1 files changed, 27 insertions, 0 deletions
diff --git a/src/opengl/util/conical_brush.glsl b/src/opengl/util/conical_brush.glsl
new file mode 100644
index 0000000000..b3ec1d7efe
--- /dev/null
+++ b/src/opengl/util/conical_brush.glsl
@@ -0,0 +1,27 @@
+// conical gradient shader
+#define M_PI  3.14159265358979323846
+uniform sampler1D palette;
+uniform float angle;
+uniform vec3 inv_matrix_m0;
+uniform vec3 inv_matrix_m1;
+uniform vec3 inv_matrix_m2;
+
+vec4 brush()
+{
+    mat3 mat;
+
+    mat[0] = inv_matrix_m0;
+    mat[1] = inv_matrix_m1;
+    mat[2] = inv_matrix_m2;
+
+    vec3 hcoords = mat * vec3(gl_FragCoord.xy, 1);
+    vec2 A = hcoords.xy / hcoords.z;
+
+/*     float val = fmod((atan2(-A.y, A.x) + angle) / (2.0 * M_PI), 1); */
+    if (abs(A.y) == abs(A.x))
+ 	A.y += 0.002;
+    float t = (atan(-A.y, A.x) + angle) / (2.0 * M_PI);
+    float val = t - floor(t);
+    return texture1D(palette, val);
+}
+