Extrusion

[nt3d] / nt3d.js

/* nt3d - Javascript library for doing some 3D stuff.
 * Copyright (C) 2012  Scott Worley <ScottWorley@ScottWorley.com>
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as
 *  published by the Free Software Foundation, either version 3 of the
 *  License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

nt3d = {
	triangle: function(a, b, c) {
		return [a, b, c];
	},
	quad: function(a, b, c, d) {
		return this.triangle(a, b, c).concat(
		       this.triangle(c, d, a));
	},
	trianglefan: function(fan) {
		var result = [];
		for (var i = 2; i < fan.length; i++) {
			result.push(fan[0], fan[i-1], fan[i]);
		}
		return result;
	},
	closed_trianglefan: function(fan) {
		return this.trianglefan(fan.concat([fan[1]]));
	},
	quadstrip: function(strip) {
		if (strip.length % 2 != 0) {
			alert("quadstrip length not divisble by 2!");
		}
		var result = [];
		for (var i = 2; i < strip.length; i += 2) {
			result = result.concat(this.quad(strip[i-2], strip[i-1], strip[i+1], strip[i]));
		}
		return result;
	},
	closed_quadstrip: function(strip) {
		return this.quadstrip(strip.concat([strip[0], strip[1]]));
	},
	extrude: function(shape, path, shapenormals, pathnormals) {
		var guts_result = nt3d._extrude_guts(shape, path, shapenormals, pathnormals);
		// Add the end-caps
		// XXX: This doesn't work if shape is not convex
		return guts_result.points.concat(
			nt3d.trianglefan(guts_result.first_loop.reverse()),
			nt3d.trianglefan(guts_result.last_loop));

	},
	closed_extrude: function(shape, path, shapenormals, pathnormals) {
		var guts_result = nt3d._extrude_guts(shape, path, shapenormals, pathnormals);
		// Stitch the ends together
		return guts_result.points.concat(
			nt3d.closed_quadstrip(nt3d.zip(guts_result.first_loop, guts_result.last_loop)));
	},
	_fix_pathnormals: function(shapenormals, pathnormals) {
		// Fix pathnormals[i] to be perfectly perpendicular to
		// shapenormals[i].  This lets extrude callers be sloppy
		// with pathnormals, which can greatly simplify things.
		var fixedpathnormals = [];
		for (var i = 0; i < pathnormals.length; i++) {
			var proj = this.project(shapenormals[i], pathnormals[i]);
			fixedpathnormals[i] = this.sub(pathnormals[i], proj);
		}
		return fixedpathnormals;
	},
	_extrude_guts: function(shape, path, shapenormals, pathnormals) {
		var fixedpathnormals = this._fix_pathnormals(shapenormals, pathnormals);
		var result = { points: [] };
		var prev_loop;
		for (var i = 0; i < path.length; i++) {
			// loop is shape in 3d with (0,0) at path[i], shape's
			// z axis in the direction of shapenormals[i], and
			// shape's x axis in the direction of pathnormals[i].
			var loop = [];
			// This is done in three steps:
			// 1. Rotate shape out of the xy plane so that [0,0,1]
			//    becomes shapenormals[i] by crossing [0,0,1] and
			//    shapenormals[i] to get a rotation axis and taking
			//    their dot product to get a rotation angle.  This
			//    puts the shape in the correct plane, but does not
			//    constrain its rotation about shapenormals[i].
			var rot1axis = this.unit(this.cross([0,0,1], shapenormals[i]));
			var rot1angle = this.angle_between([0,0,1], this.unit(shapenormals[i]));
			// 2. Rotate around shapenormals[i] so that [1,0,0]
			//    becomes fixedpathnormals[i].
			var rot2axis = this.unit(shapenormals[i]);
			var rot2angle = this.angle_between([1,0,0], this.unit(fixedpathnormals[i]));
			// 3. Translate to path[i].
			// This would probably be faster and more numerically stable
			// if the two rotations were applied as one combined operation
			// rather than separate steps.
			for (var j = 0; j < shape.length; j++) {
				var p = [shape[j][0], shape[j][1], 0];
				if (rot1angle > 1e-7) {
					p = this.rotate(p, rot1axis, rot1angle);
				}
				if (rot2angle > 1e-7) {
					p = this.rotate(p, rot2axis, rot2angle);
				}
				p = this.translate(p, path[i]);
				loop[j] = p;
			}
			if (i == 0) {
				result.first_loop = loop;
			} else {
				result.points = result.points.concat(nt3d.closed_quadstrip(nt3d.zip(loop, prev_loop)));
			}
			prev_loop = loop;
		}
		result.last_loop = prev_loop;
		return result;
	},
	zip: function(a, b) {
		var result = [];
		if (a.length != b.length) {
			alert("Zip over different-sized inputs");
		}
		for (var i = 0; i < a.length; i++) {
			result.push(a[i], b[i]);
		}
		return result;
	},
	magnitude: function(a) {
		return Math.sqrt(a[0]*a[0] + a[1]*a[1] + a[2]*a[2]);
	},
	unit: function(a) {
		return this.scale(a, 1 / this.magnitude(a));
	},
	sub: function(a, b) {
		return [a[0] - b[0],
		        a[1] - b[1],
		        a[2] - b[2]];
	},
	dot: function(a, b) {
		return a[0]*b[0] + a[1]*b[1] + a[2]*b[2];
	},
	scale: function(v, s) { // Scale vector v by scalar s
		return [s*v[0], s*v[1], s*v[2]];
	},
	cross: function(a, b) {
		return [a[1]*b[2] - a[2]*b[1],
		        a[2]*b[0] - a[0]*b[2],
		        a[0]*b[1] - a[1]*b[0]];
	},
	normal: function(a, b, c) {
		return this.cross(this.sub(a, b), this.sub(b, c));
	},
	project: function(a, b) { // Project b onto a
		var a_magnitude = this.magnitude(a);
		return this.scale(a, this.dot(a, b) / a_magnitude * a_magnitude);
	},
	translate: function(a, b) {
		return [a[0] + b[0], a[1] + b[1], a[2] + b[2]];
	},
	angle_between: function(a, b) { // a and b must be unit vectors
		return Math.acos(this.dot(a, b));
	},
	rotate: function(point, axis, angle) { // axis must be a unit vector
		// From http://inside.mines.edu/~gmurray/ArbitraryAxisRotation/
		var cosangle = Math.cos(angle);
		var sinangle = Math.sin(angle);
		var tmp = this.dot(point, axis) * (1 - cosangle);
		return [axis[0]*tmp + point[0]*cosangle + (-axis[2]*point[1] + axis[1]*point[2])*sinangle,
		        axis[1]*tmp + point[1]*cosangle + ( axis[2]*point[0] - axis[0]*point[2])*sinangle,
		        axis[2]*tmp + point[2]*cosangle + (-axis[1]*point[0] + axis[0]*point[1])*sinangle];
	},
	go: function() {
		// Get params from form
		var params = [];
		for (var i = 0; i < this.user_params.length; i++) {
			params[i] = this.form.elements["param"+i].value;
		}

		// Run user_function
		this.points = this.user_function.apply(null, params);
		if (this.points.length % 3 != 0) {
			alert("Points list length not divisble by 3!");
		}
		var n = this.points.length / 3;

		// Make STL
		this.stl = "solid " + this.user_function.name + "\n";
		for (var i = 0; i < n; i++) {
			var a = this.points[i*3+0];
			var b = this.points[i*3+1];
			var c = this.points[i*3+2];
			var normal = this.normal(a, b, c);
			this.stl += "facet normal " + normal[0] + " " + normal[1] + " " + normal[2] + "\n" +
				"outer loop\n" +
				"vertex " + a[0] + " " + a[1] + " " + a[2] + "\n"+
				"vertex " + b[0] + " " + b[1] + " " + b[2] + "\n"+
				"vertex " + c[0] + " " + c[1] + " " + c[2] + "\n"+
				"endloop\n" +
				"endfacet\n";
		}
		this.stl += "endsolid " + this.user_function.name + "\n";

		// Remove any previous download links
		var old_download_link = document.getElementById("nt3d_download");
		if (old_download_link) {
			old_download_link.parentNode.removeChild(old_download_link);
		}

		// Offer result as download
		var download_link = document.createElement("a");
		download_link.appendChild(document.createTextNode("Download!"));
		download_link.setAttribute("id", "nt3d_download");
		download_link.setAttribute("style", "background-color: blue");
		download_link.setAttribute("download", this.user_function.name + ".stl");
		download_link.setAttribute("href", "data:application/sla," + encodeURIComponent(this.stl));
		this.ui.appendChild(download_link);
		setTimeout(function() { download_link.setAttribute("style", "-webkit-transition: background-color 0.4s; -moz-transition: background-color 0.4s; -o-transition: background-color 0.4s; -ms-transition: background-color 0.4s; transition: background-color 0.4s; background-color: inherit"); }, 0);
	},
	framework: function (f, params) {
		this.user_function = f;
		this.user_params = params;

		// Make the UI
		this.ui = document.getElementById("nt3dui");
		if (!this.ui) {
			this.ui = document.createElement("div");
			this.ui.setAttribute("id", "nt3dui");
			document.body.appendChild(this.ui);
		}
		this.form = document.createElement("form");
		this.form.setAttribute("onsubmit", "nt3d.go(); return false");
		this.ui.appendChild(this.form);
		var table = document.createElement("table");
		this.form.appendChild(table);
		var tr = document.createElement("tr");
		table.appendChild(tr);
		var th = document.createElement("th");
		th.appendChild(document.createTextNode("Variable"));
		tr.appendChild(th);
		th = document.createElement("th");
		th.appendChild(document.createTextNode("Value"));
		tr.appendChild(th);
		for (var i = 0; i < params.length; i++) {
			tr = document.createElement("tr");
			table.appendChild(tr);
			var td = document.createElement("td");
			td.appendChild(document.createTextNode(params[i][0]));
			tr.appendChild(td);
			td = document.createElement("td");
			var input = document.createElement("input");
			input.setAttribute("name", "param" + i);
			input.setAttribute("value", params[i][1]);
			td.appendChild(input);
			tr.appendChild(td);
		}
		var go = document.createElement("input");
		go.setAttribute("type", "button");
		go.setAttribute("value", "Go!");
		go.setAttribute("onclick", "nt3d.go()");
		this.form.appendChild(go);
	}
};