[Bf-blender-cvs] [e87804f2ba5] greasepencil-refactor: GPencil: Refactor: Implement Miter corner logic

[Clément Foucault]

Commit: e87804f2ba597ad7b600469be16f030056536676
Author: Clément Foucault
Date:   Sun Dec 8 15:14:57 2019 +0100
Branches: greasepencil-refactor
https://developer.blender.org/rBe87804f2ba597ad7b600469be16f030056536676

GPencil: Refactor: Implement Miter corner logic

Not 100% complete, needs to fix the "corner" cases.

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

M	source/blender/draw/engines/gpencil/shaders/gpencil_vert.glsl

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

diff --git a/source/blender/draw/engines/gpencil/shaders/gpencil_vert.glsl b/source/blender/draw/engines/gpencil/shaders/gpencil_vert.glsl
index cd7b520a2c2..e65bf8d8298 100644
--- a/source/blender/draw/engines/gpencil/shaders/gpencil_vert.glsl
+++ b/source/blender/draw/engines/gpencil/shaders/gpencil_vert.glsl
@@ -23,39 +23,70 @@ vec2 project_to_screenspace(vec4 v)
   return ((v.xy / v.w) * 0.5 + 0.5) * sizeViewport;
 }
 
-void main()
+vec2 rotate_90deg(vec2 v)
 {
-  /* Trick to detect if a drawcall is stroke or fill. */
-  bool is_fill = (gl_InstanceID == 0);
+  /* Counter Clock-Wise. */
+  return vec2(-v.y, v.x);
+}
 
-  if (!is_fill) {
-    /* Enpoints, we discard the vertices. */
-    if (ma1 == -1 || ma2 == -1) {
-      discard_vert();
-      return;
-    }
+void stroke_vertex()
+{
+  /* Enpoints, we discard the vertices. */
+  if (ma1 == -1 || ma2 == -1) {
+    discard_vert();
+    return;
+  }
+
+  /* Avoid using a vertex attrib for quad positioning. */
+  float x = float((gl_VertexID & 1));
+  float y = float((gl_VertexID & 2) >> 1);
+
+  vec3 pos_adj = (x == 0.0) ? pos : pos3;
+  vec4 ndc_adj = point_world_to_ndc(pos_adj);
+  vec4 ndc1 = point_world_to_ndc(pos1);
+  vec4 ndc2 = point_world_to_ndc(pos2);
+
+  /* TODO case where ndc1 & ndc2 is behind camera */
+  vec2 ss_adj = project_to_screenspace(ndc_adj);
+  vec2 ss1 = project_to_screenspace(ndc1);
+  vec2 ss2 = project_to_screenspace(ndc2);
+  /* Screenspace Lines tangents. */
+  vec2 line = normalize(ss2 - ss1);
+  vec2 line_adj = normalize((x == 0.0) ? (ss1 - ss_adj) : (ss_adj - ss2));
+  /* Mitter tangent vector. */
+  vec2 miter_tan = normalize(line_adj + line);
+  float miter_dot = dot(miter_tan, line_adj);
+
+  vec2 miter = rotate_90deg(miter_tan / miter_dot);
+
+  gl_Position = (x == 0.0) ? ndc1 : ndc2;
+  gl_Position.xy += miter * (y - 0.5) * sizeViewportInv.xy * gl_Position.w * 10.0;
 
-    /* Avoid using a vertex attrib for quad positioning. */
-    float x = float((gl_VertexID & 1));
-    float y = float((gl_VertexID & 2) >> 1);
+  finalColor = vec4(0.0, 0.0, 0.0, 1.0);
+}
+
+void dots_vertex()
+{
+  /* TODO */
+}
 
-    vec4 ndc1 = point_world_to_ndc(pos1);
-    vec4 ndc2 = point_world_to_ndc(pos2);
+void fill_vertex()
+{
+  gl_Position = point_world_to_ndc(pos1);
+  gl_Position.z += 1e-2;
 
-    /* TODO case where ndc2 is behind camera */
-    vec2 ss1 = project_to_screenspace(ndc1);
-    vec2 ss2 = project_to_screenspace(ndc2);
-    vec2 perp = normalize(ss2 - ss1);
-    perp = vec2(-perp.y, perp.x);
+  finalColor = vec4(1.0);
+}
 
-    gl_Position = (x == 0.0) ? ndc1 : ndc2;
-    gl_Position.xy += perp * (y - 0.5) * sizeViewportInv.xy * gl_Position.w * 10.0;
+void main()
+{
+  /* Trick to detect if a drawcall is stroke or fill. */
+  bool is_fill = (gl_InstanceID == 0);
 
-    finalColor = vec4(0.0, 0.0, 0.0, 1.0);
+  if (!is_fill) {
+    stroke_vertex();
   }
   else {
-    gl_Position = point_world_to_ndc(pos1);
-
-    finalColor = vec4(1.0);
+    fill_vertex();
   }
 }