@sveltejs/gl/geometry/cone.mjs

A (very experimental) project to bring WebGL to Svelte

import Geometry from './Geometry.mjs';
import { memoize } from '../internal/utils.mjs';

function create_flat_geometry(radius, height, sides) {
	const num_vertices = sides * 3;

	const position_data = new Float32Array(num_vertices * 3 * 2);
	const normal_data = new Float32Array(num_vertices * 3 * 2);

	const ny = radius / height;

	for (let i = 0; i < sides; i += 1) {
		const start_angle = (i / sides) * Math.PI * 2;
		const end_angle = ((i + 1) / sides) * Math.PI * 2;
		const half_angle = (start_angle + end_angle) / 2;

		let o = i * 3 * 3 * 2;

		const x1 = Math.sin(start_angle) * radius;
		const z1 = Math.cos(start_angle) * radius;
		const x2 = Math.sin(end_angle) * radius;
		const z2 = Math.cos(end_angle) * radius;

		// top face
		position_data[o + 0] = x1;
		position_data[o + 1] = 0;
		position_data[o + 2] = z1;

		position_data[o + 3] = x2;
		position_data[o + 4] = 0;
		position_data[o + 5] = z2;

		position_data[o + 6] = 0;
		position_data[o + 7] = height;
		position_data[o + 8] = 0;

		const nx = Math.sin(half_angle);
		const nz = Math.cos(half_angle);

		const mag = Math.sqrt(nx * nx + ny * ny + nz * nz);

		const nnx = nx / mag;
		const nny = ny / mag;
		const nnz = nz / mag;

		normal_data[o + 0] = normal_data[o + 3] = normal_data[o + 6] = nnx;
		normal_data[o + 1] = normal_data[o + 4] = normal_data[o + 7] = nny;
		normal_data[o + 2] = normal_data[o + 5] = normal_data[o + 8] = nnz;

		o += 9;

		// bottom face
		position_data[o + 0] = x2;
		position_data[o + 1] = 0;
		position_data[o + 2] = z2;

		position_data[o + 3] = x1;
		position_data[o + 4] = 0;
		position_data[o + 5] = z1;

		position_data[o + 6] = 0;
		position_data[o + 7] = 0;
		position_data[o + 8] = 0;

		normal_data[o + 0] = normal_data[o + 3] = normal_data[o + 6] = 0;
		normal_data[o + 1] = normal_data[o + 4] = normal_data[o + 7] = -1;
		normal_data[o + 2] = normal_data[o + 5] = normal_data[o + 8] = 0;
	}

	return new Geometry({
		position: {
			data: position_data,
			size: 3
		},

		normal: {
			data: normal_data,
			size: 3
		}
	});
}

function create_smooth_geometry(radius, height, sides) {
	throw new Error('TODO');
}

export default memoize(({ radius = 1, height = 1, sides = 12, shading = 'flat' } = {}) => {
	return shading === 'flat'
		? create_flat_geometry(radius, height, sides)
		: create_smooth_geometry(radius, height, sides);
});