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use std::ops;

use nalgebra::Perspective3;

use super::{Aabb, Point, Segment, Triangle, Vector};

/// A transform
#[repr(C)]
#[derive(Debug, Clone, Copy)]
pub struct Transform(nalgebra::Transform<f64, nalgebra::TAffine, 3>);

impl Transform {
    /// Construct an identity transform
    pub fn identity() -> Self {
        Self(nalgebra::Transform::identity())
    }

    /// Construct a translation
    pub fn translation(vector: impl Into<Vector<3>>) -> Self {
        let vector = vector.into();

        Self(nalgebra::Transform::from_matrix_unchecked(
            nalgebra::OMatrix::new_translation(&vector.to_na()),
        ))
    }

    /// Construct a rotation
    ///
    /// The direction of the vector defines the rotation axis. Its length
    /// defines the angle of the rotation.
    pub fn rotation(axis_angle: impl Into<Vector<3>>) -> Self {
        let axis_angle = axis_angle.into();

        Self(nalgebra::Transform::from_matrix_unchecked(
            nalgebra::OMatrix::<_, nalgebra::Const<4>, _>::new_rotation(
                axis_angle.to_na(),
            ),
        ))
    }

    /// Transform the given point
    pub fn transform_point(&self, point: &Point<3>) -> Point<3> {
        Point::from(self.0.transform_point(&point.to_na()))
    }

    /// Inverse transform given point
    pub fn inverse_transform_point(&self, point: &Point<3>) -> Point<3> {
        Point::from(self.0.inverse_transform_point(&point.to_na()))
    }

    /// Transform the given vector
    pub fn transform_vector(&self, vector: &Vector<3>) -> Vector<3> {
        Vector::from(self.0.transform_vector(&vector.to_na()))
    }

    /// Transform the given segment
    pub fn transform_segment(&self, segment: &Segment<3>) -> Segment<3> {
        let [a, b] = &segment.points();
        Segment::from([self.transform_point(a), self.transform_point(b)])
    }

    /// Transform the given triangle
    pub fn transform_triangle(&self, triangle: &Triangle<3>) -> Triangle<3> {
        let [a, b, c] = &triangle.points();
        Triangle::from([
            self.transform_point(a),
            self.transform_point(b),
            self.transform_point(c),
        ])
    }

    /// Inverse transform
    pub fn inverse(&self) -> Transform {
        Self(self.0.inverse())
    }

    /// Transpose transform
    pub fn transpose(&self) -> Transform {
        Self(nalgebra::Transform::from_matrix_unchecked(
            self.0.to_homogeneous().transpose(),
        ))
    }

    /// Project transform according to camera specfication, return data as a slice.
    /// Used primarily for graphics code.
    pub fn project_to_slice(
        &self,
        aspect_ratio: f64,
        fovy: f64,
        znear: f64,
        zfar: f64,
    ) -> [f64; 16] {
        let projection = Perspective3::new(aspect_ratio, fovy, znear, zfar);
        let mut res = [0f64; 16];
        res.copy_from_slice(
            (projection.to_projective() * self.0).matrix().as_slice(),
        );
        res
    }

    /// Transform the given axis-aligned bounding box
    pub fn transform_aabb(&self, aabb: &Aabb<3>) -> Aabb<3> {
        Aabb {
            min: self.transform_point(&aabb.min),
            max: self.transform_point(&aabb.max),
        }
    }

    /// Exposes the data of this Transform as a slice of f64.
    pub fn data(&self) -> &[f64] {
        self.0.matrix().data.as_slice()
    }
}

impl ops::Mul<Self> for Transform {
    type Output = Self;

    fn mul(self, rhs: Self) -> Self::Output {
        Self(self.0.mul(rhs.0))
    }
}