[core] Account for overscaling in debug collision circles.

Fixes issue #11116.
Port of GL JS issue $6041.

4 files changed, 10 insertions, 3 deletions

diff --git a/src/mbgl/programs/collision_box_program.hpp b/src/mbgl/programs/collision_box_program.hpp
index 8d712a3df3..6e75adf36e 100644
--- a/src/mbgl/programs/collision_box_program.hpp
+++ b/src/mbgl/programs/collision_box_program.hpp
@@ -110,6 +110,7 @@ class CollisionCircleProgram : public Program<
     gl::Uniforms<
         uniforms::u_matrix,
         uniforms::u_extrude_scale,
+        uniforms::u_overscale_factor,
         uniforms::u_camera_to_center_distance>,
     style::Properties<>>
 {
diff --git a/src/mbgl/programs/uniforms.hpp b/src/mbgl/programs/uniforms.hpp
index 184f42e504..107c084918 100644
--- a/src/mbgl/programs/uniforms.hpp
+++ b/src/mbgl/programs/uniforms.hpp
@@ -55,6 +55,7 @@ MBGL_DEFINE_UNIFORM_SCALAR(gl::TextureUnit, u_fadetexture);
 MBGL_DEFINE_UNIFORM_SCALAR(float,    u_scale_a);
 MBGL_DEFINE_UNIFORM_SCALAR(float,    u_scale_b);
 MBGL_DEFINE_UNIFORM_SCALAR(float,    u_tile_units_to_pixels);
+MBGL_DEFINE_UNIFORM_SCALAR(float,    u_overscale_factor);
 
 } // namespace uniforms
 } // namespace mbgl
diff --git a/src/mbgl/renderer/layers/render_symbol_layer.cpp b/src/mbgl/renderer/layers/render_symbol_layer.cpp
index 04fcb2c3ab..9e493003c0 100644
--- a/src/mbgl/renderer/layers/render_symbol_layer.cpp
+++ b/src/mbgl/renderer/layers/render_symbol_layer.cpp
@@ -268,9 +268,10 @@ void RenderSymbolLayer::render(PaintParameters& parameters, RenderSource*) {
                 gl::DepthMode::disabled(),
                 gl::StencilMode::disabled(),
                 parameters.colorModeForRenderPass(),
-                CollisionBoxProgram::UniformValues {
+                CollisionCircleProgram::UniformValues {
                     uniforms::u_matrix::Value{ tile.matrix },
                     uniforms::u_extrude_scale::Value{ extrudeScale },
+                    uniforms::u_overscale_factor::Value{ float(tile.tile.id.overscaleFactor()) },
                     uniforms::u_camera_to_center_distance::Value{ parameters.state.getCameraToCenterDistance() }
                 },
                 *bucket.collisionCircle.vertexBuffer,
diff --git a/src/mbgl/shaders/collision_circle.cpp b/src/mbgl/shaders/collision_circle.cpp
index f220586245..82ebbf05a0 100644
--- a/src/mbgl/shaders/collision_circle.cpp
+++ b/src/mbgl/shaders/collision_circle.cpp
@@ -26,7 +26,10 @@ varying vec2 v_extrude_scale;
 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 = 0.5 + 0.5 * (u_camera_to_center_distance / camera_to_anchor_distance);
+    highp float collision_perspective_ratio = clamp(
+        0.5 + 0.5 * (u_camera_to_center_distance / camera_to_anchor_distance),
+        0.0, // Prevents oversized near-field circles in pitched/overzoomed tiles
+        4.0);
 
     gl_Position = u_matrix * vec4(a_pos, 0.0, 1.0);
 
@@ -43,6 +46,7 @@ void main() {
 
 )MBGL_SHADER";
 const char* collision_circle::fragmentSource = R"MBGL_SHADER(
+uniform float u_overscale_factor;
 
 varying float v_placed;
 varying float v_notUsed;
@@ -68,7 +72,7 @@ void main() {
 
     float extrude_scale_length = length(v_extrude_scale);
     float extrude_length = length(v_extrude) * extrude_scale_length;
-    float stroke_width = 15.0 * extrude_scale_length;
+    float stroke_width = 15.0 * extrude_scale_length / u_overscale_factor;
     float radius = v_radius * extrude_scale_length;
 
     float distance_to_edge = abs(extrude_length - radius);