Raycasting works!

src/app/dem_renderer/dem_renderer.wgsl

@@ -42,12 +42,16 @@ fn fs_solid(vertex: VertexOutput) -> @location(0) vec4<f32> {
     root_node.index = vec2<u32>(0);
     root_node.level = textureNumLevels(dembvh_texture) - 1;
 
+    var hit_index = vec2<u32>(0);
     if intersect_ray_with_node(dembvh_texture,
                                uniforms.dem_min_corner,
                                uniforms.dem_cell_size,
+                               uniforms.dem_z_range,
                                ray,
-                               root_node) {
+                               root_node,
-        return vec4<f32>(1.0);
+                               &hit_index) {
+        let v_i = textureLoad(dem_texture, hit_index, 0).r;
+        return vec4<f32>(vec3<f32>(v_i) / 65535.0, 1.0);
     } else {
         discard;
     }

src/app/dem_renderer/mod.rs

@@ -175,8 +175,8 @@ impl DemRenderer {
         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(
-            glam::Vec2::new(source.x_max, source.y_max)
+            (glam::Vec2::new(source.x_max, source.y_max)
-                - glam::Vec2::new(source.x_min, source.y_min)
+                - glam::Vec2::new(source.x_min, source.y_min))
                 / glam::Vec2::new(source.num_cells_x as f32, source.num_cells_y as f32),
         );
         uniforms.set_dem_z_range(glam::Vec2::new(source.z_min, source.z_max));
@@ -489,3 +489,6 @@ fn get_animated_camera_position(animation_time: std::time::Duration, dem_size: f
         dem_size * 0.7,
     )
 }
+
+#[cfg(test)]
+mod tests;

src/app/dem_renderer/ray_intersection.wgsl

@@ -12,14 +12,26 @@ struct AABB {
 
 struct Ray { origin: vec3<f32>, direction: vec3<f32> };
 
-fn intersect_ray_with_aabb(ray: Ray, aabb: AABB) -> bool {
+fn invert_ray_direction(v: vec3<f32> ) -> vec3<f32> {
-    let t1 = (aabb.min_corner - ray.origin) / ray.direction;
+    return select(vec3<f32>(1.0e+30),
-    let t2 = (aabb.max_corner - ray.origin) / ray.direction;
+                  vec3<f32>(1.0) / v,
+                  vec3<bool>(v));
+}
+
+fn intersect_ray_with_aabb(ray: Ray, aabb: AABB) -> f32 {
+  return intersect_ray_with_aabb_optimized(ray.origin,
+                                           invert_ray_direction(ray.direction),
+                                           aabb);
+}
+
+fn intersect_ray_with_aabb_optimized(ray_origin: vec3<f32>, inv_ray_direction: vec3<f32>, aabb: AABB) -> f32 {
+    let t1 = (aabb.min_corner - ray_origin) * inv_ray_direction;
+    let t2 = (aabb.max_corner - ray_origin) * inv_ray_direction;
     let t_mins = min(t1, t2);
-    let t_min = min(t_mins.x, min(t_mins.y, t_mins.z));
+    let t_min = max(t_mins.x, max(t_mins.y, t_mins.z));
     let t_maxs = max(t1, t2);
-    let t_max = max(t_maxs.x, max(t_maxs.y, t_maxs.z));
+    let t_max = min(t_maxs.x, min(t_maxs.y, t_maxs.z));
-    return t_min <= t_max;
+    return select(-1.0, max(t_min, 0.0f),  t_min <= t_max);
 }
 
 fn get_xy_min_for_node(dem_min_corner: vec2<f32>,
@@ -52,19 +64,23 @@ fn pop_node_stack(stack: ptr<function,NodeStack>) -> BoundingNode {
 fn intersect_ray_with_node(tree_texture: texture_2d<u32>,
                            dem_min_corner: vec2<f32>,
                            dem_cell_size: vec2<f32>,
+                           dem_z_range: vec2<f32>,
                            ray: Ray,
-                           root_node: BoundingNode) -> bool {
+                           root_node: BoundingNode,
+                           hit_cell: ptr<function, vec2<u32>>) -> bool {
+    let inv_ray_direction = invert_ray_direction(ray.direction);
     var node_stack: NodeStack;
     node_stack.count = 0u;
     push_node_stack(&node_stack, root_node);
+    var closest_hit_distance = 1.0e+30f;
     while node_stack.count > 0 {
         let node = pop_node_stack(&node_stack);
         let minmax_z = textureLoad(tree_texture, node.index, i32(node.level)).rg;
         if minmax_z.r == 0 {
             return false;
         }
-        let min_z = scale_u16(minmax_z.r, uniforms.dem_z_range);
+        let min_z = scale_u16(minmax_z.r, dem_z_range);
-        let max_z = scale_u16(minmax_z.g, uniforms.dem_z_range);
+        let max_z = scale_u16(minmax_z.g, dem_z_range);
         var aabb: AABB ;
         aabb.min_corner = vec3<f32>(get_xy_min_for_node(dem_min_corner,
             dem_cell_size,
@@ -74,9 +90,13 @@ fn intersect_ray_with_node(tree_texture: texture_2d<u32>,
             dem_cell_size,
             node),
             max_z);
-        if intersect_ray_with_aabb(ray, aabb) {
+        let hit_distance = intersect_ray_with_aabb_optimized(ray.origin, inv_ray_direction, aabb);
+        if hit_distance >= 0.0 {
             if node.level == 0 {
-                return true;
+                if hit_distance < closest_hit_distance {
+                    closest_hit_distance = hit_distance;
+                    *hit_cell = node.index;
+                }
             } else {
                 let next_index = node.index * 2;
                 var next_node: BoundingNode;
@@ -92,5 +112,5 @@ fn intersect_ray_with_node(tree_texture: texture_2d<u32>,
             }
         }
     }
-    return false;
+    return closest_hit_distance < 1.0e+20;
 }

src/app/dem_renderer/tests.rs

@@ -0,0 +1,153 @@
+use futures::executor::block_on;
+use std::sync::mpsc::channel;
+
+use wgsl_shader_assembler::wgsl_module;
+
+use super::*;
+
+async fn run_compute_shader_test(
+    shader_module: wgpu::ShaderModuleDescriptor<'_>,
+    test_function: impl AsRef<str>,
+    input: &[u8],
+    output_size: usize,
+) -> Vec<u8> {
+    let wgpu_instance = wgpu::Instance::default();
+    let adapter = wgpu_instance
+        .request_adapter(&wgpu::RequestAdapterOptions::default())
+        .await
+        .unwrap();
+    let (device, queue) = adapter
+        .request_device(
+            &wgpu::DeviceDescriptor {
+                label: None,
+                required_features: wgpu::Features::empty(),
+                required_limits: wgpu::Limits::downlevel_defaults(),
+                memory_hints: wgpu::MemoryHints::MemoryUsage,
+            },
+            None,
+        )
+        .await
+        .unwrap();
+
+    let shader_module = device.create_shader_module(shader_module);
+    let staging_buffer = device.create_buffer(&wgpu::BufferDescriptor {
+        label: None,
+        size: output_size as u64,
+        usage: wgpu::BufferUsages::MAP_READ | wgpu::BufferUsages::COPY_DST,
+        mapped_at_creation: false,
+    });
+    let input_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+        label: None,
+        contents: input,
+        usage: wgpu::BufferUsages::STORAGE | wgpu::BufferUsages::COPY_DST,
+    });
+    let output_buffer = device.create_buffer(&wgpu::BufferDescriptor {
+        label: None,
+        size: output_size as u64,
+        usage: wgpu::BufferUsages::STORAGE | wgpu::BufferUsages::COPY_SRC,
+        mapped_at_creation: false,
+    });
+    let compute_pipeline = device.create_compute_pipeline(&wgpu::ComputePipelineDescriptor {
+        label: None,
+        layout: None,
+        module: &shader_module,
+        entry_point: Some(test_function.as_ref()),
+        compilation_options: Default::default(),
+        cache: None,
+    });
+    let bind_group_layout = compute_pipeline.get_bind_group_layout(0);
+    let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+        label: None,
+        layout: &bind_group_layout,
+        entries: &[
+            wgpu::BindGroupEntry {
+                binding: 0,
+                resource: input_buffer.as_entire_binding(),
+            },
+            wgpu::BindGroupEntry {
+                binding: 1,
+                resource: output_buffer.as_entire_binding(),
+            },
+        ],
+    });
+    let mut encoder =
+        device.create_command_encoder(&wgpu::CommandEncoderDescriptor { label: None });
+    {
+        let mut cpass = encoder.begin_compute_pass(&wgpu::ComputePassDescriptor {
+            label: None,
+            timestamp_writes: None,
+        });
+        cpass.set_pipeline(&compute_pipeline);
+        cpass.set_bind_group(0, &bind_group, &[]);
+        cpass.dispatch_workgroups(1, 1, 1);
+    }
+    encoder.copy_buffer_to_buffer(&output_buffer, 0, &staging_buffer, 0, output_size as u64);
+    queue.submit(Some(encoder.finish()));
+
+    let (tx, rx) = channel();
+    let buffer_slice = staging_buffer.slice(..);
+    buffer_slice.map_async(wgpu::MapMode::Read, move |v| tx.send(v).unwrap());
+    device.poll(wgpu::Maintain::wait()).panic_on_timeout();
+    if let Ok(Ok(())) = rx.recv() {
+        buffer_slice.get_mapped_range().to_vec()
+    } else {
+        panic!("failed to run test on GPU")
+    }
+}
+
+#[repr(C, align(16))]
+#[derive(Clone, Copy, Pod, Zeroable)]
+struct Vec3 {
+    elements: [f32; 3],
+    _padding: f32
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Pod, Zeroable)]
+struct TestInput {
+    ray_origin: Vec3,
+    ray_direction: Vec3,
+    aabb_min_corner: Vec3,
+    aabb_max_corner: Vec3,
+}
+
+fn vec3(x: f32, y: f32, z: f32) -> Vec3 {
+    Vec3 {
+        elements: [x, y, z],
+        _padding: 0.0
+    }
+}
+
+#[test]
+fn test_shaders() {
+    let input_buffer = vec![
+        TestInput {
+            ray_origin: vec3(-5.0, 0.0, 0.0),
+            ray_direction: vec3(1.0, 0.0, 0.0),
+            aabb_min_corner: vec3(-1.0, -1.0, -1.0),
+            aabb_max_corner: vec3(1.0, 1.0, 1.0),
+        },
+        TestInput {
+            ray_origin: vec3(-5.0, 0.0, 0.0),
+            ray_direction: vec3(1.0, 0.0, 0.0),
+            aabb_min_corner: vec3(-1.0, 0.5, -1.0),
+            aabb_max_corner: vec3(1.0, 1.0, 1.0),
+        },
+        TestInput {
+            ray_origin: vec3(-5.0, 0.0, 0.0),
+            ray_direction: vec3(1.0, 0.15, 0.0),
+            aabb_min_corner: vec3(-1.5, 0.5, -1.0),
+            aabb_max_corner: vec3(1.0, 1.0, 1.0),
+        },
+    ];
+    let output_buffer: Vec<u32> = bytemuck::cast_slice(&block_on(run_compute_shader_test(
+        wgsl_module!("tests.wgsl"),
+        "test_intersect_ray_with_aabb",
+        bytemuck::cast_slice(&input_buffer),
+        input_buffer.len() * 4,
+    )))
+    .to_vec();
+    assert_eq!(output_buffer[0], 1);
+    assert_eq!(output_buffer[1], 0);
+    assert_eq!(output_buffer[2], 1);
+}

src/app/dem_renderer/tests.wgsl

@@ -0,0 +1,33 @@
+@group(0)
+@binding(0)
+var<storage, read> input_data: array<Input>;
+@group(0)
+@binding(1)
+var<storage, read_write> output_data: array<u32>;
+
+//#include ray_intersection.wgsl
+
+struct Input {
+    ray_origin: vec3<f32>,
+    ray_direction: vec3<f32>,
+    aabb_min_corner: vec3<f32>,
+    aabb_max_corner: vec3<f32>
+}
+
+@compute
+@workgroup_size(1)
+fn test_intersect_ray_with_aabb() {
+    for(var i=0u; i < arrayLength(&input_data); i++) {
+      var ray: Ray;
+      ray.origin = input_data[i].ray_origin;
+      ray.direction = input_data[i].ray_direction;
+      var aabb: AABB;
+      aabb.min_corner = input_data[i].aabb_min_corner;
+      aabb.max_corner = input_data[i].aabb_max_corner;
+      if intersect_ray_with_aabb(ray, aabb) >= 0.0 {
+          output_data[i] = 1u;
+      }else {
+          output_data[i] = 0u;
+      }
+    }
+}

src/app/mod.rs

@@ -46,12 +46,13 @@ impl MvuApp<Model> for App {
     async fn init(&mut self, instance: &Instance, surface: Surface<'static>, size: Size2i) {
         let adapter = instance
             .request_adapter(&wgpu::RequestAdapterOptions {
-                power_preference: wgpu::PowerPreference::default(),
+                power_preference: wgpu::PowerPreference::HighPerformance,
                 force_fallback_adapter: false,
                 compatible_surface: Some(&surface),
             })
             .await
             .expect("Failed to find an appropriate adapter");
+        eprintln!("Using {}", adapter.get_info().name);
 
         let (device, queue) = adapter
             .request_device(