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Fix grayscale shading gradient for 2D angle coloring #76

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Fix grayscale shading gradient for 2D angle coloring #76

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87d30a4
Fix grayscale shading gradient
kryptokommunist Dec 4, 2025
511fb20
Tie grayscale shading to pattern angles
kryptokommunist Dec 4, 2025
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9 changes: 9 additions & 0 deletions javascript/index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -654,6 +654,15 @@ <h1>Doyle Spiral Studio</h1>
<details class="advanced-settings">
<summary>Advanced settings</summary>
<div class="advanced-settings-content">
<div class="field-group">
<div class="checkbox-row">
<label>
<input type="checkbox" id="shadeByAngle" name="shade_by_angle" />
Colour 2D regions by line angle (grayscale)
</label>
</div>
<p class="hint">Fills each arc group using its normalised line angle (modulo 180°) mapped from black to white.</p>
</div>
<div class="field-group">
<label for="renderTimeoutSeconds">Render timeout (seconds)</label>
<input
Expand Down
1 change: 1 addition & 0 deletions javascript/js/app.js
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@ const DEFAULTS = {
fill_pattern_type: 'lines',
fill_pattern_rect_width: 2,
fill_pattern_animation: 'radial_bloom',
shade_by_angle: false,
highlight_rim_width: 1.2,
group_outline_width: 0.6,
pattern_stroke_width: 0.5,
Expand Down
72 changes: 67 additions & 5 deletions javascript/js/doyle_spiral_engine.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1476,6 +1476,8 @@ class ArcGroup {
lineSettings = [3, 0],
drawOutline = true,
lineOffset = 0,
solidFill = null,
solidFillOpacity = 1.0,
patternType = 'lines',
rectWidth = 2,
patternSpacingOverride = null,
Expand All @@ -1498,6 +1500,17 @@ class ArcGroup {
});
return;
}
if (solidFill) {
const stroke = drawOutline ? '#000000' : 'none';
context.drawGroupOutline(outline, {
fill: solidFill,
stroke,
strokeWidth: outlineStrokeWidth,
fillOpacity: solidFillOpacity,
drawOutline,
});
return;
}
if (patternFill) {
const stroke = this.debugStroke || '#000000';
const [lineSpacingRaw, lineAngleDeg] = lineSettings;
Expand Down Expand Up @@ -2631,7 +2644,16 @@ class DoyleSpiralEngine {
};
}

_createArcGroupsForCircles(radiusToRing, spiralCenter, debugGroups, addFillPattern, drawGroupOutline, context, outlineStrokeWidth = 0) {
_createArcGroupsForCircles(
radiusToRing,
spiralCenter,
debugGroups,
addFillPattern,
drawGroupOutline,
context,
outlineStrokeWidth = 0,
shadeByAngle = false,
) {
for (const circle of this.circles) {
if (circle.intersections.length !== 6) {
continue;
Expand All @@ -2655,7 +2677,7 @@ class DoyleSpiralEngine {
const end = circle.intersections[j][0];
const steps = estimateArcSteps(circle, start, end);
const arc = new ArcElement(circle, start, end, steps, true);
if (!addFillPattern && drawGroupOutline) {
if (!addFillPattern && drawGroupOutline && !shadeByAngle) {
context.drawScaledArc(arc, { color: '#000000', width: outlineStrokeWidth });
}
group.addArc(arc);
Expand Down Expand Up @@ -2864,6 +2886,7 @@ class DoyleSpiralEngine {
fillPatternOffset = 0.0,
fillPatternType = 'lines',
fillPatternRectWidth = 2.0,
shadeByAngle = false,
highlightRimWidth = 1.2,
groupOutlineWidth = 0.6,
patternStrokeWidth = 0.5,
Expand All @@ -2885,6 +2908,7 @@ class DoyleSpiralEngine {
const patternStroke = Number.isFinite(patternStrokeWidth)
? Math.max(0, patternStrokeWidth)
: 0;
const shouldPatternFill = addFillPattern && !shadeByAngle;

const spiralCenter = Complex.ZERO;
const radiusToRing = this._computeRingIndices();
Expand All @@ -2893,16 +2917,17 @@ class DoyleSpiralEngine {
radiusToRing,
spiralCenter,
debugGroups,
addFillPattern,
shouldPatternFill,
drawGroupOutline,
context,
outlineStrokeWidth,
shadeByAngle,
);
this._drawOuterClosureArcs(
spiralCenter,
debugGroups,
redOutline,
addFillPattern,
shouldPatternFill,
drawGroupOutline,
context,
outlineStrokeWidth,
Expand Down Expand Up @@ -2956,7 +2981,7 @@ class DoyleSpiralEngine {
}
}

if (addFillPattern) {
if (shouldPatternFill) {
for (const [key, group] of this.arcGroups.entries()) {
if (key.startsWith('outer_')) {
continue;
Expand All @@ -2981,6 +3006,41 @@ class DoyleSpiralEngine {
}
}

if (shadeByAngle) {
for (const [key, group] of this.arcGroups.entries()) {
if (key.startsWith('outer_')) {
continue;
}
const ringIdx = group.ringIndex ?? 0;
const patternAngle = Number.isFinite(group.primaryPatternAngle)
? group.primaryPatternAngle
: ringIdx * fillPatternAngle;
const referenceArc = group.arcs.find(arc => arc?.start && arc?.end);
let baseAngle = Number.isFinite(patternAngle) ? patternAngle : null;
if (!Number.isFinite(baseAngle) && referenceArc) {
const dx = referenceArc.end.re - referenceArc.start.re;
const dy = referenceArc.end.im - referenceArc.start.im;
if (Number.isFinite(dx) && Number.isFinite(dy) && Math.hypot(dx, dy) > 1e-9) {
baseAngle = (Math.atan2(dy, dx) * 180) / Math.PI;
}
}
if (!Number.isFinite(baseAngle)) {
baseAngle = 0;
}
const normalizedAngle = ((baseAngle % 180) + 180) % 180;
const intensity = clamp(normalizedAngle / 179.999, 0, 1);
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@gemini-code-assist gemini-code-assist bot Dec 4, 2025

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medium

Using 180 instead of 179.999 for normalization would be clearer and avoid a magic number. Since normalizedAngle is always in the range [0, 180), dividing by 180 will produce a value in [0, 1). When multiplied by 255 and rounded, this will correctly map to the [0, 255] integer range for the color channel, effectively covering the full black-to-white spectrum as intended.

Suggested change
const intensity = clamp(normalizedAngle / 179.999, 0, 1);
const intensity = clamp(normalizedAngle / 180, 0, 1);

const channel = Math.round(intensity * 255);
const hex = channel.toString(16).padStart(2, '0');
const fillColor = `#${hex}${hex}${hex}`;
group.toSVGFill(context, {
solidFill: fillColor,
solidFillOpacity: 1,
drawOutline: drawGroupOutline,
outlineStrokeWidth: outlineStrokeWidth,
});
}
}

if (redOutline && maxIndex !== null) {
for (const [key, group] of this.arcGroups.entries()) {
if (!key.startsWith('circle_')) {
Expand Down Expand Up @@ -3160,6 +3220,7 @@ function normaliseParams(params = {}) {
fill_pattern_type: fillPatternType,
fill_pattern_rect_width: rectWidthMm,
fill_pattern_animation: normalisePatternAnimationId(params.fill_pattern_animation),
shade_by_angle: Boolean(params.shade_by_angle ?? false),
highlight_rim_width: highlightRimWidth,
group_outline_width: groupOutlineWidth,
pattern_stroke_width: patternStrokeWidth,
Expand Down Expand Up @@ -3191,6 +3252,7 @@ function renderSpiral(params = {}, overrideMode = null) {
fillPatternType: opts.fill_pattern_type,
fillPatternRectWidth: opts.fill_pattern_rect_width,
fillPatternAnimation: opts.fill_pattern_animation,
shadeByAngle: opts.shade_by_angle,
highlightRimWidth: opts.highlight_rim_width,
groupOutlineWidth: opts.group_outline_width,
patternStrokeWidth: opts.pattern_stroke_width,
Expand Down