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Fix fast collision check
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@izb
izb committed Apr 9, 2013
1 parent 701225d commit 344ffc9
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Showing 6 changed files with 175 additions and 100 deletions.
146 changes: 107 additions & 39 deletions dist/snaps.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1354,6 +1354,15 @@ define('map/staggered-isometric',['map/tile', 'util/bitmap', 'util/debug', 'util
};
};

/** Takes a world position and tells you what tile it lies on. Take
* care with the return value, the function signature is all backwards.
* @param {Number} x A world x position
* @param {Number} y A world y position
* @param {Array} out A 2-length array that will recieve the tile x/y
* position in its 0/1 values.
* @return {Number} The distance from the given world position to the
* closest tile edge, capped at 127px.
*/
StaggeredIsometric.prototype.worldToTilePos = function(x, y, out) {
// http://gamedev.stackexchange.com/a/48507/3188

Expand All @@ -1368,22 +1377,27 @@ define('map/staggered-isometric',['map/tile', 'util/bitmap', 'util/debug', 'util
var eventilex = Math.floor(x%tw);
var eventiley = Math.floor(y%th);

if (this.hitTest[eventilex + eventiley * tw] >= 128) {
var dist = this.hitTest[eventilex + eventiley * tw];

if (dist >= 128) {
/* On even tile */

out[0] = (((x + tw) / tw)|0) - 1;
out[1] = 2 * ((((y + th) / th)|0) - 1);

return dist-128;
} else {
/* On odd tile */

out[0] = (((x + tw / 2) / tw)|0) - 1;
out[1] = 2 * (((y + th / 2) / th)|0) - 1;

return dist;
}
};

StaggeredIsometric.prototype.getTilePropAtWorldPos = function(prop, x, y) {
this.worldToTilePos(x, y, xy);
/*(void)*/this.worldToTilePos(x, y, xy);
var layers = this.data.layers;
var propval;
for (var i = layers.length - 1; i >= 0; i--) {
Expand All @@ -1403,6 +1417,15 @@ define('map/staggered-isometric',['map/tile', 'util/bitmap', 'util/debug', 'util
return undefined;
};

/** Takes a screen position and tells you what tile it lies on. Take
* care with the return value, the function signature is all backwards.
* @param {Number} x A screen x position
* @param {Number} y A screen y position
* @param {Array} out A 2-length array that will recieve the tile x/y
* position in its 0/1 values.
* @return {Number} The distance from the given screen position to the
* closest tile edge, capped at 127px.
*/
StaggeredIsometric.prototype.screenToTilePos = function(x, y, out) {
this.worldToTilePos(x+this.xoffset, y+this.yoffset, out);
};
Expand Down Expand Up @@ -1812,6 +1835,9 @@ define('plugins/sprite/track',[],function() {
var sn;

/*
* The track plugin will call a callback function only whenever a
* sprite's position changes.
*
* Example options:
*
* updates:[{
Expand Down Expand Up @@ -2509,51 +2535,44 @@ define('plugins/collision/lib/local-scanner',[],function() {



/** Returns a bitmask representing the local pixels around a point, and how
* solid they are.
*
* +-----------------+
* | 1 | 2 | 4 |
* +-----------------+
* | 8 | Pt | 16 |
* +-----------------+
* | 32 | 64 | 128 |
* +-----------------+
*
* Where Pt is the sampled point
*/
var localScan = function(sn, x, y, prop,limit){

var scanmask = sn.getTilePropAtWorldPos(prop,x+1,y+1)>limit;
scanmask = scanmask<<1|sn.getTilePropAtWorldPos(prop,x,y+1)>limit;
scanmask = scanmask<<1|sn.getTilePropAtWorldPos(prop,x-1,y+1)>limit;
scanmask = scanmask<<1|sn.getTilePropAtWorldPos(prop,x+1,y)>limit;
scanmask = scanmask<<1|sn.getTilePropAtWorldPos(prop,x-1,y)>limit;
scanmask = scanmask<<1|sn.getTilePropAtWorldPos(prop,x+1,y-1)>limit;
scanmask = scanmask<<1|sn.getTilePropAtWorldPos(prop,x,y-1)>limit;
scanmask = scanmask<<1|sn.getTilePropAtWorldPos(prop,x-1,y-1)>limit;

return scanmask;
};

var ySlip = function(sn, x0, y0, h, dx, dy) {
var ySlip = function(sn, x, y, h, dx, dy) {
var localmask;
var r = dx/dy;

if (r>=2&&r<=3) {

/* nw/se */
localmask = localScan(sn, x0, y0, 'height',h);
if (localmask===23) {

if (sn.getTilePropAtWorldPos('height',x+1,y-1)>h && // .##
sn.getTilePropAtWorldPos('height',x,y-1)>h && // .o#
sn.getTilePropAtWorldPos('height',x+1,y)>h) { // ...

/* Technically we should test that our shifted y position is not solid,
* but really if you are using collision maps that look like that then
* you're asking for trouble. */
return 1;
} else if (localmask===232) {

} else if(sn.getTilePropAtWorldPos('height',x-1,y+1)>h && // ...
sn.getTilePropAtWorldPos('height',x-1,y)>h && // #o.
sn.getTilePropAtWorldPos('height',x,y+1)>h) { // ##.

return -1;
}

} else if (r<=-2&&r>=-3) {

/* sw/ne */
localmask = localScan(sn, x0, y0, 'height',h);
if (localmask===240) {

if (sn.getTilePropAtWorldPos('height',x+1,y+1)>h && // ...
sn.getTilePropAtWorldPos('height',x,y+1)>h && // .o#
sn.getTilePropAtWorldPos('height',x+1,y)>h) { // .##

return -1;
} else if (localmask===15) {

} else if(sn.getTilePropAtWorldPos('height',x-1,y-1)>h && // ##.
sn.getTilePropAtWorldPos('height',x-1,y)>h && // #o.
sn.getTilePropAtWorldPos('height',x,y-1)>h) { // ...

return 1;
}
}
Expand All @@ -2562,7 +2581,6 @@ define('plugins/collision/lib/local-scanner',[],function() {
};

return {
localScan:localScan,
ySlip:ySlip
};
});
Expand All @@ -2583,6 +2601,7 @@ function(traceProp, localScan) {
opts = opts || {};
this.sn = sn;
this.edges = sn.getWorldEdges();
this.xy = [0,0];

if (opts.autoSlip===undefined) {
this.autoSlip = true;
Expand All @@ -2603,6 +2622,18 @@ function(traceProp, localScan) {
*/
LineTrace.prototype.test = function(x0, y0, dx, dy, h, out){

/* TODO: I don't actually think there's any reason to overload this function
* so much. Perhaps duplicate and tweak it? */
var safeDist = sn.worldToTilePos(x0, y0, this.xy);
if (dx*dx+dy*dy<=safeDist*safeDist) {
/* Trivial non-collision case */
/* TODO: There may be an issue if height is involved. */
out[0] = x0+dx;
out[1] = y0+dy;
return false;
}


if (this.autoSlip) {
/* First, distance ourself from key jagged shapes in key directions,
* to ensure the player can slip past isometric lines without getting
Expand Down Expand Up @@ -2710,6 +2741,8 @@ function(traceProp, midPtEllipse, localScan) {
throw "Circle trace requires a radius >0 in its options.";
}

this.radius = opts.radius;

this.edges = sn.getWorldEdges();

/* We call this a circle trace, but we use a half-height ellipse
Expand All @@ -2722,6 +2755,10 @@ function(traceProp, midPtEllipse, localScan) {
if (opts.autoSlip===undefined) {
this.autoSlip = true;
/* TODO: This should default to true ONLY for isometric maps. */
/* TODO: Note in manual that autoslip is only useful for main player characters
* that walk parallel to walls and that switching it off may improve performance
* in certain circumstances. */
/* TODO: Perhaps we should switch it off my default? */
} else {
this.autoSlip = opts.autoSlip;
}
Expand All @@ -2741,6 +2778,19 @@ function(traceProp, midPtEllipse, localScan) {

var sxo, syo, i;

/* TODO: I don't actually think there's any reason to overload this function
* so much. Perhaps duplicate and tweak it? */
var safeDist = sn.worldToTilePos(x0, y0, this.lineHit);
var xdx = Math.abs(dx)+this.radius;
var xdy = Math.abs(dy/2)+this.radius;
if (xdx*xdx+xdy*xdy<=safeDist*safeDist) {
/* Trivial non-collision case */
/* TODO: There may be an issue if height is involved. */
out[0] = x0+dx;
out[1] = y0+dy;
return false;
}

if (this.autoSlip) {
/* First, distance ourself from key jagged shapes in key directions,
* to ensure the player can slip past isometric lines without getting
Expand Down Expand Up @@ -3819,12 +3869,30 @@ function(SpriteDef, Sprite, Composite, Keyboard, Mouse, util, StaggeredIsometric
_this.map.screenToWorldPos(_this.mouse.x, _this.mouse.y, out);
};

/** Takes a world position and tells you what tile it lies on. Take
* care with the return value, the function signature is all backwards.
* @param {Number} x A world x position
* @param {Number} y A world y position
* @param {Array} out A 2-length array that will recieve the tile x/y
* position in its 0/1 values.
* @return {Number} The distance from the given world position to the
* closest tile edge, capped at 127px.
*/
this.worldToTilePos = function(x, y, out) {
this.map.worldToTilePos(x,y, out);
return this.map.worldToTilePos(x,y, out);
};

/** Takes a screen position and tells you what tile it lies on. Take
* care with the return value, the function signature is all backwards.
* @param {Number} x A screen x position
* @param {Number} y A screen y position
* @param {Array} out A 2-length array that will recieve the tile x/y
* position in its 0/1 values.
* @return {Number} The distance from the given screen position to the
* closest tile edge, capped at 127px.
*/
this.screenToTilePos = function(x, y, out) {
this.map.screenToTilePos(x,y, out);
return this.map.screenToTilePos(x,y, out);
};

this.screenToWorldPos = function(x, y, out) {
Expand Down
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