use crate::{
mesh::{Indices, Mesh, MeshBuilder, Meshable},
render_asset::RenderAssetUsages,
};
use bevy_math::{primitives::ConicalFrustum, Vec3};
use wgpu::PrimitiveTopology;
#[derive(Clone, Copy, Debug)]
pub struct ConicalFrustumMeshBuilder {
pub frustum: ConicalFrustum,
pub resolution: u32,
pub segments: u32,
}
impl Default for ConicalFrustumMeshBuilder {
fn default() -> Self {
Self {
frustum: ConicalFrustum::default(),
resolution: 32,
segments: 1,
}
}
}
impl ConicalFrustumMeshBuilder {
#[inline]
pub const fn new(radius_top: f32, radius_bottom: f32, height: f32, resolution: u32) -> Self {
Self {
frustum: ConicalFrustum {
radius_top,
radius_bottom,
height,
},
resolution,
segments: 1,
}
}
#[inline]
pub const fn resolution(mut self, resolution: u32) -> Self {
self.resolution = resolution;
self
}
#[inline]
pub const fn segments(mut self, segments: u32) -> Self {
self.segments = segments;
self
}
}
impl MeshBuilder for ConicalFrustumMeshBuilder {
fn build(&self) -> Mesh {
debug_assert!(self.resolution > 2);
debug_assert!(self.segments > 0);
let ConicalFrustum {
radius_top,
radius_bottom,
height,
} = self.frustum;
let half_height = height / 2.0;
let num_rings = self.segments + 1;
let num_vertices = (self.resolution * 2 + num_rings * (self.resolution + 1)) as usize;
let num_faces = self.resolution * (num_rings - 2);
let num_indices = ((2 * num_faces + 2 * (self.resolution - 1) * 2) * 3) as usize;
let mut positions = Vec::with_capacity(num_vertices);
let mut normals = Vec::with_capacity(num_vertices);
let mut uvs = Vec::with_capacity(num_vertices);
let mut indices = Vec::with_capacity(num_indices);
let step_theta = std::f32::consts::TAU / self.resolution as f32;
let step_y = height / self.segments as f32;
let step_radius = (radius_top - radius_bottom) / self.segments as f32;
for ring in 0..num_rings {
let y = -half_height + ring as f32 * step_y;
let radius = radius_bottom + ring as f32 * step_radius;
for segment in 0..=self.resolution {
let theta = segment as f32 * step_theta;
let (sin, cos) = theta.sin_cos();
positions.push([radius * cos, y, radius * sin]);
normals.push(
Vec3::new(cos, (radius_bottom - radius_top) / height, sin)
.normalize()
.to_array(),
);
uvs.push([
segment as f32 / self.resolution as f32,
ring as f32 / self.segments as f32,
]);
}
}
for i in 0..self.segments {
let ring = i * (self.resolution + 1);
let next_ring = (i + 1) * (self.resolution + 1);
for j in 0..self.resolution {
indices.extend_from_slice(&[
ring + j,
next_ring + j,
ring + j + 1,
next_ring + j,
next_ring + j + 1,
ring + j + 1,
]);
}
}
let mut build_cap = |top: bool, radius: f32| {
let offset = positions.len() as u32;
let (y, normal_y, winding) = if top {
(half_height, 1.0, (1, 0))
} else {
(-half_height, -1.0, (0, 1))
};
for i in 0..self.resolution {
let theta = i as f32 * step_theta;
let (sin, cos) = theta.sin_cos();
positions.push([cos * radius, y, sin * radius]);
normals.push([0.0, normal_y, 0.0]);
uvs.push([0.5 * (cos + 1.0), 1.0 - 0.5 * (sin + 1.0)]);
}
for i in 1..(self.resolution - 1) {
indices.extend_from_slice(&[
offset,
offset + i + winding.0,
offset + i + winding.1,
]);
}
};
build_cap(true, radius_top);
build_cap(false, radius_bottom);
Mesh::new(
PrimitiveTopology::TriangleList,
RenderAssetUsages::default(),
)
.with_inserted_indices(Indices::U32(indices))
.with_inserted_attribute(Mesh::ATTRIBUTE_POSITION, positions)
.with_inserted_attribute(Mesh::ATTRIBUTE_NORMAL, normals)
.with_inserted_attribute(Mesh::ATTRIBUTE_UV_0, uvs)
}
}
impl Meshable for ConicalFrustum {
type Output = ConicalFrustumMeshBuilder;
fn mesh(&self) -> Self::Output {
ConicalFrustumMeshBuilder {
frustum: *self,
..Default::default()
}
}
}
impl From<ConicalFrustum> for Mesh {
fn from(frustum: ConicalFrustum) -> Self {
frustum.mesh().build()
}
}