From: Scott Worley Date: Wed, 19 Dec 2012 14:38:26 +0000 (-0800) Subject: Generalize rotate() X-Git-Url: http://git.scottworley.com/nt3d/commitdiff_plain/1e62819c99e2c97c4f11c9612012c83cf36dd4ff?ds=inline;hp=2f6b97f8bc892064a1ca781c11b08104182f862a Generalize rotate() 1. Rename the old rotate() to rotate_about_origin(). 2. Add a general rotate() that can rotate about any point. 3. Add box_by_rotation.html demo. --- diff --git a/box_by_rotation.html b/box_by_rotation.html new file mode 100644 index 0000000..396c714 --- /dev/null +++ b/box_by_rotation.html @@ -0,0 +1,28 @@ + + + Box by rotation + + + + +

Box by rotation

Make a box by specifying one face, then copy-rotating it five times.

+ + diff --git a/nt3d.js b/nt3d.js index 3d87ffb..1cabfb1 100644 --- a/nt3d.js +++ b/nt3d.js @@ -92,7 +92,7 @@ nt3d = { var rot1axis = this.unit(this.cross([0,0,1], shapenormals[i])); var rot1angle = this.angle_between([0,0,1], this.unit(shapenormals[i])); if (rot1angle > 1e-7) { - loop = this.rotate(loop, rot1axis, rot1angle); + loop = this.rotate_about_origin(loop, rot1axis, rot1angle); } // 2. Rotate around shapenormals[i] so that [1,0,0] @@ -100,7 +100,7 @@ nt3d = { var rot2axis = this.unit(shapenormals[i]); var rot2angle = this.angle_between([1,0,0], this.unit(fixedpathnormals[i])); if (rot2angle > 1e-7) { - loop = this.rotate(loop, rot2axis, rot2angle); + loop = this.rotate_about_origin(loop, rot2axis, rot2angle); } // This would probably be faster and more numerically stable // if the two rotations were applied as one combined operation @@ -140,6 +140,9 @@ nt3d = { a[1] - b[1], a[2] - b[2]]; }, + neg: function(a) { + return [-a[0], -a[1], -a[2]]; + }, dot: function(a, b) { return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]; }, @@ -170,7 +173,7 @@ nt3d = { angle_between: function(a, b) { // a and b must be unit vectors return Math.acos(this.dot(a, b)); }, - rotate: function(points, axis, angle) { // axis must be a unit vector + rotate_about_origin: function(points, 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); @@ -185,6 +188,14 @@ nt3d = { } return rotated; }, + rotate: function(points, center, axis, angle) { // axis must be a unit vector + return this.translate( + this.rotate_about_origin( + this.translate(points, this.neg(center)), + axis, + angle), + center); + }, go: function() { // Get params from form var params = [];