var delta_horizontal_angle = 0;
var delta_vertical_angle = 0;
var delta_position = [0,0,0];


//  Use to rotate selected points about a vector line
var selection_rotation_axis = null;
var rotation_center = origin.slice(0);





var points = []; //global

function writeMsg(canvas, msg){
	var lines = msg.split("\n");
	var ctx = canvas.getContext("2d");
	ctx.font = "9pt sans-serif"
	for(var i = 0; i < lines.length; ++i){
		ctx.fillText(lines[i], 5, 10 + 16 *  i); }}

    
//  camera functions

function rotateView(norm, theta, cameracentric){

    // camera centric uses the camera axes to perform the rotation instead of the space axes.   
    if(cameracentric) norm = matrix_mult(view_transform, [norm])[0];
    var rotation = vector_rotation(norm, theta);
    
    view_transform = matrix_mult(rotation, view_transform); }
	
	
function rotatePoint(point, axis, angle, center){
}
    
    
    
function rotateHorizontal(theta){
    rotateView([0, 1, 0], theta, false); }
    
function rotateVertical(theta){

    ctx.stroke();
    
	ctx.fillStyle = "rgba(0, 0, 0, 0.9)";
    for(var k in solo_points){
       var pt = point_projections[k];
       if(pt) ctx.fillRect(pt[0] - 2, pt[1] - 2, 4, 4); }
        
	//
	//  The following drawing of axes is to help provide an perspective
	//  The nuances of this draw behavior are created to provide visual cues for interpreting perspective and depth.
	//  
	//

	// axis lines and dots
	ctx.beginPath();
    var faxis_pt = project(canvas, vector_add(origin, [0, 0, forward_axis_size]), view_transform, origin);
	var vaxis_pt = project(canvas, vector_add(origin, [0, -vertical_axis_size, 0]), view_transform, origin);
	
	ctx.fillStyle = "rgba(0,0,0,0.9)";
	
	var dot = vector_dot(view_transform[2], [0, 0, 1]);
	var r = 3.2 - 1.8 * dot;
	
	ctx.lineWidth = 1.333;
	
	if(dot < 0){  // draw red square first to partially occlude with axes
		ctx.fillStyle = "rgba(250, 0, 0, 0.9)";
		ctx.fillRect(w/2 - 2, h/2 - 2, 4, 4); }
		
	ctx.fillStyle = "rgba(0,0,0,0.9)";
	
	if(faxis_pt){
		ctx.moveTo(w/2, h/2);
		ctx.lineTo(faxis_pt[0], faxis_pt[1]);	
		ctx.fillRect(faxis_pt[0] - r/2, faxis_pt[1] - r/2, r, r); }
		
	if(vaxis_pt){
		ctx.moveTo(w/2, h/2);
		ctx.lineTo(vaxis_pt[0], vaxis_pt[1]);
		ctx.fillRect(vaxis_pt[0] - 2, vaxis_pt[1] - 2, 4, 4); }
	
	ctx.stroke();
	
	if(dot >= 0){  // draw red square last so it is not occluded by axes
		ctx.fillStyle = "rgba(250, 0, 0, 0.9)";
		ctx.fillRect(w/2 - 2, h/2 - 2, 4, 4); }
		
	ctx.lineWidth = 1;
	
	

    


		
	
	for(var i = 0; i < selected_points.length; ++i){
		var pt;
		
		if(selected_points[i] == -1)
			pt = [w/2, h/2];