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Make projectOriginPlane in NativeCCD numerically robust.

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PiperOrigin-RevId: 673761409
Change-Id: I64304c89f768414d60e2dcf2e71feb8a6f9b2635
This commit is contained in:
Kyle Bayes
2024-09-12 03:00:07 -07:00
committed by Copybara-Service
parent 567793c26f
commit 14f420069e
1 changed files with 30 additions and 15 deletions
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src/engine/engine_collision_gjk.c
+30 -15
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@@ -57,7 +57,6 @@ typedef struct {
int verts[3]; // indices of the three vertices of the face in the polytope
mjtNum v[3];
mjtNum dist;
mjtNum n[3];
} Face;
typedef struct {
@@ -265,17 +264,36 @@ static mjtNum det3(const mjtNum v1[3], const mjtNum v2[3], const mjtNum v3[3]) {
// res = origin projected onto plane defined by v1, v2, v3
static inline void projectOriginPlane(mjtNum res[3], mjtNum normal[3], const mjtNum v1[3],
static inline void projectOriginPlane(mjtNum res[3], const mjtNum v1[3],
const mjtNum v2[3], const mjtNum v3[3]) {
mjtNum diff1[3], diff2[3], tmp[3];
mju_sub3(diff1, v2, v1);
mju_sub3(diff2, v3, v1);
mju_cross(tmp, diff1, diff2); // vector normal to the plane
mjtNum diff21[3], diff31[3], diff32[3], n[3], nv, nn;
mju_sub3(diff21, v2, v1);
mju_sub3(diff31, v3, v1);
mju_sub3(diff32, v3, v2);
// res = tmp * <tmp, v1> / ||tmp||^2
mjtNum tmp_sqr = mju_dot3(tmp, tmp);
mju_scl3(res, tmp, mju_dot3(tmp, v1) / tmp_sqr);
if (normal) mju_scl3(normal, tmp, 1/mju_sqrt(tmp_sqr));
// n = (v1 - v2) x (v3 - v2)
mju_cross(n, diff32, diff21);
nv = mju_dot3(n, v2);
nn = mju_dot3(n, n);
if (nv != 0 && nn > mjMINVAL) {
mju_scl3(res, n, nv / nn);
return;
}
// n = (v2 - v1) x (v3 - v1)
mju_cross(n, diff21, diff31);
nv = mju_dot3(n, v1);
nn = mju_dot3(n, n);
if (nv != 0 && nn > mjMINVAL) {
mju_scl3(res, n, nv / nn);
return;
}
// n = (v1 - v3) x (v2 - v3)
mju_cross(n, diff31, diff32);
nv = mju_dot3(n, v3);
nn = mju_dot3(n, n);
mju_scl3(res, n, nv / nn);
}
@@ -438,7 +456,7 @@ static void S2D(mjtNum lambda[3], const mjtNum simplex[9]) {
// project origin onto affine hull of the simplex
mjtNum p_o[3];
projectOriginPlane(p_o, NULL, s1, s2, s3);
projectOriginPlane(p_o, s1, s2, s3);
// Below are the minors M_i4 of the matrix M given by
// [[ s1_x, s2_x, s3_x, s4_x ],
@@ -967,11 +985,8 @@ static void attachFace(Polytope* pt, int v1, int v2, int v3) {
mjtNum* pv1 = pt->verts[v1].v;
mjtNum* pv2 = pt->verts[v2].v;
mjtNum* pv3 = pt->verts[v3].v;
projectOriginPlane(face->v, face->n, pv1, pv2, pv3);
projectOriginPlane(face->v, pv1, pv2, pv3);
face->dist = mju_norm3(face->v);
// orientation check
if (mju_dot3(face->n, pv1) < 0) mju_scl3(face->n, face->n, -1);
pt->nfaces++;
}