Commit `94af22ba11`

94af22ba11829f5b5aeb59f86afccf3e689d029b

parent: 3b8c40e96a

Verified · cmc

cmc <hello@cleberg.net> · 2026-10-19 21:22 UTC

Sky chart: one fill per star bin instead of per star

Stars are grouped into half-magnitude by four-tint bins; each star keeps
its own radius.

Layout: unified · split

Packages/MoonriseKit/Sources/SkyRenderer/SkyView.swift +30 −5

         return s
     }()
-    /// Star tint from B−V colour index, kept pale.
+    /// Star colour for a tint from 0 (blue-white) to 1 (orange), kept pale.
-    func starColor(_ bv: Double) -> Color {
+    func starColor(tint t: Double) -> Color {
         if let monochromeStars { return monochromeStars }
-        let t = min(max((bv + 0.3) / 2.0, 0), 1)
         return Color(red: 0.80 + 0.20 * t, green: 0.86 - 0.06 * t, blue: 1.0 - 0.32 * t)
     }
 }
+/// Stars are filled one path per bin: half a magnitude by four tints from B−V.
+struct StarBin {
+    static let tints = 4
+    /// Magnitudes −2 to 6.5.
+    static let count = 18 * tints
+    var index: Int
+    init(index: Int) { self.index = index }
+    init(magnitude: Double, colorIndex: Double) {
+        let m = min(max(Int(((magnitude + 2) * 2).rounded()), 0), 17)
+        let t = min(max(Int(((colorIndex + 0.3) / 2 * Double(Self.tints - 1)).rounded()), 0), Self.tints - 1)
+        index = m * Self.tints + t
+    }
+    var magnitude: Double { Double(index / Self.tints) / 2 - 2 }
+    var tint: Double { Double(index % Self.tints) / Double(Self.tints - 1) }
+}
 /// Something to draw attention to, e.g. the current stop of a guided tour.
 public enum SkyHighlight: Sendable, Equatable {
     /// IAU abbreviation.
         }
     }
+    /// Each star at its own radius; colour and opacity per `StarBin`, faintest bins first.
     func drawStars(_ context: inout GraphicsContext, _ p: Projection) {
+        var bins = [Path](repeating: Path(), count: StarBin.count)
         for s in scene.stars where s.position.altitude > 0 {
             guard let pt = p.point(s.position) else { continue }
             let r = max(0.3, 2.6 - 0.42 * s.star.magnitude)
-            let opacity = min(1, max(0.25, 1.15 - 0.13 * s.star.magnitude))
+            bins[StarBin(magnitude: s.star.magnitude, colorIndex: s.star.colorIndex).index]
-            context.fill(Path(ellipseIn: CGRect(x: pt.x - r, y: pt.y - r, width: 2 * r, height: 2 * r)), with: .color(style.starColor(s.star.colorIndex).opacity(opacity)))
+                .addEllipse(in: CGRect(x: pt.x - r, y: pt.y - r, width: 2 * r, height: 2 * r))
+        }
+        for i in bins.indices.reversed() where !bins[i].isEmpty {
+            let bin = StarBin(index: i)
+            let opacity = min(1, max(0.25, 1.15 - 0.13 * bin.magnitude))
+            context.fill(bins[i], with: .color(style.starColor(tint: bin.tint).opacity(opacity)))
         }
     }

Packages/MoonriseKit/Tests/SkyRendererTests/SkyRenderTests.swift +12

	@@ -56,6 +56,18 @@ let evening = Date(timeIntervalSince1970: 1_792_202_400) // 2026-10-17T02:00:00Z
56	#expect(scene.object(at: a, projection: p) == .constellation("Aql"))	56	#expect(scene.object(at: a, projection: p) == .constellation("Aql"))
57	}	57	}
58		58
		59	@Test func starBinsStayCloseToEachStar() {
		60	var used = Set<Int>()
		61	for star in Catalog.stars where star.magnitude <= 6.5 {
		62	let bin = StarBin(magnitude: star.magnitude, colorIndex: star.colorIndex)
		63	#expect(abs(bin.magnitude - star.magnitude) <= 0.25, "HR \(star.hr)")
		64	let tint = min(max((star.colorIndex + 0.3) / 2, 0), 1)
		65	#expect(abs(bin.tint - tint) <= 1.0 / 6 + 1e-9, "HR \(star.hr)")
		66	used.insert(bin.index)
		67	}
		68	#expect(used.allSatisfy { (0..<StarBin.count).contains($0) })
		69	}
		70
59	@MainActor	71	@MainActor
60	@Test func nightStyleRenders() throws {	72	@Test func nightStyleRenders() throws {
61	let scene = try SkyScene(date: evening, observer: chicago)	73	let scene = try SkyScene(date: evening, observer: chicago)

Commit 94af22ba11

Commit `94af22ba11`