Update Hillshade Algorithms and add Color-Relief Layer support.

CMakeLists.txt

@@ -247,6 +247,7 @@ list(APPEND INCLUDE_FILES
     ${PROJECT_SOURCE_DIR}/include/mbgl/layermanager/fill_layer_factory.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/layermanager/heatmap_layer_factory.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/layermanager/hillshade_layer_factory.hpp
+    ${PROJECT_SOURCE_DIR}/include/mbgl/layermanager/color_relief_layer_factory.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/layermanager/layer_factory.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/layermanager/layer_manager.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/layermanager/line_layer_factory.hpp
@@ -358,6 +359,7 @@ list(APPEND INCLUDE_FILES
     ${PROJECT_SOURCE_DIR}/include/mbgl/style/layers/fill_layer.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/style/layers/heatmap_layer.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/style/layers/hillshade_layer.hpp
+    ${PROJECT_SOURCE_DIR}/include/mbgl/style/layers/color_relief_layer.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/style/layers/line_layer.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/style/layers/location_indicator_layer.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/style/layers/raster_layer.hpp
@@ -497,6 +499,7 @@ list(APPEND SRC_FILES
     ${PROJECT_SOURCE_DIR}/src/mbgl/layermanager/fill_layer_factory.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/layermanager/heatmap_layer_factory.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/layermanager/hillshade_layer_factory.cpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/layermanager/color_relief_layer_factory.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/layermanager/layer_factory.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/layermanager/layer_manager.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/layermanager/line_layer_factory.cpp
@@ -578,6 +581,10 @@ list(APPEND SRC_FILES
     ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_heatmap_layer.hpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_hillshade_layer.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_hillshade_layer.hpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_color_relief_layer.cpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_color_relief_layer.hpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/color_relief_layer_tweaker.cpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/color_relief_layer_tweaker.hpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_line_layer.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_line_layer.hpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/renderer/layers/render_raster_layer.cpp
@@ -676,6 +683,7 @@ list(APPEND SRC_FILES
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/conversion/light.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/conversion/position.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/conversion/property_value.cpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/style/conversion/hillshade_conversions.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/conversion/rotation.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/conversion/source.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/conversion/source_options.cpp
@@ -761,6 +769,11 @@ list(APPEND SRC_FILES
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/hillshade_layer_impl.hpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/hillshade_layer_properties.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/hillshade_layer_properties.hpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/color_relief_layer.cpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/color_relief_layer_impl.cpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/color_relief_layer_impl.hpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/color_relief_layer_properties.cpp
+    ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/color_relief_layer_properties.hpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/line_layer.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/line_layer_impl.cpp
     ${PROJECT_SOURCE_DIR}/src/mbgl/style/layers/line_layer_impl.hpp
@@ -1012,6 +1025,7 @@ if(MLN_WITH_OPENGL)
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/gl/heatmap_texture.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/gl/hillshade_prepare.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/gl/hillshade.hpp
+            ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/gl/color_relief.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/gl/line.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/gl/line_gradient.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/gl/line_pattern.hpp
@@ -1088,6 +1102,7 @@ if(MLN_WITH_OPENGL)
         ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/heatmap_layer_ubo.hpp
         ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/heatmap_texture_layer_ubo.hpp
         ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/hillshade_layer_ubo.hpp
+        ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/color_relief_layer_ubo.hpp
         ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/hillshade_prepare_layer_ubo.hpp
         ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/layer_ubo.hpp
         ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/line_layer_ubo.hpp
@@ -1163,6 +1178,7 @@ if(MLN_WITH_METAL)
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/mtl/heatmap_texture.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/mtl/hillshade.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/mtl/hillshade_prepare.hpp
+            ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/mtl/color_relief.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/mtl/line.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/mtl/location_indicator.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/mtl/raster.hpp
@@ -1204,6 +1220,7 @@ if(MLN_WITH_METAL)
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/mtl/heatmap_texture.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/mtl/hillshade.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/mtl/hillshade_prepare.cpp
+            ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/mtl/color_relief.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/mtl/line.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/mtl/location_indicator.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/mtl/raster.cpp
@@ -1264,6 +1281,7 @@ if(MLN_WITH_VULKAN)
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/vulkan/heatmap_texture.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/vulkan/hillshade.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/vulkan/hillshade_prepare.hpp
+            ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/vulkan/color_relief.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/vulkan/line.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/vulkan/location_indicator.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/vulkan/raster.hpp
@@ -1307,6 +1325,7 @@ if(MLN_WITH_VULKAN)
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/vulkan/heatmap_texture.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/vulkan/hillshade.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/vulkan/hillshade_prepare.cpp
+            ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/vulkan/color_relief.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/vulkan/line.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/vulkan/location_indicator.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/vulkan/raster.cpp
@@ -1350,6 +1369,7 @@ if(MLN_WITH_WEBGPU)
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/webgpu/heatmap_texture.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/webgpu/hillshade.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/webgpu/hillshade_prepare.cpp
+            ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/webgpu/color_relief.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/webgpu/line.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/webgpu/location_indicator.cpp
             ${PROJECT_SOURCE_DIR}/src/mbgl/shaders/webgpu/raster.cpp
@@ -1388,6 +1408,7 @@ if(MLN_WITH_WEBGPU)
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/webgpu/heatmap_texture.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/webgpu/hillshade.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/webgpu/hillshade_prepare.hpp
+            ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/webgpu/color_relief.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/webgpu/line.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/webgpu/location_indicator.hpp
             ${PROJECT_SOURCE_DIR}/include/mbgl/shaders/webgpu/raster.hpp
@@ -1587,7 +1608,7 @@ target_link_libraries(
         mbgl-vendor-unique_resource
         mbgl-vendor-vector-tile
         mbgl-vendor-wagyu
-	    mlt-cpp
+        mlt-cpp
         $<$<BOOL:${MLN_WITH_METAL}>:mbgl-vendor-metal-cpp>
         $<IF:$<BOOL:${MLN_USE_RUST}>,mbgl-rustutils,mbgl-vendor-csscolorparser>
         $<$<BOOL:${MLN_TEXT_SHAPING_HARFBUZZ}>:mbgl-freetype>

bazel/core.bzl

@@ -23,6 +23,7 @@ MLN_PUBLIC_GENERATED_STYLE_HEADERS = [
     "include/mbgl/style/layers/fill_extrusion_layer.hpp",
     "include/mbgl/style/layers/raster_layer.hpp",
     "include/mbgl/style/layers/hillshade_layer.hpp",
+    "include/mbgl/style/layers/color_relief_layer.hpp",
     "include/mbgl/style/layers/background_layer.hpp",
     "include/mbgl/style/layers/location_indicator_layer.hpp",
     "include/mbgl/style/light.hpp",
@@ -58,6 +59,8 @@ MLN_GENERATED_STYLE_SOURCE = [
     "src/mbgl/style/layers/raster_layer.cpp",
     "src/mbgl/style/layers/hillshade_layer_properties.cpp",
     "src/mbgl/style/layers/hillshade_layer.cpp",
+    "src/mbgl/style/layers/color_relief_layer_properties.cpp",
+    "src/mbgl/style/layers/color_relief_layer.cpp",
     "src/mbgl/style/layers/background_layer_properties.cpp",
     "src/mbgl/style/layers/background_layer.cpp",
     "src/mbgl/style/layers/location_indicator_layer_properties.cpp",
@@ -95,6 +98,7 @@ MLN_GENERATED_OPENGL_SHADER_HEADERS = [
     "include/mbgl/shaders/gl/heatmap_texture.hpp",
     "include/mbgl/shaders/gl/hillshade_prepare.hpp",
     "include/mbgl/shaders/gl/hillshade.hpp",
+    "include/mbgl/shaders/gl/color_relief.hpp",
     "include/mbgl/shaders/gl/line_gradient.hpp",
     "include/mbgl/shaders/gl/line_pattern.hpp",
     "include/mbgl/shaders/gl/line_sdf.hpp",
@@ -161,6 +165,7 @@ MLN_CORE_SOURCE = [
     "src/mbgl/layermanager/fill_layer_factory.cpp",
     "src/mbgl/layermanager/heatmap_layer_factory.cpp",
     "src/mbgl/layermanager/hillshade_layer_factory.cpp",
+    "src/mbgl/layermanager/color_relief_layer_factory.cpp",
     "src/mbgl/layermanager/layer_factory.cpp",
     "src/mbgl/layermanager/layer_manager.cpp",
     "src/mbgl/layermanager/line_layer_factory.cpp",
@@ -237,6 +242,8 @@ MLN_CORE_SOURCE = [
     "src/mbgl/renderer/layers/render_heatmap_layer.hpp",
     "src/mbgl/renderer/layers/render_hillshade_layer.cpp",
     "src/mbgl/renderer/layers/render_hillshade_layer.hpp",
+    "src/mbgl/renderer/layers/render_color_relief_layer.cpp",
+    "src/mbgl/renderer/layers/render_color_relief_layer.hpp",
     "src/mbgl/renderer/layers/render_line_layer.cpp",
     "src/mbgl/renderer/layers/render_line_layer.hpp",
     "src/mbgl/renderer/layers/render_location_indicator_layer.cpp",
@@ -336,6 +343,7 @@ MLN_CORE_SOURCE = [
     "src/mbgl/style/conversion/light.cpp",
     "src/mbgl/style/conversion/position.cpp",
     "src/mbgl/style/conversion/property_value.cpp",
+    "src/mbgl/style/conversion/hillshade_conversions.cpp",
     "src/mbgl/style/conversion/rotation.cpp",
     "src/mbgl/style/conversion/source.cpp",
     "src/mbgl/style/conversion/source_options.cpp",
@@ -409,6 +417,8 @@ MLN_CORE_SOURCE = [
     "src/mbgl/style/layers/heatmap_layer_impl.hpp",
     "src/mbgl/style/layers/hillshade_layer_impl.cpp",
     "src/mbgl/style/layers/hillshade_layer_impl.hpp",
+    "src/mbgl/style/layers/color_relief_layer_impl.cpp",
+    "src/mbgl/style/layers/color_relief_layer_impl.hpp",
     "src/mbgl/style/layers/line_layer_impl.cpp",
     "src/mbgl/style/layers/line_layer_impl.hpp",
     "src/mbgl/style/layers/location_indicator_layer_impl.cpp",
@@ -649,6 +659,7 @@ MLN_CORE_HEADERS = [
     "include/mbgl/layermanager/fill_layer_factory.hpp",
     "include/mbgl/layermanager/heatmap_layer_factory.hpp",
     "include/mbgl/layermanager/hillshade_layer_factory.hpp",
+    "include/mbgl/layermanager/color_relief_layer_factory.hpp",
     "include/mbgl/layermanager/layer_factory.hpp",
     "include/mbgl/layermanager/layer_manager.hpp",
     "include/mbgl/layermanager/line_layer_factory.hpp",
@@ -984,6 +995,7 @@ MLN_DRAWABLES_HEADERS = [
     "include/mbgl/shaders/heatmap_layer_ubo.hpp",
     "include/mbgl/shaders/heatmap_texture_layer_ubo.hpp",
     "include/mbgl/shaders/hillshade_layer_ubo.hpp",
+    "include/mbgl/shaders/color_relief_layer_ubo.hpp",
     "include/mbgl/shaders/hillshade_prepare_layer_ubo.hpp",
     "include/mbgl/shaders/layer_ubo.hpp",
     "include/mbgl/shaders/line_layer_ubo.hpp",
@@ -1057,6 +1069,7 @@ MLN_DRAWABLES_MTL_SOURCE = [
     "src/mbgl/shaders/mtl/heatmap_texture.cpp",
     "src/mbgl/shaders/mtl/hillshade.cpp",
     "src/mbgl/shaders/mtl/hillshade_prepare.cpp",
+    "src/mbgl/shaders/mtl/color_relief.cpp",
     "src/mbgl/shaders/mtl/line.cpp",
     "src/mbgl/shaders/mtl/location_indicator.cpp",
     "src/mbgl/shaders/mtl/raster.cpp",
@@ -1098,6 +1111,7 @@ MLN_DRAWABLES_MTL_HEADERS = [
     "include/mbgl/shaders/mtl/heatmap_texture.hpp",
     "include/mbgl/shaders/mtl/hillshade.hpp",
     "include/mbgl/shaders/mtl/hillshade_prepare.hpp",
+    "include/mbgl/shaders/mtl/color_relief.hpp",
     "include/mbgl/shaders/mtl/line.hpp",
     "include/mbgl/shaders/mtl/location_indicator.hpp",
     "include/mbgl/shaders/mtl/raster.hpp",
@@ -1142,6 +1156,7 @@ MLN_DRAWABLES_WEBGPU_SOURCE = [
     "src/mbgl/shaders/webgpu/heatmap_texture.cpp",
     "src/mbgl/shaders/webgpu/hillshade.cpp",
     "src/mbgl/shaders/webgpu/hillshade_prepare.cpp",
+    "src/mbgl/shaders/webgpu/color_relief.cpp",
     "src/mbgl/shaders/webgpu/line.cpp",
     "src/mbgl/shaders/webgpu/location_indicator.cpp",
     "src/mbgl/shaders/webgpu/raster.cpp",
@@ -1183,6 +1198,7 @@ MLN_DRAWABLES_WEBGPU_HEADERS = [
     "include/mbgl/shaders/webgpu/heatmap_texture.hpp",
     "include/mbgl/shaders/webgpu/hillshade.hpp",
     "include/mbgl/shaders/webgpu/hillshade_prepare.hpp",
+    "include/mbgl/shaders/webgpu/color_relief.hpp",
     "include/mbgl/shaders/webgpu/line.hpp",
     "include/mbgl/shaders/webgpu/location_indicator.hpp",
     "include/mbgl/shaders/webgpu/raster.hpp",

include/mbgl/layermanager/color_relief_layer_factory.hpp

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <mbgl/layermanager/layer_factory.hpp>
+
+namespace mbgl {
+
+class ColorReliefLayerFactory : public LayerFactory {
+protected:
+    const style::LayerTypeInfo* getTypeInfo() const noexcept final;
+    std::unique_ptr<style::Layer> createLayer(const std::string& id,
+                                              const style::conversion::Convertible& value) noexcept final;
+    std::unique_ptr<RenderLayer> createRenderLayer(Immutable<style::Layer::Impl>) noexcept final;
+};
+
+} // namespace mbgl

include/mbgl/shaders/color_relief_layer_ubo.hpp

@@ -0,0 +1,32 @@
+#pragma once
+#include <mbgl/shaders/layer_ubo.hpp>
+
+namespace mbgl {
+namespace shaders {
+
+struct alignas(16) ColorReliefDrawableUBO {
+    /*  0 */ std::array<float, 4 * 4> matrix;
+    /* 64 */
+};
+static_assert(sizeof(ColorReliefDrawableUBO) == 64);
+
+struct alignas(16) ColorReliefTilePropsUBO {
+    /*  0 */ std::array<float, 4> unpack;    // DEM unpack vector
+    /* 16 */ std::array<float, 2> dimension; // Texture dimensions
+    /* 24 */ int32_t color_ramp_size;        // Number of color stops
+    /* 28 */ float pad_tile0;                     // Padding for alignment
+    /* 32 */
+};
+static_assert(sizeof(ColorReliefTilePropsUBO) == 32);
+
+struct alignas(16) ColorReliefEvaluatedPropsUBO {
+    /*  0 */ float opacity;
+    /*  4 */ float pad_eval0;
+    /*  8 */ float pad_eval1;
+    /* 12 */ float pad_eval2;
+    /* 16 */
+};
+static_assert(sizeof(ColorReliefEvaluatedPropsUBO) == 16);
+
+} // namespace shaders
+} // namespace mbgl

include/mbgl/shaders/gl/color_relief.hpp

@@ -0,0 +1,115 @@
+// Generated code, do not modify this file!
+#pragma once
+#include <mbgl/shaders/shader_source.hpp>
+
+namespace mbgl {
+namespace shaders {
+
+template <>
+struct ShaderSource<BuiltIn::ColorReliefShader, gfx::Backend::Type::OpenGL> {
+    static constexpr const char* name = "ColorReliefShader";
+    static constexpr const char* vertex = R"(layout(std140) uniform ColorReliefDrawableUBO {
+    highp mat4 u_matrix;
+};
+
+layout(std140) uniform ColorReliefTilePropsUBO {
+    highp vec4 u_unpack;
+    highp vec2 u_dimension;
+    int u_color_ramp_size;
+    float pad_tile0;
+};
+
+in vec2 a_pos;
+out vec2 v_pos;
+
+void main() {
+    gl_Position = u_matrix * vec4(a_pos, 0, 1);
+
+    highp vec2 epsilon = 1.0 / u_dimension;
+    float scale = (u_dimension.x - 2.0) / u_dimension.x;
+    v_pos = (a_pos / 8192.0) * scale + epsilon;
+
+    // Handle poles
+    if (a_pos.y < -32767.5) v_pos.y = 0.0;
+    if (a_pos.y > 32766.5) v_pos.y = 1.0;
+}
+)";
+    static constexpr const char* fragment = R"(layout(std140) uniform ColorReliefDrawableUBO {
+    highp mat4 u_matrix;
+};
+
+layout(std140) uniform ColorReliefTilePropsUBO {
+    highp vec4 u_unpack;
+    highp vec2 u_dimension;
+    int u_color_ramp_size;
+    float pad_tile0;
+};
+
+layout(std140) uniform ColorReliefEvaluatedPropsUBO {
+    float u_opacity;
+    float pad_eval0;
+    float pad_eval1;
+    float pad_eval2;
+};
+
+uniform sampler2D u_image;
+uniform sampler2D u_elevation_stops;
+uniform sampler2D u_color_stops;
+
+in vec2 v_pos;
+
+float getElevation(vec2 coord) {
+    // Convert encoded elevation value to meters
+    vec4 data = texture(u_image, coord) * 255.0;
+    data.a = -1.0;
+    return dot(data, u_unpack);
+}
+
+float getElevationStop(int stop) {
+    // Elevation stops are plain float values, not terrain-RGB encoded
+    float x = (float(stop) + 0.5) / float(u_color_ramp_size);
+    return texture(u_elevation_stops, vec2(x, 0.0)).r; 
+}
+
+vec4 getColorStop(int stop) {
+    float x = (float(stop) + 0.5) / float(u_color_ramp_size);
+    return texture(u_color_stops, vec2(x, 0.0));
+}
+
+void main() {
+    float el = getElevation(v_pos);
+
+    // Binary search for color stops
+    int r = (u_color_ramp_size - 1);
+    int l = 0;
+
+    while (r - l > 1) {
+        int m = (r + l) / 2;
+        float el_m = getElevationStop(m);
+        if (el < el_m) {
+            r = m;
+        } else {
+            l = m;
+        }
+    }
+
+    // Get elevation values for interpolation
+    float el_l = getElevationStop(l);
+    float el_r = getElevationStop(r);
+
+    // Get colors for interpolation
+    vec4 color_l = getColorStop(l);
+    vec4 color_r = getColorStop(r);
+
+    // Interpolate between the two colors
+    float t = clamp((el - el_l) / (el_r - el_l), 0.0, 1.0);
+    fragColor = u_opacity * mix(color_l, color_r, t);
+
+#ifdef OVERDRAW_INSPECTOR
+    fragColor = vec4(1.0);
+#endif
+})";
+};
+
+} // namespace shaders
+} // namespace mbgl