9df476ecaac8fb82c3d28b7404374db09e73eda4
Author: mano-wii
Date:   Mon Oct 1 00:16:44 2018 -0300
Branches: blender2.8
https://developer.blender.org/rB9df476ecaac8fb82c3d28b7404374db09e73eda4

BLI_math: add `isect_seg_seg_v3` function and use in the cloth collision algorith.

In my tests a 4% improvement in performance was achieved by simulating a square cloth over the cube.

===================================================================

M	source/blender/blenkernel/intern/collision.c
M	source/blender/blenlib/BLI_math_geom.h
M	source/blender/blenlib/intern/math_geom.c

===================================================================

diff --git a/source/blender/blenkernel/intern/collision.c b/source/blender/blenkernel/intern/collision.c
index d0eac3bb713..a3e13820ee0 100644
--- a/source/blender/blenkernel/intern/collision.c
+++ b/source/blender/blenkernel/intern/collision.c
@@ -192,36 +192,6 @@ void bvhtree_update_from_mvert(
 Collision modifier code end
 ***********************************/
 
-static void clamp_point_seg(float a[3], float b[3], float p[3])
-{
-	float ap[3], bp[3], ab[3];
-
-	sub_v3_v3v3(ap, p, a);
-	sub_v3_v3v3(bp, p, b);
-	sub_v3_v3v3(ab, b, a);
-
-	if (dot_v3v3(ap, bp) > 0.0f) {
-		if (dot_v3v3(ap, ab) > 0.0f) {
-			copy_v3_v3(p, b);
-		}
-		else {
-			copy_v3_v3(p, a);
-		}
-	}
-}
-
-static bool isect_seg_seg(float a1[3], float a2[3], float b1[3], float b2[3], float r_a[3], float r_b[3])
-{
-	if (isect_line_line_epsilon_v3(a1, a2, b1, b2, r_a, r_b, 0.0f)) {
-		clamp_point_seg(a1, a2, r_a);
-		clamp_point_seg(b1, b2, r_b);
-
-		return true;
-	}
-
-	return false;
-}
-
 BLI_INLINE int next_ind(int i)
 {
 	return (++i < 3) ? i : 0;
@@ -410,14 +380,13 @@ static float compute_collision_point(float a1[3], float a2[3], float a3[3], floa
 	if (isect_count == 0) {
 		for (int i = 0; i < 3; i++) {
 			for (int j = 0; j < 3; j++) {
-				if (isect_seg_seg(a[i], a[next_ind(i)], b[j], b[next_ind(j)], tmp_co1, tmp_co2)) {
-					tmp = len_squared_v3v3(tmp_co1, tmp_co2);
+				isect_seg_seg_v3(a[i], a[next_ind(i)], b[j], b[next_ind(j)], tmp_co1, tmp_co2);
+				tmp = len_squared_v3v3(tmp_co1, tmp_co2);
 
-					if (tmp < dist) {
-						dist = tmp;
-						copy_v3_v3(r_a, tmp_co1);
-						copy_v3_v3(r_b, tmp_co2);
-					}
+				if (tmp < dist) {
+					dist = tmp;
+					copy_v3_v3(r_a, tmp_co1);
+					copy_v3_v3(r_b, tmp_co2);
 				}
 			}
 		}
diff --git a/source/blender/blenlib/BLI_math_geom.h b/source/blender/blenlib/BLI_math_geom.h
index ccdb94c3317..d5287e8d8aa 100644
--- a/source/blender/blenlib/BLI_math_geom.h
+++ b/source/blender/blenlib/BLI_math_geom.h
@@ -207,6 +207,11 @@ void limit_dist_v3(float v1[3], float v2[3], const float dist);
 #define ISECT_LINE_LINE_CROSS        2
 
 int  isect_seg_seg_v2(const float a1[2], const float a2[2], const float b1[2], const float b2[2]);
+void isect_seg_seg_v3(
+        const float a0[3], const float a1[3],
+        const float b0[3], const float b1[3],
+        float r_a[3], float r_b[3]);
+
 int  isect_seg_seg_v2_int(const int a1[2], const int a2[2], const int b1[2], const int b2[2]);
 int  isect_seg_seg_v2_point_ex(
         const float v0[2], const float v1[2], const float v2[2], const float v3[2], const float endpoint_bias,
diff --git a/source/blender/blenlib/intern/math_geom.c b/source/blender/blenlib/intern/math_geom.c
index fb2a1e47895..a5c84ed7645 100644
--- a/source/blender/blenlib/intern/math_geom.c
+++ b/source/blender/blenlib/intern/math_geom.c
@@ -1123,6 +1123,70 @@ int isect_seg_seg_v2(const float v1[2], const float v2[2], const float v3[2], co
 	return ISECT_LINE_LINE_NONE;
 }
 
+/* Returns a point on each segment that is closest to the other. */
+void isect_seg_seg_v3(
+        const float a0[3], const float a1[3],
+        const float b0[3], const float b1[3],
+        float r_a[3], float r_b[3])
+{
+	float fac_a, fac_b;
+	float a_dir[3], b_dir[3], a0b0[3], crs_ab[3];
+	sub_v3_v3v3(a_dir, a1, a0);
+	sub_v3_v3v3(b_dir, b1, b0);
+	sub_v3_v3v3(a0b0, b0, a0);
+	cross_v3_v3v3(crs_ab, b_dir, a_dir);
+	const float nlen = len_squared_v3(crs_ab);
+
+	if (nlen == 0.0f) {
+		/* Parallel Lines */
+		/* In this case return any point that
+		 * is between the closest segments. */
+		float a0b1[3], a1b0[3], len_a, len_b, fac1, fac2;
+		sub_v3_v3v3(a0b1, b1, a0);
+		sub_v3_v3v3(a1b0, b0, a1);
+		len_a = len_squared_v3(a_dir);
+		len_b = len_squared_v3(b_dir);
+
+		if (len_a) {
+			fac1 = dot_v3v3(a0b0, a_dir);
+			fac2 = dot_v3v3(a0b1, a_dir);
+			CLAMP(fac1, 0.0f, len_a);
+			CLAMP(fac2, 0.0f, len_a);
+			fac_a = (fac1 + fac2) / (2 * len_a);
+		}
+		else {
+			fac_a = 0.0f;
+		}
+
+		if (len_b) {
+			fac1 = -dot_v3v3(a0b0, b_dir);
+			fac2 = -dot_v3v3(a1b0, b_dir);
+			CLAMP(fac1, 0.0f, len_b);
+			CLAMP(fac2, 0.0f, len_b);
+			fac_b = (fac1 + fac2) / (2 * len_b);
+		}
+		else {
+			fac_b = 0.0f;
+		}
+	}
+	else {
+		float c[3], cray[3];
+		sub_v3_v3v3(c, crs_ab, a0b0);
+
+		cross_v3_v3v3(cray, c, b_dir);
+		fac_a = dot_v3v3(cray, crs_ab) / nlen;
+
+		cross_v3_v3v3(cray, c, a_dir);
+		fac_b = dot_v3v3(cray, crs_ab) / nlen;
+
+		CLAMP(fac_a, 0.0f, 1.0f);
+		CLAMP(fac_b, 0.0f, 1.0f);
+	}
+
+	madd_v3_v3v3fl(r_a, a0, a_dir, fac_a);
+	madd_v3_v3v3fl(r_b, b0, b_dir, fac_b);
+}
+
 /**
  * Get intersection point of two 2D segments.
  *