add meshgen

src/lib.rs

@@ -2,6 +2,8 @@ use std::error::Error;
 
 use glam::{UVec2, Vec4, vec4};
 
+mod mesh;
+
 const DEPTH_FORMAT: wgpu::TextureFormat = wgpu::TextureFormat::Depth16Unorm;
 const OUTPUT_FORMAT: wgpu::TextureFormat = wgpu::TextureFormat::Bgra8UnormSrgb;
 

src/mesh.rs

@@ -0,0 +1,57 @@
+use std::f32::consts::PI;
+
+use glam::{Mat2, Vec3, vec2, vec3};
+
+pub struct Mesh {
+	pub vertices: Vec<Vec3>,
+	pub faces: Vec<[usize; 3]>,
+}
+
+pub fn generate() -> Mesh {
+	let mut vertices = Vec::<Vec3>::new();
+	let mut faces = Vec::<[usize; 3]>::new();
+
+	let sides: usize = 24;
+	let layers = 12;
+	let base_layer = 4;
+	let diameter = 36.0;
+	let radius = diameter / 2.;
+	let height = 120.;
+	let bottom_angle = (PI / sides as f32) * -(base_layer as f32);
+	let top_angle = (PI / sides as f32) * (layers as f32 - base_layer as f32);
+	let bottom_y = radius * bottom_angle.tan();
+	let top_y = radius * top_angle.tan();
+	let incline = height / (top_y - bottom_y);
+
+	let base = vertices.len();
+	for side in 0..(sides - 2) {
+		faces.push([base + sides - 1, base + side + 1, base + side]);
+	}
+	for layer in 0..=layers {
+		let angle = (PI / sides as f32) * (layer as f32 - base_layer as f32);
+		let x = radius;
+		let y = angle.tan() * x;
+		let z = incline * y;
+		for side in 0..sides {
+			let angle = (2. * PI / sides as f32) * side as f32;
+			let rot = Mat2::from_angle(angle);
+			let xy = rot * vec2(x, y);
+			let v = vec3(xy.x, xy.y, z);
+			vertices.push(v);
+		}
+	}
+	for layer in 0..layers {
+		let base = base + sides * layer;
+		for side in 0..sides {
+			let index = |layer, offset| base + sides * layer + (side + offset) % sides;
+			faces.push([index(0, 0), index(0, 1), index(1, 0)]);
+			faces.push([index(0, 1), index(1, 1), index(1, 0)]);
+		}
+	}
+	let base = vertices.len() - sides;
+	for side in 0..(sides - 2) {
+		faces.push([base + sides - 1, base + side, base + side + 1]);
+	}
+
+	Mesh { vertices, faces }
+}