nsys-gl-utils 0.11.3

OpenGL and graphics utilities
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//! Mesh generation utilities.

use std::path::Path;
use bytemuck;
use derive_more::{From, TryInto};
use gltf;
use strum;
use crate::{math, math::geometry, util, vertex};

pub mod capsule;
pub mod cylinder;
pub mod grid;
pub mod hemisphere;
pub mod sphere;

#[derive(Clone, Debug, PartialEq, From, TryInto)]
pub enum Mesh {
  Lines3d (Lines3d)
}

/// Raw data defining a wireframe mesh
#[derive(Clone, Debug, PartialEq, From)]
pub struct Lines3d {
  pub vertices : Vec <vertex::Vert3dInstanced>,
  pub indices  : Vec <u32>
}

impl Mesh {
  /// Load a GLTF file containing a single mesh
  pub fn load_gltf <P : AsRef <Path>> (path : P) -> Self {
    let (document, buffers, _images) = gltf::import (path).unwrap();
    let mut meshes = document.meshes();
    let mesh = meshes.next().unwrap();
    debug_assert!(meshes.next().is_none());
    let mut primitives = mesh.primitives();
    let primitive = primitives.next().unwrap();
    debug_assert!(primitives.next().is_none());
    let reader = primitive.reader (|buffer| Some (&buffers[buffer.index()]));
    let vertices = reader.read_positions().unwrap()
      .map (|inst_position| vertex::Vert3dInstanced { inst_position }).collect();
    let indices  = reader.read_indices().unwrap().into_u32().collect();
    Lines3d { vertices, indices }.into()
  }

  /// Write mesh to an embedded `.gltf` file
  pub fn write_gltf <P : AsRef <Path>> (&self, path : P) {
    fn bounding_coords (points: &[vertex::Vert3dInstanced])
      -> ([f32; 3], [f32; 3])
    {
      let mut min = [f32::MAX, f32::MAX, f32::MAX];
      let mut max = [f32::MIN, f32::MIN, f32::MIN];
      for point in points {
        let p = point.inst_position;
        for i in 0..3 {
          min[i] = f32::min (min[i], p[i]);
          max[i] = f32::max (max[i], p[i]);
        }
      }
      (min, max)
    }
    let (vertices, indices) = match self {
      Mesh::Lines3d (Lines3d { vertices, indices }) => (vertices, indices)
    };
    let (min, max)        = bounding_coords (&vertices[..]);
    let vertices_bytes    = bytemuck::cast_slice (&vertices);
    let indices_bytes     = bytemuck::cast_slice (&indices);
    let (buffer, views)   =
      util::gltf::json_buffer_views (0, &[vertices_bytes, indices_bytes]);
    let position_accessor = util::gltf::json_accessor (0, vertices.len() as u32,
      gltf::json::accessor::Type::Vec3,
      gltf::json::accessor::ComponentType::F32, Some ([min, max]));
    let index_accessor    = util::gltf::json_accessor (1, indices.len() as u32,
      gltf::json::accessor::Type::Scalar,
      gltf::json::accessor::ComponentType::U32, None);
    let lines_primitive   = util::gltf::json_primitive (
      gltf::json::mesh::Semantic::Positions, gltf::json::mesh::Mode::Lines, 1);
    let mesh              = util::gltf::json_mesh (vec![lines_primitive]);
    let node              = util::gltf::json_node (0);
    let root              = util::gltf::json_root (
      vec![node], vec![mesh], vec![buffer], views,
      vec![position_accessor, index_accessor]);
    let writer            = std::fs::File::create (path).unwrap();
    gltf::json::serialize::to_writer_pretty (writer, &root).unwrap();
  }
}

impl Lines3d {
  pub fn empty() -> Self {
    Lines3d { vertices: vec![], indices: vec![] }
  }
}

impl From <geometry::Aabb3 <f32>> for Lines3d {
  fn from (aabb : geometry::Aabb3 <f32>) -> Self {
    use strum::IntoEnumIterator;
    let vertices = math::Octant::iter().map (|octant| vertex::Vert3dInstanced {
      inst_position: aabb.corner (octant).0.into_array()
    }).collect();
    let indices  = vec![
      0, 1, 0, 2, 0, 4,
      7, 6, 7, 5, 7, 3,
      1, 3, 1, 5,
      2, 3, 2, 6,
      4, 5, 4, 6
    ];
    Lines3d { vertices, indices }
  }
}