cca3adb375
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
136 lines
4.4 KiB
C++
136 lines
4.4 KiB
C++
#pragma once
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#include <mbgl/shaders/heatmap_layer_ubo.hpp>
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#include <mbgl/shaders/shader_source.hpp>
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#include <mbgl/shaders/mtl/common.hpp>
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#include <mbgl/shaders/mtl/shader_program.hpp>
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namespace mbgl {
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namespace shaders {
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template <>
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struct ShaderSource<BuiltIn::HeatmapShader, gfx::Backend::Type::Metal> {
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static constexpr auto name = "HeatmapShader";
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static constexpr auto vertexMainFunction = "vertexMain";
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static constexpr auto fragmentMainFunction = "fragmentMain";
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static const std::array<UniformBlockInfo, 3> uniforms;
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static const std::array<AttributeInfo, 3> attributes;
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static constexpr std::array<AttributeInfo, 0> instanceAttributes{};
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static const std::array<TextureInfo, 0> textures;
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static constexpr auto source = R"(
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struct VertexStage {
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short2 pos [[attribute(3)]];
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#if !defined(HAS_UNIFORM_u_weight)
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float2 weight [[attribute(4)]];
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#endif
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#if !defined(HAS_UNIFORM_u_radius)
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float2 radius [[attribute(5)]];
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#endif
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};
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struct FragmentStage {
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float4 position [[position, invariant]];
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float weight;
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float2 extrude;
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};
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struct alignas(16) HeatmapDrawableUBO {
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float4x4 matrix;
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float extrude_scale;
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float pad1;
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float2 pad2;
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};
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struct alignas(16) HeatmapEvaluatedPropsUBO {
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float weight;
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float radius;
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float intensity;
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float pad1;
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};
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struct alignas(16) HeatmapInterpolateUBO {
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float weight_t;
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float radius_t;
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float2 pad1;
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};
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// Effective "0" in the kernel density texture to adjust the kernel size to;
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// this empirically chosen number minimizes artifacts on overlapping kernels
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// for typical heatmap cases (assuming clustered source)
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constant const float ZERO = 1.0 / 255.0 / 16.0;
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// Gaussian kernel coefficient: 1 / sqrt(2 * PI)
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#define GAUSS_COEF 0.3989422804014327
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FragmentStage vertex vertexMain(thread const VertexStage vertx [[stage_in]],
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device const HeatmapDrawableUBO& drawable [[buffer(0)]],
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device const HeatmapEvaluatedPropsUBO& props [[buffer(1)]],
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device const HeatmapInterpolateUBO& interp [[buffer(2)]]) {
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#if defined(HAS_UNIFORM_u_weight)
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const auto weight = props.weight;
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#else
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const auto weight = unpack_mix_float(vertx.weight, interp.weight_t);
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#endif
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#if defined(HAS_UNIFORM_u_radius)
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const auto radius = props.radius;
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#else
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const auto radius = unpack_mix_float(vertx.radius, interp.radius_t);
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#endif
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// unencode the extrusion vector that we snuck into the a_pos vector
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const float2 unscaled_extrude = float2(glMod(float2(vertx.pos), 2.0) * 2.0 - 1.0);
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// This 'extrude' comes in ranging from [-1, -1], to [1, 1]. We'll use
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// it to produce the vertices of a square mesh framing the point feature
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// we're adding to the kernel density texture. We'll also pass it as
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// a varying, so that the fragment shader can determine the distance of
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// each fragment from the point feature.
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// Before we do so, we need to scale it up sufficiently so that the
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// kernel falls effectively to zero at the edge of the mesh.
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// That is, we want to know S such that
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// weight * u_intensity * GAUSS_COEF * exp(-0.5 * 3.0^2 * S^2) == ZERO
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// Which solves to:
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// S = sqrt(-2.0 * log(ZERO / (weight * u_intensity * GAUSS_COEF))) / 3.0
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const float S = sqrt(-2.0 * log(ZERO / weight / props.intensity / GAUSS_COEF)) / 3.0;
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// Pass the varying in units of radius
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const float2 extrude = S * unscaled_extrude;
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// Scale by radius and the zoom-based scale factor to produce actual
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// mesh position
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const float2 scaled_extrude = extrude * radius * drawable.extrude_scale;
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// multiply a_pos by 0.5, since we had it * 2 in order to sneak
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// in extrusion data
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const float4 pos = float4(floor(float2(vertx.pos) * 0.5) + scaled_extrude, 0, 1);
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return {
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.position = drawable.matrix * pos,
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.weight = weight,
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.extrude = extrude,
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};
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}
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half4 fragment fragmentMain(FragmentStage in [[stage_in]],
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device const HeatmapEvaluatedPropsUBO& props [[buffer(1)]]) {
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#if defined(OVERDRAW_INSPECTOR)
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return half4(1.0);
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#endif
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// Kernel density estimation with a Gaussian kernel of size 5x5
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const float d = -0.5 * 3.0 * 3.0 * dot(in.extrude, in.extrude);
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const float val = in.weight * props.intensity * GAUSS_COEF * exp(d);
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return half4(val, 1.0, 1.0, 1.0);
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}
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)";
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};
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} // namespace shaders
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} // namespace mbgl
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