openusd 0.4.0

Rust native USD library
Documentation 
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//! `BlendShape` prim authoring.

use anyhow::Result;

use crate::sdf::{Path, Value, Variability};
use crate::usd::{Prim, Stage};

use crate::schemas::skel::tokens::{
    A_NORMAL_OFFSETS, A_OFFSETS, A_POINT_INDICES, META_WEIGHT, NS_INBETWEENS, T_BLEND_SHAPE,
};

/// Author a `def BlendShape` prim at `path`. Returns a chainable
/// [`BlendShapeAuthor`] for setting the spec-defined uniform arrays:
///
/// - `offsets` (uniform vector3f[]) — required position offsets
/// - `normalOffsets` (uniform vector3f[]) — required normal offsets
/// - `pointIndices` (uniform int[]) — **optional** sparse mapping; when
///   authored, restricts `offsets` / `normalOffsets` to the listed
///   point indices on the bound mesh.
///
/// Inbetween shapes (`inbetweens:NAME` with `weight` metadata) are
/// authored separately via [`BlendShapeAuthor::add_inbetween`].
pub fn define_blend_shape<'s>(stage: &'s Stage, path: impl Into<Path>) -> Result<BlendShapeAuthor<'s>> {
    let prim = stage.define_prim(path)?.set_type_name(T_BLEND_SHAPE)?;
    Ok(BlendShapeAuthor { prim })
}

/// Chainable BlendShape authoring handle.
pub struct BlendShapeAuthor<'s> {
    prim: Prim<'s>,
}

impl<'s> BlendShapeAuthor<'s> {
    pub fn into_prim(self) -> Prim<'s> {
        self.prim
    }

    /// Set `offsets` — required position offsets. Adding these to the
    /// base pose produces the target shape.
    pub fn set_offsets(self, values: Vec<[f32; 3]>) -> Result<Self> {
        author_uniform_vec3f_array(self.prim.stage(), self.prim.path(), A_OFFSETS, values)?;
        Ok(self)
    }

    /// Set `normalOffsets` — required normal offsets paired with
    /// [`Self::set_offsets`].
    pub fn set_normal_offsets(self, values: Vec<[f32; 3]>) -> Result<Self> {
        author_uniform_vec3f_array(self.prim.stage(), self.prim.path(), A_NORMAL_OFFSETS, values)?;
        Ok(self)
    }

    /// Set `pointIndices` — optional sparse mapping. When authored,
    /// `offsets[i]` / `normalOffsets[i]` apply to the bound mesh point
    /// at `pointIndices[i]`. Per spec, the lengths of `pointIndices`
    /// and `offsets` must match when authored.
    pub fn set_point_indices(self, indices: Vec<i32>) -> Result<Self> {
        let attr_path = self.prim.path().append_property(A_POINT_INDICES)?;
        self.prim
            .stage()
            .create_attribute(attr_path, "int[]")?
            .set_variability(Variability::Uniform)?
            .set_custom(false)?
            .set(Value::IntVec(indices))?;
        Ok(self)
    }

    /// Add an inbetween shape named `name` at the given `weight` location
    /// on `[0, 1]`. Authors:
    ///
    /// - `inbetweens:NAME` (uniform vector3f[]) with `weight` metadata
    /// - `inbetweens:NAME:normalOffsets` (uniform vector3f[]) when
    ///   `normal_offsets` is provided
    ///
    /// Per Pixar's `usdSkel/inbetweenShape.h`, the `weight` is stored as
    /// a generic property-level metadata field on the offsets
    /// attribute itself — not under `customData` — which the reader
    /// pulls via `stage.field(attr_path, "weight")`.
    pub fn add_inbetween(
        self,
        name: &str,
        weight: f32,
        offsets: Vec<[f32; 3]>,
        normal_offsets: Option<Vec<[f32; 3]>>,
    ) -> Result<Self> {
        let stage = self.prim.stage();
        let prim_path = self.prim.path().clone();

        // Offsets attribute carries the weight as a property-level field.
        let attr_name = format!("{NS_INBETWEENS}{name}");
        let attr_path = prim_path.append_property(&attr_name)?;
        stage
            .create_attribute(attr_path, "vector3f[]")?
            .set_variability(Variability::Uniform)?
            .set_custom(false)?
            .set(Value::Vec3fVec(offsets))?
            .set_metadata(META_WEIGHT, Value::Float(weight))?;

        // Optional normals sibling — `inbetweens:NAME:normalOffsets`.
        if let Some(normals) = normal_offsets {
            let normals_name = format!("{NS_INBETWEENS}{name}:normalOffsets");
            let normals_path = prim_path.append_property(&normals_name)?;
            stage
                .create_attribute(normals_path, "vector3f[]")?
                .set_variability(Variability::Uniform)?
                .set_custom(false)?
                .set(Value::Vec3fVec(normals))?;
        }

        Ok(self)
    }
}

fn author_uniform_vec3f_array(stage: &Stage, prim: &Path, name: &str, values: Vec<[f32; 3]>) -> Result<()> {
    let attr_path = prim.append_property(name)?;
    stage
        .create_attribute(attr_path, "vector3f[]")?
        .set_variability(Variability::Uniform)?
        .set_custom(false)?
        .set(Value::Vec3fVec(values))?;
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::sdf;

    #[test]
    fn define_blend_shape_writes_required_arrays() -> Result<()> {
        let stage = Stage::builder().in_memory("anon.usda")?;
        define_blend_shape(&stage, sdf::path("/Smile")?)?
            .set_offsets(vec![[0.0, 0.1, 0.0], [0.0, 0.2, 0.0]])?
            .set_normal_offsets(vec![[0.0, 1.0, 0.0], [0.0, 1.0, 0.0]])?;

        let prim = sdf::path("/Smile")?;
        assert_eq!(stage.type_name(&prim)?.as_deref(), Some(T_BLEND_SHAPE));

        match stage.field::<sdf::Value>("/Smile.offsets", sdf::FieldKey::Default)? {
            Some(sdf::Value::Vec3fVec(v)) => assert_eq!(v, vec![[0.0, 0.1, 0.0], [0.0, 0.2, 0.0]]),
            other => panic!("expected Vec3fVec for offsets, got {other:?}"),
        }
        match stage.field::<sdf::Value>("/Smile.normalOffsets", sdf::FieldKey::Default)? {
            Some(sdf::Value::Vec3fVec(v)) => assert_eq!(v.len(), 2),
            other => panic!("expected Vec3fVec for normalOffsets, got {other:?}"),
        }
        assert_eq!(
            stage.field::<sdf::Value>("/Smile.offsets", sdf::FieldKey::Variability)?,
            Some(sdf::Value::Variability(sdf::Variability::Uniform)),
        );
        Ok(())
    }

    #[test]
    fn add_inbetween_writes_offsets_with_weight_metadata() -> Result<()> {
        let stage = Stage::builder().in_memory("anon.usda")?;
        define_blend_shape(&stage, sdf::path("/Smile")?)?
            .set_offsets(vec![[0.0, 0.1, 0.0], [0.0, 0.1, 0.0]])?
            .set_normal_offsets(vec![[0.0, 1.0, 0.0], [0.0, 1.0, 0.0]])?
            .add_inbetween(
                "half",
                0.5,
                vec![[0.0, 0.05, 0.0], [0.0, 0.05, 0.0]],
                Some(vec![[0.0, 1.0, 0.0], [0.0, 1.0, 0.0]]),
            )?;

        // The inbetween attribute itself.
        match stage.field::<sdf::Value>("/Smile.inbetweens:half", sdf::FieldKey::Default)? {
            Some(sdf::Value::Vec3fVec(v)) => assert_eq!(v, vec![[0.0, 0.05, 0.0], [0.0, 0.05, 0.0]]),
            other => panic!("expected Vec3fVec for inbetweens:half, got {other:?}"),
        }
        // weight property metadata (read directly by reader).
        match stage.field::<sdf::Value>("/Smile.inbetweens:half", "weight")? {
            Some(sdf::Value::Float(f)) => assert!((f - 0.5).abs() < 1e-6),
            other => panic!("expected weight = 0.5 on inbetween, got {other:?}"),
        }
        // Sibling normals attribute.
        match stage.field::<sdf::Value>("/Smile.inbetweens:half:normalOffsets", sdf::FieldKey::Default)? {
            Some(sdf::Value::Vec3fVec(v)) => assert_eq!(v.len(), 2),
            other => panic!("expected Vec3fVec for normalOffsets sibling, got {other:?}"),
        }
        Ok(())
    }

    #[test]
    fn add_inbetween_normals_are_optional() -> Result<()> {
        let stage = Stage::builder().in_memory("anon.usda")?;
        define_blend_shape(&stage, sdf::path("/Smile")?)?
            .set_offsets(vec![[0.0, 0.1, 0.0]])?
            .set_normal_offsets(vec![[0.0, 1.0, 0.0]])?
            .add_inbetween("half", 0.5, vec![[0.0, 0.05, 0.0]], None)?;

        // Offsets + weight authored, but normals sibling absent.
        assert!(stage
            .field::<sdf::Value>("/Smile.inbetweens:half", sdf::FieldKey::Default)?
            .is_some());
        assert!(stage
            .field::<sdf::Value>("/Smile.inbetweens:half:normalOffsets", sdf::FieldKey::Default)?
            .is_none());
        Ok(())
    }

    #[test]
    fn point_indices_are_optional() -> Result<()> {
        let stage = Stage::builder().in_memory("anon.usda")?;
        define_blend_shape(&stage, sdf::path("/Smile")?)?
            .set_offsets(vec![[0.0, 0.1, 0.0]])?
            .set_normal_offsets(vec![[0.0, 1.0, 0.0]])?;

        // pointIndices unauthored — no attribute spec at all.
        assert!(stage
            .field::<sdf::Value>("/Smile.pointIndices", sdf::FieldKey::Default)?
            .is_none());

        // Now set pointIndices and confirm it lands.
        define_blend_shape(&stage, sdf::path("/SmileSparse")?)?
            .set_offsets(vec![[0.0, 0.1, 0.0]])?
            .set_normal_offsets(vec![[0.0, 1.0, 0.0]])?
            .set_point_indices(vec![3])?;

        match stage.field::<sdf::Value>("/SmileSparse.pointIndices", sdf::FieldKey::Default)? {
            Some(sdf::Value::IntVec(v)) => assert_eq!(v, vec![3]),
            other => panic!("expected IntVec for pointIndices, got {other:?}"),
        }
        Ok(())
    }
}