From a63bc8a71e056572038db6a5e10c22dcf86d047d Mon Sep 17 00:00:00 2001
From: Dave Smith <david.smith@47deg.com>
Date: Wed, 27 Nov 2024 20:50:33 +0000
Subject: [PATCH] Fixed #78: Add SDF helpers

---
 .../src/test/scala/ultraviolet/sdfTests.scala | 113 ++++++++++++++++++
 .../src/main/scala/ultraviolet/sdf.scala      |  26 ++++
 2 files changed, 139 insertions(+)
 create mode 100644 ultraviolet/js/src/test/scala/ultraviolet/sdfTests.scala
 create mode 100644 ultraviolet/shared/src/main/scala/ultraviolet/sdf.scala

diff --git a/ultraviolet/js/src/test/scala/ultraviolet/sdfTests.scala b/ultraviolet/js/src/test/scala/ultraviolet/sdfTests.scala
new file mode 100644
index 0000000..908ecc7
--- /dev/null
+++ b/ultraviolet/js/src/test/scala/ultraviolet/sdfTests.scala
@@ -0,0 +1,113 @@
+package ultraviolet
+
+import ultraviolet.syntax.*
+
+class sdfTests extends munit.FunSuite {
+
+  test("A circle SDF") {
+
+    val p = vec2(1.0f, 0.0f)
+
+    val actual =
+      ultraviolet.sdf.circle(p, 1.0f)
+
+    val expected =
+      0.0f
+
+    assert(closeEnough(clue(actual), clue(expected)))
+  }
+
+  test("Circle SDF acceptance test") {
+    inline def fragment: Shader[Unit, Float] =
+      Shader { _ =>
+
+        import ultraviolet.sdf.*
+
+        def proxy: (vec2, Float) => Float = (p, r) => circle(p, r)
+
+        proxy(vec2(0.5f), 1.5f)
+      }
+
+    val actual =
+      fragment.toGLSL[WebGL2].toOutput.code
+
+    // DebugAST.toAST(fragment)
+
+    assertEquals(
+      actual,
+      s"""
+      |float def0(in vec2 p,in float r){
+      |  return length(p)-r;
+      |}
+      |def0(vec2(0.5),1.5);
+      |""".stripMargin.trim
+    )
+  }
+
+  test("Square SDF acceptance test") {
+    inline def fragment: Shader[Unit, Float] =
+      Shader { _ =>
+
+        import ultraviolet.sdf.*
+
+        def proxy: (vec2, vec2) => Float = (p, b) => square(p, b)
+
+        proxy(vec2(0.5f), vec2(1.5f))
+      }
+
+    val actual =
+      fragment.toGLSL[WebGL2].toOutput.code
+
+    // DebugAST.toAST(fragment)
+
+    assertEquals(
+      actual,
+      s"""
+      |float def0(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);
+      |}
+      |def0(vec2(0.5),vec2(1.5));
+      |""".stripMargin.trim
+    )
+  }
+
+  test("Star with five points SDF acceptance test") {
+    inline def fragment: Shader[Unit, Float] =
+      Shader { _ =>
+
+        import ultraviolet.sdf.*
+        
+        def proxy: (vec2, Float, Float) => Float = (p, r, rf) => star(p, r, rf)
+
+        proxy(vec2(0.5f), 1.5f, 1.0f)
+      }
+
+    val actual =
+      fragment.toGLSL[WebGL2].toOutput.code
+
+    // DebugAST.toAST(fragment)
+
+    assertEquals(
+      actual,
+      s"""
+      |float def0(in vec2 p,in float r,in float rf){
+      |  vec2 k1=vec2(0.80901700258255,-0.5877852439880371);
+      |  vec2 k2=vec2(-k1.x,k1.y);
+      |  vec2 p2=vec2(abs(p.x),p.y);
+      |  p2=p2-((2.0*max(dot(k1,p2),0.0))*k1);
+      |  p2=p2-((2.0*max(dot(k2,p2),0.0))*k2);
+      |  p2=vec2(abs(p2.x),p2.y-r);
+      |  vec2 ba=(rf*(vec2(-k1.y,k1.x)))-vec2(0.0,1.0);
+      |  float h=clamp(dot(p2,ba)/dot(ba,ba),0.0,r);
+      |  return (length(p2-(ba*h)))*(sign((p2.y*ba.x)-(p2.x*ba.y)));
+      |}
+      |def0(vec2(0.5),1.5,1.0);
+      |""".stripMargin.trim
+    )
+  }
+
+  def closeEnough(a: Float, b: Float): Boolean =
+    Math.abs(Math.abs(a) - Math.abs(b)) < 0.01f
+
+}
diff --git a/ultraviolet/shared/src/main/scala/ultraviolet/sdf.scala b/ultraviolet/shared/src/main/scala/ultraviolet/sdf.scala
new file mode 100644
index 0000000..231d296
--- /dev/null
+++ b/ultraviolet/shared/src/main/scala/ultraviolet/sdf.scala
@@ -0,0 +1,26 @@
+package ultraviolet
+
+import ultraviolet.syntax.*
+
+object sdf:
+
+  inline def circle(point: vec2, radius: Float): Float =
+    length(point) - radius
+
+  inline def square(point: vec2, halfSize: vec2): Float =
+    val d = abs(point) - halfSize
+    length(max(d, 0.0f)) + min(max(d.x, d.y), 0.0f)
+
+  inline def star(point: vec2, radius: Float, innerRadius: Float): Float =
+    val k1: vec2 = vec2(0.809016994375f, -0.587785252292f)
+    val k2: vec2 = vec2(-k1.x, k1.y)
+    var p2       = vec2(abs(point.x), point.y)
+
+    p2 = p2 - 2.0f * max(dot(k1, p2), 0.0f) * k1
+    p2 = p2 - 2.0f * max(dot(k2, p2), 0.0f) * k2
+    p2 = vec2(abs(p2.x), p2.y - radius)
+
+    val ba: vec2 = innerRadius * vec2(-k1.y, k1.x) - vec2(0.0f, 1.0f)
+    val h: Float = clamp(dot(p2, ba) / dot(ba, ba), 0.0f, radius)
+
+    length(p2 - ba * h) * sign(p2.y * ba.x - p2.x * ba.y)