265 lines
11 KiB
C++
265 lines
11 KiB
C++
#pragma once
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#include <mbgl/shaders/hillshade_layer_ubo.hpp>
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#include <mbgl/shaders/shader_source.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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constexpr auto hillshadeShaderPrelude = R"(
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enum {
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idHillshadeDrawableUBO = idDrawableReservedVertexOnlyUBO,
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idHillshadeTilePropsUBO = idDrawableReservedFragmentOnlyUBO,
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idHillshadeEvaluatedPropsUBO = drawableReservedUBOCount,
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hillshadeUBOCount
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};
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struct alignas(16) HillshadeDrawableUBO {
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/* 0 */ float4x4 matrix;
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/* 64 */
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};
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static_assert(sizeof(HillshadeDrawableUBO) == 4 * 16, "wrong size");
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struct alignas(16) HillshadeTilePropsUBO {
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/* 0 */ float2 latrange;
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/* 8 */ float exaggeration;
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/* 12 */ int32_t method;
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/* 16 */ int32_t num_lights;
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/* 20 */ float pad0;
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/* 24 */ float pad1;
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/* 28 */ float pad2;
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/* 32 */
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};
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static_assert(sizeof(HillshadeTilePropsUBO) == 2 * 16, "wrong size");
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/// Evaluated properties that do not depend on the tile
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struct alignas(16) HillshadeEvaluatedPropsUBO {
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/* 0 */ float4 accent;
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/* 16 */ float4 altitudes; // Up to 4 altitude values (in radians)
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/* 32 */ float4 azimuths; // Up to 4 azimuth values (in radians)
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/* 48 */ float4 shadows[4]; // Shadow colors (up to 4 lights)
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/* 112 */ float4 highlights[4]; // Highlight colors (up to 4 lights)
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/* 176 */
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};
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static_assert(sizeof(HillshadeEvaluatedPropsUBO) == 11 * 16, "wrong size");
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)";
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template <>
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struct ShaderSource<BuiltIn::HillshadeShader, gfx::Backend::Type::Metal> {
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static constexpr auto name = "HillshadeShader";
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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<AttributeInfo, 2> attributes;
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static constexpr std::array<AttributeInfo, 0> instanceAttributes{};
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static const std::array<TextureInfo, 1> textures;
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static constexpr auto prelude = hillshadeShaderPrelude;
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static constexpr auto source = R"(
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#define PI 3.141592653589793
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#define STANDARD 0
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#define COMBINED 1
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#define IGOR 2
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#define MULTIDIRECTIONAL 3
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#define BASIC 4
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struct VertexStage {
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short2 pos [[attribute(hillshadeUBOCount + 0)]];
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short2 texture_pos [[attribute(hillshadeUBOCount + 1)]];
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};
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struct FragmentStage {
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float4 position [[position, invariant]];
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float2 pos;
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};
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FragmentStage vertex vertexMain(thread const VertexStage vertx [[stage_in]],
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device const uint32_t& uboIndex [[buffer(idGlobalUBOIndex)]],
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device const HillshadeDrawableUBO* drawableVector [[buffer(idHillshadeDrawableUBO)]]) {
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device const HillshadeDrawableUBO& drawable = drawableVector[uboIndex];
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const float4 position = drawable.matrix * float4(float2(vertx.pos), 0, 1);
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float2 pos = float2(vertx.texture_pos) / 8192.0;
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// Metal's texture coordinate origin differs from some renderers;
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// restore Y-flip to match prepare pass and historical behavior.
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pos.y = 1.0 - pos.y;
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return {
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.position = position,
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.pos = pos,
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};
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}
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// Helper function to calculate aspect (normalized direction of slope)
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float get_aspect(float2 deriv) {
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return deriv.x != 0.0 ? atan2(deriv.y, -deriv.x) : PI / 2.0 * (deriv.y > 0.0 ? 1.0 : -1.0);
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}
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// MapLibre's legacy hillshade algorithm (Method 0: STANDARD)
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void standard_hillshade(float2 deriv, device const HillshadeTilePropsUBO& tileProps, device const HillshadeEvaluatedPropsUBO& props, thread half4& fragColor) {
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float azimuth = props.azimuths.x + PI;
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float slope = atan(0.625 * length(deriv));
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float aspect = get_aspect(deriv);
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float intensity = tileProps.exaggeration;
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// Scale the slope exponentially based on intensity
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float base = 1.875 - intensity * 1.75;
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float maxValue = 0.5 * PI;
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float scaledSlope = abs(intensity - 0.5) > 1e-6 ? ((pow(base, slope) - 1.0) / (pow(base, maxValue) - 1.0)) * maxValue : slope;
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float accent = cos(scaledSlope);
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float4 accent_color = (1.0 - accent) * props.accent * clamp(intensity * 2.0, 0.0, 1.0);
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float shade = abs(glMod((aspect + azimuth) / PI + 0.5, 2.0) - 1.0);
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float4 shade_color = mix(props.shadows[0], props.highlights[0], shade) * sin(scaledSlope) * clamp(intensity * 2.0, 0.0, 1.0);
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fragColor = half4(accent_color * (1.0 - shade_color.a) + shade_color);
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}
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// Basic directional hillshade (Method 4: BASIC)
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void basic_hillshade(float2 deriv, device const HillshadeTilePropsUBO& tileProps, device const HillshadeEvaluatedPropsUBO& props, thread half4& fragColor) {
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deriv = deriv * tileProps.exaggeration * 2.0;
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float azimuth = props.azimuths.x + PI;
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float cos_az = cos(azimuth);
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float sin_az = sin(azimuth);
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float cos_alt = cos(props.altitudes.x);
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float sin_alt = sin(props.altitudes.x);
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// Calculate the cosine of the angle between the light vector and the surface normal
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float cang = (sin_alt - (deriv.y * cos_az * cos_alt - deriv.x * sin_az * cos_alt)) / sqrt(1.0 + dot(deriv, deriv));
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float shade = clamp(cang, 0.0, 1.0);
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// Blend shadow and highlight based on intensity
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if (shade > 0.5) {
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fragColor = half4(props.highlights[0] * (2.0 * shade - 1.0));
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} else {
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fragColor = half4(props.shadows[0] * (1.0 - 2.0 * shade));
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}
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}
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// Multidirectional hillshade (Method 3: MULTIDIRECTIONAL)
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void multidirectional_hillshade(float2 deriv, device const HillshadeTilePropsUBO& tileProps, device const HillshadeEvaluatedPropsUBO& props, thread half4& fragColor) {
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deriv = deriv * tileProps.exaggeration * 2.0;
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float4 total_color = float4(0, 0, 0, 0);
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int num_lights = min(tileProps.num_lights, 4);
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// Iterate through all light sources
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for (int i = 0; i < num_lights; i++) {
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// Access altitude and azimuth from vec4 UBOs
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float altitude = (i == 0) ? props.altitudes.x : (i == 1) ? props.altitudes.y : (i == 2) ? props.altitudes.z : props.altitudes.w;
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float azimuth = (i == 0) ? props.azimuths.x : (i == 1) ? props.azimuths.y : (i == 2) ? props.azimuths.z : props.azimuths.w;
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float cos_alt = cos(altitude);
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float sin_alt = sin(altitude);
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// Negate cos/sin azimuth for correct light direction
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float cos_az = -cos(azimuth);
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float sin_az = -sin(azimuth);
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// Calculate the cosine of the angle between the light vector and the surface normal
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float cang = (sin_alt - (deriv.y * cos_az * cos_alt - deriv.x * sin_az * cos_alt)) / sqrt(1.0 + dot(deriv, deriv));
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float shade = clamp(cang, 0.0, 1.0);
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// Accumulate shadow/highlight contribution from each light
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if (shade > 0.5) {
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total_color += props.highlights[i] * (2.0 * shade - 1.0) / float(num_lights);
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} else {
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total_color += props.shadows[i] * (1.0 - 2.0 * shade) / float(num_lights);
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}
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}
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fragColor = half4(total_color);
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}
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// Combined shadow and highlight method (Method 1: COMBINED)
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void combined_hillshade(float2 deriv, device const HillshadeTilePropsUBO& tileProps, device const HillshadeEvaluatedPropsUBO& props, thread half4& fragColor) {
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// Only supports one light source (index 0)
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deriv = deriv * tileProps.exaggeration * 2.0;
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float azimuth = props.azimuths.x + PI;
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float cos_az = cos(azimuth);
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float sin_az = sin(azimuth);
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float cos_alt = cos(props.altitudes.x);
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float sin_alt = sin(props.altitudes.x);
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// Calculate the angle between the light vector and the surface normal
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float cang = acos((sin_alt - (deriv.y * cos_az * cos_alt - deriv.x * sin_az * cos_alt)) / sqrt(1.0 + dot(deriv, deriv)));
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cang = clamp(cang, 0.0, PI / 2.0);
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// Calculate shade and highlight components from angle and slope magnitude
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float shade = cang * atan(length(deriv)) * 4.0 / PI / PI;
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float highlight = (PI / 2.0 - cang) * atan(length(deriv)) * 4.0 / PI / PI;
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fragColor = half4(props.shadows[0] * shade + props.highlights[0] * highlight);
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}
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// Igor's shadow/highlight method (Method 2: IGOR)
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void igor_hillshade(float2 deriv, device const HillshadeTilePropsUBO& tileProps, device const HillshadeEvaluatedPropsUBO& props, thread half4& fragColor) {
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// Only supports one light source (index 0)
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deriv = deriv * tileProps.exaggeration * 2.0;
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float aspect = get_aspect(deriv);
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float azimuth = props.azimuths.x + PI;
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// Slope strength is magnitude of slope vector, normalized to [0, 1]
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float slope_strength = atan(length(deriv)) * 2.0 / PI;
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// Aspect strength is difference between aspect and light azimuth, normalized to [0, 1]
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float aspect_strength = 1.0 - abs(glMod((aspect + azimuth) / PI + 0.5, 2.0) - 1.0);
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float shadow_strength = slope_strength * aspect_strength;
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float highlight_strength = slope_strength * (1.0 - aspect_strength);
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fragColor = half4(props.shadows[0] * shadow_strength + props.highlights[0] * highlight_strength);
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}
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half4 fragment fragmentMain(FragmentStage in [[stage_in]],
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device const uint32_t& uboIndex [[buffer(idGlobalUBOIndex)]],
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device const HillshadeTilePropsUBO* tilePropsVector [[buffer(idHillshadeTilePropsUBO)]],
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device const HillshadeEvaluatedPropsUBO& props [[buffer(idHillshadeEvaluatedPropsUBO)]],
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texture2d<float, access::sample> image [[texture(0)]],
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sampler image_sampler [[sampler(0)]]) {
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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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device const HillshadeTilePropsUBO& tileProps = tilePropsVector[uboIndex];
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thread half4 fragColor;
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float4 pixel = image.sample(image_sampler, in.pos);
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// Scale the derivative based on the mercator distortion at this latitude
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float latitude = (tileProps.latrange.x - tileProps.latrange.y) * in.pos.y + tileProps.latrange.y;
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float scaleFactor = cos(radians(latitude));
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// The derivative is scaled back from [0, 1] texture range to world-space slope
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// Texture range [0, 1] corresponds to slope range [-4, 4]
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float2 deriv = ((pixel.rg * 8.0) - 4.0) / scaleFactor;
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// Dispatch to the selected hillshade method
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if (tileProps.method == BASIC) {
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basic_hillshade(deriv, tileProps, props, fragColor);
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} else if (tileProps.method == COMBINED) {
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combined_hillshade(deriv, tileProps, props, fragColor);
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} else if (tileProps.method == IGOR) {
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igor_hillshade(deriv, tileProps, props, fragColor);
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} else if (tileProps.method == MULTIDIRECTIONAL) {
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multidirectional_hillshade(deriv, tileProps, props, fragColor);
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} else {
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// Default to STANDARD
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standard_hillshade(deriv, tileProps, props, fragColor);
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}
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return fragColor;
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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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