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// 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
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