1 files changed, 20 insertions, 47 deletions

diff --git a/src/mbgl/shaders/collision_box.cpp b/src/mbgl/shaders/collision_box.cpp
index 07fa94e338..9d11640bf4 100644
--- a/src/mbgl/shaders/collision_box.cpp
+++ b/src/mbgl/shaders/collision_box.cpp
@@ -10,77 +10,50 @@ const char* collision_box::vertexSource = R"MBGL_SHADER(
 attribute vec2 a_pos;
 attribute vec2 a_anchor_pos;
 attribute vec2 a_extrude;
-attribute vec2 a_data;
+attribute vec2 a_placed;
 
 uniform mat4 u_matrix;
-uniform float u_scale;
-uniform float u_pitch;
-uniform float u_collision_y_stretch;
+uniform vec2 u_extrude_scale;
 uniform float u_camera_to_center_distance;
 
-varying float v_max_zoom;
-varying float v_placement_zoom;
-varying float v_perspective_zoom_adjust;
-varying vec2 v_fade_tex;
+varying float v_placed;
+varying float v_notUsed;
 
 void main() {
     vec4 projectedPoint = u_matrix * vec4(a_anchor_pos, 0, 1);
     highp float camera_to_anchor_distance = projectedPoint.w;
-    highp float collision_perspective_ratio = 1.0 + 0.5 * ((camera_to_anchor_distance / u_camera_to_center_distance) - 1.0);
+    highp float collision_perspective_ratio = 0.5 + 0.5 * (u_camera_to_center_distance / camera_to_anchor_distance);
 
-    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);
+    gl_Position = u_matrix * vec4(a_pos, 0.0, 1.0);
+    gl_Position.xy += a_extrude * u_extrude_scale * gl_Position.w * collision_perspective_ratio;
 
-    gl_Position = u_matrix * vec4(a_pos + a_extrude * collision_perspective_ratio * collision_adjustment / u_scale, 0.0, 1.0);
-
-    v_max_zoom = a_data.x;
-    v_placement_zoom = a_data.y;
-
-    v_perspective_zoom_adjust = floor(log2(collision_perspective_ratio * collision_adjustment) * 10.0);
-    v_fade_tex = vec2((v_placement_zoom + v_perspective_zoom_adjust) / 255.0, 0.0);
+    v_placed = a_placed.x;
+    v_notUsed = a_placed.y;
 }
 
 )MBGL_SHADER";
 const char* collision_box::fragmentSource = R"MBGL_SHADER(
-uniform float u_zoom;
-// u_maxzoom is derived from the maximum scale considered by the CollisionTile
-// Labels with placement zoom greater than this value will not be placed,
-// regardless of perspective effects.
-uniform float u_maxzoom;
-uniform sampler2D u_fadetexture;
-
-// v_max_zoom is a collision-box-specific value that controls when line-following
-// collision boxes are used.
-varying float v_max_zoom;
-varying float v_placement_zoom;
-varying float v_perspective_zoom_adjust;
-varying vec2 v_fade_tex;
+
+varying float v_placed;
+varying float v_notUsed;
 
 void main() {
 
     float alpha = 0.5;
 
-    // Green = no collisions, label is showing
-    gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0) * alpha;
+    // Red = collision, hide label
+    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0) * alpha;
 
-    // Red = collision, label hidden
-    if (texture2D(u_fadetexture, v_fade_tex).a < 1.0) {
-        gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0) * alpha;
+    // Blue = no collision, label is showing
+    if (v_placed > 0.5) {
+        gl_FragColor = vec4(0.0, 0.0, 1.0, 0.5) * alpha;
     }
 
-    // Faded black = this collision box is not used at this zoom (for curved labels)
-    if (u_zoom >= v_max_zoom + v_perspective_zoom_adjust) {
-        gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0) * alpha * 0.25;
-    }
-
-    // Faded blue = the placement scale for this label is beyond the CollisionTile
-    // max scale, so it's impossible for this label to show without collision detection
-    // being run again (the label's glyphs haven't even been added to the symbol bucket)
-    if (v_placement_zoom >= u_maxzoom) {
-        gl_FragColor = vec4(0.0, 0.0, 1.0, 1.0) * alpha * 0.2;
+    if (v_notUsed > 0.5) {
+        // This box not used, fade it out
+        gl_FragColor *= .1;
     }
 }
-
 )MBGL_SHADER";
 
 } // namespace shaders