1 files changed, 28 insertions, 0 deletions
diff --git a/src/opengl/util/radial_brush.glsl b/src/opengl/util/radial_brush.glsl
new file mode 100644
index 0000000000..84bec62e65
--- /dev/null
+++ b/src/opengl/util/radial_brush.glsl
@@ -0,0 +1,28 @@
+uniform sampler1D palette;
+uniform vec2 fmp;
+uniform float fmp2_m_radius2;
+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;
+    vec2 B = fmp;
+
+    float a = fmp2_m_radius2;
+    float b = 2.0*dot(A, B);
+    float c = -dot(A, A);
+
+    float val = (-b + sqrt(b*b - 4.0*a*c)) / (2.0*a);
+
+    return texture1D(palette, val);
+}
+