fun with dots

src/game/shaders/frag.sc

@@ -3,16 +3,57 @@ $input v_uv0
 
 #include "common.sh"
 
-float circle(vec2 uv, vec2 center, float size)
+float circle(vec2 uv, float radius)
 {
-	vec2 relPos = uv - center;
-	float distSq = relPos.x * relPos.x + relPos.y * relPos.y;
-	return sqrt(distSq) <= size ? 1.0 : 0.0;
+	radius *= 0.8;
+	float distSq = uv.x * uv.x + uv.y * uv.y;
+	float result = distSq > radius * radius;
+	return 1.0 - result;
+}
+
+float circles(vec2 uv, float level, float subLevel)
+{
+	vec2 offsetUv = uv + (0.5 + level * 0.5);
+	vec2 bigUv = (offsetUv % 1.0) - 0.5;
+	float base = 0.0;
+	if (subLevel > 0.25)
+	{
+		vec2 smallUv = (((offsetUv + 0.25) % 2.0) * 2.0) - 0.5;
+		base += circle(smallUv, 0.5);
+	}
+	if (subLevel > 0.5)
+	{
+		vec2 smallUv = (((offsetUv - 0.75) % 2.0) * 2.0) - 0.5;
+		base += circle(smallUv, 0.5);
+	}
+	if (subLevel > 0.75)
+	{
+		vec2 smallUv = (((offsetUv + 1.25) % 2.0) * 2.0) - 0.5;
+		base += circle(smallUv, 0.5);
+	}
+	base += circle(bigUv, lerp(0.25, 0.5, 1.0 - subLevel));
+
+	return base;
 }
 
 void main()
 {
-	// gl_FragColor = circle(v_uv0, vec2(0.5, 0.5), 1.0);
-	float color = v_uv0.x < 0.5 && v_uv0.y < 0.5;
-	gl_FragColor = vec4(color, color, color, 1.0);
+	float2 dx = ddx(v_uv0);
+	float2 dy = ddy(v_uv0);
+	float2x2 mat = float2x2(dx, dy);
+	float4 vectorized = float4(dx, dy);
+	float qq = dot(vectorized, vectorized);
+	float rr = determinant(mat);
+	float discriminantSqr = max(0.0, qq*qq - 4.0*rr*rr);
+	float discriminant = sqrt(discriminantSqr);	
+	float2 freq = sqrt(float2(qq + discriminant, qq - discriminant) / 2.0);
+
+	float spacing = freq.y * exp2(2.0);
+	spacing *= 128.0; // TODO: check reference to see how to calculate this!
+	float spacingLog = log2(spacing);
+	int patternScaleLevel = floor(spacingLog);
+	float patternFractional = spacingLog - patternScaleLevel;
+	
+	vec2 uv = v_uv0 * exp2(patternScaleLevel);
+	gl_FragColor = circles(uv, patternScaleLevel, patternFractional);
 }