Add UI Materials (#9506)

# Objective

- Add Ui Materials so that UI can render more complex and animated
widgets.
- Fixes #5607 

## Solution
- Create a UiMaterial trait for specifying a Shader Asset and Bind Group
Layout/Data.
- Create a pipeline for rendering these Materials inside the Ui
layout/tree.
- Create a MaterialNodeBundle for simple spawning.

## Changelog

- Created a `UiMaterial` trait for specifying a Shader asset and Bind
Group.
- Created a `UiMaterialPipeline` for rendering said Materials.
- Added Example [`ui_material`
](https://github.com/MarkusTheOrt/bevy/blob/ui_material/examples/ui/ui_material.rs)
for example usage.
- Created
[`UiVertexOutput`](https://github.com/MarkusTheOrt/bevy/blob/ui_material/crates/bevy_ui/src/render/ui_vertex_output.wgsl)
export as VertexData for shaders.
- Created
[`material_ui`](https://github.com/MarkusTheOrt/bevy/blob/ui_material/crates/bevy_ui/src/render/ui_material.wgsl)
shader as default for both Vertex and Fragment shaders.

---------

Co-authored-by: ickshonpe <david.curthoys@googlemail.com>
Co-authored-by: François <mockersf@gmail.com>

Cargo.toml

@@ -2412,6 +2412,17 @@ description = "Demonstrates resizing and responding to resizing a window"
 category = "Window"
 wasm = true
 
+[[example]]
+name = "ui_material"
+path = "examples/ui/ui_material.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.ui_material]
+name = "UI Material"
+description = "Demonstrates creating and using custom Ui materials"
+category = "UI (User Interface)"
+wasm = true
+
 [profile.wasm-release]
 inherits = "release"
 opt-level = "z"

assets/shaders/circle_shader.wgsl

@@ -0,0 +1,21 @@
+// This shader draws a circle with a given input color
+#import bevy_ui::ui_vertex_output::UiVertexOutput
+
+struct CustomUiMaterial {
+    @location(0) color: vec4<f32>
+}
+
+@group(1) @binding(0)
+var<uniform> input: CustomUiMaterial;
+
+@fragment
+fn fragment(in: UiVertexOutput) -> @location(0) vec4<f32> {
+    // the UVs are now adjusted around the middle of the rect.
+    let uv = in.uv * 2.0 - 1.0;
+
+    // circle alpha, the higher the power the harsher the falloff.
+    let alpha = 1.0 - pow(sqrt(dot(uv, uv)), 100.0);
+
+    return vec4<f32>(input.color.rgb, alpha);
+}
+

crates/bevy_ui/src/lib.rs

@@ -8,6 +8,7 @@
 pub mod camera_config;
 pub mod measurement;
 pub mod node_bundles;
+pub mod ui_material;
 pub mod update;
 pub mod widget;
 
@@ -29,15 +30,16 @@ pub use geometry::*;
 pub use layout::*;
 pub use measurement::*;
 pub use render::*;
+pub use ui_material::*;
 pub use ui_node::*;
 use widget::UiImageSize;
 
 #[doc(hidden)]
 pub mod prelude {
     #[doc(hidden)]
     pub use crate::{
-        camera_config::*, geometry::*, node_bundles::*, ui_node::*, widget::Button, widget::Label,
-        Interaction, UiScale,
+        camera_config::*, geometry::*, node_bundles::*, ui_material::*, ui_node::*, widget::Button,
+        widget::Label, Interaction, UiMaterialPlugin, UiScale,
     };
 }
 

crates/bevy_ui/src/node_bundles.rs

@@ -5,7 +5,7 @@ use crate::widget::TextFlags;
 use crate::{
     widget::{Button, UiImageSize},
     BackgroundColor, BorderColor, ContentSize, FocusPolicy, Interaction, Node, Style, UiImage,
-    UiTextureAtlasImage, ZIndex,
+    UiMaterial, UiTextureAtlasImage, ZIndex,
 };
 use bevy_asset::Handle;
 use bevy_ecs::bundle::Bundle;
@@ -342,3 +342,52 @@ impl Default for ButtonBundle {
         }
     }
 }
+
+/// A UI node that is rendered using a [`UiMaterial`]
+#[derive(Bundle, Clone, Debug)]
+pub struct MaterialNodeBundle<M: UiMaterial> {
+    /// Describes the logical size of the node
+    pub node: Node,
+    /// Styles which control the layout (size and position) of the node and it's children
+    /// In some cases these styles also affect how the node drawn/painted.
+    pub style: Style,
+    /// The [`UiMaterial`] used to render the node.
+    pub material: Handle<M>,
+    /// Whether this node should block interaction with lower nodes
+    pub focus_policy: FocusPolicy,
+    /// The transform of the node
+    ///
+    /// This field is automatically managed by the UI layout system.
+    /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+    pub transform: Transform,
+    /// The global transform of the node
+    ///
+    /// This field is automatically managed by the UI layout system.
+    /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+    pub global_transform: GlobalTransform,
+    /// Describes the visibility properties of the node
+    pub visibility: Visibility,
+    /// Inherited visibility of an entity.
+    pub inherited_visibility: InheritedVisibility,
+    /// Algorithmically-computed indication of whether an entity is visible and should be extracted for rendering
+    pub view_visibility: ViewVisibility,
+    /// Indicates the depth at which the node should appear in the UI
+    pub z_index: ZIndex,
+}
+
+impl<M: UiMaterial> Default for MaterialNodeBundle<M> {
+    fn default() -> Self {
+        Self {
+            node: Default::default(),
+            style: Default::default(),
+            material: Default::default(),
+            focus_policy: Default::default(),
+            transform: Default::default(),
+            global_transform: Default::default(),
+            visibility: Default::default(),
+            inherited_visibility: Default::default(),
+            view_visibility: Default::default(),
+            z_index: Default::default(),
+        }
+    }
+}

crates/bevy_ui/src/render/mod.rs

@@ -1,5 +1,6 @@
 mod pipeline;
 mod render_pass;
+mod ui_material_pipeline;
 
 use bevy_core_pipeline::{core_2d::Camera2d, core_3d::Camera3d};
 use bevy_hierarchy::Parent;
@@ -9,6 +10,7 @@ use bevy_render::{render_resource::BindGroupEntries, ExtractSchedule, Render};
 use bevy_window::{PrimaryWindow, Window};
 pub use pipeline::*;
 pub use render_pass::*;
+pub use ui_material_pipeline::*;
 
 use crate::Outline;
 use crate::{
@@ -253,7 +255,7 @@ pub fn extract_atlas_uinodes(
     }
 }
 
-fn resolve_border_thickness(value: Val, parent_width: f32, viewport_size: Vec2) -> f32 {
+pub(crate) fn resolve_border_thickness(value: Val, parent_width: f32, viewport_size: Vec2) -> f32 {
     match value {
         Val::Auto => 0.,
         Val::Px(px) => px.max(0.),
@@ -695,14 +697,14 @@ impl Default for UiMeta {
     }
 }
 
-const QUAD_VERTEX_POSITIONS: [Vec3; 4] = [
+pub(crate) const QUAD_VERTEX_POSITIONS: [Vec3; 4] = [
     Vec3::new(-0.5, -0.5, 0.0),
     Vec3::new(0.5, -0.5, 0.0),
     Vec3::new(0.5, 0.5, 0.0),
     Vec3::new(-0.5, 0.5, 0.0),
 ];
 
-const QUAD_INDICES: [usize; 6] = [0, 2, 3, 0, 1, 2];
+pub(crate) const QUAD_INDICES: [usize; 6] = [0, 2, 3, 0, 1, 2];
 
 #[derive(Component)]
 pub struct UiBatch {

crates/bevy_ui/src/render/ui_material.wgsl

@@ -0,0 +1,23 @@
+#import bevy_render::view::View
+#import bevy_ui::ui_vertex_output::UiVertexOutput
+
+@group(0) @binding(0)
+var<uniform> view: View;
+
+@vertex
+fn vertex(
+    @location(0) vertex_position: vec3<f32>,
+    @location(1) vertex_uv: vec2<f32>,
+    @location(2) border_widths: vec4<f32>,
+) -> UiVertexOutput {
+    var out: UiVertexOutput;
+    out.uv = vertex_uv;
+    out.position = view.view_proj * vec4<f32>(vertex_position, 1.0);
+    out.border_widths = border_widths;
+    return out;
+}
+
+@fragment
+fn fragment(in: UiVertexOutput) -> @location(0) vec4<f32> {
+    return vec4<f32>(1.0);
+}