At 4/13/09 02:34 PM, GustTheASGuy wrote:
Don't want to see what you did, the easiest way is to represent the lines with vectors a,b and a vector c between their starting points. Then
dot (c.normal, b) / dot (a.normal, b)
..will be the scalar of where the point of intersection is along a. So if that number's between 0 and 1, the lines intersect.
I've already got some code that determines if two lines intersect.
Here's the code (you need to make an object called main, and add the vcam called vcam to the stage, though you can just comment that code out.):
//var lines:Array = new Array({x:5, y:0}, {x:0,y:187},{x:159.9,y:187},{x:270.9,y:241},{x:449.9,y:226},{x:522,y:198},{x:600,y:198},{x:700,y:50},{x:650,y:0},{x:5,y:0});
var lines:Array = new Array({x:4,y:284},{x:132,y:284},{x:204,y:326},{x:278,y:328},{x:341,y:312},{x:405,y:296},{x:445,y:296},{x:507,y:281},{x:536,y:163},{x:456,y:45},{x:272,y:15},{x:145,y:26},{x:118,y:18},{x:80,y:18},{x:58,y:7},{x:4,y:184},{x:4,y:284});
var col:Point = new Point(0,0);
var op:Point = new Point(main.x,main.y);
var line:Shape = new Shape();
addChild(line);
var grav:Number = 1.1;
var yspeed:Number = 0;
var canFall = true;
var currLine:int = 0;
var speed = 5;
var js = -15;
var coll = false;
var q:int = 0;
var i:int;
var keyArray:Array = new Array();
var t:int = 0;
for (i=0; i<222; i++) {
keyArray.push([i,false]);
}
stage.addEventListener(Event.ENTER_FRAME, loop);
stage.addEventListener(KeyboardEvent.KEY_UP, checkKeysUp);
stage.addEventListener(KeyboardEvent.KEY_DOWN, checkKeysDown);
line.graphics.lineStyle(1,0);
line.graphics.moveTo(lines[0].x,lines[0].y);
for (q=1; q<lines.length; q++) {
line.graphics.lineTo(lines[q].x, lines[q].y);
}
line.graphics.lineTo(lines[0].x, lines[0].y);
function loop(e:Event):void {
txt.text = op.y.toString();
vcam.x = main.x;
vcam.y = main.y;
if (keyisdown(39)) {
op.x = main.x;
main.x += speed;
}
if (keyisdown(37)) {
op.x=main.x;
main.x-=speed;
}
if (keyisdown(38)) {
//uncomment the yspeed conditional to limit the jump
//if (yspeed==0) {
coll=false;
yspeed=js;
//}
}
/*if (op.y!=main.y+yspeed+grav) {
op.y=main.y;
trace("smae");
//t = 0;
}*/
//op.y=main.y;
yspeed+=grav;
main.y+=yspeed;
//op.y = main.y + yspeed + grav;
for (q=0; q<lines.length-1; q++) {
if (SegCollide(op,new Point(main.x,main.y),lines[q],lines[q+1])) {
coll=true;
currLine=q;
break;
}
}
if (coll) {
LineCollide();
var xs=col.x-main.x;
var ys=col.y-main.y;
trace(xs+", "+ys);
/*
//this code is usable enough. you can actually change xs and ys with
//these, vx, and vy, and it'll work almost the exact same...
var ab=Math.atan2(lines[currLine].y-lines[currLine+1].y,lines[currLine].x-lines[currLine+1].x)*180/Math.PI-180;
var ac=Math.atan2(main.y-lines[currLine].y,main.x-lines[currLine].x)*180/Math.PI;
var diff=ac-ab;
trace("ab: "+ab);
var vx = Math.sin(ab*(Math.PI/180))*yspeed*-1;
var vy = Math.cos(ab*(Math.PI/180))*yspeed*-1;
trace(vx+", "+vy);*/
main.x=col.x+xs/4;
main.y=col.y+ys/4;
coll=false;
yspeed=0;
}
}
function LineCollide():void {
var s1y=main.y-op.y;
var s1x=main.x-op.x;
var s2y=lines[currLine+1].y-lines[currLine].y;
var s2x=lines[currLine+1].x-lines[currLine].x;
var sa1yb = s1x*-(main.y);
var sa1xb = s1y*-(main.x);
var sa2yb = s2x*-(lines[currLine].y);
var sa2xb = s2y*-(lines[currLine].x);
if (s1y!=s2y&&s1x!=s2x) {
var se1x=s1y/s1x;
var se1b = (sa1xb-sa1yb)/s1x;
var se2x=s2y/s2x;
var se2b = (sa2xb-sa2yb)/s2x;
col.x = (se2b-se1b)/(se1x-se2x);
col.y = (col.x*se1x)+se1b;
if (sa1yb==0) {
col.x = -(sa1xb)/s1y;
} else if (sa1xb == 0) {
col.y = -(sa1yb)/s1x;
}
if (sa2yb==0) {
col.x = -(sa2xb)/s2y;
} else if (sa2xb == 0) {
col.y = -(sa2yb)/s2x;
}
if (s1x==0&&s2x!=0) {
col.y = (se2x*col.x)+se2b;
} else if (s2x == 0 && s1x != 0) {
col.y = (se1x*col.x)+se1b;
}
trace("2"+col);
} else {
trace("no collision, parallel");
}
}
function SegCollide(a1:Point,a2:Point,b1:Object,b2:Object):Boolean {
//----------------------------------------------------------------------
var a1yb1y,a1xb1x,a2xa1x,a2ya1y;
var crossa,crossb;
//----------------------------------------------------------------------
a1yb1y=a1.y-b1.y;
a1xb1x=a1.x-b1.x;
a2xa1x=a2.x-a1.x;
a2ya1y=a2.y-a1.y;
//----------------------------------------------------------------------
crossa = a1yb1y * ( b2.x - b1.x ) - a1xb1x * ( b2.y - b1.y );
crossb = a2xa1x * ( b2.y - b1.y ) - a2ya1y * ( b2.x - b1.x );
//----------------------------------------------------------------------
if (crossb==0) {
return false;
} else if ( Math.abs( crossa ) > Math.abs( crossb ) || crossa * crossb < 0 ) {
return false;
} else {
crossa=a1yb1y*a2xa1x-a1xb1x*a2ya1y;
if (Math.abs(crossa)>Math.abs(crossb)||crossa*crossb<0) {
return false;
}
}
//----------------------------------------------------------------------
return true;
}
function checkKeysDown(event:KeyboardEvent):void {
keyArray[event.keyCode][1]=true;
}
function checkKeysUp(event:KeyboardEvent):void {
keyArray[event.keyCode][1]=false;
}
function keyisdown(X:Number):Boolean {
return keyArray[X][1];
}
