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Add cone, make cylinder special case of a cone #10298

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8d2fbaa
Add cone, make cylinder special case of a cone
Oct 28, 2023
de33c4d
Update crates/bevy_render/src/mesh/shape/cone.rs
torsteingrindvik Oct 28, 2023
30e300b
Change cone default
Oct 29, 2023
d3888b6
Skip making cap if radius zero
Oct 29, 2023
3f1ef3f
Use higher geometry defaults for cone, add Y normal component
Nov 4, 2023
8ca6aef
Docs, diagram
Nov 4, 2023
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88 changes: 88 additions & 0 deletions assets/docs/Cone.drawio
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173 changes: 173 additions & 0 deletions crates/bevy_render/src/mesh/shape/cone.rs
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use crate::mesh::{Indices, Mesh};
use bevy_math::Vec3;
use wgpu::PrimitiveTopology;

/// A cone which stands on the XZ plane.
///
/// If either radius is 0., the tip will be sharp. Otherwise, the cone will appear truncated, with flat surfaces on either end.
///
/// # Diagram
///
/// See an illustrative diagram [here](https://github.com/bevyengine/bevy/blob/main/assets/docs/Cone.png).
/// The diagram illustrates the following properties:
///
/// * The height of the cone is evenly split by the XZ plane, so half height above, half below.
/// * A resolution of 8 means each horizontal (XZ) face has 8 vertices.
/// * A top radius of 0.0 means a sharp tip.
/// * 3 segments (divided by the dotted lines) means there are 3 segments of quads enveloping the cone.
///
/// Note that the sharp tip still contains the same amount of vertices as the bottom.
#[derive(Clone, Copy, Debug)]
pub struct Cone {
/// Radius in the XZ plane at the upper face.
///
/// Can be zero for a sharp tip, but both top and bottom should not be zero at the same time.
pub top_radius: f32,

/// Radius in the XZ plane at the bottom face.
///
/// Can be zero for a sharp tip, but both top and bottom should not be zero at the same time.
pub bottom_radius: f32,

/// Height of the cone in the Y axis.
///
/// Should be greater than zero.
pub height: f32,

/// The number of vertices around each horizontal slice of the cone. If you are looking at the cone from
/// above, this is the number of points you will see on the circle.
/// A higher number will make it appear more circular.
///
/// Should be above two.
pub resolution: u32,

/// The number of segments between the two ends. Setting this to 1 will have triangles spanning the full
/// height of the cone. Setting it to 2 will have two sets of triangles with a horizontal slice in the middle of
/// the cone. Greater numbers increase triangles/slices in the same way.
///
/// Should be greater than zero.
pub segments: u32,
}

impl Default for Cone {
fn default() -> Self {
Self {
top_radius: 0.0,
bottom_radius: 0.5,
height: 1.0,
resolution: 64,
segments: 4,
}
}
}

impl From<Cone> for Mesh {
fn from(c: Cone) -> Self {
debug_assert!(c.top_radius >= 0.0);
debug_assert!(c.bottom_radius >= 0.0);
debug_assert!(!(c.bottom_radius == 0.0 && c.top_radius == 0.0));
debug_assert!(c.height > 0.0);
debug_assert!(c.resolution > 2);
debug_assert!(c.segments > 0);

let num_rings = c.segments + 1;
let num_vertices = c.resolution * 2 + num_rings * (c.resolution + 1);
let num_faces = c.resolution * (num_rings - 2);
let num_indices = (2 * num_faces + 2 * (c.resolution - 1) * 2) * 3;

let mut positions = Vec::with_capacity(num_vertices as usize);
let mut normals = Vec::with_capacity(num_vertices as usize);
let mut uvs = Vec::with_capacity(num_vertices as usize);
let mut indices = Vec::with_capacity(num_indices as usize);

let step_theta = std::f32::consts::TAU / c.resolution as f32;
let step_y = c.height / c.segments as f32;
let step_radius = (c.top_radius - c.bottom_radius) / c.segments as f32;

// rings

for ring in 0..num_rings {
let y = -c.height / 2.0 + ring as f32 * step_y;
let radius = c.bottom_radius + ring as f32 * step_radius;

for segment in 0..=c.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, (c.bottom_radius - c.top_radius) / c.height, sin)
.normalize()
.to_array(),
);
uvs.push([
segment as f32 / c.resolution as f32,
ring as f32 / c.segments as f32,
]);
}
}

// barrel skin

for i in 0..c.segments {
let ring = i * (c.resolution + 1);
let next_ring = (i + 1) * (c.resolution + 1);

for j in 0..c.resolution {
indices.extend_from_slice(&[
ring + j,
next_ring + j,
ring + j + 1,
next_ring + j,
next_ring + j + 1,
ring + j + 1,
]);
}
}

// caps

let mut build_cap = |top: bool| {
let offset = positions.len() as u32;
let (y, normal_y, winding) = if top {
(c.height / 2., 1., (1, 0))
} else {
(c.height / -2., -1., (0, 1))
};

let radius = if top { c.top_radius } else { c.bottom_radius };

if radius == 0.0 {
return;
}

for i in 0..c.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..(c.resolution - 1) {
indices.extend_from_slice(&[
offset,
offset + i + winding.0,
offset + i + winding.1,
]);
}
};

// top

build_cap(true);
build_cap(false);

Mesh::new(PrimitiveTopology::TriangleList)
.with_indices(Some(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)
}
}
104 changes: 11 additions & 93 deletions crates/bevy_render/src/mesh/shape/cylinder.rs
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@@ -1,11 +1,13 @@
use crate::mesh::{Indices, Mesh};
use wgpu::PrimitiveTopology;
use crate::mesh::Mesh;

use super::Cone;

/// A cylinder which stands on the XZ plane
#[derive(Clone, Copy, Debug)]
pub struct Cylinder {
/// Radius in the XZ plane.
pub radius: f32,

/// Height of the cylinder in the Y axis.
pub height: f32,
/// The number of vertices around each horizontal slice of the cylinder. If you are looking at the cylinder from
Expand All @@ -31,97 +33,13 @@ impl Default for Cylinder {

impl From<Cylinder> for Mesh {
fn from(c: Cylinder) -> Self {
debug_assert!(c.radius > 0.0);
debug_assert!(c.height > 0.0);
debug_assert!(c.resolution > 2);
debug_assert!(c.segments > 0);

let num_rings = c.segments + 1;
let num_vertices = c.resolution * 2 + num_rings * (c.resolution + 1);
let num_faces = c.resolution * (num_rings - 2);
let num_indices = (2 * num_faces + 2 * (c.resolution - 1) * 2) * 3;

let mut positions = Vec::with_capacity(num_vertices as usize);
let mut normals = Vec::with_capacity(num_vertices as usize);
let mut uvs = Vec::with_capacity(num_vertices as usize);
let mut indices = Vec::with_capacity(num_indices as usize);

let step_theta = std::f32::consts::TAU / c.resolution as f32;
let step_y = c.height / c.segments as f32;

// rings

for ring in 0..num_rings {
let y = -c.height / 2.0 + ring as f32 * step_y;

for segment in 0..=c.resolution {
let theta = segment as f32 * step_theta;
let (sin, cos) = theta.sin_cos();

positions.push([c.radius * cos, y, c.radius * sin]);
normals.push([cos, 0., sin]);
uvs.push([
segment as f32 / c.resolution as f32,
ring as f32 / c.segments as f32,
]);
}
Cone {
top_radius: c.radius,
bottom_radius: c.radius,
height: c.height,
resolution: c.resolution,
segments: c.segments,
}

// barrel skin

for i in 0..c.segments {
let ring = i * (c.resolution + 1);
let next_ring = (i + 1) * (c.resolution + 1);

for j in 0..c.resolution {
indices.extend_from_slice(&[
ring + j,
next_ring + j,
ring + j + 1,
next_ring + j,
next_ring + j + 1,
ring + j + 1,
]);
}
}

// caps

let mut build_cap = |top: bool| {
let offset = positions.len() as u32;
let (y, normal_y, winding) = if top {
(c.height / 2., 1., (1, 0))
} else {
(c.height / -2., -1., (0, 1))
};

for i in 0..c.resolution {
let theta = i as f32 * step_theta;
let (sin, cos) = theta.sin_cos();

positions.push([cos * c.radius, y, sin * c.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..(c.resolution - 1) {
indices.extend_from_slice(&[
offset,
offset + i + winding.0,
offset + i + winding.1,
]);
}
};

// top

build_cap(true);
build_cap(false);

Mesh::new(PrimitiveTopology::TriangleList)
.with_indices(Some(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)
.into()
}
}
2 changes: 2 additions & 0 deletions crates/bevy_render/src/mesh/shape/mod.rs
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Expand Up @@ -262,13 +262,15 @@ impl From<Plane> for Mesh {
}

mod capsule;
mod cone;
mod cylinder;
mod icosphere;
mod regular_polygon;
mod torus;
mod uvsphere;

pub use capsule::{Capsule, CapsuleUvProfile};
pub use cone::Cone;
pub use cylinder::Cylinder;
pub use icosphere::Icosphere;
pub use regular_polygon::{Circle, RegularPolygon};
Expand Down
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