I have HTML 5 circle drag and drop example,
http://jsfiddle.net/eGjak/503/
i want to follow things
prevent drag circles outside of the canvas
hide lines over the circles
prevent drag over another circle
i play with some codes but no luck there. can anyone please help me, by logic or some helpful resource
This is an easy one. It's simply checking x doesn't leave the left or right side of the screen and y doesn't leave the top or bottom of the screen
if (x>0 || x<(canvas.width - circle.width)
&& y>0 || y<(canvas.height - circle.height)) {
...update...
}
Here you need to do a line/circle collision check. See here.
For this you need circle/circle collision detection. The below will return true if collided otherwise false:
this.isIntersecting = function(c1center, c1radius, c2center, c2radius)
{
var dX = Math.pow(c1center.x - c2center.x, 2);
var dY = Math.pow(c1center.y - c2center.y, 2);
var r2 = Math.pow(c1radius.radius() + c2radius.radius(), 2);
return (dX + dY <= r2);
}
c1center and c2center are object with x, y properties (eg: c1center = {x:0, y:0 })
Related
function distance(x1, y1, x2, y2) {
var x = x1 - x2;
var y = y1 - y2;
return(Math.sqrt((x*x) + (y*y)))
};
function collisionCirc(circ1, circ2) {
var d = distance(circ1.x, circ1.y, circ2.x, circ2.y);
var r = circ1.radius + circ2.radius;
return(r > d);
};
function collisionCircPoint(circ1, circ2) {
var cx = ((circ1.x * circ2.radius) + (circ2.x * circ1.radius)) / (circ1.radius + circ2.radius);
var cy = ((circ1.y * circ2.radius) + (circ2.y * circ1.radius)) / (circ1.radius + circ2.radius);
var p = [cx, cy];
return p;
};
function angleDegrees(x1, y1, x2, y2) {
return (Math.atan2(y2 - y1, x2 - x1) * 180 / Math.PI) + 180;
};
function updateCollisions() {
var a;
var p;
Player.hitArea = new PIXI.Circle(Player.sprite.x, Player.sprite.y, 20);
MapObjects.chest.hitArea = new PIXI.Circle(MapObjects.chest.x, MapObjects.chest.y, 20);
if (collisionCirc(Player.hitArea, MapObjects.chest.hitArea)) {
a = angleDegrees(Player.sprite.x, Player.sprite.y, MapObjects.chest.x, MapObjects.chest.y);
p = collisionCircPoint(Player.hitArea, MapObjects.chest.hitArea);
Player.sprite.x = p[0];
Player.sprite.y = p[1];
};
};
I have 2 sprites on the map and each has a circle hitArea defined. I am trying to make a smooth circular collision that the player cannot pass through. I thought I could just set the Player.sprite's coordinates to the point of collision but it just warps him to the MapObjects.chest's coordinates, even though the point of collision is correct and is 20 pixels from the MapObject.chest's center. What am I doing wrong or what more information is needed to create a collision much like the JavaScript physics libraries where I can circle around a circle object?
The collision point is between the player and the obstacle. If you move the player towards the collision point, you are actually moving the player closer. For example, if there's exactly 40 px (r1+r2) between the player and the obstacle, the collision point is between them, at only 20 px from the obstacle!
When you have multiple objects, getting it right when the collision has already happened is difficult. If there is only one obstacle nearby, you can simply move the player directly away from the obstacle. However, this way the player might actually end up inside another obstacle.
Another solution is to go back to the start and try smaller movements, until there is no collision. This way you would eventually get it right, but this might also be slow.
The mathematically correct solution is to calculate the maximum distance to move before the collision happens. This is done by solving the following vector equation:
# p = player position before moving
# o = obstacle position
# u = player direction (unit vector)
# d = distance to move
distance(o, p + d * u) = o.radius + p.radius
That's mathematics, you may solve it by yourself or using a tool like Wolfram Alpha.
Solving this equation will give you zero, one or two possible values for the distance. Negative values you can dismiss, as they mean that the player is already past the obstacle. If you get only one value, it means that the player would merely brush the obstacle, which you can also dismiss. Two values mean that the collision happens between these distances; the smaller value is where the collision starts, and the larger value is where the player would already be through the obstacle. Also, if one value is positive and the other is negative, it means that the player is already inside the obstacle, which should never happen.
You should run this check for all nearby obstacles and then move the player according to the smallest non-negative result (that is, zero or positive), or less, if the player can't move that fast.
Finally, to circle around a round object, you can move the player a little bit in a perpendicular direction (either left or right, depending on which side of the obstacle the player will be passing) after a collision, if this doesn't cause any new collisions.
There are many other possible implementations.
Player.hitArea = new PIXI.Circle(Player.sprite.x, Player.sprite.y, 20);
MapObjects.chest.hitArea = new PIXI.Circle(MapObjects.chest.x, MapObjects.chest.y, 20);
if (collisionCirc(Player.hitArea, MapObjects.chest.hitArea)) {
p = collisionCircPoint(Player.hitArea, MapObjects.chest.hitArea);
a = angleDegrees(Player.sprite.x, Player.sprite.y, MapObjects.chest.x, MapObjects.chest.y);
if (Player.sprite.x - MapObjects.chest.x > 0) {
Player.sprite.x += 1;
} else if (Player.sprite.x + MapObjects.chest.x > 0) {
Player.sprite.x -= 1;
};
if (Player.sprite.y - MapObjects.chest.y > 0) {
Player.sprite.y += 1;
} else if (Player.sprite.y + MapObjects.chest.y > 0) {
Player.sprite.y -= 1;
};
};
};
I added that and it actually works well enough minus the player speed being slightly too fast when running into the MapObjects.chest's hitArea at certain angles. Work on that later.
I am building an app using HTML5 in which a grid is drawn. I have some shapes on it that you can move.
What I'm trying to do is to snap objects to some points defined when you hover them while moving a shape.
What I tried is to save anchors points inside an array and when the shape is dropped, I draw the shape on the closest anchor point.
Easeljs is my main js lib so I want to keep it but if needed I can use an other one with easeljs.
Thanks in advance for your help!
This is pretty straightforward:
Loop over each point, and get the distance to the mouse
If the item is closer than the others, set the object to its position
Otherwise snap to the mouse instead
Here is a quick sample with the latest EaselJS: http://jsfiddle.net/lannymcnie/qk1gs3xt/
The distance check looks like this:
// Determine the distance from the mouse position to the point
var diffX = Math.abs(event.stageX - p.x);
var diffY = Math.abs(event.stageY - p.y);
var d = Math.sqrt(diffX*diffX + diffY*diffY);
// If the current point is closeEnough and the closest (so far)
// Then choose it to snap to.
var closest = (d<snapDistance && (dist == null || d < dist));
if (closest) {
neighbour = p;
}
And the snap is super simple:
// If there is a close neighbour, snap to it.
if (neighbour) {
s.x = neighbour.x;
s.y = neighbour.y;
// Otherwise snap to the mouse
} else {
s.x = event.stageX;
s.y = event.stageY;
}
Hope that helps!
Currently i am working on bouncing a ball of a wall, in classic 2D-geometry.
The wall can be hit on both vertical and horizontal sides, and the result of the reflection depends on which side the ball hits.
I have tried some different solutions, but they just make me more confused.
How can i determine whether the ball is hitting a vertical or horizontal side of the wall?
PseudoCode for the overview:
iterate through each wall
if (collision between ball and wall)
determine if vertical/horizontal hit
calculate new velocity for ball
I use this code for collision detection and it works like a charm:
source: Circle-Rectangle collision detection (intersection)
var isCollision = function (_projectile) {
if(direction != undefined){
var circleDistance = {};
circleDistance.x = Math.abs(_projectile.getCenter().x - centerX);
circleDistance.y = Math.abs(_projectile.getCenter().y - centerY);
if (circleDistance.x > (width/2 + _projectile.getRadius())) { return false; }
if (circleDistance.y > (height/2 + _projectile.getRadius())) { return false; }
if (circleDistance.x <= (width/2)) { return true; }
if (circleDistance.y <= (height/2)) { return true; }
var cornerDistance_sq = square(circleDistance.x - width/2) + square(circleDistance.y - height/2);
return (cornerDistance_sq <= (square(_projectile.getRadius())));
}
return false;
};
var square = function(_value){
return _value * _value;
};
Thank you!
update after question update
Asuming the ball has a direction/velocity vector dx,dy and has a radius of r (ball.x, ball.y are the ball positions of the ball center) do sth like this (have used similar in a billiard game, it is basic geometry and physics):
if (ball.x+ball.dx+r > wallV.x) ball.dx = -ball.dx // ball bounces off the
vertical wall
if ( ball.y+ball.dy+r > wallH.y ) ball.dy = -ball.dy // ball bounces off horizontal wall
do similar for opposite walls if needed, since velocity vector changes, the new ball position after bouncing (or anyway) will be ball.x += ball.dx; ball.y += ball.dy;
Bonus if you add some friction factor (meaning the magnitudes of dx dy eventually fade away to zero, the ball eventually stops after following a path)
To solve properly a collision, you can't just test on X => if collision solve and return THEN test on y => if collision solve on y.
You have to check which axe (x OR y) collides first, and there's also the case when the ball hits two walls at the same time.
So you can't just reason with space : you have to deal with time, and compute an ETA -Estimated Time Arrival- for all walls, based on the ball speed (assuming walls are still).
pseudo code :
minETA = a too big number;
colliderList = [];
for (each wall in walls) {
thisWallETA = computeETA(ball, wall);
if (thisWallETA > minETA) continue;
if (thisWallETA < minETA) {
minETA = thisWallETA;
colliderList.length = 0;
colliderList.push(wall);
continue;
}
if (thisWallETA == minETA) {
colliderList.push(wall);
continue;
}
}
Then when the colliderList has only one item => solve on corresponding axe. If it has two items => solve on both axes.
Then increase the current time by minETA, and try again until the currentTime + minETA you found is > to thisCycleTime + thisCycleDt.
If you're interested, i might clarify some things up.
Good luck !
In the following fiddle, you can click and drag around the image, and it will not be able to exit the blue border. By clicking the red and green rectangles, you can rotate the image. However when you click and drag a rotated object, the image does not follow the mouse. I would like the image to follow the mouse even if it is rotated.
http://jsfiddle.net/n3Sn5/
I think the issue occurs within my move function
move = function (dx, dy)
{
nowX = Math.min(boundary.attr("x")+boundary.attr("width")-this.attr("width"), this.ox + dx);
nowY = Math.min(boundary.attr("y")+boundary.attr("height")-this.attr("height"), this.oy + dy);
nowX = Math.max(boundary.attr("x"), nowX);
nowY = Math.max(boundary.attr("y"), nowY);
this.attr({x: nowX, y: nowY });
}
One thing to notice is that when you click and drag a rotated object, after you release your mouse click, if you rotate the image, it snaps to where your mouse was when you released the mouse click, even obeying the boundary.
I was able to get the rotated image to drag with the mouse previously, but by adding the boundary rectangle, i had to use a more complex approach.
If anyone has an idea of what I need to change, I would be very grateful!
Thanks!
The required output can be achieved in a bit different way. Please check the fiddle at http://jsfiddle.net/6BbRL/. I have trimmed to code to keep the basic parts for demo.
var paper = Raphael(0, 0, 475, 475),
boxX = 100,
boxY = 100,
boxWidth = 300,
boxHeight = 200,
// EDITED
imgWidth = 50,
imgHeight = 50,
box = paper.rect(boxX, boxY, boxWidth, boxHeight).attr({fill:"#ffffff"}),
// EDITED
html5 = paper.image("http://www.w3.org/html/logo/downloads/HTML5_Badge_512.png",boxX+boxWidth-imgWidth,boxY+boxHeight-imgHeight,imgWidth,imgHeight)
.attr({cursor: "move"}),
elementCounterClockwise = paper.rect(180, 0, 50, 50).attr({fill:"#ff5555", cursor:"pointer"}),
elementClockwise = paper.rect(250, 0, 50, 50).attr({ fill: "#55ff55", cursor: "pointer" }),
boundary = paper.rect(50,50,400,300).attr({stroke: '#3333FF'}),
transform,
// EDITED
xBound = {min: 50 + imgWidth/2, max: 450 - imgWidth/2},
yBound = {min: 50 + imgHeight/2, max: 350 - imgHeight/2};
start = function (x, y) {
// Find min and max values of dx and dy for "html5" element and store them for validating dx and dy in move()
// This is required to impose a rectagular bound on drag movement of "html5" element.
transform = html5.transform();
}
move = function (dx, dy, x, y) {
// To restrict movement of the dragged element, Validate dx and dy before applying below.
// Here, dx and dy are shifts along x and y axes, with respect to drag start position.
// EDITED
var deltaX = x > xBound.max && xBound.max - x || x < xBound.min && xBound.min - x || 0;
deltaY = y > yBound.max && yBound.max - y || y < yBound.min && yBound.min - y || 0;
this.attr({transform: transform + 'T'+ [dx + deltaX, dy + deltaY]});
}
up = function () {
};
html5.drag(move, start, up);
elementClockwise.click(function() {
html5.animate({transform: '...r90'}, 100);
})
elementCounterClockwise.click(function() {
html5.animate({transform: '...r-90'}, 100);
})
Use of '...' to append a transformation to the pre-existing transformation state (Raphael API) is important for the rotational issue. While, for translating the element on drag requires absolute translation, which neglects the rotational state of the element while translating the element.
//EDIT NOTE
Drag bounding is worked on and updated. However, there remains an issue with incorporating the difference between mouse position and image center.
I can help you with your rotation and drag problem, you need to store the rotation and apply it after you have moved the object.
elementClockwise.node.onclick = function()
{
html5.animate({'transform': html5.transform() +'r90'}, 100, onAnimComplete);
}
elementCounterClockwise.node.onclick = function()
{
html5.animate({'transform': html5.transform() +'r-90'}, 100, onAnimComplete);
}
function onAnimComplete(){
default_transform = html5.transform();
}
At present I can't get the boundary to work, but will have a try later.
http://jsfiddle.net/n3Sn5/2/
I'm using kineticjs to draw some widget on a canvas. This widget is 600px wide and is composed of several rectangles (24 by default). On this rectangles an other one can be dragged, let's call it "cursor".
Instead of a smooth drag, i want the cursor to jump to the other rectangles only when my mouse is far enough (like a stepped drag if you prefer).
For example if the cursor is at 0,0 and i have a total of 24 rectangles , i want my cursor to move to the next rectangle only when my mouse is at 25,0 (600px / 24 rectangles = 25px).
So to do that i have implemented :
cursor.setDragBoundFunc(function(pos){
var caseSize = WIDTH / caseNum;
var posX = Math.round(pos.x/caseNum) * caseSize;
if(posX > (WIDTH - caseSize)) {
posX = WIDTH - caseSize;
}
if(posX < 0 ) {
posX = 0;
}
return {
x: posX,
y: cursor.getAbsolutePosition().y
}
});
The problem is pos.x does not represent the mouse position in the canvas but the mouse position from the start of the drag event (pos will be 0,0 even if i start dragging from middle of the canvas).
Here a example of the problem : http://jsfiddle.net/H9rpz/
How can i get the mouse position in the canvas in setDragBoundFunc() ?
Thanks
This exact feature has been implemented in a KineticJS manual test. Here's the code you're looking for:
https://github.com/ericdrowell/KineticJS/blob/master/tests/js/manualTests.js#L1004
Give it a try :)
It seems the setDragBoundFunc function accepts two arguments and the second is an event object that might contain what you're after:
cursor.setDragBoundFunc(function(pos, event){
var posX = event.offsetX;
....
});
You also have a math logic error at the beginning of the function. It should read:
cursor.setDragBoundFunc(function(pos, event){
var caseSize = WIDTH / caseNum;
var posX = event.offsetX;
posX = Math.floor(posX / caseSize) * caseSize; // This right here
...
});
Working example:
http://jsfiddle.net/H9rpz/3/
In addition to #Jan's answer, your math is a bit off:
cursor.setDragBoundFunc(function(pos, event){
var posX = event.offsetX;
posX = Math.floor(posX/WIDTH * caseNum) * caseWidth;
...