Sculpt: Implement plane deformation falloff for Grab

The plane deformation falloff was introduced in the first version of the
cloth brush, but due to the lack of all the new features and fixes in the
solver it was causing a lot of artifacts for deformation brushes. In
order to avoid that, the cloth brush was always using radial falloff for
the grab brush.

Now the plane falloff is properly implemented using the deformation
constraints.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D9320

1 files changed, 39 insertions, 24 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt_cloth.c b/source/blender/editors/sculpt_paint/sculpt_cloth.c
index 1a1200bb6c2..ef926330ece 100644
--- a/source/blender/editors/sculpt_paint/sculpt_cloth.c
+++ b/source/blender/editors/sculpt_paint/sculpt_cloth.c
@@ -326,6 +326,9 @@ static void do_cloth_brush_build_constraints_task_cb_ex(
    * positions. */
   const bool cloth_is_deform_brush = ss->cache != NULL && brush != NULL &&
                                      SCULPT_is_cloth_deform_brush(brush);
+
+  const bool use_falloff_plane = brush->cloth_force_falloff_type ==
+                                 BRUSH_CLOTH_FORCE_FALLOFF_PLANE;
   float radius_squared = 0.0f;
   if (cloth_is_deform_brush) {
     radius_squared = ss->cache->initial_radius * ss->cache->initial_radius;
@@ -380,12 +383,21 @@ static void do_cloth_brush_build_constraints_task_cb_ex(
     if (brush && brush->sculpt_tool == SCULPT_TOOL_CLOTH) {
       /* The cloth brush works by applying forces in most of its modes, but some of them require
        * deformation coordinates to make the simulation stable. */
-      if (brush->cloth_deform_type == BRUSH_CLOTH_DEFORM_GRAB && len_squared < radius_squared) {
-        /* When the grab brush brush is used as part of the cloth brush, deformation constraints
-         * are created with different strengths and only inside the radius of the brush. */
-        const float fade = BKE_brush_curve_strength(brush, sqrtf(len_squared), ss->cache->radius);
-        cloth_brush_add_deformation_constraint(
-            data->cloth_sim, node_index, vd.index, fade * CLOTH_DEFORMATION_GRAB_STRENGTH);
+      if (brush->cloth_deform_type == BRUSH_CLOTH_DEFORM_GRAB) {
+        if (use_falloff_plane) {
+          /* With plane falloff the strength of the constraints is set when applying the
+           * deformation forces. */
+          cloth_brush_add_deformation_constraint(
+              data->cloth_sim, node_index, vd.index, CLOTH_DEFORMATION_GRAB_STRENGTH);
+        }
+        else if (len_squared < radius_squared) {
+          /* With radial falloff deformation constraints are created with different strengths and
+           * only inside the radius of the brush. */
+          const float fade = BKE_brush_curve_strength(
+              brush, sqrtf(len_squared), ss->cache->radius);
+          cloth_brush_add_deformation_constraint(
+              data->cloth_sim, node_index, vd.index, fade * CLOTH_DEFORMATION_GRAB_STRENGTH);
+        }
       }
       else if (brush->cloth_deform_type == BRUSH_CLOTH_DEFORM_SNAKE_HOOK) {
         /* Cloth Snake Hook creates deformation constraint with fixed strength because the strength
@@ -436,9 +448,8 @@ static void do_cloth_brush_apply_forces_task_cb_ex(void *__restrict userdata,
   const float *grab_delta = data->grab_delta;
   float(*imat)[4] = data->mat;
 
-  const bool use_falloff_plane = !SCULPT_is_cloth_deform_brush(brush) &&
-                                 brush->cloth_force_falloff_type ==
-                                     BRUSH_CLOTH_FORCE_FALLOFF_PLANE;
+  const bool use_falloff_plane = brush->cloth_force_falloff_type ==
+                                 BRUSH_CLOTH_FORCE_FALLOFF_PLANE;
 
   PBVHVertexIter vd;
   const float bstrength = ss->cache->bstrength;
@@ -470,12 +481,6 @@ static void do_cloth_brush_apply_forces_task_cb_ex(void *__restrict userdata,
     madd_v3_v3fl(gravity, ss->cache->gravity_direction, -data->sd->gravity_factor);
   }
 
-  /* Original data for deform brushes. */
-  SculptOrigVertData orig_data;
-  if (SCULPT_is_cloth_deform_brush(brush)) {
-    SCULPT_orig_vert_data_init(&orig_data, data->ob, data->nodes[n]);
-  }
-
   BKE_pbvh_vertex_iter_begin(ss->pbvh, data->nodes[n], vd, PBVH_ITER_UNIQUE)
   {
     float force[3];
@@ -486,8 +491,7 @@ static void do_cloth_brush_apply_forces_task_cb_ex(void *__restrict userdata,
 
     float current_vertex_location[3];
     if (brush->cloth_deform_type == BRUSH_CLOTH_DEFORM_GRAB) {
-      SCULPT_orig_vert_data_update(&orig_data, &vd);
-      copy_v3_v3(current_vertex_location, orig_data.co);
+      copy_v3_v3(current_vertex_location, ss->cache->cloth_sim->init_pos[vd.index]);
     }
     else {
       copy_v3_v3(current_vertex_location, vd.co);
@@ -504,7 +508,7 @@ static void do_cloth_brush_apply_forces_task_cb_ex(void *__restrict userdata,
       float dist = sqrtf(test.dist);
 
       if (use_falloff_plane) {
-        dist = dist_to_plane_v3(vd.co, deform_plane);
+        dist = dist_to_plane_v3(current_vertex_location, deform_plane);
       }
 
       const float fade = sim_factor * bstrength *
@@ -539,9 +543,15 @@ static void do_cloth_brush_apply_forces_task_cb_ex(void *__restrict userdata,
           break;
         case BRUSH_CLOTH_DEFORM_GRAB:
           madd_v3_v3v3fl(cloth_sim->deformation_pos[vd.index],
-                         orig_data.co,
+                         cloth_sim->init_pos[vd.index],
                          ss->cache->grab_delta_symmetry,
                          fade);
+          if (use_falloff_plane) {
+            cloth_sim->deformation_strength[vd.index] = clamp_f(fade, 0.0f, 1.0f);
+          }
+          else {
+            cloth_sim->deformation_strength[vd.index] = 1.0f;
+          }
           zero_v3(force);
           break;
         case BRUSH_CLOTH_DEFORM_SNAKE_HOOK:
@@ -965,8 +975,8 @@ static void cloth_brush_apply_brush_foces(Sculpt *sd, Object *ob, PBVHNode **nod
     }
   }
 
-  if (brush->cloth_deform_type == BRUSH_CLOTH_DEFORM_SNAKE_HOOK) {
-    /* Set the deformation strength to 0. Snake hook will initialize the strength in the required
+  if (ELEM(brush->cloth_deform_type, BRUSH_CLOTH_DEFORM_SNAKE_HOOK, BRUSH_CLOTH_DEFORM_GRAB)) {
+    /* Set the deformation strength to 0. Brushes will initialize the strength in the required
      * area. */
     const int totverts = SCULPT_vertex_count_get(ss);
     for (int i = 0; i < totverts; i++) {
@@ -1228,9 +1238,14 @@ void SCULPT_cloth_plane_falloff_preview_draw(const uint gpuattr,
                                              const float outline_col[3],
                                              float outline_alpha)
 {
-  float local_mat_inv[4][4];
-  invert_m4_m4(local_mat_inv, ss->cache->stroke_local_mat);
-  GPU_matrix_mul(ss->cache->stroke_local_mat);
+  float local_mat[4][4];
+  copy_m4_m4(local_mat, ss->cache->stroke_local_mat);
+
+  if (ss->cache->brush->cloth_deform_type == BRUSH_CLOTH_DEFORM_GRAB) {
+    add_v3_v3v3(local_mat[3], ss->cache->true_location, ss->cache->grab_delta);
+  }
+
+  GPU_matrix_mul(local_mat);
 
   const float dist = ss->cache->radius;
   const float arrow_x = ss->cache->radius * 0.2f;