[orx-shader-phrases] Add common SDF utility phrases

Introduce several new shader utility phrases for Signed Distance Functions (SDF), including operations (e.g., union, intersection, XOR), primitive shapes (e.g., box, circle, heart, segment), and supporting functions like `dot2`.

orx-shader-phrases/src/commonMain/kotlin/sdf/SDFPhrases.kt

@@ -2,6 +2,80 @@ package org.openrndr.extra.shaderphrases.sdf
 
 import kotlin.math.PI
 
+const val dot2Phrase = """#ifndef SP_DOT2
+#define SP_DOT2
+float dot2(vec2 v) { return dot(v,v); }
+#endif"""
+
+const val opXorPhrase = """#ifndef SP_OPXOR
+#define SP_OPXOR
+float opXor( float a, float b ) {
+    return max( min(a,b), -max(a,b) );
+}
+#endif    
+"""
+
+const val opUnionPhrase = """#ifndef SP_OPUNION
+#define SP_OPUNION
+float opUnion( float d1, float d2 ){
+    return min(d1,d2);
+}
+#endif"""
+
+const val opIntersectionPhrase = """#ifndef SP_OPINTERSECTION
+#define SP_OPINTERSECTION
+float opIntersection( float d1, float d2 ){
+    return max(d1,d2);
+}"""
+
+const val opSubtractionPhrase = """#ifndef SP_OPSUBTRACTION
+#define SP_OPSUBTRACTION
+float opSubtraction( float d1, float d2 ){
+    return max(-d1,d2);
+}
+"""
+
+const val sdBoxPhrase = """#ifndef SP_SDBOX
+#define SP_SDBOX
+float sdBox(in vec2 p, in vec2 b) {
+    vec2 d = abs(p) - b;
+    return length(max(d, 0.0)) + min(max(d.x, d.y), 0.0);
+}
+#endif
+"""
+
+const val sdCirclePhrase = """#ifndef SP_SDCIRCLE
+#define SP_SDCIRCLE
+float sdCircle(in vec2 p, in float r) {
+    return length(p) - r;
+}
+#endif
+"""
+
+const val sdSegmentPhrase = """#ifndef SP_SDSEGMENT
+#define SP_SDSEGMENT
+float sdSegment(in vec2 p, in vec2 a, in vec2 b) {
+    vec2 pa = p - a;
+    vec2 ba = b - a;
+    float h = clamp( dot(pa,ba)/dot(ba,ba), 0.0, 1.0 );
+    return length( pa - ba*h );
+}    
+#endif
+"""
+
+const val sdHeartPhrase = """#ifndef SP_SDHEART
+#define SP_SDHEART
+$dot2Phrase
+float sdHeart(in vec2 p) {
+    p.x = abs(p.x);
+    if (p.y+p.x>1.0) {
+        return sqrt(dot2(p-vec2(0.25,0.75))) - sqrt(2.0)/4.0;
+    }
+    return sqrt(min(dot2(p-vec2(0.00,1.00)), dot2(p-0.5*max(p.x+p.y,0.0)))) * sign(p.x-p.y);    
+}
+#endif
+"""
+
 const val sdEllipsePhrase = """#ifndef SP_SDELLIPSE
 #define SP_SDELLIPSE
 float sdEllipse( in vec2 p, in vec2 ab ) {