1 files changed, 23 insertions, 0 deletions
diff --git a/src/opengl/util/texture_brush.glsl b/src/opengl/util/texture_brush.glsl
new file mode 100644
index 0000000..93865b8
--- /dev/null
+++ b/src/opengl/util/texture_brush.glsl
@@ -0,0 +1,23 @@
+uniform sampler2D brush_texture;
+uniform vec2 inv_brush_texture_size;
+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 coords = hcoords.xy / hcoords.z;
+
+    coords *= inv_brush_texture_size;
+
+    coords.y = -coords.y;
+
+    return texture2D(brush_texture, coords);
+}