1 files changed, 115 insertions, 0 deletions
diff --git a/src/mbgl/shaders/heatmap.cpp b/src/mbgl/shaders/heatmap.cpp
new file mode 100644
index 0000000000..52bc493fe2
--- /dev/null
+++ b/src/mbgl/shaders/heatmap.cpp
@@ -0,0 +1,115 @@
+// 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
+
+
+uniform mat4 u_matrix;
+uniform float u_extrude_scale;
+uniform float u_radius;
+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
+
+
+    // 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 u_radius
+    v_extrude = S * unscaled_extrude;
+
+    // Scale by u_radius and the zoom-based scale factor to produce actual
+    // mesh position
+    vec2 extrude = v_extrude * u_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;
+uniform highp float u_radius;
+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