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Fix visual artifact for line-dasharray #9246

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merged 2 commits into from
Feb 5, 2020
Merged

Fix visual artifact for line-dasharray #9246

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2bcb4e5
Fix artifact for zero-lenghted dash array
karimnaaji Jan 29, 2020
50aa4da
combine consecutive dashes and parts
ansis Feb 5, 2020
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160 changes: 107 additions & 53 deletions src/render/line_atlas.js
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ class LineAtlas {
nextRow: number;
bytes: number;
data: Uint8Array;
positions: {[string]: any};
dashEntry: {[string]: any};
dirty: boolean;
texture: WebGLTexture;

Expand All @@ -30,7 +30,7 @@ class LineAtlas {

this.data = new Uint8Array(this.width * this.height);

this.positions = {};
this.dashEntry = {};
}

/**
Expand All @@ -44,80 +44,134 @@ class LineAtlas {
getDash(dasharray: Array<number>, round: boolean) {
const key = dasharray.join(",") + String(round);

if (!this.positions[key]) {
this.positions[key] = this.addDash(dasharray, round);
if (!this.dashEntry[key]) {
this.dashEntry[key] = this.addDash(dasharray, round);
}
return this.positions[key];
return this.dashEntry[key];
}

addDash(dasharray: Array<number>, round: boolean) {
getDashRanges(dasharray: Array<number>, lineAtlasWidth: number, stretch: number) {
// If dasharray has an odd length, both the first and last parts
// are dashes and should be joined seamlessly.
const oddDashArray = dasharray.length % 2 === 1;

const n = round ? 7 : 0;
const height = 2 * n + 1;
const offset = 128;
const ranges = [];

if (this.nextRow + height > this.height) {
warnOnce('LineAtlas out of space');
return null;
}
let left = oddDashArray ? -dasharray[dasharray.length - 1] * stretch : 0;
let right = dasharray[0] * stretch;
let isDash = true;

let length = 0;
for (let i = 0; i < dasharray.length; i++) {
length += dasharray[i];
ranges.push({left, right, isDash, zeroLength: dasharray[0] === 0});

let currentDashLength = dasharray[0];
for (let i = 1; i < dasharray.length; i++) {
isDash = !isDash;

const dashLength = dasharray[i];
left = currentDashLength * stretch;
currentDashLength += dashLength;
right = currentDashLength * stretch;

ranges.push({left, right, isDash, zeroLength: dashLength === 0});
}

const stretch = this.width / length;
const halfWidth = stretch / 2;
return ranges;
}

// If dasharray has an odd length, both the first and last parts
// are dashes and should be joined seamlessly.
const oddLength = dasharray.length % 2 === 1;
addRoundDash(ranges: Object, stretch: number, n: number) {
const halfStretch = stretch / 2;

for (let y = -n; y <= n; y++) {
const row = this.nextRow + n + y;
const index = this.width * row;

let left = oddLength ? -dasharray[dasharray.length - 1] : 0;
let right = dasharray[0];
let partIndex = 1;
let currIndex = 0;
let range = ranges[currIndex];

for (let x = 0; x < this.width; x++) {
if (x / range.right > 1) { range = ranges[++currIndex]; }

while (right < x / stretch) {
left = right;
right = right + dasharray[partIndex];

if (oddLength && partIndex === dasharray.length - 1) {
right += dasharray[0];
}

partIndex++;
}

const distLeft = Math.abs(x - left * stretch);
const distRight = Math.abs(x - right * stretch);
const dist = Math.min(distLeft, distRight);
const inside = (partIndex % 2) === 1;
const distLeft = Math.abs(x - range.left);
const distRight = Math.abs(x - range.right);
const minDist = Math.min(distLeft, distRight);
let signedDistance;

if (round) {
// Add circle caps
const distMiddle = n ? y / n * (halfWidth + 1) : 0;
if (inside) {
const distEdge = halfWidth - Math.abs(distMiddle);
signedDistance = Math.sqrt(dist * dist + distEdge * distEdge);
} else {
signedDistance = halfWidth - Math.sqrt(dist * dist + distMiddle * distMiddle);
}
const distMiddle = y / n * (halfStretch + 1);
if (range.isDash) {
const distEdge = halfStretch - Math.abs(distMiddle);
signedDistance = Math.sqrt(minDist * minDist + distEdge * distEdge);
} else {
signedDistance = (inside ? 1 : -1) * dist;
signedDistance = halfStretch - Math.sqrt(minDist * minDist + distMiddle * distMiddle);
}

this.data[index + x] = Math.max(0, Math.min(255, signedDistance + offset));
this.data[index + x] = Math.max(0, Math.min(255, signedDistance + 128));
}
}
}

addRegularDash(ranges: Object) {

// Collapse any zero-length range
// Collapse neighbouring same-type parts into a single part
for (let i = ranges.length - 1; i >= 0; --i) {
const part = ranges[i];
const next = ranges[i + 1];
if (part.zeroLength) {
ranges.splice(i, 1);
} else if (next && next.isDash === part.isDash) {
next.left = part.left;
ranges.splice(i, 1);
}
}

const pos = {
// Combine the first and last parts if possible
const first = ranges[0];
const last = ranges[ranges.length - 1];
if (first.isDash === last.isDash) {
first.left = last.left - this.width;
last.right = first.right + this.width;
}

const index = this.width * this.nextRow;
let currIndex = 0;
let range = ranges[currIndex];

for (let x = 0; x < this.width; x++) {
if (x / range.right > 1) {
range = ranges[++currIndex];
}

const distLeft = Math.abs(x - range.left);
const distRight = Math.abs(x - range.right);

const minDist = Math.min(distLeft, distRight);
const signedDistance = range.isDash ? minDist : -minDist;

this.data[index + x] = Math.max(0, Math.min(255, signedDistance + 128));
}
}

addDash(dasharray: Array<number>, round: boolean) {
const n = round ? 7 : 0;
const height = 2 * n + 1;

if (this.nextRow + height > this.height) {
warnOnce('LineAtlas out of space');
return null;
}

let length = 0;
for (let i = 0; i < dasharray.length; i++) { length += dasharray[i]; }

const stretch = this.width / length;
const ranges = this.getDashRanges(dasharray, this.width, stretch);

if (round) {
this.addRoundDash(ranges, stretch, n);
} else {
this.addRegularDash(ranges);
}

const dashEntry = {
y: (this.nextRow + n + 0.5) / this.height,
height: 2 * n / this.height,
width: length
Expand All @@ -126,7 +180,7 @@ class LineAtlas {
this.nextRow += height;
this.dirty = true;

return pos;
return dashEntry;
}

bind(context: Context) {
Expand Down
Binary file added test/integration/render-tests/line-dasharray/zero-length-gap/expected.png
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108 changes: 108 additions & 0 deletions test/integration/render-tests/line-dasharray/zero-length-gap/style.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,108 @@
{
"version": 8,
"metadata": {
"test": {
"width": 128,
"height": 132
}
},
"zoom": 0,
"sources": {
"geojson": {
"type": "geojson",
"data": {
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"properties": {
"width": 2,
"offset": 0
},
"geometry": {
"type": "LineString",
"coordinates": [ [ -40, -18 ], [ 40, -18 ] ]
}
},
{
"type": "Feature",
"properties": {
"width": 4,
"offset": 0
},
"geometry": {
"type": "LineString",
"coordinates": [ [ -40, -10 ], [ 40, -10 ] ]
}
},
{
"type": "Feature",
"properties": {
"width": 6,
"offset": 0
},
"geometry": {
"type": "LineString",
"coordinates": [ [ -40, -2 ], [ 40, -2 ] ]
}
}
]
}
}
},
"layers": [
{
"id": "road0",
"type": "line",
"source": "geojson",
"paint": {
"line-width": ["get", "width"],
"line-offset": ["+", ["get", "offset"], 32],
"line-dasharray": [1, 0, 1, 1],
"line-color": "red"
}
},
{
"id": "road1",
"type": "line",
"source": "geojson",
"paint": {
"line-width": ["get", "width"],
"line-offset": ["-", ["get", "offset"], 32],
"line-dasharray": [1, 1, 0],
"line-color": "green"
}
},
{
"id": "road2",
"type": "line",
"source": "geojson",
"paint": {
"line-width": ["get", "width"],
"line-offset": ["-", ["get", "offset"], 64],
"line-dasharray": [1, 0, 1],
"line-color": "blue"
}
},
{
"id": "road3",
"type": "line",
"source": "geojson",
"paint": {
"line-width": ["get", "width"],
"line-dasharray": [1, 0],
"line-color": "yellow"
}
},
{
"id": "road4",
"type": "line",
"source": "geojson",
"paint": {
"line-width": ["get", "width"],
"line-dasharray": [0, 1],
"line-color": "black"
}
}
]
}