Make pitched collision detection more conservative:

 When doing collision detection, assume all labels are scaled the same
 as the least scaled label in the tile.

src/data/bucket/symbol_bucket.js

@@ -597,7 +597,7 @@ class SymbolBucket {
             // Insert final placement into collision tree and add glyphs/icons to buffers
 
             if (hasText) {
-                collisionTile.insertCollisionFeature(textCollisionFeature, glyphScale, layout['text-ignore-placement']);
+                collisionTile.insertCollisionFeature(textCollisionFeature, glyphScale, layout['text-ignore-placement'], layer.getLayoutValue('text-pitch-scale'));
                 if (glyphScale <= maxScale) {
                     const textSizeData = getSizeVertexData(layer,
                         this.zoom,
@@ -619,7 +619,7 @@ class SymbolBucket {
             }
 
             if (hasIcon) {
-                collisionTile.insertCollisionFeature(iconCollisionFeature, iconScale, layout['icon-ignore-placement']);
+                collisionTile.insertCollisionFeature(iconCollisionFeature, iconScale, layout['icon-ignore-placement'], layer.getLayoutValue('icon-pitch-scale'));
                 if (iconScale <= maxScale) {
                     const iconSizeData = getSizeVertexData(
                         layer,

src/render/draw_collision_debug.js

@@ -27,8 +27,7 @@ function drawCollisionDebug(painter, sourceCache, layer, coords) {
         gl.uniform1f(program.u_collision_y_stretch, tile.collisionTile.yStretch);
         gl.uniform1f(program.u_pitch, painter.transform.pitch / 360 * 2 * Math.PI);
         gl.uniform1f(program.u_camera_to_center_distance, painter.transform.cameraToCenterDistance);
-        // TODO: Hook up to `text-pitch-scale` and `icon-pitch-scale` properties
-        gl.uniform1f(program.u_pitch_scale, 0.0);
+        gl.uniform1f(program.u_pitch_scale, tile.collisionTile.minimumPitchScaling);
 
         for (const segment of buffers.segments) {
             segment.vaos[layer.id].bind(gl, program, buffers.layoutVertexBuffer, buffers.elementBuffer, null, segment.vertexOffset);

src/render/draw_symbol.js

@@ -93,7 +93,7 @@ function drawLayerSymbols(painter, sourceCache, layer, coords, isText, translate
             program = painter.useProgram(isSDF ? 'symbolSDF' : 'symbolIcon', programConfiguration);
             programConfiguration.setUniforms(gl, program, layer, {zoom: painter.transform.zoom});
 
-            setSymbolDrawState(program, painter, layer, coord.z, isText, isSDF, rotateWithMap, pitchWithMap, bucket.fontstack, bucket.iconsNeedLinear, sizeData);
+            setSymbolDrawState(program, painter, layer, coord.z, isText, isSDF, rotateWithMap, pitchWithMap, bucket.fontstack, bucket.iconsNeedLinear, sizeData, tile.collisionTile.minimumPitchScaling);
         }
 
         painter.enableTileClippingMask(coord);
@@ -112,7 +112,7 @@ function drawLayerSymbols(painter, sourceCache, layer, coords, isText, translate
     if (!depthOn) gl.enable(gl.DEPTH_TEST);
 }
 
-function setSymbolDrawState(program, painter, layer, tileZoom, isText, isSDF, rotateWithMap, pitchWithMap, fontstack, iconsNeedLinear, sizeData) {
+function setSymbolDrawState(program, painter, layer, tileZoom, isText, isSDF, rotateWithMap, pitchWithMap, fontstack, iconsNeedLinear, sizeData, minimumPitchScaling) {
 
     const gl = painter.gl;
     const tr = painter.transform;
@@ -196,6 +196,7 @@ function setSymbolDrawState(program, painter, layer, tileZoom, isText, isSDF, ro
     }
     gl.uniform1f(program.u_camera_to_center_distance, tr.cameraToCenterDistance);
     gl.uniform1f(program.u_pitch_scale, layer.getLayoutValue(isText ? 'text-pitch-scale' : 'icon-pitch-scale'));
+    gl.uniform1f(program.u_collision_pitch_scale, minimumPitchScaling);
 }
 
 function drawTileSymbols(program, programConfiguration, painter, layer, tile, buffers, isText, isSDF, pitchWithMap) {

src/shaders/symbol_icon.vertex.glsl

@@ -11,6 +11,7 @@ uniform mediump float u_layout_size; // used when size is feature constant
 uniform mediump float u_camera_to_center_distance;
 uniform mediump float u_pitch;
 uniform mediump float u_pitch_scale;
+uniform mediump float u_collision_pitch_scale;
 uniform mediump float u_collision_y_stretch;
 
 #pragma mapbox: define lowp float opacity
@@ -91,7 +92,8 @@ void main() {
     // See comments in symbol_sdf.vertex
     highp float incidence_stretch  = camera_to_anchor_distance / (u_camera_to_center_distance * cos(u_pitch));
     highp float collision_adjustment = max(1.0, incidence_stretch / u_collision_y_stretch);
+    highp float collision_perspective_ratio = 1.0 + (1.0 - u_collision_pitch_scale)*((camera_to_anchor_distance / u_camera_to_center_distance) - 1.0);
 
-    highp float perspective_zoom_adjust = log2(perspective_ratio * collision_adjustment)*10.0 / 255.0;
+    highp float perspective_zoom_adjust = log2(collision_perspective_ratio * collision_adjustment)*10.0 / 255.0;
     v_fade_tex = vec2((a_labelminzoom / 255.0) + perspective_zoom_adjust, 0.0);
 }

src/shaders/symbol_sdf.vertex.glsl

@@ -37,6 +37,7 @@ uniform mediump float u_bearing;
 uniform mediump float u_aspect_ratio;
 uniform mediump float u_camera_to_center_distance;
 uniform mediump float u_pitch_scale;
+uniform mediump float u_collision_pitch_scale;
 uniform mediump float u_collision_y_stretch;
 uniform vec2 u_extrude_scale;
 
@@ -170,7 +171,13 @@ void main() {
     // Never make the adjustment less than 1.0: instead of allowing collisions on the x-axis, be conservative on
     // the y-axis.
     highp float collision_adjustment = max(1.0, incidence_stretch / u_collision_y_stretch);
-
-    highp float perspective_zoom_adjust = log2(perspective_ratio * collision_adjustment)*10.0 / 255.0;
+    // "collision_perspective_ratio" is based on the smallest pitch scaling of any label on the tile, instead of
+    // just the pitch scaling for this label. This is a conservative approximation that makes sure we don't collide
+    // with an unscaled (large) label even though this particular label is highly scaled (and thus small).
+    // Note that this same conservatism doesn't apply to the minzoom/maxzoom for line-following glyphs: those
+    //  zoom bounds are independent of other labels on the tile.
+    highp float collision_perspective_ratio = 1.0 + (1.0 - u_collision_pitch_scale)*((camera_to_anchor_distance / u_camera_to_center_distance) - 1.0);
+
+    highp float perspective_zoom_adjust = log2(collision_perspective_ratio * collision_adjustment)*10.0 / 255.0;
     v_fade_tex = vec2((a_labelminzoom / 255.0) + perspective_zoom_adjust, 0.0);
 }

src/symbol/collision_tile.js

@@ -33,6 +33,8 @@ class CollisionTile {
         this.angle = angle;
         this.pitch = pitch;
 
+        this.minimumPitchScaling = 1;
+
         const sin = Math.sin(angle),
             cos = Math.cos(angle);
         this.rotationMatrix = [cos, -sin, sin, cos];
@@ -314,7 +316,8 @@ class CollisionTile {
      * @param {number} minPlacementScale
      * @private
      */
-    insertCollisionFeature(collisionFeature, minPlacementScale, ignorePlacement) {
+    insertCollisionFeature(collisionFeature, minPlacementScale, ignorePlacement, pitchScaling) {
+        this.minimumPitchScaling = Math.min(pitchScaling, this.minimumPitchScaling);
 
         const grid = ignorePlacement ? this.ignoredGrid : this.grid;
         const collisionBoxArray = this.collisionBoxArray;