Collectibles not appearing in canvas - javascript

As I've ditched using Phaser, I've gotten more work done to the point of the sprite moving, and I finished programming the collision detection, but I need something more... I decided to make coins to collect for a currency. I tried programming them to appear at random points on the map using a randomRange function. I managed to get one coin spawn in the upper left corner of the canvas, but I made one slight change, and the coin just stopped spawning in the canvas at all. I've called the coins under the function collectibles, which I've called upon in the update and draw functions. Just adding them to the update and draw functions made my player sprite be locked in place! Do I need a JS library just to make the coins spawn?
Here's the code:
function collectibles () {
this.srcX = 0;
this.srcY = 0;
this.width = 20; //how wide the sprite is in pixels
this.height = 20; //how tall the sprite is in pixels
this.drawX = this.randomRange;
this.drawY = this.randomRange;
this.centerX = this.drawX + (this.width / 2);
this.centerY = this.drawY + (this.height / 2);
}

Any errors in console? If 'randomRange' is a function it lacks braces() at the end where you call it. 'this' might differ depending on where you call the function 'collectibles'.

Related

How to draw rectangles inside a polygon using p5.js

I am working on a project for a solar panel installation calculator on roofs. The solar panels are rectangular and have fixed widths and heights. But the roofs are dynamic in shape, i.e. a polygon with multiple sides. See the attached image for reference.
I am trying to find out the maximum number of panels that can be installed on the roofs. I need to place the rectangles (panels) inside the polygon (roof), which you can not overlap and can not touch the boundary.
I was trying to achieve this using p5.js.
Here are the basic codes.
function setup() {
createCanvas(800, 500);
background(220);
noLoop();
}
function draw() {
fill(237, 34, 93);
beginShape();
vertex(50, 50);
vertex(750, 50);
vertex(750, 450);
vertex(500, 450);
vertex(500, 200);
vertex(350, 200);
vertex(350, 450);
vertex(50, 450);
endShape(CLOSE);
var solarPanel = {
width: 40,
height: 40
};
//Algorithm to add the solar panels.
}
Link to p5.js editor - https://editor.p5js.org/abhishekdas/sketches/cVoxihH0n
I am new to p5.js. Can anyone please help me to find the correct Algorithm?
One simple option is to lay the panels in a grid. Your typical nested for loop should do the trick: remember to add the spacing required between panels when computing the position of each one (this should take care of overlaps).
Regarding panels laying inside the polygon of the shape you can get started with this point in polygon p5.js example. If you can test one point, you can check 4 points. If you can check 4 points (1 panel), you can check all panels) then simply remove the ones that aren't inside the roof polygon from the grid.
For reference here's function:
function pointInPoly(verts, pt) {
let c = false;
for (let i = 0, j = verts.length - 1; i < verts.length; j = i++) {
if (((verts[i].y > pt.y) != (verts[j].y > pt.y)) && (pt.x < (verts[j].x - verts[i].x) * (pt.y - verts[i].y) / (verts[j].y - verts[i].y) + verts[i].x)) c = !c;
}
return c;
}
...where verts is an array of p5.Vector objects and pt is also a p5.Vector (though a basic object .x, .y properties will also work)
That should be a simple straight forward approach.
If you need more complex options you can look into square/rectangle packing algorithms / simulations and optimisations etc. though given the point is to set up solar panels, the real world probably the simpler setup to install and maintain on the long run will outweight potentially space saving layouts that are odd shaped.

Javascript sprites moving between two points

I'm wanting to get some sprites moving between two points in my (very basic) javascript game. Each sprite is randomly placed in the level, so I want them to move back and forth between their base position. I have the code below
function Taniwha(pos) {
this.basePos = this.pos;
this.size = new Vector(0.6, 1);
this.move = basePos + moveDist(5,0));
}
Taniwha.prototype.type = "taniwha"
var moveSpeed = 4;
Taniwha.prototype.act = function(step) {
this.move = ???
and this is where I get stuck. I'm not sure how to tell it to go left, back to base pos, right then back to base pos again (I plan to loop this). Does anyone have any advice? (also using Eloquen Javascript's example game as an outline/guide for this, if how I'm doing things seems odd!)
For horizontal movement, change x coordinate of the position.
var pos = { x: 1, y: 2 };
pos.x++ ; // This will move right
pos.x-- ; // This will move left
Likewise for vertical movement. You also need to update the coordinates after change for the object which you are drawing.
In truth ,there are lots of library to develop a game.
Use those, control a sprite is very easy.
Like:
Pixijs
CreateJS
Both of them are opensource project, you can watch and learn the source.
And have lots of examples and document.

HTML5 Canvas not drawing lines past 2040 in either direction

Edit: Ran the code on a more powerful computer and the grid rendered correctly. Possible hardware limitation? Computer where the problem occurred was a Samsung series 3 Chromebook. I'm thinking it has to do with trying to draw too many lines at the same time. Will test later.
I'm trying to draw a grid onto a canvas using the lineTo() method. The lines draw properly in the beginning, but any line that is drawn completely past 2048 pixels either down or to the right doesn't show up. Line going from inside this point to past it still show up on the other side, just lines that only are only drawn past the point don't show up.
Here's my JavaScript:
function drawGrid() {
//data.tiles is the map stored as an array of arrays
//tilesize = 60
var bw = data.tiles[0].length * tilesize;
var bh = data.tiles.length * tilesize;
ctx.beginPath();
for (i = bw; i >= 0; i -= tilesize) {
ctx.moveTo(i, 0);
ctx.lineTo(i, bh);
}
for (i = bh; i >= 0; i -= tilesize) {
ctx.moveTo(0, i);
ctx.lineTo(bw,i);
}
ctx.strokeStyle = "black";
ctx.stroke();
}
I've checked the data.tiles variable, and it's reading the right number. Really have no idea what I messed up here.
HTML Canvas has a maximum render area depending on your browser & hardware.
once you exceed these limits well your done pretty much.
try pre-rendering or use multiple canvas' positioned with CSS.
If you can see images drawn beyond 2048 then there's no reason a lineTo wouldn't be drawn also.
In the code you calculate bw and bh in different ways. You might check if this is a problem. If not, we'll need to see more code.
// bw uses data.tiles[0]
var bw = data.tiles[0].length * tilesize;
// bh uses data.tiles with no subscript
var bh = data.tiles.length * tilesize;

Cheat for hidden game "Atari Breakout" in Google Image Search

How would a cheat/auto moving paddle in this hidden html game look like?
There is a
<div id="breakout-ball"><span>●</span></div>
and a
<div id="breakout-paddle"></div>
when moving the mouse the paddle is moved horizontally. How can I connect the movement of the ball with the paddle?
This question will become "community wiki" as soon as possible.
function cheat() {
var ball = document.getElementById('breakout-ball');
var paddle = document.getElementById('breakout-paddle');
paddle.style.left = ball.style.left;
setTimeout(cheat, 20);
}
cheat();
// Add this via the FireBug console.
I modified your solution slightly to account for the scenario of the ball going off screen and breaking the hack and also the ball getting jammed into the corner.
function cheat() {
var ball = document.getElementById('breakout-ball');
var paddle = document.getElementById('breakout-paddle');
var buffer = Math.floor((Math.random()*100)+1);
var leftVal = parseInt(ball.style.left, 10);
if (ball.style.left) {
paddle.style.left = (leftVal - buffer) + 'px';
}
setTimeout(cheat, 100);
}
cheat();
To be honest though, if you are going down that road why not do this?
function cheat() {
var paddle = document.getElementById('breakout-paddle');
paddle.style.width = '100%';
}
cheat();
Anyway I'm going to continue to dig into the code and do some deeper manipulation
in chrome, search the game, ctrl+J, paste the following in, and press enter.
This is a simple goal:
//get the ball's X position from its CSS
function ballx(){
return parseFloat(document.querySelector("#breakout-ball").style.left.split("px")[0]);
}
function update(e){
//throws an exception when the game isn't up. Can be really annoying.
try{document.querySelector("#breakout-paddle").style.left = (ballx() - 75)+"px";}
catch(ex){}
}
var intervalTimer = setInterval(update, 125);//let it have a single weakness in case someone else tries it while I am around.
The lower the interval rate, the faster the paddle will move relative to the ball, but the slower the game goes. The maximum rate can be given with a simple requestAnimationFrame cycle, but that slows the browser down a lot(at least on my laptop).
I tried changing the paddle's size. It doesn't really work.
I'm sure it would be simpler with jQuery, but why make cheating easy when doing it hard core is already so easy?
I have come up with a new way to solve this problem. Whenever the screen size or window size changes, the paddle changes size based on the screen size. To combat this, I simply just added another section that splits the size of the paddle in half then uses that value to find the centre of the paddle. Very simple and very effective.
function autoMove() {
var ball = document.getElementById('breakout-ball')
var paddle = document.getElementById('breakout-paddle')
var leftVal = parseInt(ball.style.left, 10)
var paddleWidth = parseFloat(paddle.style.width, 10) / 2
paddle.style.left = (leftVal - paddleWidth) + 'px'
setTimeout(autoMove, 20)
}
autoMove();
Also, didn't like the function name. It looks way too suspicious so changed it. Hope this helps.

Collision detection on a canvas in JavaScript

I'm working on a game for a university assignment. The idea is that you defend the centre circle from the incoming asteroids (lines) by drawing a line (click, drag & release to draw a line) which blocks them. An asteroid hitting a line should destroy both the asteroid the line.
The problem I'm currently having is that the collision isn't being detected.
I have arrays of objects of both lines & asteroids. The lines consist of simply start & end x & y, the asteroids consist of a random speed & a random angle (their incoming angle) - the context is rotated, the asteroid drawn, & then it reset for the next line.
To detect collision, I use getImageData & check in front of the asteroids however many pixels the line will progress in that iteration (basically, their speed) & if the colour is red, it will destroy the asteroid - I haven't got round to destroying the line yet, will tackle that hurdle when I come to it (suggestions are welcome though).
function asteroids_draw() {
for (var i = 0; i < asteroids.length; i++) {
// Drawing setup
context.save();
context.translate(width / 2, height / 2);
context.rotate(asteroids[i].angle);
// Detecting close asteroids
if ((asteroids[i].distance - asteroids[i].speed) < planet.size) {
asteroids.splice(i, 1);
game_life_lost();
context.restore();
return;
} else if ((asteroids[i].distance - asteroids[i].speed) < 150){
asteroids[i].colour = '#FF0000';
}
// Scanning ahead for lines
for (var j = 0; j < asteroids[i].speed; j++) {
if (context.getImageData(asteroids[i].distance - j, 0, 1, 1).data[0] == 255) {
asteroids.splice(i, 1);
context.restore();
return;
}
}
// Drawing asteroid
context.beginPath();
context.moveTo(asteroids[i].distance -= asteroids[i].speed, 0);
context.lineTo(trig, 0);
context.strokeStyle = asteroids[i].colour;
context.stroke();
context.closePath();
context.restore();
}
}
The problem is, the asteroids never collide with the lines & I can't for the life of me see why, or see another simple way of doing it. Any advice would be much appreciated, thanks in advance.
I think your problem is that when you rotate the context, previously drawn items(lines) don't get rotated, only objects drawn after the rotation are rotated. See this page for more info.
You could try performing your asteroid/line intersection test before you translate and rotate the canvas, and use cosine and sine to find the x and y coordinates of the pixels you want to get image data from.
var pixelLocation =
[Math.cos(asteroids[i].angle) * j, Math.sin(asteroids[i].angle) * j];
if (context.getImageData(pixelLocation[0], pixelLocation[1], 1, 1).data[0] == 255) {
Just make sure your angle is in radians before passing to cos and sin.
I thought about the problem some more, & realised this method of doing things definitely isn't the best way. It should be doable without a view - a la Model View Controller design pattern. The best way to solve it would be to use maths!
There's simple maths for the intersection of two lines, but this needs intersection of two lines in a range. I found an algorithm which simplifies this further, using eight coordinates - the start x & y & the end x & y of the two lines.
I've posted the results. Thanks for the help.

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