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Fix for particle instance modifier: use a stable parallel-transport

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framing method instead of the Frenet frame.

The Frenet frame is very succeptible to sudden twists along straight
sections of a curve where the second derivative (curvature) becomes 0.
This commit is contained in:
Lukas Tönne 2014-11-17 14:16:35 +01:00
parent 674c98bd06
commit bd033721c2
1 changed files with 42 additions and 3 deletions
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45
source/blender/modifiers/intern/MOD_particleinstance.c
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@ -43,6 +43,7 @@
#include "BLI_utildefines.h"
#include "BKE_cdderivedmesh.h"
#include "BKE_global.h"
#include "BKE_lattice.h"
#include "BKE_modifier.h"
#include "BKE_particle.h"
@ -276,6 +277,9 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
orig_mloop = dm->getLoopArray(dm);
for (p = 0, p_skip = 0; p < totpart; p++) {
float prev_dir[3];
float frame[4]; /* frame orientation quaternion */
/* skip particle? */
if (particle_skip(pimd, psys, p))
continue;
@ -321,19 +325,54 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
normalize_v3(state.vel);
/* TODO: incremental rotations somehow */
/* Incrementally Rotating Frame (Bishop Frame) */
if (k == 0) {
float mat[3][3];
float temp[3] = {0.0f, 0.0f, 0.0f};
temp[axis] = 1.0f;
/* normal direction */
copy_v3_v3(mat[0], state.vel);
/* tangent from projecting axis onto the surface plane */
project_v3_plane(mat[1], state.vel, temp);
normalize_v3(mat[1]);
/* cotangent */
cross_v3_v3v3(mat[2], mat[0], mat[1]);
/* to quaternion */
mat3_to_quat(frame, mat);
/* note: direction is same as normal vector currently,
* but best to keep this separate so the frame can be
* rotated later if necessary
*/
copy_v3_v3(prev_dir, state.vel);
}
else {
float rot[4];
/* incrementally rotate along bend direction */
rotation_between_vecs_to_quat(rot, prev_dir, state.vel);
mul_qt_qtqt(frame, rot, frame);
copy_v3_v3(prev_dir, state.vel);
}
copy_qt_qt(state.rot, frame);
#if 0
/* Absolute Frame (Frenet Frame) */
if (state.vel[axis] < -0.9999f || state.vel[axis] > 0.9999f) {
unit_qt(state.rot);
}
else {
float temp[3] = {0.0f, 0.0f, 0.0f};
temp[axis] = 1.0f;
cross_v3_v3v3(cross, temp, state.vel);
/* state.vel[axis] is the only component surviving from a dot product with the axis */
axis_angle_to_quat(state.rot, cross, saacos(state.vel[axis]));
}
#endif
}
else {
state.time = -1.0;