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Diffstat (limited to 'source/blender/simulation/intern/hair_volume.cpp')
| -rw-r--r-- | source/blender/simulation/intern/hair_volume.cpp | 1274 |
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diff --git a/source/blender/simulation/intern/hair_volume.cpp b/source/blender/simulation/intern/hair_volume.cpp new file mode 100644 index 00000000000..c80ae69ce73 --- /dev/null +++ b/source/blender/simulation/intern/hair_volume.cpp @@ -0,0 +1,1274 @@ +/* + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software Foundation, + * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * + * The Original Code is Copyright (C) Blender Foundation + * All rights reserved. + */ + +/** \file + * \ingroup bph + */ + +#include "MEM_guardedalloc.h" + +#include "BLI_math.h" +#include "BLI_utildefines.h" + +#include "DNA_texture_types.h" + +#include "BKE_effect.h" + +#include "eigen_utils.h" +#include "implicit.h" + +/* ================ Volumetric Hair Interaction ================ + * adapted from + * + * Volumetric Methods for Simulation and Rendering of Hair + * (Petrovic, Henne, Anderson, Pixar Technical Memo #06-08, Pixar Animation Studios) + * + * as well as + * + * "Detail Preserving Continuum Simulation of Straight Hair" + * (McAdams, Selle 2009) + */ + +/* Note about array indexing: + * Generally the arrays here are one-dimensional. + * The relation between 3D indices and the array offset is + * offset = x + res_x * y + res_x * res_y * z + */ + +static float I[3][3] = {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}}; + +BLI_INLINE int floor_int(float value) +{ + return value > 0.0f ? (int)value : ((int)value) - 1; +} + +BLI_INLINE float floor_mod(float value) +{ + return value - floorf(value); +} + +BLI_INLINE int hair_grid_size(const int res[3]) +{ + return res[0] * res[1] * res[2]; +} + +typedef struct HairGridVert { + int samples; + float velocity[3]; + float density; + + float velocity_smooth[3]; +} HairGridVert; + +typedef struct HairGrid { + HairGridVert *verts; + int res[3]; + float gmin[3], gmax[3]; + float cellsize, inv_cellsize; +} HairGrid; + +#define HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, axis) \ + (min_ii(max_ii((int)((vec[axis] - gmin[axis]) * scale), 0), res[axis] - 2)) + +BLI_INLINE int hair_grid_offset(const float vec[3], + const int res[3], + const float gmin[3], + float scale) +{ + int i, j, k; + i = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 0); + j = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 1); + k = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 2); + return i + (j + k * res[1]) * res[0]; +} + +BLI_INLINE int hair_grid_interp_weights( + const int res[3], const float gmin[3], float scale, const float vec[3], float uvw[3]) +{ + int i, j, k, offset; + + i = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 0); + j = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 1); + k = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 2); + offset = i + (j + k * res[1]) * res[0]; + + uvw[0] = (vec[0] - gmin[0]) * scale - (float)i; + uvw[1] = (vec[1] - gmin[1]) * scale - (float)j; + uvw[2] = (vec[2] - gmin[2]) * scale - (float)k; + + // BLI_assert(0.0f <= uvw[0] && uvw[0] <= 1.0001f); + // BLI_assert(0.0f <= uvw[1] && uvw[1] <= 1.0001f); + // BLI_assert(0.0f <= uvw[2] && uvw[2] <= 1.0001f); + + return offset; +} + +BLI_INLINE void hair_grid_interpolate(const HairGridVert *grid, + const int res[3], + const float gmin[3], + float scale, + const float vec[3], + float *density, + float velocity[3], + float vel_smooth[3], + float density_gradient[3], + float velocity_gradient[3][3]) +{ + HairGridVert data[8]; + float uvw[3], muvw[3]; + int res2 = res[1] * res[0]; + int offset; + + offset = hair_grid_interp_weights(res, gmin, scale, vec, uvw); + muvw[0] = 1.0f - uvw[0]; + muvw[1] = 1.0f - uvw[1]; + muvw[2] = 1.0f - uvw[2]; + + data[0] = grid[offset]; + data[1] = grid[offset + 1]; + data[2] = grid[offset + res[0]]; + data[3] = grid[offset + res[0] + 1]; + data[4] = grid[offset + res2]; + data[5] = grid[offset + res2 + 1]; + data[6] = grid[offset + res2 + res[0]]; + data[7] = grid[offset + res2 + res[0] + 1]; + + if (density) { + *density = muvw[2] * (muvw[1] * (muvw[0] * data[0].density + uvw[0] * data[1].density) + + uvw[1] * (muvw[0] * data[2].density + uvw[0] * data[3].density)) + + uvw[2] * (muvw[1] * (muvw[0] * data[4].density + uvw[0] * data[5].density) + + uvw[1] * (muvw[0] * data[6].density + uvw[0] * data[7].density)); + } + + if (velocity) { + int k; + for (k = 0; k < 3; k++) { + velocity[k] = muvw[2] * + (muvw[1] * (muvw[0] * data[0].velocity[k] + uvw[0] * data[1].velocity[k]) + + uvw[1] * (muvw[0] * data[2].velocity[k] + uvw[0] * data[3].velocity[k])) + + uvw[2] * + (muvw[1] * (muvw[0] * data[4].velocity[k] + uvw[0] * data[5].velocity[k]) + + uvw[1] * (muvw[0] * data[6].velocity[k] + uvw[0] * data[7].velocity[k])); + } + } + + if (vel_smooth) { + int k; + for (k = 0; k < 3; k++) { + vel_smooth[k] = muvw[2] * (muvw[1] * (muvw[0] * data[0].velocity_smooth[k] + + uvw[0] * data[1].velocity_smooth[k]) + + uvw[1] * (muvw[0] * data[2].velocity_smooth[k] + + uvw[0] * data[3].velocity_smooth[k])) + + uvw[2] * (muvw[1] * (muvw[0] * data[4].velocity_smooth[k] + + uvw[0] * data[5].velocity_smooth[k]) + + uvw[1] * (muvw[0] * data[6].velocity_smooth[k] + + uvw[0] * data[7].velocity_smooth[k])); + } + } + + if (density_gradient) { + density_gradient[0] = muvw[1] * muvw[2] * (data[0].density - data[1].density) + + uvw[1] * muvw[2] * (data[2].density - data[3].density) + + muvw[1] * uvw[2] * (data[4].density - data[5].density) + + uvw[1] * uvw[2] * (data[6].density - data[7].density); + + density_gradient[1] = muvw[2] * muvw[0] * (data[0].density - data[2].density) + + uvw[2] * muvw[0] * (data[4].density - data[6].density) + + muvw[2] * uvw[0] * (data[1].density - data[3].density) + + uvw[2] * uvw[0] * (data[5].density - data[7].density); + + density_gradient[2] = muvw[2] * muvw[0] * (data[0].density - data[4].density) + + uvw[2] * muvw[0] * (data[1].density - data[5].density) + + muvw[2] * uvw[0] * (data[2].density - data[6].density) + + uvw[2] * uvw[0] * (data[3].density - data[7].density); + } + + if (velocity_gradient) { + /* XXX TODO */ + zero_m3(velocity_gradient); + } +} + +void SIM_hair_volume_vertex_grid_forces(HairGrid *grid, + const float x[3], + const float v[3], + float smoothfac, + float pressurefac, + float minpressure, + float f[3], + float dfdx[3][3], + float dfdv[3][3]) +{ + float gdensity, gvelocity[3], ggrad[3], gvelgrad[3][3], gradlen; + + hair_grid_interpolate(grid->verts, + grid->res, + grid->gmin, + grid->inv_cellsize, + x, + &gdensity, + gvelocity, + NULL, + ggrad, + gvelgrad); + + zero_v3(f); + sub_v3_v3(gvelocity, v); + mul_v3_v3fl(f, gvelocity, smoothfac); + + gradlen = normalize_v3(ggrad) - minpressure; + if (gradlen > 0.0f) { + mul_v3_fl(ggrad, gradlen); + madd_v3_v3fl(f, ggrad, pressurefac); + } + + zero_m3(dfdx); + + sub_m3_m3m3(dfdv, gvelgrad, I); + mul_m3_fl(dfdv, smoothfac); +} + +void SIM_hair_volume_grid_interpolate(HairGrid *grid, + const float x[3], + float *density, + float velocity[3], + float velocity_smooth[3], + float density_gradient[3], + float velocity_gradient[3][3]) +{ + hair_grid_interpolate(grid->verts, + grid->res, + grid->gmin, + grid->inv_cellsize, + x, + density, + velocity, + velocity_smooth, + density_gradient, + velocity_gradient); +} + +void SIM_hair_volume_grid_velocity( + HairGrid *grid, const float x[3], const float v[3], float fluid_factor, float r_v[3]) +{ + float gdensity, gvelocity[3], gvel_smooth[3], ggrad[3], gvelgrad[3][3]; + float v_pic[3], v_flip[3]; + + hair_grid_interpolate(grid->verts, + grid->res, + grid->gmin, + grid->inv_cellsize, + x, + &gdensity, + gvelocity, + gvel_smooth, + ggrad, + gvelgrad); + + /* velocity according to PIC method (Particle-in-Cell) */ + copy_v3_v3(v_pic, gvel_smooth); + + /* velocity according to FLIP method (Fluid-Implicit-Particle) */ + sub_v3_v3v3(v_flip, gvel_smooth, gvelocity); + add_v3_v3(v_flip, v); + + interp_v3_v3v3(r_v, v_pic, v_flip, fluid_factor); +} + +void SIM_hair_volume_grid_clear(HairGrid *grid) +{ + const int size = hair_grid_size(grid->res); + int i; + for (i = 0; i < size; i++) { + zero_v3(grid->verts[i].velocity); + zero_v3(grid->verts[i].velocity_smooth); + grid->verts[i].density = 0.0f; + grid->verts[i].samples = 0; + } +} + +BLI_INLINE bool hair_grid_point_valid(const float vec[3], const float gmin[3], const float gmax[3]) +{ + return !(vec[0] < gmin[0] || vec[1] < gmin[1] || vec[2] < gmin[2] || vec[0] > gmax[0] || + vec[1] > gmax[1] || vec[2] > gmax[2]); +} + +BLI_INLINE float dist_tent_v3f3(const float a[3], float x, float y, float z) +{ + float w = (1.0f - fabsf(a[0] - x)) * (1.0f - fabsf(a[1] - y)) * (1.0f - fabsf(a[2] - z)); + return w; +} + +BLI_INLINE float weights_sum(const float weights[8]) +{ + float totweight = 0.0f; + int i; + for (i = 0; i < 8; i++) { + totweight += weights[i]; + } + return totweight; +} + +/* returns the grid array offset as well to avoid redundant calculation */ +BLI_INLINE int hair_grid_weights( + const int res[3], const float gmin[3], float scale, const float vec[3], float weights[8]) +{ + int i, j, k, offset; + float uvw[3]; + + i = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 0); + j = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 1); + k = HAIR_GRID_INDEX_AXIS(vec, res, gmin, scale, 2); + offset = i + (j + k * res[1]) * res[0]; + + uvw[0] = (vec[0] - gmin[0]) * scale; + uvw[1] = (vec[1] - gmin[1]) * scale; + uvw[2] = (vec[2] - gmin[2]) * scale; + + weights[0] = dist_tent_v3f3(uvw, (float)i, (float)j, (float)k); + weights[1] = dist_tent_v3f3(uvw, (float)(i + 1), (float)j, (float)k); + weights[2] = dist_tent_v3f3(uvw, (float)i, (float)(j + 1), (float)k); + weights[3] = dist_tent_v3f3(uvw, (float)(i + 1), (float)(j + 1), (float)k); + weights[4] = dist_tent_v3f3(uvw, (float)i, (float)j, (float)(k + 1)); + weights[5] = dist_tent_v3f3(uvw, (float)(i + 1), (float)j, (float)(k + 1)); + weights[6] = dist_tent_v3f3(uvw, (float)i, (float)(j + 1), (float)(k + 1)); + weights[7] = dist_tent_v3f3(uvw, (float)(i + 1), (float)(j + 1), (float)(k + 1)); + + // BLI_assert(fabsf(weights_sum(weights) - 1.0f) < 0.0001f); + + 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 SIM_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]}; + float weights[8]; + int di, dj, dk; + int offset; + + if (!hair_grid_point_valid(x, grid->gmin, grid->gmax)) { + return; + } + + offset = hair_grid_weights(res, grid->gmin, grid->inv_cellsize, x, weights); + + for (di = 0; di < 2; di++) { + for (dj = 0; dj < 2; dj++) { + for (dk = 0; dk < 2; dk++) { + int voffset = offset + di + (dj + dk * res[1]) * res[0]; + int iw = di + dj * 2 + dk * 4; + + grid->verts[voffset].density += weights[iw]; + madd_v3_v3fl(grid->verts[voffset].velocity, v, weights[iw]); + } + } + } +} + +#if 0 +BLI_INLINE void hair_volume_eval_grid_vertex(HairGridVert *vert, + const float loc[3], + float radius, + float dist_scale, + const float x2[3], + const float v2[3], + const float x3[3], + const float v3[3]) +{ + float closest[3], lambda, dist, weight; + + lambda = closest_to_line_v3(closest, loc, x2, x3); + dist = len_v3v3(closest, loc); + + weight = (radius - dist) * dist_scale; + + if (weight > 0.0f) { + float vel[3]; + + interp_v3_v3v3(vel, v2, v3, lambda); + madd_v3_v3fl(vert->velocity, vel, weight); + vert->density += weight; + vert->samples += 1; + } +} + +BLI_INLINE int major_axis_v3(const float v[3]) +{ + const float a = fabsf(v[0]); + const float b = fabsf(v[1]); + const float c = fabsf(v[2]); + return a > b ? (a > c ? 0 : 2) : (b > c ? 1 : 2); +} + +BLI_INLINE void hair_volume_add_segment_2D(HairGrid *grid, + const float UNUSED(x1[3]), + const float UNUSED(v1[3]), + const float x2[3], + const float v2[3], + const float x3[3], + const float v3[3], + const float UNUSED(x4[3]), + const float UNUSED(v4[3]), + const float UNUSED(dir1[3]), + const float dir2[3], + const float UNUSED(dir3[3]), + int resj, + int resk, + int jmin, + int jmax, + int kmin, + int kmax, + HairGridVert *vert, + int stride_j, + int stride_k, + const float loc[3], + int axis_j, + int axis_k, + int debug_i) +{ + const float radius = 1.5f; + const float dist_scale = grid->inv_cellsize; + + int j, k; + + /* boundary checks to be safe */ + CLAMP_MIN(jmin, 0); + CLAMP_MAX(jmax, resj - 1); + CLAMP_MIN(kmin, 0); + CLAMP_MAX(kmax, resk - 1); + + HairGridVert *vert_j = vert + jmin * stride_j; + float loc_j[3] = {loc[0], loc[1], loc[2]}; + loc_j[axis_j] += (float)jmin; + for (j = jmin; j <= jmax; j++, vert_j += stride_j, loc_j[axis_j] += 1.0f) { + + HairGridVert *vert_k = vert_j + kmin * stride_k; + float loc_k[3] = {loc_j[0], loc_j[1], loc_j[2]}; + loc_k[axis_k] += (float)kmin; + for (k = kmin; k <= kmax; k++, vert_k += stride_k, loc_k[axis_k] += 1.0f) { + + hair_volume_eval_grid_vertex(vert_k, loc_k, radius, dist_scale, x2, v2, x3, v3); + +# if 0 + { + float wloc[3], x2w[3], x3w[3]; + grid_to_world(grid, wloc, loc_k); + grid_to_world(grid, x2w, x2); + grid_to_world(grid, x3w, x3); + + if (vert_k->samples > 0) { + BKE_sim_debug_data_add_circle(wloc, 0.01f, 1.0, 1.0, 0.3, "grid", 2525, debug_i, j, k); + } + + if (grid->debug_value) { + BKE_sim_debug_data_add_dot(wloc, 1, 0, 0, "grid", 93, debug_i, j, k); + BKE_sim_debug_data_add_dot(x2w, 0.1, 0.1, 0.7, "grid", 649, debug_i, j, k); + BKE_sim_debug_data_add_line(wloc, x2w, 0.3, 0.8, 0.3, "grid", 253, debug_i, j, k); + BKE_sim_debug_data_add_line(wloc, x3w, 0.8, 0.3, 0.3, "grid", 254, debug_i, j, k); + // BKE_sim_debug_data_add_circle( + // x2w, len_v3v3(wloc, x2w), 0.2, 0.7, 0.2, + // "grid", 255, i, j, k); + } + } +# endif + } + } +} + +/* Uses a variation of Bresenham's algorithm for rasterizing a 3D grid with a line segment. + * + * The radius of influence around a segment is assumed to be at most 2*cellsize, + * i.e. only cells containing the segment and their direct neighbors are examined. + */ +void SIM_hair_volume_add_segment(HairGrid *grid, + const float x1[3], + const float v1[3], + const float x2[3], + const float v2[3], + const float x3[3], + const float v3[3], + const float x4[3], + const float v4[3], + const float dir1[3], + const float dir2[3], + const float dir3[3]) +{ + const int res[3] = {grid->res[0], grid->res[1], grid->res[2]}; + + /* find the primary direction from the major axis of the direction vector */ + const int axis0 = major_axis_v3(dir2); + const int axis1 = (axis0 + 1) % 3; + const int axis2 = (axis0 + 2) % 3; + + /* vertex buffer offset factors along cardinal axes */ + const int strides[3] = {1, res[0], res[0] * res[1]}; + const int stride0 = strides[axis0]; + const int stride1 = strides[axis1]; + const int stride2 = strides[axis2]; + + /* increment of secondary directions per step in the primary direction + * note: we always go in the positive direction along axis0, so the sign can be inverted + */ + const float inc1 = dir2[axis1] / dir2[axis0]; + const float inc2 = dir2[axis2] / dir2[axis0]; + + /* start/end points, so increment along axis0 is always positive */ + const float *start = x2[axis0] < x3[axis0] ? x2 : x3; + const float *end = x2[axis0] < x3[axis0] ? x3 : x2; + const float start0 = start[axis0], start1 = start[axis1], start2 = start[axis2]; + const float end0 = end[axis0]; + + /* range along primary direction */ + const int imin = max_ii(floor_int(start[axis0]) - 1, 0); + const int imax = min_ii(floor_int(end[axis0]) + 2, res[axis0] - 1); + + float h = 0.0f; + HairGridVert *vert0; + float loc0[3]; + int j0, k0, j0_prev, k0_prev; + int i; + + for (i = imin; i <= imax; i++) { + float shift1, shift2; /* fraction of a full cell shift [0.0, 1.0) */ + int jmin, jmax, kmin, kmax; + + h = CLAMPIS((float)i, start0, end0); + + shift1 = start1 + (h - start0) * inc1; + shift2 = start2 + (h - start0) * inc2; + + j0_prev = j0; + j0 = floor_int(shift1); + + k0_prev = k0; + k0 = floor_int(shift2); + + if (i > imin) { + jmin = min_ii(j0, j0_prev); + jmax = max_ii(j0, j0_prev); + kmin = min_ii(k0, k0_prev); + kmax = max_ii(k0, k0_prev); + } + else { + jmin = jmax = j0; + kmin = kmax = k0; + } + + vert0 = grid->verts + i * stride0; + loc0[axis0] = (float)i; + loc0[axis1] = 0.0f; + loc0[axis2] = 0.0f; + + hair_volume_add_segment_2D(grid, + x1, + v1, + x2, + v2, + x3, + v3, + x4, + v4, + dir1, + dir2, + dir3, + res[axis1], + res[axis2], + jmin - 1, + jmax + 2, + kmin - 1, + kmax + 2, + vert0, + stride1, + stride2, + loc0, + axis1, + axis2, + i); + } +} +#else +BLI_INLINE void hair_volume_eval_grid_vertex_sample(HairGridVert *vert, + const float loc[3], + float radius, + float dist_scale, + const float x[3], + const float v[3]) +{ + float dist, weight; + + dist = len_v3v3(x, loc); + + weight = (radius - dist) * dist_scale; + + if (weight > 0.0f) { + madd_v3_v3fl(vert->velocity, v, weight); + vert->density += weight; + vert->samples += 1; + } +} + +/* XXX simplified test implementation using a series of discrete sample along the segment, + * instead of finding the closest point for all affected grid vertices. + */ +void SIM_hair_volume_add_segment(HairGrid *grid, + const float UNUSED(x1[3]), + const float UNUSED(v1[3]), + const float x2[3], + const float v2[3], + const float x3[3], + const float v3[3], + const float UNUSED(x4[3]), + const float UNUSED(v4[3]), + const float UNUSED(dir1[3]), + const float UNUSED(dir2[3]), + const float UNUSED(dir3[3])) +{ + const float radius = 1.5f; + const float dist_scale = grid->inv_cellsize; + + const int res[3] = {grid->res[0], grid->res[1], grid->res[2]}; + const int stride[3] = {1, res[0], res[0] * res[1]}; + const int num_samples = 10; + + int s; + + for (s = 0; s < num_samples; s++) { + float x[3], v[3]; + int i, j, k; + + float f = (float)s / (float)(num_samples - 1); + interp_v3_v3v3(x, x2, x3, f); + interp_v3_v3v3(v, v2, v3, f); + + int imin = max_ii(floor_int(x[0]) - 2, 0); + int imax = min_ii(floor_int(x[0]) + 2, res[0] - 1); + int jmin = max_ii(floor_int(x[1]) - 2, 0); + int jmax = min_ii(floor_int(x[1]) + 2, res[1] - 1); + int kmin = max_ii(floor_int(x[2]) - 2, 0); + int kmax = min_ii(floor_int(x[2]) + 2, res[2] - 1); + + for (k = kmin; k <= kmax; k++) { + for (j = jmin; j <= jmax; j++) { + for (i = imin; i <= imax; i++) { + float loc[3] = {(float)i, (float)j, (float)k}; + HairGridVert *vert = grid->verts + i * stride[0] + j * stride[1] + k * stride[2]; + + hair_volume_eval_grid_vertex_sample(vert, loc, radius, dist_scale, x, v); + } + } + } + } +} +#endif + +void SIM_hair_volume_normalize_vertex_grid(HairGrid *grid) +{ + int i, size = hair_grid_size(grid->res); + /* divide velocity with density */ + for (i = 0; i < size; i++) { + float density = grid->verts[i].density; + if (density > 0.0f) { + mul_v3_fl(grid->verts[i].velocity, 1.0f / density); + } + } +} + +/* Cells with density below this are considered empty. */ +static const float density_threshold = 0.001f; + +/* Contribution of target density pressure to the laplacian in the pressure poisson equation. + * This is based on the model found in + * "Two-way Coupled SPH and Particle Level Set Fluid Simulation" (Losasso et al., 2008) + */ +BLI_INLINE float hair_volume_density_divergence(float density, + float target_density, + float strength) +{ + if (density > density_threshold && density > target_density) { + return strength * logf(target_density / density); + } + else { + return 0.0f; + } +} + +bool SIM_hair_volume_solve_divergence(HairGrid *grid, + float /*dt*/, + float target_density, + float target_strength) +{ + 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]}; + const int resA[3] = {grid->res[0] + 2, grid->res[1] + 2, grid->res[2] + 2}; + + const int stride0 = 1; + const int stride1 = grid->res[0]; + const int stride2 = grid->res[1] * grid->res[0]; + const int strideA0 = 1; + const int strideA1 = grid->res[0] + 2; + const int strideA2 = (grid->res[1] + 2) * (grid->res[0] + 2); + + const int num_cells = res[0] * res[1] * res[2]; + const int num_cellsA = (res[0] + 2) * (res[1] + 2) * (res[2] + 2); + + HairGridVert *vert_start = grid->verts - (stride0 + stride1 + stride2); + HairGridVert *vert; + int i, j, k; + +#define MARGIN_i0 (i < 1) +#define MARGIN_j0 (j < 1) +#define MARGIN_k0 (k < 1) +#define MARGIN_i1 (i >= resA[0] - 1) +#define MARGIN_j1 (j >= resA[1] - 1) +#define MARGIN_k1 (k >= resA[2] - 1) + +#define NEIGHBOR_MARGIN_i0 (i < 2) +#define NEIGHBOR_MARGIN_j0 (j < 2) +#define NEIGHBOR_MARGIN_k0 (k < 2) +#define NEIGHBOR_MARGIN_i1 (i >= resA[0] - 2) +#define NEIGHBOR_MARGIN_j1 (j >= resA[1] - 2) +#define NEIGHBOR_MARGIN_k1 (k >= resA[2] - 2) + + BLI_assert(num_cells >= 1); + + /* Calculate divergence */ + lVector B(num_cellsA); + for (k = 0; k < resA[2]; k++) { + for (j = 0; j < resA[1]; j++) { + for (i = 0; i < resA[0]; i++) { + int u = i * strideA0 + j * strideA1 + k * strideA2; + bool is_margin = MARGIN_i0 || MARGIN_i1 || MARGIN_j0 || MARGIN_j1 || MARGIN_k0 || + MARGIN_k1; + + if (is_margin) { + B[u] = 0.0f; + continue; + } + + vert = vert_start + i * stride0 + j * stride1 + k * stride2; + + 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 = -0.5f * flowfac * (dx + dy + dz); + + /* adjustment term for target density */ + float target = hair_volume_density_divergence( + vert->density, target_density, target_strength); + + /* B vector contains the finite difference approximation of the velocity divergence. + * Note: according to the discretized Navier-Stokes equation the rhs vector + * and resulting pressure gradient should be multiplied by the (inverse) density; + * however, this is already included in the weighting of hair velocities on the grid! + */ + B[u] = divergence - target; + +#if 0 + { + float wloc[3], loc[3]; + float col0[3] = {0.0, 0.0, 0.0}; + float colp[3] = {0.0, 1.0, 1.0}; + float coln[3] = {1.0, 0.0, 1.0}; + float col[3]; + float fac; + + loc[0] = (float)(i - 1); + loc[1] = (float)(j - 1); + loc[2] = (float)(k - 1); + grid_to_world(grid, wloc, loc); + + if (divergence > 0.0f) { + fac = CLAMPIS(divergence * target_strength, 0.0, 1.0); + interp_v3_v3v3(col, col0, colp, fac); + } + else { + fac = CLAMPIS(-divergence * target_strength, 0.0, 1.0); + interp_v3_v3v3(col, col0, coln, fac); + } + if (fac > 0.05f) { + BKE_sim_debug_data_add_circle( + grid->debug_data, wloc, 0.01f, col[0], col[1], col[2], "grid", 5522, i, j, k); + } + } +#endif + } + } + } + + /* Main Poisson equation system: + * This is derived from the discretezation of the Poisson equation + * div(grad(p)) = div(v) + * + * The finite difference approximation yields the linear equation system described here: + * https://en.wikipedia.org/wiki/Discrete_Poisson_equation + */ + lMatrix A(num_cellsA, num_cellsA); + /* Reserve space for the base equation system (without boundary conditions). + * Each column contains a factor 6 on the diagonal + * and up to 6 factors -1 on other places. + */ + A.reserve(Eigen::VectorXi::Constant(num_cellsA, 7)); + + for (k = 0; k < resA[2]; k++) { + for (j = 0; j < resA[1]; j++) { + for (i = 0; i < resA[0]; i++) { + int u = i * strideA0 + j * strideA1 + k * strideA2; + bool is_margin = MARGIN_i0 || MARGIN_i1 || MARGIN_j0 || MARGIN_j1 || MARGIN_k0 || + MARGIN_k1; + + vert = vert_start + i * stride0 + j * stride1 + k * stride2; + if (!is_margin && vert->density > density_threshold) { + int neighbors_lo = 0; + int neighbors_hi = 0; + int non_solid_neighbors = 0; + int neighbor_lo_index[3]; + int neighbor_hi_index[3]; + int n; + + /* check for upper bounds in advance + * to get the correct number of neighbors, + * needed for the diagonal element + */ + if (!NEIGHBOR_MARGIN_k0 && (vert - stride2)->density > density_threshold) { + neighbor_lo_index[neighbors_lo++] = u - strideA2; + } + if (!NEIGHBOR_MARGIN_j0 && (vert - stride1)->density > density_threshold) { + neighbor_lo_index[neighbors_lo++] = u - strideA1; + } + if (!NEIGHBOR_MARGIN_i0 && (vert - stride0)->density > density_threshold) { + neighbor_lo_index[neighbors_lo++] = u - strideA0; + } + if (!NEIGHBOR_MARGIN_i1 && (vert + stride0)->density > density_threshold) { + neighbor_hi_index[neighbors_hi++] = u + strideA0; + } + if (!NEIGHBOR_MARGIN_j1 && (vert + stride1)->density > density_threshold) { + neighbor_hi_index[neighbors_hi++] = u + strideA1; + } + if (!NEIGHBOR_MARGIN_k1 && (vert + stride2)->density > density_threshold) { + neighbor_hi_index[neighbors_hi++] = u + strideA2; + } + + /*int liquid_neighbors = neighbors_lo + neighbors_hi;*/ + non_solid_neighbors = 6; + + for (n = 0; n < neighbors_lo; n++) { + A.insert(neighbor_lo_index[n], u) = -1.0f; + } + A.insert(u, u) = (float)non_solid_neighbors; + for (n = 0; n < neighbors_hi; n++) { + A.insert(neighbor_hi_index[n], u) = -1.0f; + } + } + else { + A.insert(u, u) = 1.0f; + } + } + } + } + + ConjugateGradient cg; + cg.setMaxIterations(100); + cg.setTolerance(0.01f); + + cg.compute(A); + + lVector p = cg.solve(B); + + if (cg.info() == Eigen::Success) { + /* Calculate velocity = grad(p) */ + for (k = 0; k < resA[2]; k++) { + for (j = 0; j < resA[1]; j++) { + for (i = 0; i < resA[0]; i++) { + int u = i * strideA0 + j * strideA1 + k * strideA2; + bool is_margin = MARGIN_i0 || MARGIN_i1 || MARGIN_j0 || MARGIN_j1 || MARGIN_k0 || + MARGIN_k1; + if (is_margin) { + continue; + } + + vert = vert_start + i * stride0 + j * stride1 + k * stride2; + if (vert->density > density_threshold) { + float p_left = p[u - strideA0]; + float p_right = p[u + strideA0]; + float p_down = p[u - strideA1]; + float p_up = p[u + strideA1]; + float p_bottom = p[u - strideA2]; + float p_top = p[u + strideA2]; + + /* finite difference estimate of pressure gradient */ + 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 */ + add_v3_v3v3(vert->velocity_smooth, vert->velocity, dvel); + } + else { + zero_v3(vert->velocity_smooth); + } + } + } + } + +#if 0 + { + int axis = 0; + float offset = 0.0f; + + int slice = (offset - grid->gmin[axis]) / grid->cellsize; + + for (k = 0; k < resA[2]; k++) { + for (j = 0; j < resA[1]; j++) { + for (i = 0; i < resA[0]; i++) { + int u = i * strideA0 + j * strideA1 + k * strideA2; + bool is_margin = MARGIN_i0 || MARGIN_i1 || MARGIN_j0 || MARGIN_j1 || MARGIN_k0 || + MARGIN_k1; + if (i != slice) { + continue; + } + + vert = vert_start + i * stride0 + j * stride1 + k * stride2; + + float wloc[3], loc[3]; + float col0[3] = {0.0, 0.0, 0.0}; + float colp[3] = {0.0, 1.0, 1.0}; + float coln[3] = {1.0, 0.0, 1.0}; + float col[3]; + float fac; + + loc[0] = (float)(i - 1); + loc[1] = (float)(j - 1); + loc[2] = (float)(k - 1); + grid_to_world(grid, wloc, loc); + + float pressure = p[u]; + if (pressure > 0.0f) { + fac = CLAMPIS(pressure * grid->debug1, 0.0, 1.0); + interp_v3_v3v3(col, col0, colp, fac); + } + else { + fac = CLAMPIS(-pressure * grid->debug1, 0.0, 1.0); + interp_v3_v3v3(col, col0, coln, fac); + } + if (fac > 0.05f) { + BKE_sim_debug_data_add_circle( + grid->debug_data, wloc, 0.01f, col[0], col[1], col[2], "grid", 5533, i, j, k); + } + + if (!is_margin) { + float dvel[3]; + sub_v3_v3v3(dvel, vert->velocity_smooth, vert->velocity); + // BKE_sim_debug_data_add_vector( + // grid->debug_data, wloc, dvel, 1, 1, 1, + // "grid", 5566, i, j, k); + } + + if (!is_margin) { + float d = CLAMPIS(vert->density * grid->debug2, 0.0f, 1.0f); + float col0[3] = {0.3, 0.3, 0.3}; + float colp[3] = {0.0, 0.0, 1.0}; + float col[3]; + + interp_v3_v3v3(col, col0, colp, d); + // if (d > 0.05f) { + // BKE_sim_debug_data_add_dot( + // grid->debug_data, wloc, col[0], col[1], col[2], + // "grid", 5544, i, j, k); + // } + } + } + } + } + } +#endif + + return true; + } + else { + /* Clear result in case of error */ + for (i = 0, vert = grid->verts; i < num_cells; i++, vert++) { + zero_v3(vert->velocity_smooth); + } + + return false; + } +} + +#if 0 /* XXX weighting is incorrect, disabled for now */ +/* Velocity filter kernel + * See https://en.wikipedia.org/wiki/Filter_%28large_eddy_simulation%29 + */ + +BLI_INLINE void hair_volume_filter_box_convolute( + HairVertexGrid *grid, float invD, const int kernel_size[3], int i, int j, int k) +{ + int res = grid->res; + int p, q, r; + int minp = max_ii(i - kernel_size[0], 0), maxp = min_ii(i + kernel_size[0], res - 1); + int minq = max_ii(j - kernel_size[1], 0), maxq = min_ii(j + kernel_size[1], res - 1); + int minr = max_ii(k - kernel_size[2], 0), maxr = min_ii(k + kernel_size[2], res - 1); + int offset, kernel_offset, kernel_dq, kernel_dr; + HairGridVert *verts; + float *vel_smooth; + + offset = i + (j + k * res) * res; + verts = grid->verts; + vel_smooth = verts[offset].velocity_smooth; + + kernel_offset = minp + (minq + minr * res) * res; + kernel_dq = res; + kernel_dr = res * res; + for (r = minr; r <= maxr; r++) { + for (q = minq; q <= maxq; q++) { + for (p = minp; p <= maxp; p++) { + + madd_v3_v3fl(vel_smooth, verts[kernel_offset].velocity, invD); + + kernel_offset += 1; + } + kernel_offset += kernel_dq; + } + kernel_offset += kernel_dr; + } +} + +void SIM_hair_volume_vertex_grid_filter_box(HairVertexGrid *grid, int kernel_size) +{ + int size = hair_grid_size(grid->res); + int kernel_sizev[3] = {kernel_size, kernel_size, kernel_size}; + int tot; + float invD; + int i, j, k; + + if (kernel_size <= 0) { + return; + } + + tot = kernel_size * 2 + 1; + invD = 1.0f / (float)(tot * tot * tot); + + /* clear values for convolution */ + for (i = 0; i < size; i++) { + zero_v3(grid->verts[i].velocity_smooth); + } + + for (i = 0; i < grid->res; i++) { + for (j = 0; j < grid->res; j++) { + for (k = 0; k < grid->res; k++) { + hair_volume_filter_box_convolute(grid, invD, kernel_sizev, i, j, k); + } + } + } + + /* apply as new velocity */ + for (i = 0; i < size; i++) { + copy_v3_v3(grid->verts[i].velocity, grid->verts[i].velocity_smooth); + } +} +#endif + +HairGrid *SIM_hair_volume_create_vertex_grid(float cellsize, + const float gmin[3], + const float gmax[3]) +{ + float scale; + float extent[3]; + int resmin[3], resmax[3], res[3]; + float gmin_margin[3], gmax_margin[3]; + int size; + HairGrid *grid; + int i; + + /* sanity check */ + if (cellsize <= 0.0f) { + cellsize = 1.0f; + } + scale = 1.0f / cellsize; + + sub_v3_v3v3(extent, gmax, gmin); + for (i = 0; i < 3; i++) { + resmin[i] = floor_int(gmin[i] * scale); + resmax[i] = floor_int(gmax[i] * scale) + 1; + + /* add margin of 1 cell */ + resmin[i] -= 1; + resmax[i] += 1; + + res[i] = resmax[i] - resmin[i] + 1; + /* sanity check: avoid null-sized grid */ + if (res[i] < 4) { + res[i] = 4; + resmax[i] = resmin[i] + 4; + } + /* sanity check: avoid too large grid size */ + if (res[i] > MAX_HAIR_GRID_RES) { + res[i] = MAX_HAIR_GRID_RES; + resmax[i] = resmin[i] + MAX_HAIR_GRID_RES; + } + + gmin_margin[i] = (float)resmin[i] * cellsize; + gmax_margin[i] = (float)resmax[i] * cellsize; + } + size = hair_grid_size(res); + + grid = (HairGrid *)MEM_callocN(sizeof(HairGrid), "hair grid"); + grid->res[0] = res[0]; + grid->res[1] = res[1]; + grid->res[2] = res[2]; + copy_v3_v3(grid->gmin, gmin_margin); + copy_v3_v3(grid->gmax, gmax_margin); + grid->cellsize = cellsize; + grid->inv_cellsize = scale; + grid->verts = (HairGridVert *)MEM_callocN(sizeof(HairGridVert) * size, "hair voxel data"); + + return grid; +} + +void SIM_hair_volume_free_vertex_grid(HairGrid *grid) +{ + if (grid) { + if (grid->verts) { + MEM_freeN(grid->verts); + } + MEM_freeN(grid); + } +} + +void SIM_hair_volume_grid_geometry( + HairGrid *grid, float *cellsize, int res[3], float gmin[3], float gmax[3]) +{ + if (cellsize) { + *cellsize = grid->cellsize; + } + if (res) { + copy_v3_v3_int(res, grid->res); + } + if (gmin) { + copy_v3_v3(gmin, grid->gmin); + } + if (gmax) { + copy_v3_v3(gmax, grid->gmax); + } +} + +#if 0 +static HairGridVert *hair_volume_create_collision_grid(ClothModifierData *clmd, + lfVector *lX, + unsigned int numverts) +{ + int res = hair_grid_res; + int size = hair_grid_size(res); + HairGridVert *collgrid; + ListBase *colliders; + ColliderCache *col = NULL; + float gmin[3], gmax[3], scale[3]; + /* 2.0f is an experimental value that seems to give good results */ + float collfac = 2.0f * clmd->sim_parms->collider_friction; + unsigned int v = 0; + int i = 0; + + hair_volume_get_boundbox(lX, numverts, gmin, gmax); + hair_grid_get_scale(res, gmin, gmax, scale); + + collgrid = MEM_mallocN(sizeof(HairGridVert) * size, "hair collider voxel data"); + + /* initialize grid */ + for (i = 0; i < size; i++) { + zero_v3(collgrid[i].velocity); + collgrid[i].density = 0.0f; + } + + /* gather colliders */ + colliders = BKE_collider_cache_create(depsgraph, NULL, NULL); + if (colliders && collfac > 0.0f) { + for (col = colliders->first; col; col = col->next) { + MVert *loc0 = col->collmd->x; + MVert *loc1 = col->collmd->xnew; + float vel[3]; + float weights[8]; + int di, dj, dk; + + for (v = 0; v < col->collmd->numverts; v++, loc0++, loc1++) { + int offset; + + if (!hair_grid_point_valid(loc1->co, gmin, gmax)) { + continue; + } + + offset = hair_grid_weights(res, gmin, scale, lX[v], weights); + + sub_v3_v3v3(vel, loc1->co, loc0->co); + + for (di = 0; di < 2; di++) { + for (dj = 0; dj < 2; dj++) { + for (dk = 0; dk < 2; dk++) { + int voffset = offset + di + (dj + dk * res) * res; + int iw = di + dj * 2 + dk * 4; + + collgrid[voffset].density += weights[iw]; + madd_v3_v3fl(collgrid[voffset].velocity, vel, weights[iw]); + } + } + } + } + } + } + BKE_collider_cache_free(&colliders); + + /* divide velocity with density */ + for (i = 0; i < size; i++) { + float density = collgrid[i].density; + if (density > 0.0f) { + mul_v3_fl(collgrid[i].velocity, 1.0f / density); + } + } + + return collgrid; +} +#endif |