fixed sorting for transparent voxels

Author: hacknus

CHANGELOG.MD

@@ -8,6 +8,10 @@ All notable changes to the `bevy voxel plot` crate will be documented in this fi
 
 * ...
 
+# 2.3.0
+
+* Fixed the sorting for transparent voxels.
+
 # 2.2.0
 
 * Assume voxel vertices are real world coordinates in shader.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bevy_voxel_plot"
-version = "2.2.0"
+version = "2.3.0"
 edition = "2021"
 authors = ["Linus Leo Stöckli"]
 repository = "https://github.com/hacknus/bevy_voxel_plot"

examples/bevy_egui.rs

@@ -86,11 +86,11 @@ fn voxel_plot_setup(
     let mut instances: Vec<InstanceData> = instances.into_iter().collect();
 
     // Sort by opacity (color alpha channel) descending
-    instances.sort_by(|a, b| {
-        b.color[3]
-            .partial_cmp(&a.color[3])
-            .unwrap_or(std::cmp::Ordering::Equal)
-    });
+    // instances.sort_by(|a, b| {
+    //     b.color[3]
+    //         .partial_cmp(&a.color[3])
+    //         .unwrap_or(std::cmp::Ordering::Equal)
+    // });
 
     // Truncate to top 2 million most opaque points
     const MAX_INSTANCES: usize = 1_000_000;
@@ -102,6 +102,7 @@ fn voxel_plot_setup(
         let threshold = instances.last().unwrap().color[3];
         println!("Auto threshold for opacity was: {}", threshold);
     }
+    let first_pass_layer = RenderLayers::layer(1);
 
     commands.spawn((
         Mesh3d(meshes.add(Cuboid::new(cube_width, cube_height, cube_depth))),
@@ -114,6 +115,7 @@ fn voxel_plot_setup(
         // We must disable the built-in frustum culling by adding the `NoFrustumCulling` marker
         // component to avoid incorrect culling.
         NoFrustumCulling,
+        first_pass_layer.clone(),
     ));
 
     commands.insert_resource(AmbientLight {
@@ -153,7 +155,6 @@ fn voxel_plot_setup(
     commands.insert_resource(RenderImage(image_handle.clone()));
 
     // This specifies the layer used for the first pass, which will be attached to the first pass camera and cube.
-    let first_pass_layer = RenderLayers::layer(0);
 
     let pan_orbit_id = commands
         .spawn((

examples/simple_cubes.rs

@@ -0,0 +1,52 @@
+use bevy::prelude::*;
+use bevy::pbr::AmbientLight;
+use bevy_voxel_plot::{InstanceData, InstanceMaterialData, VoxelMaterialPlugin};
+use bevy_panorbit_camera::{PanOrbitCamera, PanOrbitCameraPlugin};
+
+fn setup(mut commands: Commands, mut meshes: ResMut<Assets<Mesh>>) {
+    // Two cubes: one red (alpha 1.0), one blue (alpha 0.5)
+    let instances = vec![
+        InstanceData {
+            pos_scale: [0.0, 0.0, 0.0, 1.0],
+            color: LinearRgba::from(Color::srgba(1.0, 0.0, 0.0, 0.5))
+                .to_f32_array()
+        },
+        InstanceData {
+            pos_scale: [0.3, 0.0, 0.0, 1.0],
+            color: LinearRgba::from(Color::srgba(0.0, 1.0, 0.0, 0.5))
+                .to_f32_array()
+        },
+        InstanceData {
+            pos_scale: [0.6, 0.0, 0.0, 1.0],
+            color: LinearRgba::from(Color::srgba(0.0, 0.0, 1.0, 0.5))
+                .to_f32_array()
+        },
+    ];
+
+    let cube_mesh = meshes.add(Cuboid::new(0.2, 0.2, 0.2));
+
+    commands.spawn((
+        Mesh3d(cube_mesh),
+        InstanceMaterialData { instances },
+    ));
+
+    commands.insert_resource(AmbientLight {
+        color: Color::WHITE,
+        brightness: 1.5,
+        affects_lightmapped_meshes: false,
+    });
+
+    // Camera
+    commands.spawn((
+        Camera3d::default(),
+        Transform::from_xyz(1.5, 1.0, 1.5).looking_at(Vec3::ZERO, Vec3::Y),
+        PanOrbitCamera::default(),
+    ));
+}
+
+fn main() {
+    App::new()
+        .add_plugins((DefaultPlugins, VoxelMaterialPlugin, PanOrbitCameraPlugin))
+        .add_systems(Startup, setup)
+        .run();
+}

src/bevy_voxel_plot.rs

@@ -63,6 +63,8 @@ pub const SHADER_HANDLE: Handle<Shader> = weak_handle!("123e4567-e89b-12d3-a456-
 impl Plugin for VoxelMaterialPlugin {
     fn build(&self, app: &mut App) {
         app.add_plugins(ExtractComponentPlugin::<InstanceMaterialData>::default());
+        app.add_plugins(ExtractComponentPlugin::<CameraPosition>::default()); // Add this line
+
         app.sub_app_mut(RenderApp)
             .add_render_command::<Transparent3d, DrawCustom>()
             .init_resource::<SpecializedMeshPipelines<CustomPipeline>>()
@@ -86,6 +88,7 @@ impl Plugin for VoxelMaterialPlugin {
     }
 }
 
+
 /// Single instance data containing position, scale and color.
 #[derive(Clone, Copy, Pod, Zeroable)]
 #[repr(C)]
@@ -155,34 +158,57 @@ struct InstanceBuffer {
     length: usize,
 }
 
+#[derive(Component, Clone)]
+struct CameraPosition(Vec3);
+
+impl ExtractComponent for CameraPosition {
+    type QueryData = &'static GlobalTransform;
+    type QueryFilter = With<Camera3d>;
+    type Out = Self;
+
+    fn extract_component(transform: QueryItem<'_, Self::QueryData>) -> Option<Self> {
+        Some(CameraPosition(transform.translation()))
+    }
+}
+
+
 /// Prepares instance buffers each frame, sorting instances by distance to camera.
 fn prepare_instance_buffers(
     mut commands: Commands,
     query: Query<(Entity, &InstanceMaterialData)>,
     render_device: Res<RenderDevice>,
-    views: Query<&GlobalTransform, With<Camera>>,
+    camera_query: Query<&CameraPosition>,
 ) {
-    // Get the first camera's position, or use a default if none exist
-    let camera_pos = views
+    let camera_pos = camera_query
         .iter()
         .next()
-        .map(|transform| transform.translation())
+        .map(|pos| pos.0)
         .unwrap_or(Vec3::ZERO);
 
+    // // Debug: Print camera position
+    // println!("Camera position: {:?}", camera_pos);
+
     for (entity, instance_data) in &query {
         if instance_data.instances.is_empty() {
             commands.entity(entity).remove::<InstanceBuffer>();
             continue;
         }
 
-        // Sort back-to-front by distance from camera
         let mut sorted_instances = instance_data.instances.clone();
         sorted_instances.sort_by(|a, b| {
             let dist_a = camera_pos.distance_squared(Vec3::from_slice(&a.pos_scale[0..3]));
             let dist_b = camera_pos.distance_squared(Vec3::from_slice(&b.pos_scale[0..3]));
             dist_b.partial_cmp(&dist_a).unwrap_or(std::cmp::Ordering::Equal)
         });
 
+        // Debug: Print instance order and distances
+        // println!("Sorted instances (far to near):");
+        // for inst in &sorted_instances {
+        //     let pos = Vec3::from_slice(&inst.pos_scale[0..3]);
+        //     let dist = camera_pos.distance(pos);
+        //     println!("  pos: {:?}, distance: {:.3}, color: {:?}", pos, dist, inst.color);
+        // }
+
         let buffer = render_device.create_buffer_with_data(&BufferInitDescriptor {
             label: Some("instance data buffer"),
             contents: bytemuck::cast_slice(sorted_instances.as_slice()),
@@ -239,7 +265,18 @@ impl SpecializedMeshPipeline for CustomPipeline {
 
         descriptor.fragment.as_mut().unwrap().targets[0] = Some(ColorTargetState {
             format: color_format,
-            blend: Some(BlendState::ALPHA_BLENDING),
+            blend: Some(BlendState {
+                color: BlendComponent {
+                    src_factor: BlendFactor::SrcAlpha,
+                    dst_factor: BlendFactor::OneMinusSrcAlpha,
+                    operation: BlendOperation::Add,
+                },
+                alpha: BlendComponent {
+                    src_factor: BlendFactor::SrcAlpha,
+                    dst_factor: BlendFactor::OneMinusSrcAlpha,
+                    operation: BlendOperation::Add,
+                },
+            }),
             write_mask: ColorWrites::ALL,
         });