Add SDFBlend filter to orx-jumpflood

orx-jumpflood/src/main/kotlin/ops/SDFOps.kt

@@ -84,3 +84,19 @@ class SDFOnion : Filter(filterShaderFromUrl(resourceUrl("/shaders/gl3/ops/sdf-on
         super.apply(source, target)
     }
 }
+
+class SDFBlend : Filter(filterShaderFromUrl(resourceUrl("/shaders/gl3/ops/sdf-blend.frag"))) {
+    var factor: Double by parameters
+
+    init {
+        factor = 0.5
+    }
+
+    override fun apply(source: Array<ColorBuffer>, target: Array<ColorBuffer>) {
+        require(target[0].type == ColorType.FLOAT16 || target[0].type == ColorType.FLOAT32) {
+            "needs a floating point target"
+        }
+        super.apply(source, target)
+    }
+
+}

orx-jumpflood/src/main/resources/shaders/gl3/ops/sdf-blend.frag

@@ -0,0 +1,15 @@
+#version 330 core
+
+uniform sampler2D tex0;// signed distance
+uniform sampler2D tex1;// signed distance
+uniform float factor;
+
+in vec2 v_texCoord0;
+out vec4 o_color;
+
+void main() {
+    float d0 = texture(tex0, v_texCoord0).r;
+    float d1 = texture(tex1, v_texCoord0).r;
+    float d = mix(d0, d1, factor);
+    o_color = vec4(d, 0.0, 0.0, 1.0);
+}