Region blur becomes a fixed-set dropdown (2/4/6/8/10, default 6)

Non-integer blur radii broke the rendering (the log slider mapped to
fractional values), so the control is now integer-only by design:
REGION_BLUR_OPTIONS with snap-to-nearest sanitization for any input,
same law as the bitmap resolution. The old off zone (blur 0) is gone;
stored 0s snap back into the set.

components/graph-view.tsx

@@ -83,7 +83,7 @@ import {
 	LINK_STRENGTH_RANGE,
 	NODE_SIZE_RANGE,
 	REGION_BITMAP_OPTIONS,
-	REGION_BLUR_RANGE,
+	REGION_BLUR_OPTIONS,
 	REGION_DILATION_RANGE,
 	REGION_EDGE_ALPHA_RANGE,
 	VELOCITY_DECAY_RANGE,
@@ -625,19 +625,25 @@ export function GraphView() {
 										regions: { ...cur.regions, dilation: fromSliderPosition(p, REGION_DILATION_RANGE.min, REGION_DILATION_RANGE.max) },
 									}))}
 							/>
-							<SettingSlider
-								label="Blur"
-								min={0}
-								max={100}
-								step={5}
-								value={toOffSliderPosition(regionTuning.blur, REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max)}
-								display={regionTuning.blur <= 0 ? "off" : sizeDisplay(regionTuning.blur)}
-								onChange={(p) =>
-									changeSettings((cur) => ({
-										...cur,
-										regions: { ...cur.regions, blur: fromOffSliderPosition(p, REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max) },
-									}))}
-							/>
+							<label className="flex items-center justify-between gap-2 text-[11px] text-muted-foreground">
+								<span>Blur</span>
+								<select
+									className="rounded-md border bg-background px-1.5 py-0.5 text-xs tabular-nums text-foreground"
+									value={regionTuning.blur}
+									onChange={(e) =>
+										changeSettings((cur) => ({
+											...cur,
+											regions: { ...cur.regions, blur: Number(e.target.value) },
+										}))
+									}
+								>
+									{REGION_BLUR_OPTIONS.map((o) => (
+										<option key={o} value={o}>
+											{o}
+										</option>
+									))}
+								</select>
+							</label>
 							<SettingSlider
 								label="Edge alpha"
 								min={0}

src/core/render-settings.ts

@@ -88,7 +88,9 @@ export interface RegionTuning {
 	/** Dilation half-width of the round-cap edge strokes, screen px at
 	 *  fit zoom (the expansion of the cluster skeleton). */
 	dilation: number;
-	/** Box-blur radius in bitmap px (3 passes ≈ Gaussian). 0 = off. */
+	/** Box-blur radius in bitmap px (3 passes ≈ Gaussian). Fixed set:
+	 *  see REGION_BLUR_OPTIONS (dropdown in the panel — non-integer
+	 *  radii broke the rendering, so the control is integer-only). */
 	blur: number;
 	/** Max bitmap dimension (cell = worldSpan / this). Fixed set:
 	 *  see REGION_BITMAP_OPTIONS (dropdown in the panel). */
@@ -98,16 +100,22 @@ export interface RegionTuning {
 }
 
 export const REGION_BITMAP_OPTIONS = [128, 192, 256, 384, 512] as const;
+export const REGION_BLUR_OPTIONS = [2, 4, 6, 8, 10] as const;
 
 export const DEFAULT_REGION_TUNING: RegionTuning = {
 	dilation: 28,
-	blur: 10,
+	blur: 6,
 	bitmap: 384,
 	edgeAlpha: 0.35,
 };
 
-/** Clamp/validate a region tuning. `bitmap` snaps to the nearest allowed
- *  option (it's a fixed set — a dropdown, not a free number). */
+/** Nearest member of a fixed option set (dropdowns have no free values). */
+function snapToOption(value: number, options: readonly number[]): number {
+	return options.reduce((best, o) => (Math.abs(o - value) < Math.abs(best - value) ? o : best), options[0] as number);
+}
+
+/** Clamp/validate a region tuning. `bitmap` and `blur` snap to the nearest
+ *  allowed option (they're fixed sets — dropdowns, not free numbers). */
 export function sanitizeRegionTuning(input: Partial<RegionTuning> | null | undefined): RegionTuning {
 	const d = DEFAULT_REGION_TUNING;
 	const num = (v: unknown, fallback: number): number =>
@@ -115,11 +123,8 @@ export function sanitizeRegionTuning(input: Partial<RegionTuning> | null | undef
 	const bitmap = num(input?.bitmap, d.bitmap);
 	return {
 		dilation: Math.min(Math.max(num(input?.dilation, d.dilation), REGION_DILATION_RANGE.min), REGION_DILATION_RANGE.max),
-		blur: Math.min(Math.max(num(input?.blur, d.blur), 0), REGION_BLUR_RANGE.max),
-		bitmap: REGION_BITMAP_OPTIONS.reduce(
-			(best, o) => (Math.abs(o - bitmap) < Math.abs(best - bitmap) ? o : best),
-			REGION_BITMAP_OPTIONS[0] as number,
-		),
+		blur: snapToOption(num(input?.blur, d.blur), REGION_BLUR_OPTIONS),
+		bitmap: snapToOption(bitmap, REGION_BITMAP_OPTIONS),
 		edgeAlpha: Math.min(Math.max(num(input?.edgeAlpha, d.edgeAlpha), REGION_EDGE_ALPHA_RANGE.min), 1),
 	};
 }
@@ -221,11 +226,11 @@ export const LABEL_ZOOM_MAX = 4; // slider far right: labels visible at fit zoom
 // the geometric mean of its ends), coarse 5-step tracks. Signed/zeroed
 // fields get special treatment:
 //   chargeStrength is NEGATIVE — the slider maps |charge| and displays "-x";
-//   clusterPull and region blur have an OFF zone — position 0 is exactly 0
-//   (see toOffSliderPosition), the log range starts one step in.
+//   clusterPull has an OFF zone — position 0 is exactly 0 (see
+//   toOffSliderPosition), the log range starts one step in. Blur used to
+//   have one too; it's a dropdown since 2026-09-13 (non-integers broke).
 
 export const REGION_DILATION_RANGE = { min: 7, max: 112 } as const; // gm = 28
-export const REGION_BLUR_RANGE = { min: 2.5, max: 40 } as const; // gm = 10; 0 = off
 export const REGION_EDGE_ALPHA_RANGE = { min: 0.12, max: 1 } as const; // gm ≈ 0.35
 
 export const CHARGE_RANGE = { min: -480, max: -30 } as const; // |gm| = 120

tests/graph-canvas.test.ts

@@ -150,15 +150,15 @@ describe("sanitizeRegionTuning (dev number inputs)", () => {
 	test("defaults survive untouched; partial input keeps the rest", () => {
 		const t = sanitizeRegionTuning(undefined);
 		assert.deepEqual(t, DEFAULT_REGION_TUNING);
-		const half = sanitizeRegionTuning({ blur: 0 });
-		assert.equal(half.blur, 0);
+		const half = sanitizeRegionTuning({ blur: 7.2 });
+		assert.equal(half.blur, 8); // snaps into the fixed set
 		assert.equal(half.dilation, DEFAULT_REGION_TUNING.dilation);
 	});
 
 	test("garbage clamps: NaN falls back, out-of-range clamps", () => {
 		const t = sanitizeRegionTuning({ dilation: Number.NaN, blur: -5, bitmap: 99999, edgeAlpha: 42 });
 		assert.equal(t.dilation, DEFAULT_REGION_TUNING.dilation); // NaN -> default
-		assert.equal(t.blur, 0);
+		assert.equal(t.blur, 2); // snaps into the fixed set
 		assert.equal(t.bitmap, REGION_BITMAP_OPTIONS[REGION_BITMAP_OPTIONS.length - 1]); // 99999 snaps to the largest option
 		assert.equal(t.edgeAlpha, 1);
 	});

tests/render-settings.test.ts

@@ -23,7 +23,8 @@ import {
 	LINK_DISTANCE_RANGE,
 	LINK_STRENGTH_RANGE,
 	NODE_SIZE_RANGE,
-	REGION_BLUR_RANGE,
+	REGION_BLUR_OPTIONS,
+	sanitizeRegionTuning,
 	REGION_DILATION_RANGE,
 	REGION_EDGE_ALPHA_RANGE,
 	VELOCITY_DECAY_RANGE,
@@ -109,7 +110,7 @@ describe("sanitizeRenderSettings", () => {
 			physics: { linkStrength: 99, gravity: 7, depthMode: "sideways" },
 		});
 		assert.equal(s.nodeSize, 3);
-		assert.equal(s.regions.blur, 0);
+		assert.equal(s.regions.blur, 2); // snaps into the fixed set {2,4,6,8,10}
 		assert.equal(s.regions.bitmap, 512); // snaps to the nearest fixed option
 		assert.equal(s.regions.edgeAlpha, 1);
 		assert.equal(s.regions.dilation, DEFAULT_REGION_TUNING.dilation);
@@ -188,18 +189,29 @@ describe("slider mapping (log scale, default-centered)", () => {
 		}
 		// Off-zone fields: the default sits at 50 INSIDE the on-part.
 		assert.ok(Math.abs(toOffSliderPosition(DEFAULT_PHYSICS_TUNING.clusterPull, CLUSTER_PULL_RANGE.min, CLUSTER_PULL_RANGE.max) - 50) < 0.6);
-		assert.ok(Math.abs(toOffSliderPosition(DEFAULT_REGION_TUNING.blur, REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max) - 50) < 0.6);
 	});
 
 	test("off-slider mapping: position 0 ↔ value 0; the log part round-trips", () => {
-		assert.equal(toOffSliderPosition(0, REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max), 0);
-		assert.equal(fromOffSliderPosition(0, REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max), 0);
-		const v = fromOffSliderPosition(toOffSliderPosition(10, REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max), REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max);
-		assert.ok(Math.abs(v - 10) < 1e-9);
+		assert.equal(toOffSliderPosition(0, CLUSTER_PULL_RANGE.min, CLUSTER_PULL_RANGE.max), 0);
+		assert.equal(fromOffSliderPosition(0, CLUSTER_PULL_RANGE.min, CLUSTER_PULL_RANGE.max), 0);
+		const v = fromOffSliderPosition(toOffSliderPosition(0.15, CLUSTER_PULL_RANGE.min, CLUSTER_PULL_RANGE.max), CLUSTER_PULL_RANGE.min, CLUSTER_PULL_RANGE.max);
+		assert.ok(Math.abs(v - 0.15) < 1e-9);
 		// One step in (position 5) sits just above the log floor:
 		// min * (max/min)^(5/100), NOT the floor itself (that's position 0,
 		// the off zone).
-		const stepIn = REGION_BLUR_RANGE.min * (REGION_BLUR_RANGE.max / REGION_BLUR_RANGE.min) ** (5 / 100);
-		assert.ok(Math.abs(fromOffSliderPosition(5, REGION_BLUR_RANGE.min, REGION_BLUR_RANGE.max) - stepIn) < 1e-9);
+		const stepIn = CLUSTER_PULL_RANGE.min * (CLUSTER_PULL_RANGE.max / CLUSTER_PULL_RANGE.min) ** (5 / 100);
+		assert.ok(Math.abs(fromOffSliderPosition(5, CLUSTER_PULL_RANGE.min, CLUSTER_PULL_RANGE.max) - stepIn) < 1e-9);
+	});
+
+	test("blur is a fixed set: the default is 6, non-members snap to the nearest", () => {
+		// Non-integer radii broke the rendering, so the control became a
+		// dropdown — the sanitizer enforces the set for ANY input.
+		assert.equal(DEFAULT_REGION_TUNING.blur, 6);
+		assert.equal(sanitizeRegionTuning({ blur: 3.7 }).blur, 4);
+		assert.equal(sanitizeRegionTuning({ blur: 7.2 }).blur, 8);
+		assert.equal(sanitizeRegionTuning({ blur: -5 }).blur, 2);
+		assert.equal(sanitizeRegionTuning({ blur: 99 }).blur, 10);
+		// Stored blur 0 (the old off zone) snaps back into the set.
+		assert.equal(sanitizeRegionTuning({ blur: 0 }).blur, 2);
 	});
 });