From b3deecc02f3e31762d403cbf0d4d7f4f8be426bc Mon Sep 17 00:00:00 2001
From: Matthew Gordon <matthew@gordon.earth>
Date: Mon, 2 Jun 2025 15:10:28 -0300
Subject: [PATCH] Add colours

---
 .gitattributes                         |  1 +
 data/colormap.data                     |  3 ++
 src/app/dem_renderer/dem_renderer.wgsl | 10 +++-
 src/app/dem_renderer/mod.rs            | 64 ++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 1 deletion(-)
 create mode 100644 data/colormap.data

diff --git a/.gitattributes b/.gitattributes
index 4fae6dc..15f0a09 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1 +1,2 @@
 *.jpg filter=lfs diff=lfs merge=lfs -text
+*.data filter=lfs diff=lfs merge=lfs -text
diff --git a/data/colormap.data b/data/colormap.data
new file mode 100644
index 0000000..6566e08
--- /dev/null
+++ b/data/colormap.data
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:cf44f8b9d69f641466f1c65e308f446e2c46b022108059dc55076e2459151413
+size 48
diff --git a/src/app/dem_renderer/dem_renderer.wgsl b/src/app/dem_renderer/dem_renderer.wgsl
index dab531a..0b500c5 100644
--- a/src/app/dem_renderer/dem_renderer.wgsl
+++ b/src/app/dem_renderer/dem_renderer.wgsl
@@ -21,6 +21,9 @@ var dem_texture: texture_2d<u32>;
 @group(0) @binding(2)
 var dembvh_texture: texture_2d<u32>;
 
+@group(0) @binding(3)
+var colormap_texture: texture_1d<f32>;
+
 //#include ray_intersection.wgsl
 
 @vertex
@@ -100,7 +103,12 @@ fn fs_solid(vertex: VertexOutput) -> @location(0) vec4<f32> {
            let fill_lambertian_value = dot(hit_normal, sun_direction * vec3(1.0, -1.0, 1.0));
            let fill_strength = 0.25;
            let l = fill_strength * fill_lambertian_value + (1.0 - fill_strength) * sun_lambertian_value * shadow_value;
-           color_accumulator += 0.25 * vec4<f32>(vec3<f32>(l), 1.0);
+           let colormap_color = textureLoad(colormap_texture,
+                                            u32(clamp((hit_location.z - uniforms.dem_z_range.x)
+                                                      / (uniforms.dem_z_range.y - uniforms.dem_z_range.x), 0.0, 1.0)
+                                                * 15.9),
+                                            0).rgb;
+           color_accumulator += 0.25 * vec4<f32>(colormap_color * l, 1.0);
         }
     }
     if color_accumulator.a == 0.0 {
diff --git a/src/app/dem_renderer/mod.rs b/src/app/dem_renderer/mod.rs
index b672a1c..a9d0196 100644
--- a/src/app/dem_renderer/mod.rs
+++ b/src/app/dem_renderer/mod.rs
@@ -186,6 +186,8 @@ impl DemRenderer {
 
         let camera = Camera::new(surface_config.width as f32 / surface_config.height as f32);
 
+        let colormap_texture_view = create_colormap_texture(device, queue);
+
         let mut uniforms = UniformBufferManager::new(device);
         uniforms.set_dem_min_corner(glam::Vec2::new(source.x_min, source.y_min));
         uniforms.set_dem_cell_size(
@@ -228,6 +230,16 @@ impl DemRenderer {
                     },
                     count: None,
                 },
+                wgpu::BindGroupLayoutEntry {
+                    binding: 3,
+                    visibility: wgpu::ShaderStages::FRAGMENT,
+                    ty: wgpu::BindingType::Texture {
+                        multisampled: false,
+                        sample_type: wgpu::TextureSampleType::Float { filterable: false },
+                        view_dimension: wgpu::TextureViewDimension::D1,
+                    },
+                    count: None,
+                },
             ],
         });
 
@@ -246,6 +258,10 @@ impl DemRenderer {
                     binding: 2,
                     resource: wgpu::BindingResource::TextureView(&dembvh_texture_view),
                 },
+                wgpu::BindGroupEntry {
+                    binding: 3,
+                    resource: wgpu::BindingResource::TextureView(&colormap_texture_view),
+                },
             ],
             label: Some("DemRendererBindGroup"),
         });
@@ -505,6 +521,54 @@ fn create_dembvh_texture(
     texture.create_view(&wgpu::TextureViewDescriptor::default())
 }
 
+fn create_colormap_texture(device: &wgpu::Device, queue: &wgpu::Queue) -> wgpu::TextureView {
+    let texture = device.create_texture(&wgpu::TextureDescriptor {
+        label: Some("Colormap Texture"),
+        size: wgpu::Extent3d {
+            width: 16,
+            height: 1,
+            depth_or_array_layers: 1,
+        },
+        mip_level_count: 1,
+        sample_count: 1,
+        dimension: wgpu::TextureDimension::D1,
+        format: wgpu::TextureFormat::Rgba8Unorm,
+        usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
+        view_formats: &[],
+    });
+
+    let colormap_data_rgb = include_bytes!("../../../data/colormap.data");
+    assert!(dbg!(colormap_data_rgb.len()) == 16 * 3);
+    let mut colormap_data = [0 as u8; 16 * 4];
+    for i in 0..16 {
+        for j in 0..3 {
+            colormap_data[(15 - i) * 4 + j] = colormap_data_rgb[i * 3 + j];
+        }
+    }
+
+    queue.write_texture(
+        wgpu::TexelCopyTextureInfo {
+            texture: &texture,
+            mip_level: 0,
+            origin: wgpu::Origin3d::ZERO,
+            aspect: wgpu::TextureAspect::All,
+        },
+        &colormap_data[..],
+        wgpu::TexelCopyBufferLayout {
+            offset: 0,
+            bytes_per_row: Some(std::mem::size_of::<u8>() as u32 * 4 * 16),
+            rows_per_image: None,
+        },
+        wgpu::Extent3d {
+            width: 16,
+            height: 1,
+            depth_or_array_layers: 1,
+        },
+    );
+
+    texture.create_view(&wgpu::TextureViewDescriptor::default())
+}
+
 fn get_animated_camera_position(animation_phase: f32, dem_size: f32) -> glam::Vec3 {
     glam::Vec3::new(
         dem_size * f32::sin(animation_phase),