1 files changed, 98 insertions, 0 deletions
diff --git a/source/blender/draw/engines/overlay/shaders/edit_uv_stretching_vert.glsl b/source/blender/draw/engines/overlay/shaders/edit_uv_stretching_vert.glsl
new file mode 100644
index 00000000000..ce97f1e27ac
--- /dev/null
+++ b/source/blender/draw/engines/overlay/shaders/edit_uv_stretching_vert.glsl
@@ -0,0 +1,98 @@
+#pragma BLENDER_REQUIRE(common_view_lib.glsl)
+
+uniform vec2 aspect;
+in vec2 pos;
+
+#ifdef STRETCH_ANGLE
+in vec2 uv_angles;
+in float angle;
+
+#else
+in float ratio;
+uniform float totalAreaRatio;
+uniform float totalAreaRatioInv;
+
+#endif
+
+noperspective out vec4 finalColor;
+
+vec3 weight_to_rgb(float weight)
+{
+  vec3 r_rgb;
+  float blend = ((weight / 2.0) + 0.5);
+
+  if (weight <= 0.25) { /* blue->cyan */
+    r_rgb[0] = 0.0;
+    r_rgb[1] = blend * weight * 4.0;
+    r_rgb[2] = blend;
+  }
+  else if (weight <= 0.50) { /* cyan->green */
+    r_rgb[0] = 0.0;
+    r_rgb[1] = blend;
+    r_rgb[2] = blend * (1.0 - ((weight - 0.25) * 4.0));
+  }
+  else if (weight <= 0.75) { /* green->yellow */
+    r_rgb[0] = blend * ((weight - 0.50) * 4.0);
+    r_rgb[1] = blend;
+    r_rgb[2] = 0.0;
+  }
+  else if (weight <= 1.0) { /* yellow->red */
+    r_rgb[0] = blend;
+    r_rgb[1] = blend * (1.0 - ((weight - 0.75) * 4.0));
+    r_rgb[2] = 0.0;
+  }
+  else {
+    /* exceptional value, unclamped or nan,
+     * avoid uninitialized memory use */
+    r_rgb[0] = 1.0;
+    r_rgb[1] = 0.0;
+    r_rgb[2] = 1.0;
+  }
+
+  return r_rgb;
+}
+
+#define M_PI 3.1415926535897932
+
+vec2 angle_to_v2(float angle)
+{
+  return vec2(cos(angle), sin(angle));
+}
+
+/* Adapted from BLI_math_vector.h */
+float angle_normalized_v2v2(vec2 v1, vec2 v2)
+{
+  v1 = normalize(v1 * aspect);
+  v2 = normalize(v2 * aspect);
+  /* this is the same as acos(dot_v3v3(v1, v2)), but more accurate */
+  bool q = (dot(v1, v2) >= 0.0);
+  vec2 v = (q) ? (v1 - v2) : (v1 + v2);
+  float a = 2.0 * asin(length(v) / 2.0);
+  return (q) ? a : M_PI - a;
+}
+
+float area_ratio_to_stretch(float ratio, float tot_ratio, float inv_tot_ratio)
+{
+  ratio *= (ratio > 0.0f) ? tot_ratio : -inv_tot_ratio;
+  return (ratio > 1.0f) ? (1.0f / ratio) : ratio;
+}
+
+void main()
+{
+  vec3 world_pos = point_object_to_world(vec3(pos, 0.0));
+  gl_Position = point_world_to_ndc(world_pos);
+
+#ifdef STRETCH_ANGLE
+  vec2 v1 = angle_to_v2(uv_angles.x * M_PI);
+  vec2 v2 = angle_to_v2(uv_angles.y * M_PI);
+  float uv_angle = angle_normalized_v2v2(v1, v2) / M_PI;
+  float stretch = 1.0 - abs(uv_angle - angle);
+  stretch = stretch;
+  stretch = 1.0 - stretch * stretch;
+#else
+  float stretch = 1.0 - area_ratio_to_stretch(ratio, totalAreaRatio, totalAreaRatioInv);
+
+#endif
+
+  finalColor = vec4(weight_to_rgb(stretch), 1.0);
+}