Added star demo

build.sc

@@ -42,6 +42,11 @@ object shaders extends mill.Module {
         makeIndigoOptions("PulsingBox")
     }
 
+    object star extends shadermodule.ShaderModule {
+      val indigoOptions: IndigoOptions =
+        makeIndigoOptions("StarDemo")
+    }
+
   }
 
   object noise extends mill.Module {

shaders/demos/star/src/StarDemo.scala

@@ -0,0 +1,123 @@
+import indigo.*
+
+import scala.scalajs.js.annotation.*
+import generated.*
+
+@JSExportTopLevel("IndigoGame")
+object StarDemo extends IndigoShader:
+
+  val config: GameConfig =
+    Config.config.noResize
+
+  val assets: Set[AssetType]      = Assets.assets.assetSet
+  val channel0: Option[AssetPath] = None
+  val channel1: Option[AssetPath] = None
+  val channel2: Option[AssetPath] = None
+  val channel3: Option[AssetPath] = None
+
+  val shader: Shader =
+    CustomShader.shader
+
+object CustomShader:
+
+  val shader: Shader =
+    UltravioletShader.entityFragment(
+      ShaderId("shader"),
+      EntityShader.fragment[FragmentEnv](fragment, FragmentEnv.reference)
+    )
+
+  import ultraviolet.syntax.*
+
+  inline def fragment: Shader[FragmentEnv, Unit] =
+    Shader[FragmentEnv] { env =>
+
+      // Calculate the distance of the point p from the radius r.
+      def sdCircle(p: vec2, r: Float): Float =
+        length(p) - r
+
+      /** Calculate the distance of the point p from the star with radius r, and
+        * a relative value rf controlling the depth of the stars points.
+        */
+      def sdStar5(p: vec2, r: Float, rf: Float): Float =
+        @const val k1: vec2 = vec2(0.809016994375f, -0.587785252292f)
+        @const val k2: vec2 = vec2(-k1.x, k1.y)
+
+        var p2 = vec2(abs(p.x), p.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 - r)
+
+        val ba: vec2 = rf * vec2(-k1.y, k1.x) - vec2(0.0f, 1.0f)
+        val h: Float = clamp(dot(p2, ba) / dot(ba, ba), 0.0f, r)
+
+        length(p2 - ba * h) * sign(p2.y * ba.x - p2.x * ba.y)
+
+      def drawSdfCircle(sdf: Float): vec4 =
+        val col = step(0.0f, -sdf)
+
+        vec4(vec3(col), 1.0f)
+
+      def drawSdfCircle2(sdf: Float): vec4 =
+        val col = cos(abs(sdf) * 100.0f)
+
+        vec4(vec3(col), 1.0f)
+
+      def drawStarStep1(sdf: Float): vec4 =
+        val col = step(0.0f, -sdf)
+
+        vec4(vec3(col), 1.0f)
+
+      def drawStarStep2(sdf: Float): vec4 =
+        val col = 1.0f - step(0.025f, abs(sdf))
+
+        vec4(vec3(col), 1.0f)
+
+      def drawStarStep3(sdf: Float): vec4 =
+        val col = smoothstep(0.8f, 1.0f, 1.0f - sdf) * 0.5f
+
+        vec4(vec3(col), 1.0f)
+
+      def drawStarStep4(sdf: Float): vec4 =
+        val glowAmount     = smoothstep(0.9f, 1.0f, 1.0f - sdf) * 0.3f
+        val starFillAmount = step(0.0f, -sdf)
+        val strokeAmount   = 1.0f - step(0.025f, abs(sdf))
+
+        val orange      = vec4(1.0f, 0.75f, 0.0f, 1.0f)
+        val yellow      = vec4(1.0f, 1.0f, 0.0f, 1.0f)
+        val lightYellow = vec4(1.0f, 1.0f, 0.75f, 1.0f)
+
+        val glowColour = vec4(orange.rgb * glowAmount, glowAmount)
+        val starColour = vec4(
+          mix(
+            yellow.rgb,
+            orange.rgb,
+            smoothstep(0.0f, 0.1f, abs(sdf))
+          ) * starFillAmount,
+          starFillAmount
+        )
+        val strokeColour = vec4(lightYellow.rgb * strokeAmount, strokeAmount)
+
+        mix(
+          glowColour,
+          mix(
+            starColour,
+            strokeColour,
+            strokeAmount
+          ),
+          starFillAmount
+        )
+
+      def fragment(color: vec4): vec4 =
+        // val circleSDF = sdCircle(env.UV - 0.5f, 0.25f)
+
+        // drawSdfCircle(circleSDF)  // Simple SDF
+        // drawSdfCircle2(circleSDF) // Using it as a cos wave
+
+        val starSDF = sdStar5((env.UV - 0.5f) * vec2(1.0f, -1.0f), 0.25f, 0.6f)
+
+        // drawStarStep1(starSDF) // SDF
+        // drawStarStep2(starSDF) // Annular
+        // drawStarStep3(starSDF) // Glow
+        drawStarStep4(starSDF) // Putting it all together in color
+    }