1 files changed, 28 insertions, 16 deletions

diff --git a/src/mbgl/shaders/symbol_icon.cpp b/src/mbgl/shaders/symbol_icon.cpp
index bc570cf361..8960e02c28 100644
--- a/src/mbgl/shaders/symbol_icon.cpp
+++ b/src/mbgl/shaders/symbol_icon.cpp
@@ -7,17 +7,20 @@ namespace shaders {
 
 const char* symbol_icon::name = "symbol_icon";
 const char* symbol_icon::vertexSource = R"MBGL_SHADER(
-
 attribute vec4 a_pos_offset;
+attribute vec2 a_label_pos;
 attribute vec4 a_data;
 
 // icon-size data (see symbol_sdf.vertex.glsl for more)
 attribute vec3 a_size;
 uniform bool u_is_size_zoom_constant;
 uniform bool u_is_size_feature_constant;
-uniform mediump float u_size_t; // used to interpolate between zoom stops when size is a composite function
-uniform mediump float u_size; // used when size is both zoom and feature constant
-uniform mediump float u_layout_size; // used when size is feature constant
+uniform highp float u_size_t; // used to interpolate between zoom stops when size is a composite function
+uniform highp float u_size; // used when size is both zoom and feature constant
+uniform highp float u_layout_size; // used when size is feature constant
+uniform highp float u_camera_to_center_distance;
+uniform highp float u_pitch;
+uniform highp float u_collision_y_stretch;
 
 
 #ifndef HAS_UNIFORM_u_opacity
@@ -32,7 +35,7 @@ uniform lowp float u_opacity;
 uniform mat4 u_matrix;
 
 uniform bool u_is_text;
-uniform mediump float u_zoom;
+uniform highp float u_zoom;
 uniform bool u_rotate_with_map;
 uniform vec2 u_extrude_scale;
 
@@ -53,11 +56,11 @@ void main() {
     vec2 a_offset = a_pos_offset.zw;
 
     vec2 a_tex = a_data.xy;
-    mediump vec2 label_data = unpack_float(a_data[2]);
-    mediump float a_labelminzoom = label_data[0];
-    mediump vec2 a_zoom = unpack_float(a_data[3]);
-    mediump float a_minzoom = a_zoom[0];
-    mediump float a_maxzoom = a_zoom[1];
+    highp vec2 label_data = unpack_float(a_data[2]);
+    highp float a_labelminzoom = label_data[0];
+    highp vec2 a_zoom = unpack_float(a_data[3]);
+    highp float a_minzoom = a_zoom[0];
+    highp float a_maxzoom = a_zoom[1];
 
     float size;
     // In order to accommodate placing labels around corners in
@@ -68,7 +71,7 @@ void main() {
     // currently rendered zoom level if text-size is zoom-dependent.
     // Thus, we compensate for this difference by calculating an adjustment
     // based on the scale of rendered text size relative to layout text size.
-    mediump float layoutSize;
+    highp float layoutSize;
     if (!u_is_size_zoom_constant && !u_is_size_feature_constant) {
         size = mix(a_size[0], a_size[1], u_size_t) / 10.0;
         layoutSize = a_size[2] / 10.0;
@@ -85,12 +88,16 @@ void main() {
 
     float fontScale = u_is_text ? size / 24.0 : size;
 
-    mediump float zoomAdjust = log2(size / layoutSize);
-    mediump float adjustedZoom = (u_zoom - zoomAdjust) * 10.0;
+    highp float zoomAdjust = log2(size / layoutSize);
+    highp float adjustedZoom = (u_zoom - zoomAdjust) * 10.0;
     // result: z = 0 if a_minzoom <= adjustedZoom < a_maxzoom, and 1 otherwise
-    mediump float z = 2.0 - step(a_minzoom, adjustedZoom) - (1.0 - step(a_maxzoom, adjustedZoom));
+    highp float z = 2.0 - step(a_minzoom, adjustedZoom) - (1.0 - step(a_maxzoom, adjustedZoom));
+
+    vec4 projectedPoint = u_matrix * vec4(a_label_pos, 0, 1);
+    highp float camera_to_anchor_distance = projectedPoint.w;
+    highp float perspective_ratio = 1.0 + 0.5*((camera_to_anchor_distance / u_camera_to_center_distance) - 1.0);
 
-    vec2 extrude = fontScale * u_extrude_scale * (a_offset / 64.0);
+    vec2 extrude = fontScale * u_extrude_scale * perspective_ratio * (a_offset / 64.0);
     if (u_rotate_with_map) {
         gl_Position = u_matrix * vec4(a_pos + extrude, 0, 1);
         gl_Position.z += z * gl_Position.w;
@@ -99,7 +106,12 @@ void main() {
     }
 
     v_tex = a_tex / u_texsize;
-    v_fade_tex = vec2(a_labelminzoom / 255.0, 0.0);
+    // 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 perspective_zoom_adjust = log2(perspective_ratio * collision_adjustment) * 10.0;
+    v_fade_tex = vec2((a_labelminzoom + perspective_zoom_adjust) / 255.0, 0.0);
 }
 
 )MBGL_SHADER";