115 lines
3.0 KiB
JavaScript
115 lines
3.0 KiB
JavaScript
"use strict";
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import Vector from './Vector';
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import random from './Random';
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class Star
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{
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constructor(inCanvas, inPosition, inSize)
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{
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this.canvas = inCanvas;
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this.position = inPosition; // The position
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this.rotation = 0; // The rotation
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this.rotationStep = 0; // The amount (in rads / sec) the star turns by
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this.scale = 1;
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this.alpha = 1; // The opacity
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this.pointCount = 5; // The number of points
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this.startSize = inSize; // The initial radius
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this.size = this.startSize; // The current radius
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this.innerRingRatio = 0.5; // The radius of the inner ring (for the inner points)
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this.twinkleSize = 2; // The size multiplier when twinkling
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this.twinkling = false; // Whether we're twinkling
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this.twinkleDuration = 1; // The duration of a twinkle (in seconds)
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this.twinkleTimer = 0; // The current point along the twinkle we are at now
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this.colour = "white"; // The colour of the star
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}
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/**
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* The step around a circle (in radians) between each point (both inner and
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* outer) on the star.
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* Used by recalculatePoints().
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* @return {number} The step around a circle between each point on the star.
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*/
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get pointStep()
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{
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return (Math.PI * 2) / (this.pointCount * 2);
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}
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get innerRingSize()
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{
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return this.innerRingRatio * this.size;
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}
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recalculatePoints()
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{
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this.points = [];
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for (let n = 0, i = 0; n < Math.PI * 2; n += this.pointStep, i++)
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{
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let currentSize = i % 2 == 0 ? this.size : this.innerRingSize;
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this.points.push(new Vector(
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currentSize * Math.cos(Math.PI * 2 * (n / (Math.PI * 2)) - Math.PI / 2),
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currentSize * Math.sin(Math.PI * 2 * (n / (Math.PI * 2)) - Math.PI / 2)
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));
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}
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}
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update(dt)
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{
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// Rotate (slowly I hope)
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this.rotation += this.rotationStep * dt;
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if(this.rotation > Math.PI * 2)
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this.rotation -= Math.PI * 2;
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if(this.rotation < 0)
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this.rotation += Math.PI * 2;
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// Randomly begin a twinkle
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if(!this.twinkling && dt != 0 && Math.floor(random(0, 50000)*dt) == 0)
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this.twinkling = true;
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if(this.twinkling)
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{
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// Calculate the new size quadratically
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let sizeMultiplier = (1 - Math.pow(2*(this.twinkleTimer / this.twinkleDuration) - 1, 2));
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sizeMultiplier *= this.twinkleSize;
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// Go from 0 - size to 1 - (size + 1) (because a size of 0 makes things disappear)
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sizeMultiplier += 1;
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this.scale = sizeMultiplier;
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this.twinkleTimer += dt;
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if(this.twinkleTimer >= this.twinkleDuration)
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this.twinkling = false, this.twinkleTimer = 0;
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}
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}
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render(context)
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{
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if(!(this.points instanceof Array))
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this.recalculatePoints();
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context.save();
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context.translate(this.position.x, this.position.y);
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context.rotate(this.rotation);
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context.scale(this.scale, this.scale);
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context.beginPath();
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context.moveTo(this.points[0].x, this.points[0].y);
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for (let point of this.points) {
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context.lineTo(point.x, point.y);
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}
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context.closePath();
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context.globalAlpha = this.alpha;
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context.fillStyle = this.colour;
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context.fill();
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context.restore();
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}
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}
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export default Star;
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