Commit: ee3b3f766936c7f5fa773faca1498f0c733541ec
Author: Lukas Tönne
Date: Fri Nov 14 14:41:55 2014 +0100
Branches: hair_immediate_fixes
https://developer.blender.org/rBee3b3f766936c7f5fa773faca1498f0c733541ec
Corrected the divergence and gradient calculation for the hair grid
solver input and output.
This uses the central difference method (instead of combined forward/
backward difference), which makes it easier to correctly account for
grid borders.
===================================================================
M source/blender/physics/intern/hair_volume.cpp
===================================================================
diff --git a/source/blender/physics/intern/hair_volume.cpp
b/source/blender/physics/intern/hair_volume.cpp
index ddc5066..49b8af4 100644
--- a/source/blender/physics/intern/hair_volume.cpp
+++ b/source/blender/physics/intern/hair_volume.cpp
@@ -310,6 +310,13 @@ BLI_INLINE int hair_grid_weights(const int res[3], const
float gmin[3], float sc
return offset;
}
+BLI_INLINE void grid_to_world(HairGrid *grid, float vecw[3], const float
vec[3])
+{
+ copy_v3_v3(vecw, vec);
+ mul_v3_fl(vecw, grid->cellsize);
+ add_v3_v3(vecw, grid->gmin);
+}
+
void BPH_hair_volume_add_vertex(HairGrid *grid, const float x[3], const float
v[3])
{
const int res[3] = { grid->res[0], grid->res[1], grid->res[2] };
@@ -364,13 +371,6 @@ BLI_INLINE int major_axis_v3(const float v[3])
return a > b ? (a > c ? 0 : 2) : (b > c ? 1 : 2);
}
-BLI_INLINE void grid_to_world(HairGrid *grid, float vecw[3], const float
vec[3])
-{
- copy_v3_v3(vecw, vec);
- mul_v3_fl(vecw, grid->cellsize);
- add_v3_v3(vecw, grid->gmin);
-}
-
void BPH_hair_volume_set_debug_value(HairGrid *grid, int debug_value)
{
grid->debug_value = debug_value;
@@ -609,8 +609,8 @@ BLI_INLINE float hair_volume_density_divergence(float
density, float target_dens
bool BPH_hair_volume_solve_divergence(HairGrid *grid, float dt, float
target_density, float target_strength)
{
- const float flowfac = grid->cellsize / dt;
- const float inv_flowfac = dt / grid->cellsize;
+ const float flowfac = grid->cellsize;
+ const float inv_flowfac = 1.0f / grid->cellsize;
/*const int num_cells = hair_grid_size(grid->res);*/
const int res[3] = { grid->res[0], grid->res[1], grid->res[2] };
@@ -660,16 +660,23 @@ bool BPH_hair_volume_solve_divergence(HairGrid *grid,
float dt, float target_den
}
vert = vert_start + i * stride0 + j * stride1 +
k * stride2;
- HairGridVert *vert_px = vert + stride0;
- HairGridVert *vert_py = vert + stride1;
- HairGridVert *vert_pz = vert + stride2;
- const float *v = vert->velocity;
- float dx = NEIGHBOR_MARGIN_i1 ? 0.0f :
vert_px->velocity[0] - v[0];
- float dy = NEIGHBOR_MARGIN_j1 ? 0.0f :
vert_py->velocity[1] - v[1];
- float dz = NEIGHBOR_MARGIN_k1 ? 0.0f :
vert_pz->velocity[2] - v[2];
+ const float *v0 = vert->velocity;
+ float dx = 0.0f, dy = 0.0f, dz = 0.0f;
+ if (!NEIGHBOR_MARGIN_i0)
+ dx += v0[0] - (vert -
stride0)->velocity[0];
+ if (!NEIGHBOR_MARGIN_i1)
+ dx += (vert + stride0)->velocity[0] -
v0[0];
+ if (!NEIGHBOR_MARGIN_j0)
+ dy += v0[1] - (vert -
stride1)->velocity[1];
+ if (!NEIGHBOR_MARGIN_j1)
+ dy += (vert + stride1)->velocity[1] -
v0[1];
+ if (!NEIGHBOR_MARGIN_k0)
+ dz += v0[2] - (vert -
stride2)->velocity[2];
+ if (!NEIGHBOR_MARGIN_k1)
+ dz += (vert + stride2)->velocity[2] -
v0[2];
- float divergence = (dx + dy + dz) * flowfac;
+ float divergence = -0.5f * flowfac * (dx + dy +
dz);
/* adjustment term for target density */
float target =
hair_volume_density_divergence(vert->density, target_density, target_strength);
@@ -766,16 +773,22 @@ bool BPH_hair_volume_solve_divergence(HairGrid *grid,
float dt, float target_den
vert = vert_start + i * stride0 + j *
stride1 + k * stride2;
if (vert->density > density_threshold) {
- float p0 = p[u];
+ float p_left = p[u - stride0];
+ float p_right = p[u + stride0];
+ float p_down = p[u - stride1];
+ float p_up = p[u + stride1];
+ float p_bottom = p[u - stride2];
+ float p_top = p[u + stride2];
/* finite difference estimate
of pressure gradient */
- float grad_p[3];
- grad_p[0] = p0 - p[u - stride0];
- grad_p[1] = p0 - p[u - stride1];
- grad_p[2] = p0 - p[u - stride2];
+ float dvel[3];
+ dvel[0] = p_right - p_left;
+ dvel[1] = p_up - p_down;
+ dvel[2] = p_top - p_bottom;
+ mul_v3_fl(dvel, -0.5f *
inv_flowfac);
/* pressure gradient describes
velocity delta */
-
madd_v3_v3v3fl(vert->velocity_smooth, vert->velocity, grad_p, inv_flowfac);
+
add_v3_v3v3(vert->velocity_smooth, vert->velocity, dvel);
}
else {
zero_v3(vert->velocity_smooth);
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