LineArt: Stroke offset towards camera.

Allows the user to turn off in_front option for grease pencil object
and offset strokes towards camera to allow depth interaction of the
rest of the scene.

Reviewed By: Antonio Vazquez (antoniov)

Differential Revision: https://developer.blender.org/D12046

4 files changed, 46 insertions, 7 deletions

diff --git a/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h b/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h
index c00f34185dd..d170a6033fa 100644
--- a/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h
+++ b/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h
@@ -595,13 +595,15 @@ void MOD_lineart_chain_connect(LineartRenderBuffer *rb);
 void MOD_lineart_chain_discard_short(LineartRenderBuffer *rb, const float threshold);
 void MOD_lineart_chain_split_angle(LineartRenderBuffer *rb, float angle_threshold_rad);
 void MOD_lineart_smooth_chains(LineartRenderBuffer *rb, float tolerance);
+void MOD_lineart_chain_offset_towards_camera(LineartRenderBuffer *rb, float dist);
 
 int MOD_lineart_chain_count(const LineartEdgeChain *ec);
 void MOD_lineart_chain_clear_picked_flag(LineartCache *lc);
 
 bool MOD_lineart_compute_feature_lines(struct Depsgraph *depsgraph,
                                        struct LineartGpencilModifierData *lmd,
-                                       LineartCache **cached_result);
+                                       struct LineartCache **cached_result,
+                                       bool enable_stroke_offset);
 
 struct Scene;
 
diff --git a/source/blender/gpencil_modifiers/intern/lineart/lineart_chain.c b/source/blender/gpencil_modifiers/intern/lineart/lineart_chain.c
index 8935bdd1870..57eeeb96541 100644
--- a/source/blender/gpencil_modifiers/intern/lineart/lineart_chain.c
+++ b/source/blender/gpencil_modifiers/intern/lineart/lineart_chain.c
@@ -926,9 +926,9 @@ void MOD_lineart_chain_clear_picked_flag(LineartCache *lc)
 
 void MOD_lineart_smooth_chains(LineartRenderBuffer *rb, float tolerance)
 {
-  LISTBASE_FOREACH (LineartEdgeChain *, rlc, &rb->chains) {
+  LISTBASE_FOREACH (LineartEdgeChain *, ec, &rb->chains) {
     LineartEdgeChainItem *next_eci;
-    for (LineartEdgeChainItem *eci = rlc->chain.first; eci; eci = next_eci) {
+    for (LineartEdgeChainItem *eci = ec->chain.first; eci; eci = next_eci) {
       next_eci = eci->next;
       LineartEdgeChainItem *eci2, *eci3, *eci4;
 
@@ -944,7 +944,7 @@ void MOD_lineart_smooth_chains(LineartRenderBuffer *rb, float tolerance)
       if (dist_to_line_segment_v2(eci3->pos, eci->pos, eci2->pos) < tolerance) {
         /* And if p4 is on the extension of p1-p2 , we remove p3. */
         if ((eci4 = eci3->next) && (dist_to_line_v2(eci4->pos, eci->pos, eci2->pos) < tolerance)) {
-          BLI_remlink(&rlc->chain, eci3);
+          BLI_remlink(&ec->chain, eci3);
           next_eci = eci;
         }
       }
@@ -1008,3 +1008,35 @@ void MOD_lineart_chain_split_angle(LineartRenderBuffer *rb, float angle_threshol
     }
   }
 }
+
+void MOD_lineart_chain_offset_towards_camera(LineartRenderBuffer *rb, float dist)
+{
+  float dir[3];
+  float cam[3];
+  float view[3];
+  float view_clamp[3];
+  copy_v3fl_v3db(cam, rb->camera_pos);
+  copy_v3fl_v3db(view, rb->view_vector);
+  if (rb->cam_is_persp) {
+    LISTBASE_FOREACH (LineartEdgeChain *, ec, &rb->chains) {
+      LISTBASE_FOREACH (LineartEdgeChainItem *, eci, &ec->chain) {
+        sub_v3_v3v3(dir, cam, eci->gpos);
+        float orig_len = len_v3(dir);
+        normalize_v3(dir);
+        mul_v3_fl(dir, MIN2(dist, orig_len - rb->near_clip));
+        add_v3_v3(eci->gpos, dir);
+      }
+    }
+  }
+  else {
+    LISTBASE_FOREACH (LineartEdgeChain *, ec, &rb->chains) {
+      LISTBASE_FOREACH (LineartEdgeChainItem *, eci, &ec->chain) {
+        sub_v3_v3v3(dir, cam, eci->gpos);
+        float len_lim = dot_v3v3(view, dir) - rb->near_clip;
+        normalize_v3_v3(view_clamp, view);
+        mul_v3_fl(view_clamp, MIN2(dist, len_lim));
+        add_v3_v3(eci->gpos, view_clamp);
+      }
+    }
+  }
+}
diff --git a/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c b/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c
index 6660da79b40..f8dda2f9174 100644
--- a/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c
+++ b/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c
@@ -4076,7 +4076,8 @@ static LineartBoundingArea *lineart_bounding_area_next(LineartBoundingArea *this
  */
 bool MOD_lineart_compute_feature_lines(Depsgraph *depsgraph,
                                        LineartGpencilModifierData *lmd,
-                                       LineartCache **cached_result)
+                                       LineartCache **cached_result,
+                                       bool enable_stroke_depth_offset)
 {
   LineartRenderBuffer *rb;
   Scene *scene = DEG_get_evaluated_scene(depsgraph);
@@ -4189,6 +4190,10 @@ bool MOD_lineart_compute_feature_lines(Depsgraph *depsgraph,
       MOD_lineart_chain_split_angle(rb, rb->angle_splitting_threshold);
     }
 
+    if (enable_stroke_depth_offset && lmd->stroke_depth_offset > FLT_EPSILON) {
+      MOD_lineart_chain_offset_towards_camera(rb, lmd->stroke_depth_offset);
+    }
+
     /* Finally transfer the result list into cache. */
     memcpy(&lc->chains, &rb->chains, sizeof(ListBase));
 
diff --git a/source/blender/gpencil_modifiers/intern/lineart/lineart_ops.c b/source/blender/gpencil_modifiers/intern/lineart/lineart_ops.c
index 988c90483a6..b74499daf6b 100644
--- a/source/blender/gpencil_modifiers/intern/lineart/lineart_ops.c
+++ b/source/blender/gpencil_modifiers/intern/lineart/lineart_ops.c
@@ -118,12 +118,12 @@ static bool bake_strokes(Object *ob,
   }
   LineartCache *local_lc = *lc;
   if (!(*lc)) {
-    MOD_lineart_compute_feature_lines(dg, lmd, lc);
+    MOD_lineart_compute_feature_lines(dg, lmd, lc, (!(ob->dtx & OB_DRAW_IN_FRONT)));
     MOD_lineart_destroy_render_data(lmd);
   }
   else {
     if (is_first || (!(lmd->flags & LRT_GPENCIL_USE_CACHE))) {
-      MOD_lineart_compute_feature_lines(dg, lmd, &local_lc);
+      MOD_lineart_compute_feature_lines(dg, lmd, &local_lc, (!(ob->dtx & OB_DRAW_IN_FRONT)));
       MOD_lineart_destroy_render_data(lmd);
     }
     MOD_lineart_chain_clear_picked_flag(local_lc);