From 0df3735906445a653547b5639479fd8c2ec5b71e Mon Sep 17 00:00:00 2001
From: Robin KAY <komadori@gekkou.co.uk>
Date: Tue, 7 Mar 2023 23:46:58 +0000
Subject: [PATCH] Fix bad clipping of triangles behind the camera.

---
 examples/animated_fox.rs | 15 +++++++++------
 src/outline.wgsl         | 10 ++++------
 src/pipeline.rs          |  9 ++++++++-
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/examples/animated_fox.rs b/examples/animated_fox.rs
index cb2d921..68d738d 100644
--- a/examples/animated_fox.rs
+++ b/examples/animated_fox.rs
@@ -1,6 +1,6 @@
 use std::f32::consts::PI;
 
-use bevy::{prelude::*, window::close_on_esc};
+use bevy::{prelude::*, scene::SceneInstance, window::close_on_esc};
 use bevy_mod_outline::{
     AutoGenerateOutlineNormalsPlugin, OutlineBundle, OutlinePlugin, OutlineVolume,
 };
@@ -66,15 +66,17 @@ fn setup(
 // Once the scene is loaded, start the animation and add an outline
 fn setup_scene_once_loaded(
     mut commands: Commands,
+    scene_query: Query<&SceneInstance>,
+    scene_manager: Res<SceneSpawner>,
+    mut player_query: Query<&mut AnimationPlayer>,
     animation: Res<Fox>,
-    mut player: Query<&mut AnimationPlayer>,
-    entities: Query<Entity, With<Handle<Mesh>>>,
     mut done: Local<bool>,
 ) {
     if !*done {
-        if let Ok(mut player) = player.get_single_mut() {
-            player.play(animation.0.clone_weak()).repeat();
-            for entity in entities.iter() {
+        if let (Ok(scene), Ok(mut player)) =
+            (scene_query.get_single(), player_query.get_single_mut())
+        {
+            for entity in scene_manager.iter_instance_entities(**scene) {
                 commands.entity(entity).insert(OutlineBundle {
                     outline: OutlineVolume {
                         visible: true,
@@ -84,6 +86,7 @@ fn setup_scene_once_loaded(
                     ..default()
                 });
             }
+            player.play(animation.0.clone_weak()).repeat();
             *done = true;
         }
     }
diff --git a/src/outline.wgsl b/src/outline.wgsl
index a29e493..0993fc6 100644
--- a/src/outline.wgsl
+++ b/src/outline.wgsl
@@ -61,18 +61,16 @@ fn vertex(vertex: VertexInput) -> @builtin(position) vec4<f32> {
 #endif
     let clip_pos = view.view_proj * (model * vec4<f32>(vertex.position, 1.0));
 #ifdef FLAT_DEPTH
-    let ndc_pos = clip_pos.xy / clip_pos.w;
-    let out_zw = vec2<f32>(model_origin_z(vstage.origin, view.view_proj), 1.0);
+    let out_zw = vec2<f32>(model_origin_z(vstage.origin, view.view_proj) * clip_pos.w, clip_pos.w);
 #else
-    let ndc_pos = clip_pos.xy;
-    let out_zw = clip_pos.zw;
+    let out_zw = clip_pos.wz;
 #endif
 #ifdef OFFSET_ZERO
-    let out_xy = ndc_pos;
+    let out_xy = clip_pos.xy;
 #else
     let clip_norm = mat4to3(view.view_proj) * (mat4to3(model) * vertex.normal);
     let ndc_delta = vstage.offset * normalize(clip_norm.xy) * view_uniform.scale * out_zw.y;
-    let out_xy = ndc_pos + ndc_delta;
+    let out_xy = clip_pos.xy + ndc_delta;
 #endif
     return vec4<f32>(out_xy, out_zw);
 }
diff --git a/src/pipeline.rs b/src/pipeline.rs
index 20eda8b..1224c08 100644
--- a/src/pipeline.rs
+++ b/src/pipeline.rs
@@ -303,7 +303,14 @@ impl SpecializedMeshPipeline for OutlinePipeline {
                 depth_write_enabled: true,
                 depth_compare: CompareFunction::Greater,
                 stencil: StencilState::default(),
-                bias: DepthBiasState::default(),
+                bias: DepthBiasState {
+                    constant: if key.pass_type() == PassType::Stencil {
+                        2 // 1 is empirically not enough to prevent Z-fighting.
+                    } else {
+                        0
+                    },
+                    ..default()
+                },
             }),
             multisample: MultisampleState {
                 count: key.msaa_samples(),