Difference between revisions of "Turtle Graphics"

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This is a very basic implementation of turtle graphics in JavaScript with [http://jsxgraph.org JSXGraph].
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[http://u2d.com/turtle_js/index.html CanvasTurtle] does the same on browsers which support the ''canvas'' element.
 +
 +
* [[List of available commands]]
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 +
===Snowflake and Branches Example===
 
<html>
 
<html>
<link rel="stylesheet" type="text/css" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css" />
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<form><textarea id="input1" rows=7 cols=35 wrap="off" style="width:300px; float:left;">
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/prototype.js"></script>
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function side(size, level) {
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
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    if (level==0) {
<form><textarea id="input" rows=7 cols=35 wrap="off" style="width:600px">
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        t.fd(size);
</textarea><br />
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        return;
<input type="button" value="run" onClick="run()">
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    }
</form>
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    side(size/3, level-1);
<div id="box" class="jxgbox" style="width:600px; height:600px;"></div>
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    t.lt(60);
<script language="JavaScript">
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    side(size/3, level-1);
            var turtleObj = function(board,attributes) {
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    t.rt(120);
                this.board = board;
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    side(size/3, level-1);
                if (attributes==null) {
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    t.lt(60);
                    this.attributes = {
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    side(size/3, level-1);
                        strokeColor:'#000000'
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}
                    };
 
                } else {
 
                    this.attributes = attributes;
 
                }
 
                this.attributes.straightFirst = false;
 
                this.attributes.straightLast = false;
 
                this.init();
 
            };
 
  
            turtleObj.prototype.init = function() {
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function snowflake(size, level) {
                this.points = [];
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    for (var i=0;i<3;i++) {
                this.pos = [0,0];
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        side(size, level);
                this.isPenDown = true;
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        t.rt(120);
                this.dir = 90;
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    };
                var p = this.board.createElement('point',this.pos,{fixed:true,name:' ',visible:false});
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}
                this.points.push(p);
 
                this.turtle = this.board.createElement('point',this.pos,{fixed:true,name:' ',visible:false});
 
                this.turtle2 = this.board.createElement('point',[this.pos[0],this.pos[1]+20],{fixed:true,name:' ',visible:false});
 
                this.board.createElement('line',[this.turtle,this.turtle2],
 
                        {lastArrow:true,strokeColor:'#ff0000',straightFirst:false,straightLast:false});
 
            }
 
  
            turtleObj.prototype.forward = function(len) {
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t.clearScreen();
                if (len==0) { return; }
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t.hideTurtle();
                var dx = -len*Math.cos(this.dir*Math.PI/180.0);
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t.setPenSize(1)
                var dy = len*Math.sin(this.dir*Math.PI/180.0);
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t.setPenColor("#000000")
                var t = this.board.createElement('transform', [dx,dy], {type:'translate'});
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t.lt(30);
                t.applyOnce(this.turtle);
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t.setPos(0,-100);
                t.applyOnce(this.turtle2);
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snowflake(250, 4);
                this.pos[0] += dx;
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</textarea>
                this.pos[1] += dy;
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<textarea id="input2" rows=7 cols=35 wrap="off" style="width:300px">
                var p = this.board.createElement('point',this.pos,{fixed:true,name:' ',visible:false});
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function branch(length, level)
                this.points.push(p);
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{
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    if(level == 0) return
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    t.fd(length)
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    t.lt(45)
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    branch(length/2, level-1)
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    t.rt(90)
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    branch(length/2, level-1)
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    t.lt(45)
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    t.bk(length)
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}
  
                if (this.isPenDown) {
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function lbranch(length, angle, level)
                    this.board.createElement('line',[this.points[this.points.length-2],p],this.attributes);
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{
                }
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    t.fd(2*length)
                this.board.update();
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    node(length, angle, level)
            };
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    t.bk(2*length)
           
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}
            turtleObj.prototype.back = function(len) {
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function rbranch(length, angle, level)
                this.forward(-len);
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{
            }
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    t.fd(length)
           
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    node(length, angle, level)
            turtleObj.prototype.right = function(angle) {
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    t.bk(length)
                this.dir += angle;
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}
                var t = this.board.createElement('transform', [-angle*Math.PI/180.0,this.turtle], {type:'rotate'});
 
                t.applyOnce(this.turtle2);
 
                this.board.update();
 
            }
 
           
 
            turtleObj.prototype.left = function(angle) {
 
                this.right(-angle);
 
            }
 
           
 
            turtleObj.prototype.penUp = function() {
 
                this.isPenDown = false;
 
            }
 
           
 
            turtleObj.prototype.penDown = function() {
 
                this.isPenDown = true;
 
            }
 
  
            turtleObj.prototype.clear = function() {
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function node(length, angle, level)
                for(var el in this.board.objects) {
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{
                    this.board.removeObject(el);
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    if (level == 0) return;
                }
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    t.lt(angle)
                this.init();
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    lbranch(length, angle, level -1)
            }
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    t.rt(2*angle)
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    rbranch(length, angle, level-1)
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    t.lt(angle)
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}
  
            turtleObj.prototype.fd = function(len) { this.forward(len); };
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t.clearScreen()
            turtleObj.prototype.bk = function(len) { this.back(len); };
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t.hideTurtle();
            turtleObj.prototype.lt = function(angle) { this.left(angle); };
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//branch(100,6)
            turtleObj.prototype.rt = function(angle) { this.right(angle); };
 
  
            var brd = JXG.JSXGraph.initBoard('box', {originX: 300, originY: 300, unitX: 1, unitY: 1});
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t.setPenSize(5)
            var t = new turtleObj(brd);
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t.setPenColor("#008800")
</script>
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t.setPos(30, -150)
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lbranch(25, 20, 7)
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</textarea><br />
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<input type="button" value="run example 1" onClick="run(1)">
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<input type="button" value="run example 2" onClick="run(2)">
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</form>
 
</html>
 
</html>
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<jsxgraph width="600" height="600" box="box">
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var brd = JXG.JSXGraph.initBoard('box', {boundingbox: [-300, 300, 300, -300]});
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var t = brd.create('turtle');
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function run(nr) {
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  brd.suspendUpdate();
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  eval(document.getElementById('input'+nr).value);
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  brd.unsuspendUpdate();
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}
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</jsxgraph>
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===References===
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* The snowflake and branches example have been adapted from the excellent [http://u2d.com/turtle_js/index.html CanvasTurtle]
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 +
===The turtle graphics code===
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<source lang="html4strict">
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<form><textarea id="input1" rows=7 cols=35 wrap="off" style="width:300px; float:left;">
 +
turtle code...
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</textarea>
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<input type="button" value="run example 1" onClick="run(1)">
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</source>
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<source lang="javascript">
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var brd = JXG.JSXGraph.initBoard('box', {boundingbox: [-300, 300, 300, -300]});
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var t = brd.create('turtle');
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function run(nr) {
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  brd.suspendUpdate();
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  eval($('input'+nr).value);
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  brd.unsuspendUpdate();
 +
}
 +
</source>
  
 
[[Category:Examples]]
 
[[Category:Examples]]
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[[Category:Turtle Graphics]]
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[[Category:Fractals]]

Latest revision as of 08:40, 9 June 2011

This is a very basic implementation of turtle graphics in JavaScript with JSXGraph. CanvasTurtle does the same on browsers which support the canvas element.

Snowflake and Branches Example


References

  • The snowflake and branches example have been adapted from the excellent CanvasTurtle

The turtle graphics code

<form><textarea id="input1" rows=7 cols=35 wrap="off" style="width:300px; float:left;">
turtle code...
</textarea>
<input type="button" value="run example 1" onClick="run(1)">
var brd = JXG.JSXGraph.initBoard('box', {boundingbox: [-300, 300, 300, -300]});
var t = brd.create('turtle');

function run(nr) {
  brd.suspendUpdate();
  eval($('input'+nr).value);
  brd.unsuspendUpdate();
}