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Remove usage of NaN and align algorithm with GL native #4028

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Jan 20, 2017
Merged

Remove usage of NaN and align algorithm with GL native #4028

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19 changes: 8 additions & 11 deletions js/data/bucket/line_bucket.js
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Original file line number Diff line number Diff line change
Expand Up @@ -159,16 +159,13 @@ class LineBucket extends Bucket {

// Determine the normal of the join extrusion. It is the angle bisector
// of the segments between the previous line and the next line.
let joinNormal = prevNormal.add(nextNormal)._unit();

if (isNaN(joinNormal.x) && isNaN(joinNormal.y) && join === 'miter') {
// In the case of 180° angles, the prev and next normals cancel
// each other out: prevNormal + nextNormal = (0, 0), its
// magnitude is 0, so the unit vector becomes (NaN, NaN). We
// can use the prevNormal, though, since we are confident this
// is a 180° angle.
joinNormal = prevNormal;
nextNormal._mult(-1);
// In the case of 180° angles, the prev and next normals cancel each other out:
// prevNormal + nextNormal = (0, 0), its magnitude is 0, so the unit vector would be
// undefined. In that case, we're keeping the joinNormal at (0, 0), so that the cosHalfAngle
// below will also become 0 and miterLength will become Infinity.
let joinNormal = prevNormal.add(nextNormal);
if (joinNormal.x !== 0 || joinNormal.y !== 0) {
joinNormal._unit();
}
/* joinNormal prevNormal
* ↖ ↑
Expand All @@ -184,7 +181,7 @@ class LineBucket extends Bucket {
// Find the cosine of the angle between the next and join normals
// using dot product. The inverse of that is the miter length.
const cosHalfAngle = joinNormal.x * nextNormal.x + joinNormal.y * nextNormal.y;
const miterLength = 1 / cosHalfAngle;
const miterLength = cosHalfAngle !== 0 ? 1 / cosHalfAngle : Infinity;

const isSharpCorner = cosHalfAngle < COS_HALF_SHARP_CORNER && prevVertex && nextVertex;

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