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writing gltf using indices
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@francisdb
francisdb committed Jun 22, 2024
1 parent 048ac0a commit dc5d20f
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Showing 2 changed files with 67 additions and 30 deletions.
1 change: 1 addition & 0 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ weezl = "0.1.8"
regex = "1.10.5"
gltf = "1.4.1"
unicase = "2.7.0"
bytemuck = "1.16.1"

[dev-dependencies]
dirs = "5.0.1"
Expand Down
96 changes: 66 additions & 30 deletions src/vpx/gltf.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,8 +46,8 @@ fn bounding_coords(points: &[Vertex]) -> ([f32; 3], [f32; 3]) {
(min, max)
}

fn align_to_multiple_of_four(n: &mut usize) {
*n = (*n + 3) & !3;
fn align_to_multiple_of_four(n: usize) -> usize {
(n + 3) & !3
}

fn to_padded_byte_vector<T>(vec: Vec<T>) -> Vec<u8> {
Expand Down Expand Up @@ -95,7 +95,7 @@ pub(crate) fn write_gltf(

let material = material(mat, image_rel_path, &mut root);

let (vertices, buffer_length, primitive) =
let (vertices, indices, buffer_length, primitive) =
primitive(&mesh, output, &bin_path, &mut root, material);

let mesh = root.push(json::Mesh {
Expand All @@ -121,7 +121,7 @@ pub(crate) fn write_gltf(

match output {
Output::Standard => {
write_vertices_binary(bin_path, vertices)?;
write_vertices_binary(bin_path, vertices, indices)?;
write_gltf_file(gltf_file_path, root)?;
}
Output::Binary => {
Expand All @@ -137,10 +137,15 @@ fn write_gltf_file(gltf_file_path: &PathBuf, root: Root) -> Result<(), Box<dyn E
Ok(())
}

fn write_vertices_binary(bin_path: PathBuf, vertices: Vec<Vertex>) -> Result<(), Box<dyn Error>> {
fn write_vertices_binary(
bin_path: PathBuf,
vertices: Vec<Vertex>,
indices: Vec<u32>,
) -> Result<(), Box<dyn Error>> {
let bin = to_padded_byte_vector(vertices);
let mut writer = File::create(bin_path)?;
writer.write_all(&bin)?;
writer.write_all(bytemuck::cast_slice(&indices))?;
Ok(())
}

Expand All @@ -151,8 +156,7 @@ fn write_glb_file(
buffer_length: usize,
) -> Result<(), Box<dyn Error>> {
let json_string = json::serialize::to_string(&root)?;
let mut json_offset = json_string.len();
align_to_multiple_of_four(&mut json_offset);
let json_offset = align_to_multiple_of_four(json_string.len());
let glb = gltf::binary::Glb {
header: gltf::binary::Header {
magic: *b"glTF",
Expand All @@ -172,29 +176,32 @@ fn write_glb_file(
}

fn primitive(
mesh: &&ReadMesh,
mesh: &ReadMesh,
output: Output,
bin_path: &Path,
root: &mut Root,
material: Index<Material>,
) -> (Vec<Vertex>, usize, Primitive) {
// use the indices to look up the vertices
let vertices = mesh
.indices
) -> (Vec<Vertex>, Vec<u32>, usize, Primitive) {
let vertices_data = mesh
.vertices
.iter()
.map(|i| {
let v = &mesh.vertices[*i as usize];
Vertex {
position: [v.vertex.x, v.vertex.y, v.vertex.z],
normal: [v.vertex.nx, v.vertex.ny, v.vertex.nz],
uv: [v.vertex.tu, v.vertex.tv],
}
.map(|v| Vertex {
position: [v.vertex.x, v.vertex.y, v.vertex.z],
normal: [v.vertex.nx, v.vertex.ny, v.vertex.nz],
uv: [v.vertex.tu, v.vertex.tv],
})
.collect::<Vec<Vertex>>();

let (min, max) = bounding_coords(&vertices);
let indices_data = mesh.indices.iter().map(|i| *i as u32).collect::<Vec<u32>>();

let (min, max) = bounding_coords(&vertices_data);

let vertices_data_len = vertices_data.len() * mem::size_of::<Vertex>();
let vertices_data_len_padded = align_to_multiple_of_four(vertices_data_len);
let indices_data_len = indices_data.len() * mem::size_of::<u32>();
let indices_data_len_padded = align_to_multiple_of_four(indices_data_len);
let buffer_length = vertices_data_len_padded + indices_data_len_padded;

let buffer_length = vertices.len() * mem::size_of::<Vertex>();
let buffer = root.push(json::Buffer {
byte_length: USize64::from(buffer_length),
extensions: Default::default(),
Expand All @@ -212,7 +219,7 @@ fn primitive(
None
},
});
let buffer_view = root.push(json::buffer::View {
let positions_buffer_view = root.push(json::buffer::View {
buffer,
byte_length: USize64::from(buffer_length),
byte_offset: None,
Expand All @@ -223,9 +230,9 @@ fn primitive(
target: Some(Valid(json::buffer::Target::ArrayBuffer)),
});
let positions = root.push(json::Accessor {
buffer_view: Some(buffer_view),
buffer_view: Some(positions_buffer_view),
byte_offset: Some(USize64(0)),
count: USize64::from(vertices.len()),
count: USize64::from(vertices_data.len()),
component_type: Valid(json::accessor::GenericComponentType(
json::accessor::ComponentType::F32,
)),
Expand All @@ -238,11 +245,40 @@ fn primitive(
normalized: false,
sparse: None,
});

let indices_buffer_view = root.push(json::buffer::View {
buffer,
byte_length: USize64::from(indices_data_len),
byte_offset: Some(USize64::from(vertices_data_len_padded)),
byte_stride: None,
extensions: Default::default(),
extras: Default::default(),
name: None,
target: Some(Valid(json::buffer::Target::ElementArrayBuffer)),
});
let indices = root.push(json::Accessor {
buffer_view: Some(indices_buffer_view),
byte_offset: Some(USize64(0)),
count: USize64::from(mesh.indices.len()),
component_type: Valid(json::accessor::GenericComponentType(
// TODO maybe use U16 if indices.len() < 65536
json::accessor::ComponentType::U32,
)),
extensions: None,
extras: Default::default(),
type_: Valid(json::accessor::Type::Scalar),
min: None,
max: None,
name: None,
normalized: false,
sparse: None,
});

let normals = root.push(json::Accessor {
buffer_view: Some(buffer_view),
buffer_view: Some(positions_buffer_view),
// we have to skip the first 3 floats to get to the normals
byte_offset: Some(USize64::from(3 * mem::size_of::<f32>())),
count: USize64::from(vertices.len()),
count: USize64::from(vertices_data.len()),
component_type: Valid(json::accessor::GenericComponentType(
json::accessor::ComponentType::F32,
)),
Expand All @@ -257,10 +293,10 @@ fn primitive(
});

let tex_coords = root.push(json::Accessor {
buffer_view: Some(buffer_view),
buffer_view: Some(positions_buffer_view),
// we have to skip the first 5 floats to get to the texture coordinates
byte_offset: Some(USize64::from(6 * mem::size_of::<f32>())),
count: USize64::from(vertices.len()),
count: USize64::from(vertices_data.len()),
component_type: Valid(json::accessor::GenericComponentType(
json::accessor::ComponentType::F32,
)),
Expand All @@ -286,11 +322,11 @@ fn primitive(
},
extensions: Default::default(),
extras: Default::default(),
indices: None,
indices: Some(indices),
mode: Valid(json::mesh::Mode::Triangles),
targets: None,
};
(vertices, buffer_length, primitive)
(vertices_data, indices_data, buffer_length, primitive)
}

fn material(
Expand Down

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