X-Git-Url: http://git.scottworley.com/nt3d/blobdiff_plain/1a18e646fe84c30984a5298c284d959e925e6a54..8d119f4c44e035f04c11e5fee7f17d26ba57f44a:/nt3d.js diff --git a/nt3d.js b/nt3d.js index 0443913..7e0fa25 100644 --- a/nt3d.js +++ b/nt3d.js @@ -62,55 +62,135 @@ nt3d = { return this.closed_trianglefan([apex].concat(base)).concat( this.trianglefan(base.reverse())); }, - extrude: function(shape, path, shapenormals, pathnormals) { - var guts_result = nt3d._extrude_guts(shape, path, shapenormals, pathnormals); + sphere: function(center, radius, latitude_steps, longitude_steps) { + return this.oriented_sphere(center, radius, [0,0,1], [1,0,0], latitude_steps, longitude_steps); + }, + oriented_sphere: function(center, radius, north, greenwich, latitude_steps, longitude_steps) { + var unit_north = this.unit(north); + var north_pole = this.translate_point(this.scale(unit_north, radius), center); + var south_pole = this.translate_point(this.scale(unit_north, -radius), center); + return this.spheroid(north_pole, south_pole, radius, greenwich, latitude_steps, longitude_steps); + }, + spheroid: function(north_pole, south_pole, radius, greenwich, latitude_steps, longitude_steps) { + var delta = this.sub(north_pole, south_pole); + var path = []; + for (var i = 0; i < latitude_steps-1; i++) { + path.push(this.translate_point(south_pole, this.scale(delta, (1-Math.cos(Math.PI*i/(latitude_steps-1)))/2))); + } + path.push(north_pole); + function shape(i) { + return nt3d.circle(radius*Math.sin(Math.PI*i/(latitude_steps-1)), longitude_steps); + } + return this.extrude(path, shape, delta, greenwich); + }, + shapenormals_from_closed_path: function(path) { + return function(i) { + var prev = (i == 0) ? path.length-1 : i-1; + var next = (i == path.length-1) ? 0 : i+1; + return nt3d.sub(path[next], path[prev]); + }; + }, + shapenormals_from_path_and_extra_points: function(path, first_point, last_point) { + return function(i) { + var prev = (i == 0) ? first_point : path[i-1]; + var next = (i == path.length-1) ? last_point : path[i+1]; + return nt3d.sub(next, prev); + }; + }, + shapenormals_from_path_and_first_and_last_normals: function(path, first_normal, last_normal) { + return function(i) { + if (i == 0) { return first_normal; } + if (i == path.length-1) { return last_normal; } + return nt3d.sub(path[i+1], path[i-1]); + }; + }, + pathnormals_from_point: function(path, p) { + // Use this with any point that is not on any path tangent line + var pathnormals = []; + for (var i = 0; i < path.length; i++) { + pathnormals.push(this.sub(path[i], p)); + } + return pathnormals; + }, + to_function: function(thing, make_indexer) { + // If thing is a point, just yield thing every time. + // If thing is a list of points && make_indexer, index into thing. + // If thing is already a function, just return it. + if (({}).toString.call(thing) === "[object Function]") { + return thing; // Already a function + } + if (make_indexer && Array.isArray(thing[0])) { + // Looks like a list of points. + return function(i) { return thing[i]; } + } + return function() { return thing; } + }, + extrude: function(path, shape, shapenormals, pathnormals) { + + var guts_result = this._extrude_guts(path, shape, 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)); + this.trianglefan(guts_result.first_loop.reverse()), + this.trianglefan(guts_result.last_loop)); }, - closed_extrude: function(shape, path, shapenormals, pathnormals) { - var guts_result = nt3d._extrude_guts(shape, path, shapenormals, pathnormals); + closed_extrude: function(path, shape, shapenormals, pathnormals) { + var guts_result = this._extrude_guts(path, shape, 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; + this.closed_quadstrip(this.zip(guts_result.first_loop, guts_result.last_loop))); }, - _extrude_guts: function(shape, path, shapenormals, pathnormals) { - var fixedpathnormals = this._fix_pathnormals(shapenormals, pathnormals); + _extrude_guts: function(path, shape, shapenormals, pathnormals) { + var shape_fun = this.to_function(shape, false); + var shapenormal_fun = this.to_function(shapenormals, true); + var pathnormal_fun = this.to_function(pathnormals, true); 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]. - // We tack [1,0,0] onto the end as a hack to see where - // it ends up after rotation. This is removed later. - var loop = shape.concat([[1,0,0]]); + var shapenormali = shapenormal_fun(i, path[i]); + var pathnormali = pathnormal_fun(i, path[i], shapenormali); + + // Fix pathnormali to be perfectly perpendicular to + // shapenormali. pathnormali must be perpendicular to + // shapenormali or the second rotation will take loop + // back out of the shapenormali plane that the first + // rotation so carefully placed it in. But, letting + // callers be sloppy with the pathnormals can greatly + // simplify generating them -- so much so that you can + // often just pass a constant to use the same value + // along the whole path. + pathnormali = this.project_to_orthogonal(shapenormali, pathnormali); + + var shapei = shape_fun(i, path[i], shapenormali, pathnormali); + + // loop is shapei in 3d with (0,0) at path[i], shape's + // z axis in the direction of shapenormali, and shape's + // x axis in the direction of pathnormali. We tack + // [1,0,0] onto the end as a hack to see where it ends + // up after the first rotation. This is removed later. + var loop = shapei.concat([[1,0,0]]); // This is done in three steps: // 1. Rotate shape out of the xy plane so that [0,0,1] - // becomes shapenormals[i]. This puts the shape in + // becomes shapenormali. This puts the shape in // the correct plane, but does not constrain its - // rotation about shapenormals[i]. - loop = this.rotate_onto(loop, [0,0,1], shapenormals[i]); + // rotation about shapenormali. + loop = this.rotate_onto(loop, [0,0,1], shapenormali); var shapex = loop.pop(); - // 2. Rotate around shapenormals[i] so that [1,0,0] - // becomes fixedpathnormals[i]. - loop = this.rotate_onto(loop, shapex, fixedpathnormals[i]); + // 2. Rotate around shapenormali so that [1,0,0] + // becomes pathnormali. + if (!this.opposite(shapex, pathnormali)) { + loop = this.rotate_onto(loop, shapex, pathnormali); + } else { + // Rare edge case: When shapex and pathnormali are + // opposite, rotate_onto cannot cross them to get + // an axis of rotation. In this case, we (extrude) + // already know what to do -- just rotate PI around + // shapenormali! + loop = this.rotate_about_origin(loop, shapenormali, Math.PI); + } // (This would probably be faster and more numerically stable // if the two rotations were applied as one combined operation @@ -122,7 +202,7 @@ nt3d = { if (i == 0) { result.first_loop = loop; } else { - result.points = result.points.concat(nt3d.closed_quadstrip(nt3d.zip(loop, prev_loop))); + result.points = result.points.concat(this.closed_quadstrip(this.zip(loop, prev_loop))); } prev_loop = loop; } @@ -169,19 +249,33 @@ nt3d = { }, 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); + return this.scale(a, this.dot(a, b) / (a_magnitude * a_magnitude)); + }, + project_to_orthogonal: function(a, b) { + // The nearest thing to b that is orthogonal to a + return this.sub(b, this.project(a, b)); }, translate: function(points, offset) { var translated = []; for (var i = 0; i < points.length; i++) { - translated[i] = [points[i][0] + offset[0], - points[i][1] + offset[1], - points[i][2] + offset[2]]; + translated[i] = this.translate_point(points[i], offset); } return translated; }, + translate_point: function(point, offset) { + return [point[0] + offset[0], + point[1] + offset[1], + point[2] + offset[2]]; + }, angle_between: function(a, b) { // a and b must be unit vectors - return Math.acos(this.dot(a, b)); + var the_dot = this.dot(a, b); + if (the_dot <= -1) { + return Math.PI; + } + if (the_dot >= 1) { + return 0; + } + return Math.acos(the_dot); }, rotate_about_origin: function(points, axis, angle) { // axis must be a unit vector // From http://inside.mines.edu/~gmurray/ArbitraryAxisRotation/ @@ -198,17 +292,40 @@ nt3d = { } return rotated; }, + angle_epsilon: 1e-7, + opposite: function(a, b) { + // Do a and b point in exactly opposite directions? + return Math.abs(this.angle_between(this.unit(a), this.unit(b)) - Math.PI) < this.angle_epsilon; + }, rotate_onto: function(points, a, b) { // Rotate points such that a (in points-space) maps onto b // by crossing a and b to get a rotation axis and using // angle_between to get a rotation angle. var angle = this.angle_between(this.unit(a), this.unit(b)); - if (Math.abs(angle) < 1e-15) { - // No siginificant rotation to perform. Bail to avoid + var abs_angle = Math.abs(angle); + if (Math.abs(angle) < this.angle_epsilon) { + // No significant rotation to perform. Bail to avoid // NaNs and numerical error return points; } - var axis = this.unit(this.cross(a, b)); + var axis; + if (Math.abs(abs_angle - Math.PI) < this.angle_epsilon) { + // a and b point in opposite directions, so + // we cannot cross them. So just pick something. + // If the caller wishes to avoid this behaviour, + // they should check with this.opposite() first. + axis = this.project_to_orthogonal(a, [1,0,0]); + console.log("rotate_onto: a and b are opposite! If you carefully chose them to meet some other constraint, you will be sad! Arbitrarily using axis [1,0,0] ->", axis); + if (this.magnitude(axis) < this.angle_epsilon) { + // Oh, double bad luck! Our arbitrary choice + // lines up too! A second, orthogonal arbitrary + // choice is now guaranteed to succeed. + axis = this.project_to_orthogonal(a, [0,1,0]); + console.log("rotate_onto: Double bad luck! Arbitrarily using axis [0,1,0] ->", axis); + } + } else { + axis = this.unit(this.cross(a, b)); + } return this.rotate_about_origin(points, axis, angle); }, rotate: function(points, center, axis, angle) { // axis must be a unit vector @@ -219,6 +336,17 @@ nt3d = { angle), center); }, + point_equal: function(a, b, epsilon) { + return Math.abs(a[0] - b[0]) < epsilon && + Math.abs(a[1] - b[1]) < epsilon && + Math.abs(a[2] - b[2]) < epsilon; + }, + degenerate_face_epsilon: 1e-10, + is_degenerate: function(a, b, c) { + return this.point_equal(a, b, this.degenerate_face_epsilon) || + this.point_equal(b, c, this.degenerate_face_epsilon) || + this.point_equal(c, a, this.degenerate_face_epsilon); + }, go: function() { // Remove any previous download links var old_download_link = document.getElementById("nt3d_download"); @@ -240,14 +368,51 @@ nt3d = { // Run user_function this.points = this.user_function.apply(null, params); + + // Do a little validation if (this.points.length % 3 != 0) { alert("Points list length not divisble by 3!"); } - var n = this.points.length / 3; + var nan_count = 0; + var nan_point_count = 0; + var nan_face_count = 0; + for (var i = 0; i < this.points.length/3; i++) { + var nan_in_face = false; + for (var j = 0; j < 3; j++) { + var nan_in_point = false; + for (var k = 0; k < 3; k++) { + if (isNaN(this.points[i*3+j][k])) { + nan_count++; + nan_in_point = true; + nan_in_face = true; + } + } + if (nan_in_point) nan_point_count ++; + } + if (nan_in_face) nan_face_count ++; + } + if (nan_count != 0) { + alert(nan_count + " NaNs in " + nan_point_count + " points in " + nan_face_count + " faces (" + (100 * nan_face_count / (this.points.length/3)) + "% of faces)."); + } + + // Remove degenerate faces + var degenerate_face_count = 0; + for (var i = 0; i < this.points.length/3; i++) { + if (this.is_degenerate(this.points[i*3+0], + this.points[i*3+1], + this.points[i*3+2])) { + this.points.splice(i*3, 3); + i--; + degenerate_face_count ++; + } + } + if (degenerate_face_count != 0) { + console.log("Removed " + degenerate_face_count + " degenerate faces"); + } // Make STL this.stl = "solid " + this.user_function.name + "\n"; - for (var i = 0; i < n; i++) { + for (var i = 0; i < this.points.length/3; i++) { var a = this.points[i*3+0]; var b = this.points[i*3+1]; var c = this.points[i*3+2];