Added Depth-based Outlines

assets/shaders/outline_post_process.wgsl

@@ -1,62 +1,87 @@
 #import bevy_core_pipeline::fullscreen_vertex_shader::FullscreenVertexOutput;
 #import bevy_pbr::{ rgb9e5 };
+#import bevy_pbr::view_transformations::{
+    perspective_camera_near,
+};
+#import bevy_pbr::mesh_view_bindings as view_bindings;
 
 struct OutlinePostProcessSettings {
 	weight: f32,
 	normal_threshold: f32,
-    	adaptive: u32,
+	depth_threshold: f32,
-	light_threshold: f32,
+    adaptive: u32,
+    camera_near: f32,
 }
 
 @group(0) @binding(0) var screen_texture: texture_2d<f32>;
 @group(0) @binding(1) var screen_sampler: sampler;
 @group(0) @binding(2) var normal_texture: texture_2d<f32>;
 @group(0) @binding(3) var normal_sampler: sampler;
-@group(0) @binding(4) var deferred_texture: texture_2d<u32>;
+@group(0) @binding(4) var depth_texture: texture_depth_2d;
-@group(0) @binding(5) var<uniform> settings: OutlinePostProcessSettings;
+@group(0) @binding(5) var depth_sampler: sampler;
+@group(0) @binding(6) var<uniform> settings: OutlinePostProcessSettings;
 
 @fragment
 fn fragment(
 	in: FullscreenVertexOutput
 ) -> @location(0) vec4<f32> {
     let screen_color = textureSample(screen_texture, screen_sampler, in.uv);
-    let deferred_dimensions = textureDimensions(deferred_texture);
-    let deferred_texel = textureLoad(deferred_texture, vec2u(vec2f(deferred_dimensions) * in.uv), 0);
-    let deferred_color = vec4f(vec3f(unpack4x8unorm(deferred_texel.r).rgb), 1.0);
-    let emissive = vec4f(rgb9e5::rgb9e5_to_vec3_(deferred_texel.g), 1.0);
-    let light = screen_color / ((deferred_color) + vec4f(0.001, 0.001, 0.001, 1.0));
-
     let luma = (0.2126 * screen_color.r + 0.7152 * screen_color.g + 0.0722 * screen_color.b);
-    let light_luma = (0.2126 * light.r + 0.7152 * light.g + 0.0722 * light.b);
-    let emissive_luma = (0.2126 * emissive.r + 0.7152 * emissive.g + 0.0722 * emissive.b);
-    let final_luma = luma + light_luma + emissive_luma;
 
-	if final_luma > settings.light_threshold {
+    let outline_width = settings.weight / vec2f(textureDimensions(screen_texture)); 
-	    let outline_width = settings.weight / vec2f(textureDimensions(screen_texture)); 
+    let uv_top = vec2f(in.uv.x, in.uv.y - outline_width.y);
+    let uv_right = vec2f(in.uv.x + outline_width.x, in.uv.y);
+    let uv_top_right = vec2f(in.uv.x + outline_width.x, in.uv.y - outline_width.y);
 
-	    let uv_top = vec2f(in.uv.x, in.uv.y - outline_width.y);
+    // NORMAL FACTOR {{{
-	    let uv_right = vec2f(in.uv.x + outline_width.x, in.uv.y);
+        let normal = textureSample(normal_texture, normal_sampler, in.uv);
-	    let uv_top_right = vec2f(in.uv.x + outline_width.x, in.uv.y - outline_width.y);
+        let normal_top = textureSample(normal_texture, normal_sampler, uv_top);
+        let normal_right = textureSample(normal_texture, normal_sampler, uv_right);
+        let normal_top_right = textureSample(normal_texture, normal_sampler, uv_top_right);
 
-	    let normal = textureSample(normal_texture, normal_sampler, in.uv);
+        let normal_delta_top = abs(normal - normal_top);
-	    let normal_top = textureSample(normal_texture, normal_sampler, uv_top);
+        let normal_delta_right = abs(normal - normal_right);
-	    let normal_right = textureSample(normal_texture, normal_sampler, uv_right);
+        let normal_delta_top_right = abs(normal - normal_top_right);
-	    let normal_top_right = textureSample(normal_texture, normal_sampler, uv_top_right);
 
-	    let normal_delta_top = abs(normal - normal_top);
+        let normal_delta_max = max(normal_delta_top, max(normal_delta_right, normal_delta_top_right));
-	    let normal_delta_right = abs(normal - normal_right);
+        let normal_delta_raw = max(normal_delta_max.x, max(normal_delta_max.y, normal_delta_max.z));
-	    let normal_delta_top_right = abs(normal - normal_top_right);
 
-	    let normal_delta_max = max(normal_delta_top, max(normal_delta_right, normal_delta_top_right));
+        let show_outline_normal = f32(normal_delta_raw > settings.normal_threshold);
-	    let normal_delta_raw = max(normal_delta_max.x, max(normal_delta_max.y, normal_delta_max.z));
+        let normal_outline = vec4f(show_outline_normal, show_outline_normal, show_outline_normal, 0.0);
+    // }}}
 
-	    let show_outline = f32(normal_delta_raw > settings.normal_threshold);
+    let frag_width = settings.weight / vec2f(textureDimensions(screen_texture)); 
+    let depth_uv_top_right = vec2f(in.uv.x + frag_width.x, in.uv.y - frag_width.y);
+    let depth_uv_top_left = vec2f(in.uv.x - frag_width.x, in.uv.y - frag_width.y);
+    let depth_uv_bottom_right = vec2f(in.uv.x + frag_width.x, in.uv.y + frag_width.y);
+    let depth_uv_bottom_left = vec2f(in.uv.x - frag_width.x, in.uv.y + frag_width.y);
+    // DEPTH FACTOR {{{
+        let depth_color = textureSample(depth_texture, depth_sampler, in.uv);
+        let depth = linearize_depth(depth_color);
+        let depth_top_right = linearize_depth(textureSample(depth_texture, depth_sampler, depth_uv_top_right));
+        let depth_top_left = linearize_depth(textureSample(depth_texture, depth_sampler, depth_uv_top_left));
+        let depth_bottom_right = linearize_depth(textureSample(depth_texture, depth_sampler, depth_uv_bottom_right));
+        let depth_bottom_left = linearize_depth(textureSample(depth_texture, depth_sampler, depth_uv_bottom_left));
 
-	    var outline = vec4f(show_outline, show_outline, show_outline, 0.0);
+        var depth_delta = 0.0;
-	    if settings.adaptive != 0 && luma < 0.5 {
+        depth_delta = depth_delta + depth - depth_top_right;
-		outline = outline * -1;
+        depth_delta = depth_delta + depth - depth_top_left;
-	    }
+        depth_delta = depth_delta + depth - depth_bottom_right;
-	    return screen_color - outline + emissive;
+        depth_delta = depth_delta + depth - depth_bottom_left;
-	}
+
-	return screen_color + emissive;
+        var depth_outline = vec4(step(settings.depth_threshold, depth_delta));
+        if depth_color == 0.0 {
+            depth_outline = vec4(0.0);
+        }
+    // }}}
+    
+    var outline = (depth_outline + normal_outline);
+    if settings.adaptive != 0 && luma < 0.5 {
+        outline = outline * -1;
+    }
+	return screen_color - outline ;
+}
+
+fn linearize_depth(depth: f32) -> f32 {
+    return settings.camera_near / depth;
 }

src/components.rs

@@ -1,7 +1,7 @@
 use bevy::{
+    core_pipeline::prepass::{DeferredPrepass, DepthPrepass, NormalPrepass},
     prelude::*,
     render::{extract_component::ExtractComponent, render_resource::ShaderType},
-    core_pipeline::prepass::{NormalPrepass, DepthPrepass, DeferredPrepass},
 };
 
 /// Component which, when inserted into an entity with a camera and normal prepass, enables an outline effect for that
@@ -14,20 +14,29 @@ pub struct OutlinePostProcessSettings {
     /// A threshold for normal differences, values below this threshold will not become outlines.
     /// Higher values will result in more outlines which may look better on smooth surfaces.
     normal_threshold: f32,
+    /// A threshold for depth differences (in units), values below this threshold will not become outlines.
+    /// Higher values will result in more outlines which may look better on smooth surfaces.
+    depth_threshold: f32,
     /// Whether to use adaptive outlines. White outlines will be drawn around darker objects, while black ones will be drawn around lighter ones.
     adaptive: u32,
-    /// Threshold of illumination for outlines to apply. Requires deferred prepass.
+    /// Near plane depth of camera, used for linearization of depth buffer values
-    light_threshold: f32,
+    pub(crate) camera_near: f32,
 }
 
 impl OutlinePostProcessSettings {
     /// Create a new instance with the given settings
-    pub fn new(weight: f32, normal_threshold: f32, adaptive: bool, light_threshold: f32) -> Self {
+    pub fn new(
+        weight: f32,
+        normal_threshold: f32,
+        depth_threshold: f32,
+        adaptive: bool,
+    ) -> Self {
         Self {
             weight,
             normal_threshold,
             adaptive: adaptive as u32,
-            light_threshold,
+            depth_threshold,
+            camera_near: 0.0,
         }
     }
 }
@@ -38,7 +47,8 @@ impl Default for OutlinePostProcessSettings {
             weight: 1.0,
             normal_threshold: 0.0,
             adaptive: 0,
-            light_threshold: 0.0,
+            depth_threshold: 0.05,
+            camera_near: 0.0,
         }
     }
 }

src/lib.rs

@@ -1,7 +1,7 @@
 #![warn(missing_docs)]
 
 //! A plugin for the Bevy game engine which provides an outline post-process effect. The effect
-//! makes use of a normal prepass to generate outlines where differences in the normal buffer
+//! makes use of a normal and depth prepass to generate outlines where significant differences in the values
 //! occur.
 
 use bevy::{
@@ -9,12 +9,11 @@ use bevy::{
     core_pipeline::core_3d::graph::{Core3d, Node3d},
     prelude::*,
     render::{
-        extract_component::{ExtractComponentPlugin, UniformComponentPlugin},
+        extract_component::{ExtractComponentPlugin, UniformComponentPlugin}, render_graph::{RenderGraphApp, ViewNodeRunner}, RenderApp
-        render_graph::{RenderGraphApp, ViewNodeRunner},
-        RenderApp,
     },
 };
 
+use components::OutlinePostProcessSettings;
 pub use nodes::OutlineRenderLabel;
 
 /// Components used by this plugin.
@@ -32,7 +31,7 @@ impl Plugin for OutlinePostProcessPlugin {
         app.add_plugins((
             UniformComponentPlugin::<components::OutlinePostProcessSettings>::default(),
             ExtractComponentPlugin::<components::OutlinePostProcessSettings>::default(),
-        ));
+        )).add_systems(Update, update_shader_clip_planes);
 
         let Some(render_app) = app.get_sub_app_mut(RenderApp) else {
             return;
@@ -61,3 +60,15 @@ impl Plugin for OutlinePostProcessPlugin {
         render_app.init_resource::<resources::OutlinePostProcessPipeline>();
     }
 }
+
+fn update_shader_clip_planes(
+    mut settings_query: Query<(Ref<Projection>, &mut OutlinePostProcessSettings)>,
+) {
+    for (projection, mut settings) in settings_query.iter_mut() {
+        if projection.is_changed() {
+            if let Projection::Perspective(projection) = projection.into_inner() {
+                settings.camera_near = projection.near;
+            }
+        }
+    }
+}

src/nodes.rs

@@ -57,8 +57,8 @@ impl ViewNode for OutlineRenderNode {
             return Ok(());
         };
 
-        let Some(deferred_buffer_view) = view_prepass_textures.deferred_view() else {
+        let Some(depth_buffer_view) = view_prepass_textures.depth_view() else {
-            error!("Failed to get deferred buffer view");
+            error!("Failed to get normal buffer view");
             return Ok(());
         };
 
@@ -72,7 +72,8 @@ impl ViewNode for OutlineRenderNode {
                 &render_pipeline.screen_sampler,
                 normal_buffer_view,
                 &render_pipeline.normal_sampler,
-                deferred_buffer_view,
+                depth_buffer_view,
+                &render_pipeline.depth_sampler,
                 uniform_binding,
             )),
         );

src/resources.rs

@@ -20,6 +20,7 @@ pub struct OutlinePostProcessPipeline {
     pub layout: BindGroupLayout,
     pub screen_sampler: Sampler,
     pub normal_sampler: Sampler,
+    pub depth_sampler: Sampler,
     pub pipeline_id: CachedRenderPipelineId,
 }
 
@@ -36,7 +37,8 @@ impl FromWorld for OutlinePostProcessPipeline {
                     sampler(SamplerBindingType::Filtering),
                     texture_2d(TextureSampleType::Float { filterable: true }),
                     sampler(SamplerBindingType::Filtering),
-                    texture_2d(TextureSampleType::Uint),
+                    texture_2d(TextureSampleType::Depth),
+                    sampler(SamplerBindingType::NonFiltering),
                     uniform_buffer::<components::OutlinePostProcessSettings>(false),
                 ),
             ),
@@ -44,6 +46,7 @@ impl FromWorld for OutlinePostProcessPipeline {
 
         let screen_sampler = render_device.create_sampler(&SamplerDescriptor::default());
         let normal_sampler = render_device.create_sampler(&SamplerDescriptor::default());
+        let depth_sampler = render_device.create_sampler(&SamplerDescriptor::default());
 
         let shader = world.resource::<AssetServer>().load::<Shader>(
             "embedded://bevy_outline_post_process/../assets/shaders/outline_post_process.wgsl",
@@ -77,6 +80,7 @@ impl FromWorld for OutlinePostProcessPipeline {
             layout,
             screen_sampler,
             normal_sampler,
+            depth_sampler,
             pipeline_id,
         }
     }