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[core] fix rendering 180° line joins

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This commit is contained in:
Konstantin Käfer
2017-01-19 16:36:19 +01:00
parent f1c3cfb7e2
commit a37ae27aed
3 changed files with 14 additions and 6 deletions
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2
mapbox-gl-js

Submodule mapbox-gl-js updated: 8780088951...2663093c9d

2
src/mbgl/programs/line_program.hpp
View File

@@ -49,7 +49,7 @@ struct LineAttributes : gl::Attributes<
static_cast<int16_t>((p.y * 2) | t.y)
},
{
// add 128 to store an byte in an unsigned byte
// add 128 to store a byte in an unsigned byte
static_cast<uint8_t>(::round(extrudeScale * e.x) + 128),
static_cast<uint8_t>(::round(extrudeScale * e.y) + 128),

16
src/mbgl/renderer/line_bucket.cpp
View File

@@ -139,7 +139,14 @@ void LineBucket::addGeometry(const GeometryCoordinates& coordinates) {
// Determine the normal of the join extrusion. It is the angle bisector
// of the segments between the previous line and the next line.
Point<double> joinNormal = util::unit(*prevNormal + *nextNormal);
// 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.
Point<double> joinNormal = *prevNormal + *nextNormal;
if (joinNormal.x != 0 || joinNormal.y != 0) {
joinNormal = util::unit(joinNormal);
}
/* joinNormal prevNormal
* ↖ ↑
@@ -155,7 +162,8 @@ void LineBucket::addGeometry(const GeometryCoordinates& coordinates) {
// Find the cosine of the angle between the next and join normals
// using dot product. The inverse of that is the miter length.
const double cosHalfAngle = joinNormal.x * nextNormal->x + joinNormal.y * nextNormal->y;
const double miterLength = cosHalfAngle != 0 ? 1 / cosHalfAngle: 1;
const double miterLength =
cosHalfAngle != 0 ? 1 / cosHalfAngle : std::numeric_limits<double>::infinity();
const bool isSharpCorner = cosHalfAngle < COS_HALF_SHARP_CORNER && prevCoordinate && nextCoordinate;
@@ -189,7 +197,7 @@ void LineBucket::addGeometry(const GeometryCoordinates& coordinates) {
if (currentJoin == LineJoinType::Bevel) {
// The maximum extrude length is 128 / 63 = 2 times the width of the line
// so if miterLength >= 2 we need to draw a different type of bevel where.
// so if miterLength >= 2 we need to draw a different type of bevel here.
if (miterLength > 2) {
currentJoin = LineJoinType::FlipBevel;
}
@@ -216,7 +224,7 @@ void LineBucket::addGeometry(const GeometryCoordinates& coordinates) {
if (miterLength > 100) {
// Almost parallel lines
joinNormal = *nextNormal;
joinNormal = *nextNormal * -1.0;
} else {
const double direction = prevNormal->x * nextNormal->y - prevNormal->y * nextNormal->x > 0 ? -1 : 1;
const double bevelLength = miterLength * util::mag(*prevNormal + *nextNormal) /