Sculpt/Paint: Move Elastic Deform Kelvinlets to BKE

After this commit it should be possible to share the same deformation
formulas that are used in the Elastic Deform brush with other areas of
Blender such as Grease Pencil or proportional editing.

This also removes a lot of code from sculpt.c that is not direclty
related to sculpting.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D6281

1 files changed, 215 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/kelvinlet.c b/source/blender/blenkernel/intern/kelvinlet.c
new file mode 100644
index 00000000000..a7b48107873
--- /dev/null
+++ b/source/blender/blenkernel/intern/kelvinlet.c
@@ -0,0 +1,215 @@
+/*
+ * 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 bke
+ */
+
+#include "BKE_kelvinlet.h"
+
+/* Regularized Kelvinlets: Sculpting Brushes based on Fundamental Solutions of Elasticity
+ * Pixar Technical Memo #17-03 */
+
+void BKE_kelvinlet_init_params(
+    KelvinletParams *params, float radius, float force, float shear_modulus, float poisson_ratio)
+{
+  params->a = 1.0f / (4.0f * (float)M_PI * shear_modulus);
+  params->b = params->a / (4.0f * (1.0f - poisson_ratio));
+  params->c = 2 * (3.0f * params->a - 2.0f * params->b);
+
+  /* Used in scale and twist. */
+  params->f = force;
+
+  /* This can be exposed if needed */
+  const float radius_e[KELVINLET_MAX_ITERATIONS] = {1.0f, 2.0f, 2.0f};
+  params->radius_scaled[0] = radius * radius_e[0];
+  params->radius_scaled[1] = params->radius_scaled[0] * radius_e[1];
+  params->radius_scaled[2] = params->radius_scaled[1] * radius_e[2];
+}
+
+static void init_kelvinlet_grab(float radius_e[3],
+                                float kelvinlet[3],
+                                const float radius,
+                                const KelvinletParams *params,
+                                const int num_iterations)
+{
+  const float a = params->a;
+  const float b = params->b;
+  const float *radius_scaled = params->radius_scaled;
+
+  for (int i = 0; i < num_iterations; i++) {
+    radius_e[i] = sqrtf(pow2f(radius) + pow2f(params->radius_scaled[i]));
+  }
+
+  /* Regularized Kelvinlets: Formula (6) */
+  for (int i = 0; i < num_iterations; i++) {
+    kelvinlet[i] = ((a - b) / radius_e[i]) + ((b * pow2f(radius)) / pow3f(radius_e[i])) +
+                   ((a * pow2f(radius_scaled[i])) / (2.0f * pow3f(radius_e[i])));
+  }
+}
+
+void BKE_kelvinlet_grab(float radius_elem_disp[3],
+                        const KelvinletParams *params,
+                        const float elem_orig_co[3],
+                        const float brush_location[3],
+                        const float brush_delta[3])
+{
+  float radius_e[3], kelvinlet[3];
+  const float c = params->c;
+  const float radius = len_v3v3(brush_location, elem_orig_co);
+
+  init_kelvinlet_grab(radius_e, kelvinlet, radius, params, 1);
+
+  const float fade = kelvinlet[0] * c;
+
+  mul_v3_v3fl(radius_elem_disp, brush_delta, fade);
+}
+
+void BKE_kelvinlet_grab_biscale(float radius_elem_disp[3],
+                                const KelvinletParams *params,
+                                const float elem_orig_co[3],
+                                const float brush_location[3],
+                                const float brush_delta[3])
+{
+  float radius_e[3], kelvinlet[3];
+  const float c = params->c;
+  const float *radius_scaled = params->radius_scaled;
+  float radius = len_v3v3(brush_location, elem_orig_co);
+
+  init_kelvinlet_grab(radius_e, kelvinlet, radius, params, 2);
+
+  const float u = kelvinlet[0] - kelvinlet[1];
+  const float fade = u * c / ((1.0f / radius_scaled[0]) - (1.0f / radius_scaled[1]));
+
+  mul_v3_v3fl(radius_elem_disp, brush_delta, fade);
+}
+
+void BKE_kelvinlet_grab_triscale(float radius_elem_disp[3],
+                                 const KelvinletParams *params,
+                                 const float elem_orig_co[3],
+                                 const float brush_location[3],
+                                 const float brush_delta[3])
+{
+  float radius_e[3], kelvinlet[3], weights[3];
+  const float c = params->c;
+  const float *radius_scaled = params->radius_scaled;
+  const float radius = len_v3v3(brush_location, elem_orig_co);
+
+  init_kelvinlet_grab(radius_e, kelvinlet, radius, params, 3);
+
+  weights[0] = 1.0f;
+  weights[1] = -((pow2f(radius_scaled[2]) - pow2f(radius_scaled[0])) /
+                 (pow2f(radius_scaled[2]) - pow2f(radius_scaled[1])));
+  weights[2] = ((pow2f(radius_scaled[1]) - pow2f(radius_scaled[0])) /
+                (pow2f(radius_scaled[2]) - pow2f(radius_scaled[1])));
+
+  const float u = weights[0] * kelvinlet[0] + weights[1] * kelvinlet[1] +
+                  weights[2] * kelvinlet[2];
+  const float fade = u * c /
+                     (weights[0] / radius_scaled[0] + weights[1] / radius_scaled[1] +
+                      weights[2] / radius_scaled[2]);
+
+  mul_v3_v3fl(radius_elem_disp, brush_delta, fade);
+}
+
+typedef void (*kelvinlet_fn)(
+    float[3], const float *, const float *, const float *, const KelvinletParams *);
+
+static void sculpt_kelvinet_integrate(kelvinlet_fn kelvinlet,
+                                      float r_disp[3],
+                                      const float vertex_co[3],
+                                      const float location[3],
+                                      const float normal[3],
+                                      const KelvinletParams *p)
+{
+  float k[4][3], k_it[4][3];
+  kelvinlet(k[0], vertex_co, location, normal, p);
+  copy_v3_v3(k_it[0], k[0]);
+  mul_v3_fl(k_it[0], 0.5f);
+  add_v3_v3v3(k_it[0], vertex_co, k_it[0]);
+  kelvinlet(k[1], k_it[0], location, normal, p);
+  copy_v3_v3(k_it[1], k[1]);
+  mul_v3_fl(k_it[1], 0.5f);
+  add_v3_v3v3(k_it[1], vertex_co, k_it[1]);
+  kelvinlet(k[2], k_it[1], location, normal, p);
+  copy_v3_v3(k_it[2], k[2]);
+  add_v3_v3v3(k_it[2], vertex_co, k_it[2]);
+  sub_v3_v3v3(k_it[2], k_it[2], location);
+  kelvinlet(k[3], k_it[2], location, normal, p);
+  copy_v3_v3(r_disp, k[0]);
+  madd_v3_v3fl(r_disp, k[1], 2.0f);
+  madd_v3_v3fl(r_disp, k[2], 2.0f);
+  add_v3_v3(r_disp, k[3]);
+  mul_v3_fl(r_disp, 1.0f / 6.0f);
+}
+
+/* Regularized Kelvinlets: Formula (16) */
+static void kelvinlet_scale(float disp[3],
+                            const float vertex_co[3],
+                            const float location[3],
+                            const float UNUSED(normal[3]),
+                            const KelvinletParams *p)
+{
+  float radius_vertex[3];
+  sub_v3_v3v3(radius_vertex, vertex_co, location);
+  const float radius = len_v3(radius_vertex);
+  const float radius_e = sqrtf(pow2f(radius) + pow2f(p->radius_scaled[0]));
+  const float u = (2.0f * p->b - p->a) * ((1.0f / pow3f(radius_e))) +
+                  ((3.0f * pow2f(p->radius_scaled[0])) / (2.0f * pow5f(radius_e)));
+  const float fade = u * p->c;
+  mul_v3_v3fl(disp, radius_vertex, fade * p->f);
+}
+
+void BKE_kelvinlet_scale(float radius_elem_disp[3],
+                         const KelvinletParams *params,
+                         const float elem_orig_co[3],
+                         const float brush_location[3],
+                         const float surface_normal[3])
+{
+  sculpt_kelvinet_integrate(
+      kelvinlet_scale, radius_elem_disp, elem_orig_co, brush_location, surface_normal, params);
+}
+
+/* Regularized Kelvinlets: Formula (15) */
+static void kelvinlet_twist(float disp[3],
+                            const float vertex_co[3],
+                            const float location[3],
+                            const float normal[3],
+                            const KelvinletParams *p)
+{
+  float radius_vertex[3], q_r[3];
+  sub_v3_v3v3(radius_vertex, vertex_co, location);
+  const float radius = len_v3(radius_vertex);
+  const float radius_e = sqrtf(pow2f(radius) + pow2f(p->radius_scaled[0]));
+  const float u = -p->a * ((1.0f / pow3f(radius_e))) +
+                  ((3.0f * pow2f(p->radius_scaled[0])) / (2.0f * pow5f(radius_e)));
+  const float fade = u * p->c;
+  cross_v3_v3v3(q_r, normal, radius_vertex);
+  mul_v3_v3fl(disp, q_r, fade * p->f);
+}
+
+void BKE_kelvinlet_twist(float radius_elem_disp[3],
+                         const KelvinletParams *params,
+                         const float elem_orig_co[3],
+                         const float brush_location[3],
+                         const float surface_normal[3])
+{
+  sculpt_kelvinet_integrate(
+      kelvinlet_twist, radius_elem_disp, elem_orig_co, brush_location, surface_normal, params);
+}