[Bf-blender-cvs] [69edb9c7d96] blender-v2.93-release: LineArt: Occlusion accuracy fix.

[YimingWu]

Commit: 69edb9c7d969934e40414ee30bf8a29cf69c4a30
Author: YimingWu
Date:   Tue Jul 27 14:02:22 2021 +0800
Branches: blender-v2.93-release
https://developer.blender.org/rB69edb9c7d969934e40414ee30bf8a29cf69c4a30

LineArt: Occlusion accuracy fix.

This patch fixes occlusion function to handle one specific case (when an edge shares a point with triangle) better,especially when there's overlapping edges in this case.

===================================================================

M	source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h
M	source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c

===================================================================

diff --git a/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h b/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h
index 56cd7fa1456..05222a2fdfb 100644
--- a/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h
+++ b/source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h
@@ -413,7 +413,8 @@ typedef struct LineartBoundingArea {
 BLI_INLINE int lineart_LineIntersectTest2d(
     const double *a1, const double *a2, const double *b1, const double *b2, double *aRatio)
 {
-#define USE_VECTOR_LINE_INTERSECTION
+/* Legacy intersection math aligns better with occlusion function quirks. */
+/* #define USE_VECTOR_LINE_INTERSECTION */
 #ifdef USE_VECTOR_LINE_INTERSECTION
 
   /* from isect_line_line_v2_point() */
diff --git a/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c b/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c
index ab1b0b9bac7..805c864566a 100644
--- a/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c
+++ b/source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c
@@ -2141,8 +2141,8 @@ static bool lineart_triangle_edge_image_space_occlusion(SpinLock *UNUSED(spl),
       }
     }
     else if (st_r == 0) {
-      INTERSECT_JUST_GREATER(is, order, 0, LCross);
-      if (LRT_ABC(LCross) && is[LCross] > 0) {
+      INTERSECT_JUST_GREATER(is, order, DBL_TRIANGLE_LIM, LCross);
+      if (LRT_ABC(LCross) && is[LCross] > DBL_TRIANGLE_LIM) {
         INTERSECT_JUST_GREATER(is, order, is[LCross], RCross);
       }
       else {