373 lines
17 KiB
C++
373 lines
17 KiB
C++
#include <mbgl/text/collision_index.hpp>
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#include <mbgl/layout/symbol_instance.hpp>
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#include <mbgl/geometry/feature_index.hpp>
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#include <mbgl/math/log2.hpp>
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#include <mbgl/util/constants.hpp>
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#include <mbgl/util/math.hpp>
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#include <mbgl/math/minmax.hpp>
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#include <mbgl/util/intersection_tests.hpp>
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#include <mbgl/layout/symbol_projection.hpp>
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#include <mapbox/geometry/envelope.hpp>
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#include <mbgl/renderer/buckets/symbol_bucket.hpp> // For PlacedSymbol: pull out to another location
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#include <cmath>
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namespace mbgl {
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// When a symbol crosses the edge that causes it to be included in
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// collision detection, it will cause changes in the symbols around
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// it. This constant specifies how many pixels to pad the edge of
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// the viewport for collision detection so that the bulk of the changes
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// occur offscreen. Making this constant greater increases label
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// stability, but it's expensive.
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static const float viewportPadding = 100;
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CollisionIndex::CollisionIndex(const TransformState& transformState_)
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: transformState(transformState_)
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, collisionGrid(transformState.getSize().width + 2 * viewportPadding, transformState.getSize().height + 2 * viewportPadding, 25)
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, ignoredGrid(transformState.getSize().width + 2 * viewportPadding, transformState.getSize().height + 2 * viewportPadding, 25)
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, screenRightBoundary(transformState.getSize().width + viewportPadding)
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, screenBottomBoundary(transformState.getSize().height + viewportPadding)
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, gridRightBoundary(transformState.getSize().width + 2 * viewportPadding)
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, gridBottomBoundary(transformState.getSize().height + 2 * viewportPadding)
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, pitchFactor(std::cos(transformState.getPitch()) * transformState.getCameraToCenterDistance())
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{}
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float CollisionIndex::approximateTileDistance(const TileDistance& tileDistance, const float lastSegmentAngle, const float pixelsToTileUnits, const float cameraToAnchorDistance, const bool pitchWithMap) {
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// This is a quick and dirty solution for chosing which collision circles to use (since collision circles are
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// laid out in tile units). Ideally, I think we should generate collision circles on the fly in viewport coordinates
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// at the time we do collision detection.
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// incidenceStretch is the ratio of how much y space a label takes up on a tile while drawn perpendicular to the viewport vs
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// how much space it would take up if it were drawn flat on the tile
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// Using law of sines, camera_to_anchor/sin(ground_angle) = camera_to_center/sin(incidence_angle)
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// Incidence angle 90 -> head on, sin(incidence_angle) = 1, no stretch
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// Incidence angle 1 -> very oblique, sin(incidence_angle) =~ 0, lots of stretch
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// ground_angle = u_pitch + PI/2 -> sin(ground_angle) = cos(u_pitch)
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// incidenceStretch = 1 / sin(incidenceAngle)
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const float incidenceStretch = pitchWithMap ? 1 : cameraToAnchorDistance / pitchFactor;
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const float lastSegmentTile = tileDistance.lastSegmentViewportDistance * pixelsToTileUnits;
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return tileDistance.prevTileDistance +
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lastSegmentTile +
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(incidenceStretch - 1) * lastSegmentTile * std::abs(std::sin(lastSegmentAngle));
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}
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bool CollisionIndex::isOffscreen(const CollisionBox& box) const {
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return box.px2 < viewportPadding || box.px1 >= screenRightBoundary || box.py2 < viewportPadding || box.py1 >= screenBottomBoundary;
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}
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bool CollisionIndex::isInsideGrid(const CollisionBox& box) const {
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return box.px2 >= 0 && box.px1 < gridRightBoundary && box.py2 >= 0 && box.py1 < gridBottomBoundary;
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}
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CollisionTileBoundaries CollisionIndex::projectTileBoundaries(const mat4& posMatrix) const {
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Point<float> topLeft = projectPoint(posMatrix, { 0, 0 });
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Point<float> bottomRight = projectPoint(posMatrix, { util::EXTENT, util::EXTENT });
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return {{ topLeft.x, topLeft.y, bottomRight.x, bottomRight.y }};
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}
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bool CollisionIndex::isInsideTile(const CollisionBox& box, const CollisionTileBoundaries& tileBoundaries) const {
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// This check is only well defined when the tile boundaries are axis-aligned
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// We are relying on it only being used in MapMode::Tile, where that is always the case
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return box.px1 >= tileBoundaries[0] && box.py1 >= tileBoundaries[1] && box.px2 < tileBoundaries[2] && box.py2 < tileBoundaries[3];
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}
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std::pair<bool,bool> CollisionIndex::placeFeature(CollisionFeature& feature,
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Point<float> shift,
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const mat4& posMatrix,
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const mat4& labelPlaneMatrix,
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const float textPixelRatio,
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PlacedSymbol& symbol,
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const float scale,
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const float fontSize,
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const bool allowOverlap,
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const bool pitchWithMap,
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const bool collisionDebug,
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const optional<CollisionTileBoundaries>& avoidEdges,
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const optional<std::function<bool(const IndexedSubfeature&)>> collisionGroupPredicate) {
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if (!feature.alongLine) {
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CollisionBox& box = feature.boxes.front();
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const auto projectedPoint = projectAndGetPerspectiveRatio(posMatrix, box.anchor);
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const float tileToViewport = textPixelRatio * projectedPoint.second;
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box.px1 = (box.x1 + shift.x) * tileToViewport + projectedPoint.first.x;
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box.py1 = (box.y1 + shift.y) * tileToViewport + projectedPoint.first.y;
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box.px2 = (box.x2 + shift.x) * tileToViewport + projectedPoint.first.x;
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box.py2 = (box.y2 + shift.y) * tileToViewport + projectedPoint.first.y;
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if ((avoidEdges && !isInsideTile(box, *avoidEdges)) ||
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!isInsideGrid(box) ||
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(!allowOverlap && collisionGrid.hitTest({{ box.px1, box.py1 }, { box.px2, box.py2 }}, collisionGroupPredicate))) {
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return { false, false };
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}
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return {true, isOffscreen(box)};
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} else {
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return placeLineFeature(feature, posMatrix, labelPlaneMatrix, textPixelRatio, symbol, scale, fontSize, allowOverlap, pitchWithMap, collisionDebug, avoidEdges, collisionGroupPredicate);
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}
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}
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std::pair<bool,bool> CollisionIndex::placeLineFeature(CollisionFeature& feature,
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const mat4& posMatrix,
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const mat4& labelPlaneMatrix,
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const float textPixelRatio,
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PlacedSymbol& symbol,
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const float scale,
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const float fontSize,
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const bool allowOverlap,
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const bool pitchWithMap,
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const bool collisionDebug,
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const optional<CollisionTileBoundaries>& avoidEdges,
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const optional<std::function<bool(const IndexedSubfeature&)>> collisionGroupPredicate) {
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const auto tileUnitAnchorPoint = symbol.anchorPoint;
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const auto projectedAnchor = projectAnchor(posMatrix, tileUnitAnchorPoint);
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const float fontScale = fontSize / 24;
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const float lineOffsetX = symbol.lineOffset[0] * fontSize;
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const float lineOffsetY = symbol.lineOffset[1] * fontSize;
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const auto labelPlaneAnchorPoint = project(tileUnitAnchorPoint, labelPlaneMatrix).first;
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const auto firstAndLastGlyph = placeFirstAndLastGlyph(
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fontScale,
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lineOffsetX,
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lineOffsetY,
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/*flip*/ false,
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labelPlaneAnchorPoint,
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tileUnitAnchorPoint,
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symbol,
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labelPlaneMatrix,
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/*return tile distance*/ true);
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bool collisionDetected = false;
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bool inGrid = false;
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bool entirelyOffscreen = true;
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const auto tileToViewport = projectedAnchor.first * textPixelRatio;
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// pixelsToTileUnits is used for translating line geometry to tile units
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// ... so we care about 'scale' but not 'perspectiveRatio'
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// equivalent to pixel_to_tile_units
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const auto pixelsToTileUnits = 1 / (textPixelRatio * scale);
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float firstTileDistance = 0, lastTileDistance = 0;
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if (firstAndLastGlyph) {
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firstTileDistance = approximateTileDistance(*(firstAndLastGlyph->first.tileDistance), firstAndLastGlyph->first.angle, pixelsToTileUnits, projectedAnchor.second, pitchWithMap);
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lastTileDistance = approximateTileDistance(*(firstAndLastGlyph->second.tileDistance), firstAndLastGlyph->second.angle, pixelsToTileUnits, projectedAnchor.second, pitchWithMap);
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}
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bool atLeastOneCirclePlaced = false;
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for (size_t i = 0; i < feature.boxes.size(); i++) {
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CollisionBox& circle = feature.boxes[i];
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const float boxSignedDistanceFromAnchor = circle.signedDistanceFromAnchor;
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if (!firstAndLastGlyph ||
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(boxSignedDistanceFromAnchor < -firstTileDistance) ||
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(boxSignedDistanceFromAnchor > lastTileDistance)) {
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// The label either doesn't fit on its line or we
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// don't need to use this circle because the label
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// doesn't extend this far. Either way, mark the circle unused.
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circle.used = false;
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continue;
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}
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const auto projectedPoint = projectPoint(posMatrix, circle.anchor);
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const float tileUnitRadius = (circle.x2 - circle.x1) / 2;
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const float radius = tileUnitRadius * tileToViewport;
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if (atLeastOneCirclePlaced) {
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const CollisionBox& previousCircle = feature.boxes[i - 1];
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const float dx = projectedPoint.x - previousCircle.px;
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const float dy = projectedPoint.y - previousCircle.py;
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// The circle edges touch when the distance between their centers is 2x the radius
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// When the distance is 1x the radius, they're doubled up, and we could remove
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// every other circle while keeping them all in touch.
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// We actually start removing circles when the distance is √2x the radius:
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// thinning the number of circles as much as possible is a major performance win,
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// and the small gaps introduced don't make a very noticeable difference.
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const bool placedTooDensely = radius * radius * 2 > dx * dx + dy * dy;
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if (placedTooDensely) {
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const bool atLeastOneMoreCircle = (i + 1) < feature.boxes.size();
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if (atLeastOneMoreCircle) {
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const CollisionBox& nextCircle = feature.boxes[i + 1];
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const float nextBoxDistanceFromAnchor = nextCircle.signedDistanceFromAnchor;
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if ((nextBoxDistanceFromAnchor > -firstTileDistance) &&
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(nextBoxDistanceFromAnchor < lastTileDistance)) {
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// Hide significantly overlapping circles, unless this is the last one we can
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// use, in which case we want to keep it in place even if it's tightly packed
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// with the one before it.
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circle.used = false;
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continue;
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}
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}
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}
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}
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atLeastOneCirclePlaced = true;
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circle.px1 = projectedPoint.x - radius;
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circle.px2 = projectedPoint.x + radius;
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circle.py1 = projectedPoint.y - radius;
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circle.py2 = projectedPoint.y + radius;
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circle.used = true;
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circle.px = projectedPoint.x;
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circle.py = projectedPoint.y;
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circle.radius = radius;
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entirelyOffscreen &= isOffscreen(circle);
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inGrid |= isInsideGrid(circle);
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if ((avoidEdges && !isInsideTile(circle, *avoidEdges)) ||
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(!allowOverlap && collisionGrid.hitTest({{circle.px, circle.py}, circle.radius}, collisionGroupPredicate))) {
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if (!collisionDebug) {
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return {false, false};
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} else {
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// Don't early exit if we're showing the debug circles because we still want to calculate
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// which circles are in use
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collisionDetected = true;
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}
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}
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}
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return {!collisionDetected && firstAndLastGlyph && inGrid, entirelyOffscreen};
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}
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void CollisionIndex::insertFeature(CollisionFeature& feature, bool ignorePlacement, uint32_t bucketInstanceId, uint16_t collisionGroupId) {
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if (feature.alongLine) {
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for (auto& circle : feature.boxes) {
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if (!circle.used) {
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continue;
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}
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if (ignorePlacement) {
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ignoredGrid.insert(
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IndexedSubfeature(feature.indexedFeature, bucketInstanceId, collisionGroupId),
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{{ circle.px, circle.py }, circle.radius}
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);
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} else {
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collisionGrid.insert(
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IndexedSubfeature(feature.indexedFeature, bucketInstanceId, collisionGroupId),
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{{ circle.px, circle.py }, circle.radius}
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);
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}
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}
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} else {
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assert(feature.boxes.size() == 1);
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auto& box = feature.boxes[0];
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if (ignorePlacement) {
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ignoredGrid.insert(
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IndexedSubfeature(feature.indexedFeature, bucketInstanceId, collisionGroupId),
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{{ box.px1, box.py1 }, { box.px2, box.py2 }}
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);
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} else {
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collisionGrid.insert(
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IndexedSubfeature(feature.indexedFeature, bucketInstanceId, collisionGroupId),
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{{ box.px1, box.py1 }, { box.px2, box.py2 }}
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);
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}
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}
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}
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bool polygonIntersectsBox(const LineString<float>& polygon, const GridIndex<IndexedSubfeature>::BBox& bbox) {
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// This is just a wrapper that allows us to use the integer-based util::polygonIntersectsPolygon
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// Conversion limits our query accuracy to single-pixel resolution
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GeometryCoordinates integerPolygon;
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for (const auto& point : polygon) {
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integerPolygon.push_back(convertPoint<int16_t>(point));
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}
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int16_t minX1 = bbox.min.x;
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int16_t maxY1 = bbox.max.y;
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int16_t minY1 = bbox.min.y;
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int16_t maxX1 = bbox.max.x;
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auto bboxPoints = GeometryCoordinates {
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{ minX1, minY1 }, { maxX1, minY1 }, { maxX1, maxY1 }, { minX1, maxY1 }
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};
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return util::polygonIntersectsPolygon(integerPolygon, bboxPoints);
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}
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std::unordered_map<uint32_t, std::vector<IndexedSubfeature>> CollisionIndex::queryRenderedSymbols(const ScreenLineString& queryGeometry) const {
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std::unordered_map<uint32_t, std::vector<IndexedSubfeature>> result;
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if (queryGeometry.empty() || (collisionGrid.empty() && ignoredGrid.empty())) {
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return result;
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}
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LineString<float> gridQuery;
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for (const auto& point : queryGeometry) {
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gridQuery.emplace_back(point.x + viewportPadding, point.y + viewportPadding);
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}
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auto envelope = mapbox::geometry::envelope(gridQuery);
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using QueryResult = std::pair<IndexedSubfeature, GridIndex<IndexedSubfeature>::BBox>;
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std::vector<QueryResult> features = collisionGrid.queryWithBoxes(envelope);
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std::vector<QueryResult> ignoredFeatures = ignoredGrid.queryWithBoxes(envelope);
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features.insert(features.end(), ignoredFeatures.begin(), ignoredFeatures.end());
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std::unordered_map<uint32_t, std::unordered_set<size_t>> seenBuckets;
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for (auto& queryResult : features) {
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auto& feature = queryResult.first;
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auto& bbox = queryResult.second;
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// Skip already seen features.
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auto& seenFeatures = seenBuckets[feature.bucketInstanceId];
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if (seenFeatures.find(feature.index) != seenFeatures.end())
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continue;
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if (!polygonIntersectsBox(gridQuery, bbox)) {
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continue;
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}
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seenFeatures.insert(feature.index);
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result[feature.bucketInstanceId].push_back(feature);
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}
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return result;
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}
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std::pair<float,float> CollisionIndex::projectAnchor(const mat4& posMatrix, const Point<float>& point) const {
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vec4 p = {{ point.x, point.y, 0, 1 }};
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matrix::transformMat4(p, p, posMatrix);
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return std::make_pair(
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0.5 + 0.5 * (transformState.getCameraToCenterDistance() / p[3]),
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p[3]
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);
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}
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std::pair<Point<float>,float> CollisionIndex::projectAndGetPerspectiveRatio(const mat4& posMatrix, const Point<float>& point) const {
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vec4 p = {{ point.x, point.y, 0, 1 }};
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matrix::transformMat4(p, p, posMatrix);
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return std::make_pair(
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Point<float>(
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(((p[0] / p[3] + 1) / 2) * transformState.getSize().width) + viewportPadding,
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(((-p[1] / p[3] + 1) / 2) * transformState.getSize().height) + viewportPadding
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),
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// See perspective ratio comment in symbol_sdf.vertex
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// We're doing collision detection in viewport space so we need
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// to scale down boxes in the distance
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0.5 + 0.5 * (transformState.getCameraToCenterDistance() / p[3])
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);
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}
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Point<float> CollisionIndex::projectPoint(const mat4& posMatrix, const Point<float>& point) const {
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vec4 p = {{ point.x, point.y, 0, 1 }};
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matrix::transformMat4(p, p, posMatrix);
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return Point<float>(
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(((p[0] / p[3] + 1) / 2) * transformState.getSize().width) + viewportPadding,
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(((-p[1] / p[3] + 1) / 2) * transformState.getSize().height) + viewportPadding
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);
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}
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} // namespace mbgl
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