1 files changed, 25 insertions, 0 deletions
diff --git a/src/quickshapes/shaders/radialgradient.frag b/src/quickshapes/shaders/radialgradient.frag
new file mode 100644
index 0000000000..0f503bc0f7
--- /dev/null
+++ b/src/quickshapes/shaders/radialgradient.frag
@@ -0,0 +1,25 @@
+uniform sampler2D gradTabTexture;
+uniform lowp float opacity;
+
+uniform highp vec2 focalToCenter;
+uniform highp float centerRadius;
+uniform highp float focalRadius;
+
+varying highp vec2 coord;
+
+void main()
+{
+    highp float rd = centerRadius - focalRadius;
+    highp float b = 2.0 * (rd * focalRadius + dot(coord, focalToCenter));
+    highp float fmp2_m_radius2 = -focalToCenter.x * focalToCenter.x - focalToCenter.y * focalToCenter.y + rd * rd;
+    highp float inverse_2_fmp2_m_radius2 = 1.0 / (2.0 * fmp2_m_radius2);
+    highp float det = b * b - 4.0 * fmp2_m_radius2 * ((focalRadius * focalRadius) - dot(coord, coord));
+    lowp vec4 result = vec4(0.0);
+    if (det >= 0.0) {
+        highp float detSqrt = sqrt(det);
+        highp float w = max((-b - detSqrt) * inverse_2_fmp2_m_radius2, (-b + detSqrt) * inverse_2_fmp2_m_radius2);
+        if (focalRadius + w * (centerRadius - focalRadius) >= 0.0)
+            result = texture2D(gradTabTexture, vec2(w, 0.5)) * opacity;
+    }
+    gl_FragColor = result;
+}