Add support for custom glTF vertex attributes. (#5370)

# Objective The objective is to be able to load data from "application-specific" (see glTF spec 3.7.2.1.) vertex attribute semantics from glTF files into Bevy meshes. ## Solution Rather than probe the glTF for the specific attributes supported by Bevy, this PR changes the loader to iterate through all the attributes and map them onto `MeshVertexAttribute`s. This mapping includes all the previously supported attributes, plus it is now possible to add mappings using the `add_custom_vertex_attribute()` method on `GltfPlugin`. ## Changelog - Add support for loading custom vertex attributes from glTF files. - Add the `custom_gltf_vertex_attribute.rs` example to illustrate loading custom vertex attributes. ## Migration Guide - If you were instantiating `GltfPlugin` using the unit-like struct syntax, you must instead use `GltfPlugin::default()` as the type is no longer unit-like.
bevyengine · Apr 24, 2023 · d74533b · d74533b
1 parent 5dec323
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diff --git a/CREDITS.md b/CREDITS.md
@@ -25,3 +25,4 @@
   * Low poly fox [by PixelMannen](https://opengameart.org/content/fox-and-shiba) (CC0 1.0 Universal)
   * Rigging and animation [by @tomkranis on Sketchfab](https://sketchfab.com/models/371dea88d7e04a76af5763f2a36866bc) ([CC-BY 4.0](https://creativecommons.org/licenses/by/4.0/))
 * FiraMono by The Mozilla Foundation and Telefonica S.A (SIL Open Font License, Version 1.1: assets/fonts/FiraMono-LICENSE)
+* Barycentric from [mk_bary_gltf](https://github.com/komadori/mk_bary_gltf) (MIT OR Apache-2.0)
diff --git a/Cargo.toml b/Cargo.toml
@@ -326,6 +326,16 @@ description = "Renders a rectangle, circle, and hexagon"
 category = "2D Rendering"
 wasm = true
 
+[[example]]
+name = "custom_gltf_vertex_attribute"
+path = "examples/2d/custom_gltf_vertex_attribute.rs"
+
+[package.metadata.example.custom_gltf_vertex_attribute]
+name = "Custom glTF vertex attribute 2D"
+description = "Renders a glTF mesh in 2D with a custom vertex attribute"
+category = "2D Rendering"
+wasm = true
+
 [[example]]
 name = "2d_gizmos"
 path = "examples/2d/2d_gizmos.rs"

diff --git a/assets/models/barycentric/barycentric.gltf b/assets/models/barycentric/barycentric.gltf
@@ -0,0 +1,80 @@
+{
+  "accessors": [
+    {
+      "bufferView": 0,
+      "byteOffset": 0,
+      "count": 4,
+      "componentType": 5126,
+      "type": "VEC3",
+      "min": [
+        -1.0,
+        -1.0,
+        0.0
+      ],
+      "max": [
+        1.0,
+        1.0,
+        0.0
+      ]
+    },
+    {
+      "bufferView": 0,
+      "byteOffset": 12,
+      "count": 4,
+      "componentType": 5126,
+      "type": "VEC4"
+    },
+    {
+      "bufferView": 0,
+      "byteOffset": 28,
+      "count": 4,
+      "componentType": 5126,
+      "type": "VEC3"
+    },
+    {
+      "bufferView": 1,
+      "byteOffset": 0,
+      "count": 6,
+      "componentType": 5123,
+      "type": "SCALAR"
+    }
+  ],
+  "asset": {
+    "version": "2.0"
+  },
+  "buffers": [
+    {
+      "byteLength": 172,
+      "uri": "data:application/gltf-buffer;base64,AACAvwAAgL8AAAAAAACAPwAAAAAAAAAAAACAPwAAgD8AAAAAAAAAAAAAgD8AAIC/AAAAAAAAAD8AAAA/AAAAAAAAgD8AAAAAAACAPwAAAAAAAIC/AACAPwAAAAAAAAA/AAAAPwAAAAAAAIA/AAAAAAAAAAAAAIA/AACAPwAAgD8AAAAAAAAAAAAAgD8AAAAAAACAPwAAgD8AAAAAAAAAAAAAAQACAAIAAQADAA=="
+    }
+  ],
+  "bufferViews": [
+    {
+      "buffer": 0,
+      "byteLength": 160,
+      "byteOffset": 0,
+      "byteStride": 40,
+      "target": 34962
+    },
+    {
+      "buffer": 0,
+      "byteLength": 12,
+      "byteOffset": 160,
+      "target": 34962
+    }
+  ],
+  "meshes": [
+    {
+      "primitives": [
+        {
+          "attributes": {
+            "POSITION": 0,
+            "COLOR_0": 1,
+            "__BARYCENTRIC": 2
+          },
+          "indices": 3
+        }
+      ]
+    }
+  ]
+}
diff --git a/assets/shaders/custom_gltf_2d.wgsl b/assets/shaders/custom_gltf_2d.wgsl
@@ -0,0 +1,36 @@
+#import bevy_sprite::mesh2d_view_bindings
+#import bevy_sprite::mesh2d_bindings
+#import bevy_sprite::mesh2d_functions
+
+struct Vertex {
+    @location(0) position: vec3<f32>,
+    @location(1) color: vec4<f32>,
+    @location(2) barycentric: vec3<f32>,
+};
+
+struct VertexOutput {
+    @builtin(position) clip_position: vec4<f32>,
+    @location(0) color: vec4<f32>,
+    @location(1) barycentric: vec3<f32>,
+};
+
+@vertex
+fn vertex(vertex: Vertex) -> VertexOutput {
+    var out: VertexOutput;
+    out.clip_position = mesh2d_position_local_to_clip(mesh.model, vec4<f32>(vertex.position, 1.0));
+    out.color = vertex.color;
+    out.barycentric = vertex.barycentric;
+    return out;
+}
+
+struct FragmentInput {
+    @location(0) color: vec4<f32>,
+    @location(1) barycentric: vec3<f32>,
+};
+
+@fragment
+fn fragment(input: FragmentInput) -> @location(0) vec4<f32> {
+    let d = min(input.barycentric.x, min(input.barycentric.y, input.barycentric.z));
+    let t = 0.05 * (0.85 + sin(5.0 * globals.time));
+    return mix(vec4(1.0,1.0,1.0,1.0), input.color, smoothstep(t, t+0.01, d));
+}
diff --git a/crates/bevy_gltf/src/lib.rs b/crates/bevy_gltf/src/lib.rs
@@ -5,28 +5,55 @@ use bevy_animation::AnimationClip;
 use bevy_utils::HashMap;
 
 mod loader;
+mod vertex_attributes;
 pub use loader::*;
 
 use bevy_app::prelude::*;
 use bevy_asset::{AddAsset, Handle};
 use bevy_ecs::{prelude::Component, reflect::ReflectComponent};
 use bevy_pbr::StandardMaterial;
 use bevy_reflect::{Reflect, TypeUuid};
-use bevy_render::mesh::Mesh;
+use bevy_render::{
+    mesh::{Mesh, MeshVertexAttribute},
+    renderer::RenderDevice,
+    texture::CompressedImageFormats,
+};
 use bevy_scene::Scene;
 
 /// Adds support for glTF file loading to the app.
 #[derive(Default)]
-pub struct GltfPlugin;
+pub struct GltfPlugin {
+    custom_vertex_attributes: HashMap<String, MeshVertexAttribute>,
+}
+
+impl GltfPlugin {
+    pub fn add_custom_vertex_attribute(
+        mut self,
+        name: &str,
+        attribute: MeshVertexAttribute,
+    ) -> Self {
+        self.custom_vertex_attributes
+            .insert(name.to_string(), attribute);
+        self
+    }
+}
 
 impl Plugin for GltfPlugin {
     fn build(&self, app: &mut App) {
-        app.init_asset_loader::<GltfLoader>()
-            .register_type::<GltfExtras>()
-            .add_asset::<Gltf>()
-            .add_asset::<GltfNode>()
-            .add_asset::<GltfPrimitive>()
-            .add_asset::<GltfMesh>();
+        let supported_compressed_formats = match app.world.get_resource::<RenderDevice>() {
+            Some(render_device) => CompressedImageFormats::from_features(render_device.features()),
+
+            None => CompressedImageFormats::all(),
+        };
+        app.add_asset_loader::<GltfLoader>(GltfLoader {
+            supported_compressed_formats,
+            custom_vertex_attributes: self.custom_vertex_attributes.clone(),
+        })
+        .register_type::<GltfExtras>()
+        .add_asset::<Gltf>()
+        .add_asset::<GltfNode>()
+        .add_asset::<GltfPrimitive>()
+        .add_asset::<GltfMesh>();
     }
 }
 

diff --git a/crates/bevy_gltf/src/loader.rs b/crates/bevy_gltf/src/loader.rs
@@ -4,7 +4,7 @@ use bevy_asset::{
 };
 use bevy_core::Name;
 use bevy_core_pipeline::prelude::Camera3dBundle;
-use bevy_ecs::{entity::Entity, prelude::FromWorld, world::World};
+use bevy_ecs::{entity::Entity, world::World};
 use bevy_hierarchy::{BuildWorldChildren, WorldChildBuilder};
 use bevy_log::warn;
 use bevy_math::{Mat4, Vec3};
@@ -17,12 +17,11 @@ use bevy_render::{
     color::Color,
     mesh::{
         skinning::{SkinnedMesh, SkinnedMeshInverseBindposes},
-        Indices, Mesh, VertexAttributeValues,
+        Indices, Mesh, MeshVertexAttribute, VertexAttributeValues,
     },
     prelude::SpatialBundle,
     primitives::Aabb,
     render_resource::{AddressMode, Face, FilterMode, PrimitiveTopology, SamplerDescriptor},
-    renderer::RenderDevice,
     texture::{CompressedImageFormats, Image, ImageSampler, ImageType, TextureError},
 };
 use bevy_scene::Scene;
@@ -32,13 +31,14 @@ use bevy_transform::components::Transform;
 
 use bevy_utils::{HashMap, HashSet};
 use gltf::{
-    mesh::Mode,
+    mesh::{util::ReadIndices, Mode},
     texture::{MagFilter, MinFilter, WrappingMode},
     Material, Node, Primitive,
 };
 use std::{collections::VecDeque, path::Path};
 use thiserror::Error;
 
+use crate::vertex_attributes::*;
 use crate::{Gltf, GltfExtras, GltfNode};
 
 /// An error that occurs when loading a glTF file.
@@ -68,7 +68,8 @@ pub enum GltfError {
 
 /// Loads glTF files with all of their data as their corresponding bevy representations.
 pub struct GltfLoader {
-    supported_compressed_formats: CompressedImageFormats,
+    pub(crate) supported_compressed_formats: CompressedImageFormats,
+    pub(crate) custom_vertex_attributes: HashMap<String, MeshVertexAttribute>,
 }
 
 impl AssetLoader for GltfLoader {
@@ -77,34 +78,19 @@ impl AssetLoader for GltfLoader {
         bytes: &'a [u8],
         load_context: &'a mut LoadContext,
     ) -> BoxedFuture<'a, Result<()>> {
-        Box::pin(async move {
-            Ok(load_gltf(bytes, load_context, self.supported_compressed_formats).await?)
-        })
+        Box::pin(async move { Ok(load_gltf(bytes, load_context, self).await?) })
     }
 
     fn extensions(&self) -> &[&str] {
         &["gltf", "glb"]
     }
 }
 
-impl FromWorld for GltfLoader {
-    fn from_world(world: &mut World) -> Self {
-        let supported_compressed_formats = match world.get_resource::<RenderDevice>() {
-            Some(render_device) => CompressedImageFormats::from_features(render_device.features()),
-
-            None => CompressedImageFormats::all(),
-        };
-        Self {
-            supported_compressed_formats,
-        }
-    }
-}
-
 /// Loads an entire glTF file.
 async fn load_gltf<'a, 'b>(
     bytes: &'a [u8],
     load_context: &'a mut LoadContext<'b>,
-    supported_compressed_formats: CompressedImageFormats,
+    loader: &GltfLoader,
 ) -> Result<(), GltfError> {
     let gltf = gltf::Gltf::from_slice(bytes)?;
     let buffer_data = load_buffers(&gltf, load_context, load_context.path()).await?;
@@ -233,53 +219,31 @@ async fn load_gltf<'a, 'b>(
         let mut primitives = vec![];
         for primitive in mesh.primitives() {
             let primitive_label = primitive_label(&mesh, &primitive);
-            let reader = primitive.reader(|buffer| Some(&buffer_data[buffer.index()]));
             let primitive_topology = get_primitive_topology(primitive.mode())?;
 
             let mut mesh = Mesh::new(primitive_topology);
 
-            if let Some(vertex_attribute) = reader
-                .read_positions()
-                .map(|v| VertexAttributeValues::Float32x3(v.collect()))
-            {
-                mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, vertex_attribute);
-            }
-
-            if let Some(vertex_attribute) = reader
-                .read_normals()
-                .map(|v| VertexAttributeValues::Float32x3(v.collect()))
-            {
-                mesh.insert_attribute(Mesh::ATTRIBUTE_NORMAL, vertex_attribute);
-            }
-
-            if let Some(vertex_attribute) = reader
-                .read_tex_coords(0)
-                .map(|v| VertexAttributeValues::Float32x2(v.into_f32().collect()))
-            {
-                mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, vertex_attribute);
-            }
-
-            if let Some(vertex_attribute) = reader
-                .read_colors(0)
-                .map(|v| VertexAttributeValues::Float32x4(v.into_rgba_f32().collect()))
-            {
-                mesh.insert_attribute(Mesh::ATTRIBUTE_COLOR, vertex_attribute);
-            }
-
-            if let Some(iter) = reader.read_joints(0) {
-                let vertex_attribute = VertexAttributeValues::Uint16x4(iter.into_u16().collect());
-                mesh.insert_attribute(Mesh::ATTRIBUTE_JOINT_INDEX, vertex_attribute);
-            }
-
-            if let Some(vertex_attribute) = reader
-                .read_weights(0)
-                .map(|v| VertexAttributeValues::Float32x4(v.into_f32().collect()))
-            {
-                mesh.insert_attribute(Mesh::ATTRIBUTE_JOINT_WEIGHT, vertex_attribute);
+            // Read vertex attributes
+            for (semantic, accessor) in primitive.attributes() {
+                match convert_attribute(
+                    semantic,
+                    accessor,
+                    &buffer_data,
+                    &loader.custom_vertex_attributes,
+                ) {
+                    Ok((attribute, values)) => mesh.insert_attribute(attribute, values),
+                    Err(err) => warn!("{}", err),
+                }
             }
 
+            // Read vertex indices
+            let reader = primitive.reader(|buffer| Some(buffer_data[buffer.index()].as_slice()));
             if let Some(indices) = reader.read_indices() {
-                mesh.set_indices(Some(Indices::U32(indices.into_u32().collect())));
+                mesh.set_indices(Some(match indices {
+                    ReadIndices::U8(is) => Indices::U16(is.map(|x| x as u16).collect()),
+                    ReadIndices::U16(is) => Indices::U16(is.collect()),
+                    ReadIndices::U32(is) => Indices::U32(is.collect()),
+                }));
             };
 
             if mesh.attribute(Mesh::ATTRIBUTE_NORMAL).is_none()
@@ -403,7 +367,7 @@ async fn load_gltf<'a, 'b>(
                 &buffer_data,
                 &linear_textures,
                 load_context,
-                supported_compressed_formats,
+                loader.supported_compressed_formats,
             )
             .await?;
             load_context.set_labeled_asset(&label, LoadedAsset::new(texture));
@@ -422,7 +386,7 @@ async fn load_gltf<'a, 'b>(
                             buffer_data,
                             linear_textures,
                             load_context,
-                            supported_compressed_formats,
+                            loader.supported_compressed_formats,
                         )
                         .await
                     });