6 files changed, 213 insertions, 6 deletions
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);
diff --git a/src/mbgl/shaders/heatmap.cpp b/src/mbgl/shaders/heatmap.cpp
new file mode 100644
index 0000000000..19927cfcc6
--- /dev/null
+++ b/src/mbgl/shaders/heatmap.cpp
@@ -0,0 +1,128 @@
+// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.
+
+#include <mbgl/shaders/heatmap.hpp>
+
+namespace mbgl {
+namespace shaders {
+
+const char* heatmap::name = "heatmap";
+const char* heatmap::vertexSource = R"MBGL_SHADER(
+
+#ifndef HAS_UNIFORM_u_weight
+uniform lowp float a_weight_t;
+attribute highp vec2 a_weight;
+varying highp float weight;
+#else
+uniform highp float u_weight;
+#endif
+
+
+#ifndef HAS_UNIFORM_u_radius
+uniform lowp float a_radius_t;
+attribute mediump vec2 a_radius;
+#else
+uniform mediump float u_radius;
+#endif
+
+
+uniform mat4 u_matrix;
+uniform float u_extrude_scale;
+uniform float u_opacity;
+uniform float u_intensity;
+
+attribute vec2 a_pos;
+
+varying vec2 v_extrude;
+
+// Effective "0" in the kernel density texture to adjust the kernel size to;
+// this empirically chosen number minimizes artifacts on overlapping kernels
+// for typical heatmap cases (assuming clustered source)
+const highp float ZERO = 1.0 / 255.0 / 16.0;
+
+// Gaussian kernel coefficient: 1 / sqrt(2 * PI)
+#define GAUSS_COEF 0.3989422804014327
+
+void main(void) {
+    
+#ifndef HAS_UNIFORM_u_weight
+    weight = unpack_mix_vec2(a_weight, a_weight_t);
+#else
+    highp float weight = u_weight;
+#endif
+
+    
+#ifndef HAS_UNIFORM_u_radius
+    mediump float radius = unpack_mix_vec2(a_radius, a_radius_t);
+#else
+    mediump float radius = u_radius;
+#endif
+
+
+    // unencode the extrusion vector that we snuck into the a_pos vector
+    vec2 unscaled_extrude = vec2(mod(a_pos, 2.0) * 2.0 - 1.0);
+
+    // This 'extrude' comes in ranging from [-1, -1], to [1, 1].  We'll use
+    // it to produce the vertices of a square mesh framing the point feature
+    // we're adding to the kernel density texture.  We'll also pass it as
+    // a varying, so that the fragment shader can determine the distance of
+    // each fragment from the point feature.
+    // Before we do so, we need to scale it up sufficiently so that the
+    // kernel falls effectively to zero at the edge of the mesh.
+    // That is, we want to know S such that
+    // weight * u_intensity * GAUSS_COEF * exp(-0.5 * 3.0^2 * S^2) == ZERO
+    // Which solves to:
+    // S = sqrt(-2.0 * log(ZERO / (weight * u_intensity * GAUSS_COEF))) / 3.0
+    float S = sqrt(-2.0 * log(ZERO / weight / u_intensity / GAUSS_COEF)) / 3.0;
+
+    // Pass the varying in units of radius
+    v_extrude = S * unscaled_extrude;
+
+    // Scale by radius and the zoom-based scale factor to produce actual
+    // mesh position
+    vec2 extrude = v_extrude * radius * u_extrude_scale;
+
+    // multiply a_pos by 0.5, since we had it * 2 in order to sneak
+    // in extrusion data
+    vec4 pos = vec4(floor(a_pos * 0.5) + extrude, 0, 1);
+
+    gl_Position = u_matrix * pos;
+}
+
+)MBGL_SHADER";
+const char* heatmap::fragmentSource = R"MBGL_SHADER(
+
+#ifndef HAS_UNIFORM_u_weight
+varying highp float weight;
+#else
+uniform highp float u_weight;
+#endif
+
+
+uniform highp float u_intensity;
+varying vec2 v_extrude;
+
+// Gaussian kernel coefficient: 1 / sqrt(2 * PI)
+#define GAUSS_COEF 0.3989422804014327
+
+void main() {
+    
+#ifdef HAS_UNIFORM_u_weight
+    highp float weight = u_weight;
+#endif
+
+
+    // Kernel density estimation with a Gaussian kernel of size 5x5
+    float d = -0.5 * 3.0 * 3.0 * dot(v_extrude, v_extrude);
+    float val = weight * u_intensity * GAUSS_COEF * exp(d);
+
+    gl_FragColor = vec4(val, 1.0, 1.0, 1.0);
+
+#ifdef OVERDRAW_INSPECTOR
+    gl_FragColor = vec4(1.0);
+#endif
+}
+
+)MBGL_SHADER";
+
+} // namespace shaders
+} // namespace mbgl
diff --git a/src/mbgl/shaders/heatmap.hpp b/src/mbgl/shaders/heatmap.hpp
new file mode 100644
index 0000000000..a3c64db942
--- /dev/null
+++ b/src/mbgl/shaders/heatmap.hpp
@@ -0,0 +1,16 @@
+// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.
+
+#pragma once
+
+namespace mbgl {
+namespace shaders {
+
+class heatmap {
+public:
+    static const char* name;
+    static const char* vertexSource;
+    static const char* fragmentSource;
+};
+
+} // namespace shaders
+} // namespace mbgl
diff --git a/src/mbgl/shaders/heatmap_texture.cpp b/src/mbgl/shaders/heatmap_texture.cpp
new file mode 100644
index 0000000000..c5d35c48ae
--- /dev/null
+++ b/src/mbgl/shaders/heatmap_texture.cpp
@@ -0,0 +1,42 @@
+// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.
+
+#include <mbgl/shaders/heatmap_texture.hpp>
+
+namespace mbgl {
+namespace shaders {
+
+const char* heatmap_texture::name = "heatmap_texture";
+const char* heatmap_texture::vertexSource = R"MBGL_SHADER(
+uniform mat4 u_matrix;
+uniform vec2 u_world;
+attribute vec2 a_pos;
+varying vec2 v_pos;
+
+void main() {
+    gl_Position = u_matrix * vec4(a_pos * u_world, 0, 1);
+
+    v_pos.x = a_pos.x;
+    v_pos.y = 1.0 - a_pos.y;
+}
+
+)MBGL_SHADER";
+const char* heatmap_texture::fragmentSource = R"MBGL_SHADER(
+uniform sampler2D u_image;
+uniform sampler2D u_color_ramp;
+uniform float u_opacity;
+varying vec2 v_pos;
+
+void main() {
+    float t = texture2D(u_image, v_pos).r;
+    vec4 color = texture2D(u_color_ramp, vec2(t, 0.5));
+    gl_FragColor = color * u_opacity;
+
+#ifdef OVERDRAW_INSPECTOR
+    gl_FragColor = vec4(0.0);
+#endif
+}
+
+)MBGL_SHADER";
+
+} // namespace shaders
+} // namespace mbgl
diff --git a/src/mbgl/shaders/heatmap_texture.hpp b/src/mbgl/shaders/heatmap_texture.hpp
new file mode 100644
index 0000000000..c51dc6b178
--- /dev/null
+++ b/src/mbgl/shaders/heatmap_texture.hpp
@@ -0,0 +1,16 @@
+// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.
+
+#pragma once
+
+namespace mbgl {
+namespace shaders {
+
+class heatmap_texture {
+public:
+    static const char* name;
+    static const char* vertexSource;
+    static const char* fragmentSource;
+};
+
+} // namespace shaders
+} // namespace mbgl
diff --git a/src/mbgl/shaders/hillshade_prepare.cpp b/src/mbgl/shaders/hillshade_prepare.cpp
index 733658435e..8d0571f6a4 100644
--- a/src/mbgl/shaders/hillshade_prepare.cpp
+++ b/src/mbgl/shaders/hillshade_prepare.cpp
@@ -29,6 +29,7 @@ uniform sampler2D u_image;
 varying vec2 v_pos;
 uniform vec2 u_dimension;
 uniform float u_zoom;
+uniform float u_maxzoom;
 
 float getElevation(vec2 coord, float bias) {
     // Convert encoded elevation value to meters
@@ -71,16 +72,16 @@ void main() {
     // which can be reduced to: pow(2, 19.25619978527 - u_zoom)
     // we want to vertically exaggerate the hillshading though, because otherwise
     // it is barely noticeable at low zooms. to do this, we multiply this by some
-    // scale factor pow(2, (u_zoom - 14) * a) where a is an arbitrary value and 14 is the
-    // maxzoom of the tile source. here we use a=0.3 which works out to the
-    // expression below. see nickidlugash's awesome breakdown for more info
+    // scale factor pow(2, (u_zoom - u_maxzoom) * a) where a is an arbitrary value
+    // Here we use a=0.3 which works out to the expression below. see 
+    // nickidlugash's awesome breakdown for more info
     // https://github.com/mapbox/mapbox-gl-js/pull/5286#discussion_r148419556
     float exaggeration = u_zoom < 2.0 ? 0.4 : u_zoom < 4.5 ? 0.35 : 0.3;
 
     vec2 deriv = vec2(
         (c + f + f + i) - (a + d + d + g),
         (g + h + h + i) - (a + b + b + c)
-    ) /  pow(2.0, (u_zoom - 14.0) * exaggeration + 19.2562 - u_zoom);
+    ) /  pow(2.0, (u_zoom - u_maxzoom) * exaggeration + 19.2562 - u_zoom);
 
     gl_FragColor = clamp(vec4(
         deriv.x / 2.0 + 0.5,