Add Complex Solidify option for thickness per face

Add an option to solidify complex which will make faces which have thickness
controlled by vertex weights flat/even, and parallel to their original face.

For each face it uses the minimal weight assigned to its vertices to control
the thickness.

This will help users for example in architecture or basic CAD design by finally
making solidify work there at all if altering thickness is needed.

Differential Revision: https://developer.blender.org/D7340

Reviewed and minor cleanups by Batien Montagne (@mont29).

1 files changed, 46 insertions, 2 deletions

diff --git a/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c b/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c
index 70aec2d797b..e56ae82379e 100644
--- a/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c
+++ b/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c
@@ -186,6 +186,8 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
 
   MOD_get_vgroup(ctx->object, mesh, smd->defgrp_name, &dvert, &defgrp_index);
 
+  const bool do_flat_faces = dvert && (smd->flag & MOD_SOLIDIFY_NONMANIFOLD_FLAT_FACES);
+
   orig_mvert = mesh->mvert;
   orig_medge = mesh->medge;
   orig_mloop = mesh->mloop;
@@ -1305,6 +1307,30 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
 
   /* Calculate EdgeGroup vertex coordinates. */
   {
+    float *face_weight = NULL;
+
+    if (do_flat_faces) {
+      face_weight = MEM_malloc_arrayN(numPolys, sizeof(*face_weight), "face_weight in solidify");
+
+      mp = orig_mpoly;
+      for (uint i = 0; i < numPolys; i++, mp++) {
+        float scalar_vgroup = 1.0f;
+        int loopend = mp->loopstart + mp->totloop;
+        ml = orig_mloop + mp->loopstart;
+        for (int j = mp->loopstart; j < loopend; j++, ml++) {
+          MDeformVert *dv = &dvert[ml->v];
+          if (defgrp_invert) {
+            scalar_vgroup = min_ff(1.0f - BKE_defvert_find_weight(dv, defgrp_index),
+                                   scalar_vgroup);
+          }
+          else {
+            scalar_vgroup = min_ff(BKE_defvert_find_weight(dv, defgrp_index), scalar_vgroup);
+          }
+        }
+        face_weight[i] = scalar_vgroup;
+      }
+    }
+
     mv = orig_mvert;
     gs_ptr = orig_vert_groups_arr;
     for (uint i = 0; i < numVerts; i++, mv++, gs_ptr++) {
@@ -1337,14 +1363,22 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
                     NewFaceRef *face = edge->faces[l];
                     if (face && (first_edge == NULL ||
                                  (first_edge->faces[0] != face && first_edge->faces[1] != face))) {
-                      const float ofs = face->reversed ? ofs_back_clamped : ofs_front_clamped;
+                      float ofs = face->reversed ? ofs_back_clamped : ofs_front_clamped;
+                      /* Use face_weight here to make faces thinner. */
+                      if (do_flat_faces) {
+                        ofs *= face_weight[face->index];
+                      }
+
                       if (!null_faces[face->index]) {
+                        /* And normal to the queue. */
                         mul_v3_v3fl(normals_queue[queue_index],
                                     poly_nors[face->index],
                                     face->reversed ? -1 : 1);
                         normals_queue[queue_index++][3] = ofs;
                       }
                       else {
+                        /* Just use this approximate normal of the null face if there is no other
+                         * normal to use. */
                         mul_v3_v3fl(face_nors[0], poly_nors[face->index], face->reversed ? -1 : 1);
                         nor_ofs[0] = ofs;
                       }
@@ -1446,6 +1480,7 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
                 }
               }
               MEM_freeN(normals_queue);
+
               /* When up to 3 constraint normals are found. */
               if (ELEM(face_nors_len, 2, 3)) {
                 const float q = dot_v3v3(face_nors[0], face_nors[1]);
@@ -1500,6 +1535,11 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
                                  (first_edge->faces[0] != face && first_edge->faces[1] != face))) {
                       float angle = 1.0f;
                       float ofs = face->reversed ? -ofs_back_clamped : ofs_front_clamped;
+                      /* Use face_weight here to make faces thinner. */
+                      if (do_flat_faces) {
+                        ofs *= face_weight[face->index];
+                      }
+
                       if (smd->nonmanifold_offset_mode ==
                           MOD_SOLIDIFY_NONMANIFOLD_OFFSET_MODE_EVEN) {
                         MLoop *ml_next = orig_mloop + face->face->loopstart;
@@ -1669,7 +1709,7 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
             }
             float scalar_vgroup = 1;
             /* Use vertex group. */
-            if (dvert) {
+            if (dvert && !do_flat_faces) {
               MDeformVert *dv = &dvert[i];
               if (defgrp_invert) {
                 scalar_vgroup = 1.0f - BKE_defvert_find_weight(dv, defgrp_index);
@@ -1728,6 +1768,10 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
         }
       }
     }
+
+    if (do_flat_faces) {
+      MEM_freeN(face_weight);
+    }
   }
 
   MEM_freeN(orig_mvert_co);