422 lines
22 KiB
C++
422 lines
22 KiB
C++
#include <mbgl/layout/symbol_projection.hpp>
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#include <mbgl/map/transform_state.hpp>
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#include <mbgl/renderer/render_tile.hpp>
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#include <mbgl/renderer/buckets/symbol_bucket.hpp>
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#include <mbgl/renderer/layers/render_symbol_layer.hpp>
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#include <mbgl/util/optional.hpp>
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#include <mbgl/util/math.hpp>
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namespace mbgl {
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/*
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* # Overview of coordinate spaces
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*
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* ## Tile coordinate spaces
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* Each label has an anchor. Some labels have corresponding line geometries.
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* The points for both anchors and lines are stored in tile units. Each tile has it's own
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* coordinate space going from (0, 0) at the top left to (EXTENT, EXTENT) at the bottom right.
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*
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* ## GL coordinate space
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* At the end of everything, the vertex shader needs to produce a position in GL coordinate space,
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* which is (-1, 1) at the top left and (1, -1) in the bottom right.
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*
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* ## Map pixel coordinate spaces
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* Each tile has a pixel coordinate space. It's just the tile units scaled so that one unit is
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* whatever counts as 1 pixel at the current zoom.
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* This space is used for pitch-alignment=map, rotation-alignment=map
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*
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* ## Rotated map pixel coordinate spaces
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* Like the above, but rotated so axis of the space are aligned with the viewport instead of the tile.
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* This space is used for pitch-alignment=map, rotation-alignment=viewport
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*
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* ## Viewport pixel coordinate space
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* (0, 0) is at the top left of the canvas and (pixelWidth, pixelHeight) is at the bottom right corner
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* of the canvas. This space is used for pitch-alignment=viewport
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*
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*
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* # Vertex projection
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* It goes roughly like this:
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* 1. project the anchor and line from tile units into the correct label coordinate space
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* - map pixel space pitch-alignment=map rotation-alignment=map
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* - rotated map pixel space pitch-alignment=map rotation-alignment=viewport
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* - viewport pixel space pitch-alignment=viewport rotation-alignment=*
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* 2. if the label follows a line, find the point along the line that is the correct distance from the anchor.
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* 3. add the glyph's corner offset to the point from step 3
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* 4. convert from the label coordinate space to gl coordinates
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*
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* For horizontal labels we want to do step 1 in the shader for performance reasons (no cpu work).
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* This is what `u_label_plane_matrix` is used for.
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* For labels aligned with lines we have to steps 1 and 2 on the cpu since we need access to the line geometry.
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* This is what `updateLineLabels(...)` does.
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* Since the conversion is handled on the cpu we just set `u_label_plane_matrix` to an identity matrix.
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*
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* Steps 3 and 4 are done in the shaders for all labels.
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*/
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/*
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* Returns a matrix for converting from tile units to the correct label coordinate space.
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*/
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mat4 getLabelPlaneMatrix(const mat4& posMatrix, const bool pitchWithMap, const bool rotateWithMap, const TransformState& state, const float pixelsToTileUnits) {
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mat4 m;
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matrix::identity(m);
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if (pitchWithMap) {
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matrix::scale(m, m, 1 / pixelsToTileUnits, 1 / pixelsToTileUnits, 1);
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if (!rotateWithMap) {
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matrix::rotate_z(m, m, state.getAngle());
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}
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} else {
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matrix::scale(m, m, state.getSize().width / 2.0, -(state.getSize().height / 2.0), 1.0);
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matrix::translate(m, m, 1, -1, 0);
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matrix::multiply(m, m, posMatrix);
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}
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return m;
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}
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/*
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* Returns a matrix for converting from the correct label coordinate space to gl coords.
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*/
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mat4 getGlCoordMatrix(const mat4& posMatrix, const bool pitchWithMap, const bool rotateWithMap, const TransformState& state, const float pixelsToTileUnits) {
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mat4 m;
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matrix::identity(m);
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if (pitchWithMap) {
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matrix::multiply(m, m, posMatrix);
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matrix::scale(m, m, pixelsToTileUnits, pixelsToTileUnits, 1);
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if (!rotateWithMap) {
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matrix::rotate_z(m, m, -state.getAngle());
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}
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} else {
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matrix::scale(m, m, 1, -1, 1);
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matrix::translate(m, m, -1, -1, 0);
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matrix::scale(m, m, 2.0 / state.getSize().width, 2.0 / state.getSize().height, 1.0);
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}
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return m;
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}
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PointAndCameraDistance project(const Point<float>& point, const mat4& matrix) {
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vec4 pos = {{ point.x, point.y, 0, 1 }};
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matrix::transformMat4(pos, pos, matrix);
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return {{ static_cast<float>(pos[0] / pos[3]), static_cast<float>(pos[1] / pos[3]) }, pos[3] };
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}
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float evaluateSizeForFeature(const ZoomEvaluatedSize& zoomEvaluatedSize, const PlacedSymbol& placedSymbol) {
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if (zoomEvaluatedSize.isFeatureConstant) {
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return zoomEvaluatedSize.size;
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} else {
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if (zoomEvaluatedSize.isZoomConstant) {
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return placedSymbol.lowerSize;
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} else {
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return placedSymbol.lowerSize + zoomEvaluatedSize.sizeT * (placedSymbol.upperSize - placedSymbol.lowerSize);
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}
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}
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}
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bool isVisible(const vec4& anchorPos, const std::array<double, 2>& clippingBuffer) {
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const float x = anchorPos[0] / anchorPos[3];
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const float y = anchorPos[1] / anchorPos[3];
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const bool inPaddedViewport = (
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x >= -clippingBuffer[0] &&
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x <= clippingBuffer[0] &&
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y >= -clippingBuffer[1] &&
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y <= clippingBuffer[1]);
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return inPaddedViewport;
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}
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void addDynamicAttributes(const Point<float>& anchorPoint, const float angle,
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gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray) {
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auto dynamicVertex = SymbolDynamicLayoutAttributes::vertex(anchorPoint, angle);
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dynamicVertexArray.emplace_back(dynamicVertex);
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dynamicVertexArray.emplace_back(dynamicVertex);
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dynamicVertexArray.emplace_back(dynamicVertex);
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dynamicVertexArray.emplace_back(dynamicVertex);
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}
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void hideGlyphs(size_t numGlyphs, gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray) {
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const Point<float> offscreenPoint = { -INFINITY, -INFINITY };
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for (size_t i = 0; i < numGlyphs; i++) {
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addDynamicAttributes(offscreenPoint, 0, dynamicVertexArray);
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}
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}
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enum PlacementResult {
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OK,
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NotEnoughRoom,
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NeedsFlipping,
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UseVertical
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};
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Point<float> projectTruncatedLineSegment(const Point<float>& previousTilePoint, const Point<float>& currentTilePoint, const Point<float>& previousProjectedPoint, const float minimumLength, const mat4& projectionMatrix) {
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// We are assuming "previousTilePoint" won't project to a point within one unit of the camera plane
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// If it did, that would mean our label extended all the way out from within the viewport to a (very distant)
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// point near the plane of the camera. We wouldn't be able to render the label anyway once it crossed the
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// plane of the camera.
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const Point<float> projectedUnitVertex = project(previousTilePoint + util::unit<float>(previousTilePoint - currentTilePoint), projectionMatrix).first;
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const Point<float> projectedUnitSegment = previousProjectedPoint - projectedUnitVertex;
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return previousProjectedPoint + (projectedUnitSegment * (minimumLength / util::mag<float>(projectedUnitSegment)));
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}
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optional<PlacedGlyph> placeGlyphAlongLine(const float offsetX, const float lineOffsetX, const float lineOffsetY, const bool flip,
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const Point<float>& projectedAnchorPoint, const Point<float>& tileAnchorPoint, const uint16_t anchorSegment, const GeometryCoordinates& line, const std::vector<float>& tileDistances, const mat4& labelPlaneMatrix, const bool returnTileDistance) {
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const float combinedOffsetX = flip ?
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offsetX - lineOffsetX :
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offsetX + lineOffsetX;
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int16_t dir = combinedOffsetX > 0 ? 1 : -1;
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float angle = 0.0;
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if (flip) {
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// The label needs to be flipped to keep text upright.
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// Iterate in the reverse direction.
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dir *= -1;
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angle = M_PI;
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}
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if (dir < 0) angle += M_PI;
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int32_t currentIndex = dir > 0 ? anchorSegment : anchorSegment + 1;
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const int32_t initialIndex = currentIndex;
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Point<float> current = projectedAnchorPoint;
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Point<float> prev = projectedAnchorPoint;
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float distanceToPrev = 0.0;
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float currentSegmentDistance = 0.0;
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const float absOffsetX = std::abs(combinedOffsetX);
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while (distanceToPrev + currentSegmentDistance <= absOffsetX) {
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currentIndex += dir;
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// offset does not fit on the projected line
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if (currentIndex < 0 || currentIndex >= static_cast<int32_t>(line.size())) {
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return {};
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}
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prev = current;
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PointAndCameraDistance projection = project(convertPoint<float>(line.at(currentIndex)), labelPlaneMatrix);
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if (projection.second > 0) {
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current = projection.first;
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} else {
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// The vertex is behind the plane of the camera, so we can't project it
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// Instead, we'll create a vertex along the line that's far enough to include the glyph
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const Point<float> previousTilePoint = distanceToPrev == 0 ?
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tileAnchorPoint :
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convertPoint<float>(line.at(currentIndex - dir));
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const Point<float> currentTilePoint = convertPoint<float>(line.at(currentIndex));
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current = projectTruncatedLineSegment(previousTilePoint, currentTilePoint, prev, absOffsetX - distanceToPrev + 1, labelPlaneMatrix);
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}
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distanceToPrev += currentSegmentDistance;
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currentSegmentDistance = util::dist<float>(prev, current);
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}
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// The point is on the current segment. Interpolate to find it.
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const float segmentInterpolationT = (absOffsetX - distanceToPrev) / currentSegmentDistance;
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const Point<float> prevToCurrent = current - prev;
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Point<float> p = (prevToCurrent * segmentInterpolationT) + prev;
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// offset the point from the line to text-offset and icon-offset
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p += util::perp(prevToCurrent) * static_cast<float>(lineOffsetY * dir / util::mag(prevToCurrent));
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const float segmentAngle = angle + std::atan2(current.y - prev.y, current.x - prev.x);
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return {{
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p,
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segmentAngle,
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returnTileDistance ?
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TileDistance(
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(currentIndex - dir) == initialIndex ? 0 : tileDistances[currentIndex - dir],
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absOffsetX - distanceToPrev
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) :
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optional<TileDistance>()
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}};
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}
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optional<std::pair<PlacedGlyph, PlacedGlyph>> placeFirstAndLastGlyph(const float fontScale,
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const float lineOffsetX,
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const float lineOffsetY,
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const bool flip,
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const Point<float>& anchorPoint,
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const Point<float>& tileAnchorPoint,
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const PlacedSymbol& symbol,
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const mat4& labelPlaneMatrix,
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const bool returnTileDistance) {
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const float firstGlyphOffset = symbol.glyphOffsets.front();
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const float lastGlyphOffset = symbol.glyphOffsets.back();;
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optional<PlacedGlyph> firstPlacedGlyph = placeGlyphAlongLine(fontScale * firstGlyphOffset, lineOffsetX, lineOffsetY, flip, anchorPoint, tileAnchorPoint, symbol.segment, symbol.line, symbol.tileDistances, labelPlaneMatrix, returnTileDistance);
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if (!firstPlacedGlyph)
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return optional<std::pair<PlacedGlyph, PlacedGlyph>>();
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optional<PlacedGlyph> lastPlacedGlyph = placeGlyphAlongLine(fontScale * lastGlyphOffset, lineOffsetX, lineOffsetY, flip, anchorPoint, tileAnchorPoint, symbol.segment, symbol.line, symbol.tileDistances, labelPlaneMatrix, returnTileDistance);
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if (!lastPlacedGlyph)
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return optional<std::pair<PlacedGlyph, PlacedGlyph>>();
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return std::make_pair(*firstPlacedGlyph, *lastPlacedGlyph);
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}
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optional<PlacementResult> requiresOrientationChange(const WritingModeType writingModes, const Point<float>& firstPoint, const Point<float>& lastPoint, const float aspectRatio) {
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if (writingModes == (WritingModeType::Horizontal | WritingModeType::Vertical)) {
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// On top of choosing whether to flip, choose whether to render this version of the glyphs or the alternate
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// vertical glyphs. We can't just filter out vertical glyphs in the horizontal range because the horizontal
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// and vertical versions can have slightly different projections which could lead to angles where both or
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// neither showed.
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auto rise = std::abs(lastPoint.y - firstPoint.y);
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auto run = std::abs(lastPoint.x - firstPoint.x) * aspectRatio;
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if (rise > run) {
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return PlacementResult::UseVertical;
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}
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}
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if ((writingModes == WritingModeType::Vertical) ?
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(firstPoint.y < lastPoint.y) :
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(firstPoint.x > lastPoint.x)) {
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// Includes "horizontalOnly" case for labels without vertical glyphs
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return PlacementResult::NeedsFlipping;
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}
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return {};
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}
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PlacementResult placeGlyphsAlongLine(const PlacedSymbol& symbol,
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const float fontSize,
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const bool flip,
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const bool keepUpright,
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const mat4& posMatrix,
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const mat4& labelPlaneMatrix,
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const mat4& glCoordMatrix,
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gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray,
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const Point<float>& projectedAnchorPoint,
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const float aspectRatio) {
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const float fontScale = fontSize / 24.0;
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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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std::vector<PlacedGlyph> placedGlyphs;
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if (symbol.glyphOffsets.size() > 1) {
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const optional<std::pair<PlacedGlyph, PlacedGlyph>> firstAndLastGlyph =
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placeFirstAndLastGlyph(fontScale, lineOffsetX, lineOffsetY, flip, projectedAnchorPoint, symbol.anchorPoint, symbol, labelPlaneMatrix, false);
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if (!firstAndLastGlyph) {
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return PlacementResult::NotEnoughRoom;
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}
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const Point<float> firstPoint = project(firstAndLastGlyph->first.point, glCoordMatrix).first;
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const Point<float> lastPoint = project(firstAndLastGlyph->second.point, glCoordMatrix).first;
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if (keepUpright && !flip) {
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auto orientationChange = requiresOrientationChange(symbol.writingModes, firstPoint, lastPoint, aspectRatio);
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if (orientationChange) {
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return *orientationChange;
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}
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}
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placedGlyphs.push_back(firstAndLastGlyph->first);
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for (size_t glyphIndex = 1; glyphIndex < symbol.glyphOffsets.size() - 1; glyphIndex++) {
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const float glyphOffsetX = symbol.glyphOffsets[glyphIndex];
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// Since first and last glyph fit on the line, we're sure that the rest of the glyphs can be placed
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auto placedGlyph = placeGlyphAlongLine(glyphOffsetX * fontScale, lineOffsetX, lineOffsetY, flip, projectedAnchorPoint, symbol.anchorPoint, symbol.segment, symbol.line, symbol.tileDistances, labelPlaneMatrix, false);
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placedGlyphs.push_back(*placedGlyph);
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}
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placedGlyphs.push_back(firstAndLastGlyph->second);
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} else if (symbol.glyphOffsets.size() == 1) {
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// Only a single glyph to place
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// So, determine whether to flip based on projected angle of the line segment it's on
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if (keepUpright && !flip) {
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const Point<float> a = project(symbol.anchorPoint, posMatrix).first;
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const Point<float> tileSegmentEnd = convertPoint<float>(symbol.line.at(symbol.segment + 1));
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const PointAndCameraDistance projectedVertex = project(tileSegmentEnd, posMatrix);
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// We know the anchor will be in the viewport, but the end of the line segment may be
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// behind the plane of the camera, in which case we can use a point at any arbitrary (closer)
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// point on the segment.
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const Point<float> b = (projectedVertex.second > 0) ?
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projectedVertex.first :
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projectTruncatedLineSegment(symbol.anchorPoint,tileSegmentEnd, a, 1, posMatrix);
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auto orientationChange = requiresOrientationChange(symbol.writingModes, a, b, aspectRatio);
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if (orientationChange) {
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return *orientationChange;
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}
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}
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const float glyphOffsetX = symbol.glyphOffsets.front();
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optional<PlacedGlyph> singleGlyph = placeGlyphAlongLine(fontScale * glyphOffsetX, lineOffsetX, lineOffsetY, flip, projectedAnchorPoint, symbol.anchorPoint, symbol.segment,
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symbol.line, symbol.tileDistances, labelPlaneMatrix, false);
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if (!singleGlyph)
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return PlacementResult::NotEnoughRoom;
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placedGlyphs.push_back(*singleGlyph);
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}
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// The number of placedGlyphs must equal the number of glyphOffsets, which must correspond to the number of glyph vertices
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// There may be 0 glyphs here, if a label consists entirely of glyphs that have 0x0 dimensions
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for (auto& placedGlyph : placedGlyphs) {
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addDynamicAttributes(placedGlyph.point, placedGlyph.angle, dynamicVertexArray);
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}
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return PlacementResult::OK;
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}
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void reprojectLineLabels(gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray, const std::vector<PlacedSymbol>& placedSymbols,
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const mat4& posMatrix, const style::SymbolPropertyValues& values,
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const RenderTile& tile, const SymbolSizeBinder& sizeBinder, const TransformState& state) {
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const ZoomEvaluatedSize partiallyEvaluatedSize = sizeBinder.evaluateForZoom(state.getZoom());
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const std::array<double, 2> clippingBuffer = {{ 256.0 / state.getSize().width * 2.0 + 1.0, 256.0 / state.getSize().height * 2.0 + 1.0 }};
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const bool pitchWithMap = values.pitchAlignment == style::AlignmentType::Map;
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const bool rotateWithMap = values.rotationAlignment == style::AlignmentType::Map;
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const float pixelsToTileUnits = tile.id.pixelsToTileUnits(1, state.getZoom());
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const mat4 labelPlaneMatrix = getLabelPlaneMatrix(posMatrix, pitchWithMap,
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rotateWithMap, state, pixelsToTileUnits);
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const mat4 glCoordMatrix = getGlCoordMatrix(posMatrix, pitchWithMap, rotateWithMap, state, pixelsToTileUnits);
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dynamicVertexArray.clear();
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bool useVertical = false;
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for (auto& placedSymbol : placedSymbols) {
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// Don't do calculations for vertical glyphs unless the previous symbol was horizontal
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// and we determined that vertical glyphs were necessary.
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// Also don't do calculations for symbols that are collided and fully faded out
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if (placedSymbol.hidden || (placedSymbol.writingModes == WritingModeType::Vertical && !useVertical)) {
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hideGlyphs(placedSymbol.glyphOffsets.size(), dynamicVertexArray);
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continue;
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}
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// Awkward... but we're counting on the paired "vertical" symbol coming immediately after its horizontal counterpart
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useVertical = false;
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vec4 anchorPos = {{ placedSymbol.anchorPoint.x, placedSymbol.anchorPoint.y, 0, 1 }};
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matrix::transformMat4(anchorPos, anchorPos, posMatrix);
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// Don't bother calculating the correct point for invisible labels.
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if (!isVisible(anchorPos, clippingBuffer)) {
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hideGlyphs(placedSymbol.glyphOffsets.size(), dynamicVertexArray);
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continue;
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}
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const float cameraToAnchorDistance = anchorPos[3];
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const float perspectiveRatio = 0.5 + 0.5 * (cameraToAnchorDistance / state.getCameraToCenterDistance());
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const float fontSize = evaluateSizeForFeature(partiallyEvaluatedSize, placedSymbol);
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const float pitchScaledFontSize = values.pitchAlignment == style::AlignmentType::Map ?
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fontSize * perspectiveRatio :
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fontSize / perspectiveRatio;
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const Point<float> anchorPoint = project(placedSymbol.anchorPoint, labelPlaneMatrix).first;
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PlacementResult placeUnflipped = placeGlyphsAlongLine(placedSymbol, pitchScaledFontSize, false /*unflipped*/, values.keepUpright, posMatrix, labelPlaneMatrix, glCoordMatrix, dynamicVertexArray, anchorPoint, state.getSize().aspectRatio());
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useVertical = placeUnflipped == PlacementResult::UseVertical;
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if (placeUnflipped == PlacementResult::NotEnoughRoom || useVertical ||
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(placeUnflipped == PlacementResult::NeedsFlipping &&
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placeGlyphsAlongLine(placedSymbol, pitchScaledFontSize, true /*flipped*/, values.keepUpright, posMatrix, labelPlaneMatrix, glCoordMatrix, dynamicVertexArray, anchorPoint, state.getSize().aspectRatio()) == PlacementResult::NotEnoughRoom)) {
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hideGlyphs(placedSymbol.glyphOffsets.size(), dynamicVertexArray);
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}
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}
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}
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} // end namespace mbgl
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