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2dmap_raycast.htm
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<html>
<head>
<title>JavaScript Wolfenstein 3D Engine - 2D ray casting</title>
<!--
/*
* Example code from the article at: http://dev.opera.com/articles/view/creating-pseudo-3d-games-with-html-5-can-1/
* Copyright (c) 2008 Jacob Seidelin, [email protected], http://blog.nihilogic.dk/
* The code is available to use under the terms of the MIT License
* [http://www.opensource.org/licenses/mit-license.php]
*/
-->
<style>
div#minimapcontainer {
}
canvas#minimap {
position : absolute;
}
canvas#minimapobjects {
position : absolute;
}
</style>
<script src="excanvas.js" type="text/javascript"></script>
</head>
<body>
<div id="minimapcontainer">
<canvas id="minimap"></canvas>
<canvas id="minimapobjects"></canvas>
</div>
<script type="text/javascript">
var $ = function(id) { return document.getElementById(id); };
var dc = function(tag) { return document.createElement(tag); };
var map = [
[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1],
[1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,3,0,3,0,0,1,1,1,2,1,1,1,1,1,2,1,1,1,2,1,0,0,0,0,0,0,0,0,1],
[1,0,0,3,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,1,1,1,1,1],
[1,0,0,3,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,3,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2],
[1,0,0,3,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,1,1,1,1,1],
[1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,0,0,0,0,0,0,3,3,3,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2],
[1,0,0,0,0,0,0,0,0,3,3,3,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,0,0,0,0,0,0,3,3,3,0,0,3,3,3,0,0,0,0,0,0,0,0,0,3,1,1,1,1,1],
[1,0,0,0,0,0,0,0,0,3,3,3,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,4,0,0,4,2,0,2,2,2,2,2,2,2,2,0,2,4,4,0,0,4,0,0,0,0,0,0,0,1],
[1,0,0,4,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,4,0,0,0,0,0,0,0,1],
[1,0,0,4,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,4,0,0,0,0,0,0,0,1],
[1,0,0,4,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,4,0,0,0,0,0,0,0,1],
[1,0,0,4,3,3,4,2,2,2,2,2,2,2,2,2,2,2,2,2,4,3,3,4,0,0,0,0,0,0,0,1],
[1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1],
[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1]
];
var player = {
x : 16, // current x, y position
y : 10,
dir : 0, // the direction that the player is turning, either -1 for left or 1 for right.
rot : 0, // the current angle of rotation
speed : 0, // is the playing moving forward (speed = 1) or backwards (speed = -1).
moveSpeed : 0.18, // how far (in map units) does the player move each step/update
rotSpeed : 6 * Math.PI / 180 // how much does the player rotate each step/update (in radians)
}
var mapWidth = 0;
var mapHeight = 0;
var miniMapScale = 8;
var screenWidth = 320;
var stripWidth = 4;
var fov = 60 * Math.PI / 180;
var numRays = Math.ceil(screenWidth / stripWidth);
var fovHalf = fov / 2;
var viewDist = (screenWidth/2) / Math.tan((fov / 2));
var twoPI = Math.PI * 2;
function init() {
mapWidth = map[0].length;
mapHeight = map.length;
bindKeys();
drawMiniMap();
gameCycle();
}
// bind keyboard events to game functions (movement, etc)
function bindKeys() {
document.onkeydown = function(e) {
e = e || window.event;
switch (e.keyCode) { // which key was pressed?
case 38: // up, move player forward, ie. increase speed
player.speed = 1;
break;
case 40: // down, move player backward, set negative speed
player.speed = -1;
break;
case 37: // left, rotate player left
player.dir = -1;
break;
case 39: // right, rotate player right
player.dir = 1;
break;
}
}
document.onkeyup = function(e) {
e = e || window.event;
switch (e.keyCode) {
case 38:
case 40:
player.speed = 0; // stop the player movement when up/down key is released
break;
case 37:
case 39:
player.dir = 0;
break;
}
}
}
function gameCycle() {
move();
updateMiniMap();
castRays();
setTimeout(gameCycle,1000/30);
}
function castRays() {
var stripIdx = 0;
for (var i=0;i<numRays;i++) {
// where on the screen does ray go through?
var rayScreenPos = (-numRays/2 + i) * stripWidth;
// the distance from the viewer to the point on the screen, simply Pythagoras.
var rayViewDist = Math.sqrt(rayScreenPos*rayScreenPos + viewDist*viewDist);
// the angle of the ray, relative to the viewing direction.
// right triangle: a = sin(A) * c
var rayAngle = Math.asin(rayScreenPos / rayViewDist);
castSingleRay(
player.rot + rayAngle, // add the players viewing direction to get the angle in world space
stripIdx++
);
}
}
function castSingleRay(rayAngle, stripIdx) {
// first make sure the angle is between 0 and 360 degrees
rayAngle %= twoPI;
if (rayAngle < 0) rayAngle += twoPI;
// moving right/left? up/down? Determined by which quadrant the angle is in.
var right = (rayAngle > twoPI * 0.75 || rayAngle < twoPI * 0.25);
var up = (rayAngle < 0 || rayAngle > Math.PI);
// only do these once
var angleSin = Math.sin(rayAngle);
var angleCos = Math.cos(rayAngle);
var dist = 0; // the distance to the block we hit
var xHit = 0; // the x and y coord of where the ray hit the block
var yHit = 0;
var textureX; // the x-coord on the texture of the block, ie. what part of the texture are we going to render
var wallX; // the (x,y) map coords of the block
var wallY;
// first check against the vertical map/wall lines
// we do this by moving to the right or left edge of the block we're standing in
// and then moving in 1 map unit steps horizontally. The amount we have to move vertically
// is determined by the slope of the ray, which is simply defined as sin(angle) / cos(angle).
var slope = angleSin / angleCos; // the slope of the straight line made by the ray
var dX = right ? 1 : -1; // we move either 1 map unit to the left or right
var dY = dX * slope; // how much to move up or down
var x = right ? Math.ceil(player.x) : Math.floor(player.x); // starting horizontal position, at one of the edges of the current map block
var y = player.y + (x - player.x) * slope; // starting vertical position. We add the small horizontal step we just made, multiplied by the slope.
while (x >= 0 && x < mapWidth && y >= 0 && y < mapHeight) {
var wallX = Math.floor(x + (right ? 0 : -1));
var wallY = Math.floor(y);
// is this point inside a wall block?
if (map[wallY][wallX] > 0) {
var distX = x - player.x;
var distY = y - player.y;
dist = distX*distX + distY*distY; // the distance from the player to this point, squared.
textureX = y % 1; // where exactly are we on the wall? textureX is the x coordinate on the texture that we'll use when texturing the wall.
if (!right) textureX = 1 - textureX; // if we're looking to the left side of the map, the texture should be reversed
xHit = x; // save the coordinates of the hit. We only really use these to draw the rays on minimap.
yHit = y;
break;
}
x += dX;
y += dY;
}
// now check against horizontal lines. It's basically the same, just "turned around".
// the only difference here is that once we hit a map block,
// we check if there we also found one in the earlier, vertical run. We'll know that if dist != 0.
// If so, we only register this hit if this distance is smaller.
var slope = angleCos / angleSin;
var dY = up ? -1 : 1;
var dX = dY * slope;
var y = up ? Math.floor(player.y) : Math.ceil(player.y);
var x = player.x + (y - player.y) * slope;
while (x >= 0 && x < mapWidth && y >= 0 && y < mapHeight) {
var wallY = Math.floor(y + (up ? -1 : 0));
var wallX = Math.floor(x);
if (map[wallY][wallX] > 0) {
var distX = x - player.x;
var distY = y - player.y;
var blockDist = distX*distX + distY*distY;
if (!dist || blockDist < dist) {
dist = blockDist;
xHit = x;
yHit = y;
textureX = x % 1;
if (up) textureX = 1 - textureX;
}
break;
}
x += dX;
y += dY;
}
if (dist) {
drawRay(xHit, yHit);
}
}
function drawRay(rayX, rayY) {
var miniMapObjects = $("minimapobjects");
var objectCtx = miniMapObjects.getContext("2d");
objectCtx.strokeStyle = "rgba(0,100,0,0.3)";
objectCtx.lineWidth = 0.5;
objectCtx.beginPath();
objectCtx.moveTo(player.x * miniMapScale, player.y * miniMapScale);
objectCtx.lineTo(
rayX * miniMapScale,
rayY * miniMapScale
);
objectCtx.closePath();
objectCtx.stroke();
}
function move() {
var moveStep = player.speed * player.moveSpeed; // player will move this far along the current direction vector
player.rot += player.dir * player.rotSpeed; // add rotation if player is rotating (player.dir != 0)
// make sure the angle is between 0 and 360 degrees
while (player.rot < 0) player.rot += twoPI;
while (player.rot >= twoPI) player.rot -= twoPI;
var newX = player.x + Math.cos(player.rot) * moveStep; // calculate new player position with simple trigonometry
var newY = player.y + Math.sin(player.rot) * moveStep;
if (isBlocking(newX, newY)) { // are we allowed to move to the new position?
return; // no, bail out.
}
player.x = newX; // set new position
player.y = newY;
}
function isBlocking(x,y) {
// first make sure that we cannot move outside the boundaries of the level
if (y < 0 || y >= mapHeight || x < 0 || x >= mapWidth)
return true;
// return true if the map block is not 0, ie. if there is a blocking wall.
return (map[Math.floor(y)][Math.floor(x)] != 0);
}
function updateMiniMap() {
var miniMap = $("minimap");
var miniMapObjects = $("minimapobjects");
var objectCtx = miniMapObjects.getContext("2d");
miniMapObjects.width = miniMapObjects.width;
objectCtx.fillStyle = "red";
objectCtx.fillRect( // draw a dot at the current player position
player.x * miniMapScale - 2,
player.y * miniMapScale - 2,
4, 4
);
objectCtx.strokeStyle = "red";
objectCtx.beginPath();
objectCtx.moveTo(player.x * miniMapScale, player.y * miniMapScale);
objectCtx.lineTo(
(player.x + Math.cos(player.rot) * 4) * miniMapScale,
(player.y + Math.sin(player.rot) * 4) * miniMapScale
);
objectCtx.closePath();
objectCtx.stroke();
}
function drawMiniMap() {
// draw the topdown view minimap
var miniMap = $("minimap"); // the actual map
var miniMapCtr = $("minimapcontainer"); // the container div element
var miniMapObjects = $("minimapobjects"); // the canvas used for drawing the objects on the map (player character, etc)
miniMap.width = mapWidth * miniMapScale; // resize the internal canvas dimensions
miniMap.height = mapHeight * miniMapScale; // of both the map canvas and the object canvas
miniMapObjects.width = miniMap.width;
miniMapObjects.height = miniMap.height;
var w = (mapWidth * miniMapScale) + "px" // minimap CSS dimensions
var h = (mapHeight * miniMapScale) + "px"
miniMap.style.width = miniMapObjects.style.width = miniMapCtr.style.width = w;
miniMap.style.height = miniMapObjects.style.height = miniMapCtr.style.height = h;
var ctx = miniMap.getContext("2d");
ctx.fillStyle = "white";
ctx.fillRect(0,0,miniMap.width,miniMap.height);
// loop through all blocks on the map
for (var y=0;y<mapHeight;y++) {
for (var x=0;x<mapWidth;x++) {
var wall = map[y][x];
if (wall > 0) { // if there is a wall block at this (x,y) ...
ctx.fillStyle = "rgb(200,200,200)";
ctx.fillRect( // ... then draw a block on the minimap
x * miniMapScale,
y * miniMapScale,
miniMapScale,miniMapScale
);
}
}
}
updateMiniMap();
}
setTimeout(init, 1);
</script>
</body>