[HTML5] 3D model--an example of implementing a rotating three-dimensional Rubik's cube with a hundred lines of code

Recently studying how to play the Rubik's Cube, I suddenly wanted to use HMTL5 to write a Rubik's Cube model. Since the Rubik's Cube is a 3D cube, I tried to write a simple 3D model using HTML5 this time.

The following is the preview screen.



Production process

First you need to download the Html5 open source library lufylegend-1.4.0

The Rubik's Cube is divided into 6 faces, each face is composed of 9 small rectangles. Now I encapsulate each small rectangle as a class.

Because what is being built now is a 3D Rubik's Cube, so I have to draw it For each small rectangle, you need to know the 4 fixed points of the small rectangle, and these 4 fixed points will transform according to the rotation angle of the space. Therefore, in order to calculate the coordinates of these 4 fixed points, you need to know the angle of rotation of the Rubik's Cube around the x-axis and z-axis. .

So, create a rectangle class as follows

function Rect(pointA,pointB,pointC,pointD,angleX,angleZ,color){  
    base(this,LSprite,[]);  
    this.pointZ=[(pointA[0]+pointB[0]+pointC[0]+pointD[0])/4,(pointA[1]+pointB[1]+pointC[1]+pointD[1])/4,(pointA[2]+pointB[2]+pointC[2]+pointD[2])/4];  
    this.z = this.pointZ[2];  
    this.pointA=pointA,this.pointB=pointB,this.pointC=pointC,this.pointD=pointD,this.angleX=angleX,this.angleZ=angleZ,this.color=color;  
}  
  
Rect.prototype.setAngle = function(a,b){  
    this.angleX = a;  
    this.angleZ = b;  
    this.z=this.getPoint(this.pointZ)[2];  
};

pointA, pointB, pointC, pointD are the four vertices of the small rectangle, angleX, angleZ respectively is the angle of rotation between the x-axis and z-axis, and color is the color of the small rectangle.

The Rubik's Cube is divided into 6 faces. Let's take a look at the front face first. If the center of the cube is used as the center of the 3D coordinate system, then the coordinates corresponding to each fixed point of the 9 small rectangles are as shown in the figure below



So, the 9 small rectangles on the previous surface can be created by the following code

for(var x=0;x<3;x++){  
    for(var y=0;y<3;y++){  
        z = 3;  
        var rect = new Rect([-3*step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],[-step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],
        [-step + x*2*step,-step + y*2*step,-3*step + z*2*step],[-3*step + x*2*step,-step + y*2*step,-3*step + z*2*step],0,0,"#FF0000");  
        backLayer.addChild(rect);  
    }  
}

Among them, backLayer is an LSprite class, and step is the length of half a small rectangle. In the same way, the other five faces can also be obtained.

Six faces have been established. Before drawing these six faces, we must first calculate the coordinates of each fixed point based on the angle of rotation. See the picture below



According to the above picture, use the following formula to get the transformed fixed-point coordinates

Rect.prototype.getPoint = function(p){  
    var u2,v2,w2,u=p[0],v=p[1],w=p[2];  
    u2 = u * Math.cos(this.angleX) - v * Math.sin(this.angleX);  
    v2 = u * Math.sin(this.angleX) + v * Math.cos(this.angleX);  
    w2 = w;  
    u = u2; v = v2; w = w2;  
    u2 = u;  
    v2 = v * Math.cos(this.angleZ) - w * Math.sin(this.angleZ);  
    w2 = v * Math.sin(this.angleZ) + w * Math.cos(this.angleZ);  
    u = u2; v = v2; w = w2;  
    return [u2,v2,w2];  
};

Finally, based on the four fixed-point coordinates of the small rectangle, Draw this rectangle,

Rect.prototype.draw = function(layer){  
    this.graphics.clear();  
    this.graphics.drawVertices(1,"#000000",[this.getPoint(this.pointA),this.getPoint(this.pointB),
    this.getPoint(this.pointC),this.getPoint(this.pointD)],true,this.color);  
};

where drawVertices is a method of the LGraphics class in the lufylegend.js library, which can draw a rectangle based on the incoming fixed-point coordinate array polygon.

Finally, the complete code is given. There is very little code and a total of 91 lines of JS code.

One, index.html

<!DOCTYPE html>  
<html>  
<head>  
<meta charset="UTF-8">  
<title>3D魔方</title>  
</head>  
<body>  
<p id="mylegend">loading……</p>  
<script type="text/javascript" src="../lufylegend-1.4.0.min.js"></script>   
<script type="text/javascript" src="./Main.js"></script>   
<script type="text/javascript" src="./Rect.js"></script>   
</body>  
</html>

Two, Rect class

function Rect(pointA,pointB,pointC,pointD,angleX,angleZ,color){  
    base(this,LSprite,[]);  
    this.pointZ=[(pointA[0]+pointB[0]+pointC[0]+pointD[0])/4,(pointA[1]+pointB[1]+pointC[1]+pointD[1])/4,(pointA[2]+pointB[2]+pointC[2]+pointD[2])/4];  
    this.z = this.pointZ[2];  
    this.pointA=pointA,this.pointB=pointB,this.pointC=pointC,this.pointD=pointD,this.angleX=angleX,this.angleZ=angleZ,this.color=color;  
}  
Rect.prototype.draw = function(layer){  
    this.graphics.clear();  
    this.graphics.drawVertices(1,"#000000",[this.getPoint(this.pointA),this.getPoint(this.pointB),
this.getPoint(this.pointC),this.getPoint(this.pointD)],true,this.color);  
};Rect.prototype.setAngle = function(a,b){  
    this.angleX = a;  
    this.angleZ = b;  
    this.z=this.getPoint(this.pointZ)[2];  
};  
Rect.prototype.getPoint = function(p){  
    var u2,v2,w2,u=p[0],v=p[1],w=p[2];  
    u2 = u * Math.cos(this.angleX) - v * Math.sin(this.angleX);  
    v2 = u * Math.sin(this.angleX) + v * Math.cos(this.angleX);  
    w2 = w;  
    u = u2; v = v2; w = w2;  
    u2 = u;  
    v2 = v * Math.cos(this.angleZ) - w * Math.sin(this.angleZ);  
    w2 = v * Math.sin(this.angleZ) + w * Math.cos(this.angleZ);  
    u = u2; v = v2; w = w2;  
    return [u2,v2,w2];  
};

Three, Main.js

init(50,"mylegend",400,400,main);  
var a = 0,b=0,backLayer,step = 20,key = null;  
function main(){  
    backLayer = new LSprite();  
    addChild(backLayer);  
    backLayer.x = 120,backLayer.y = 120;  
    //后  
    for(var x=0;x<3;x++){  
        for(var y=0;y<3;y++){  
            z = 0;  
            var rect = new Rect([-3*step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],[-step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],
            [-step + x*2*step,-step + y*2*step,-3*step + z*2*step],[-3*step + x*2*step,-step + y*2*step,-3*step + z*2*step],0,0,"#FF4500");  
            backLayer.addChild(rect);  
        }  
    }  
    //前  
    for(var x=0;x<3;x++){  
        for(var y=0;y<3;y++){  
            z = 3;  
            var rect = new Rect([-3*step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],[-step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],
            [-step + x*2*step,-step + y*2*step,-3*step + z*2*step],[-3*step + x*2*step,-step + y*2*step,-3*step + z*2*step],0,0,"#FF0000");  
            backLayer.addChild(rect);  
        }  
    }  
    //上  
    for(var x=0;x<3;x++){  
        for(var z=0;z<3;z++){  
            y = 0;  
            var rect = new Rect([-3*step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],[-step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],
            [-step + x*2*step,-3*step + y*2*step,-step + z*2*step],[-3*step + x*2*step,-3*step + y*2*step,-step + z*2*step],0,0,"#FFFFFF");  
            backLayer.addChild(rect);  
        }  
    }  
    //下  
    for(var x=0;x<3;x++){  
        for(var z=0;z<3;z++){  
            y = 3;  
            var rect = new Rect([-3*step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],[-step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],
            [-step + x*2*step,-3*step + y*2*step,-step + z*2*step],[-3*step + x*2*step,-3*step + y*2*step,-step + z*2*step],0,0,"#FFFF00");  
            backLayer.addChild(rect);  
        }  
    }  
    //左  
    for(var y=0;y<3;y++){  
        for(var z=0;z<3;z++){  
            x = 0;  
            var rect = new Rect([-3*step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],[-3*step + x*2*step,-3*step + y*2*step,-step + z*2*step],
            [-3*step + x*2*step,-step + y*2*step,-step + z*2*step],[-3*step + x*2*step,-step + y*2*step,-3*step + z*2*step],0,0,"#008000");  
            backLayer.addChild(rect);  
        }  
    }  
    //右  
    for(var y=0;y<3;y++){  
        for(var z=0;z<3;z++){  
            x = 3;  
            var rect = new Rect([-3*step + x*2*step,-3*step + y*2*step,-3*step + z*2*step],[-3*step + x*2*step,-3*step + y*2*step,-step + z*2*step],
            [-3*step + x*2*step,-step + y*2*step,-step + z*2*step],[-3*step + x*2*step,-step + y*2*step,-3*step + z*2*step],0,0,"#0000FF");  
            backLayer.addChild(rect);  
        }  
    }  
    backLayer.addEventListener(LEvent.ENTER_FRAME,onframe);  
}  
function onframe(){  
    a += 0.1 , b += 0.1;  
    backLayer.childList = backLayer.childList.sort(function(a,b){return a.z - b.z;});  
    for(key in backLayer.childList){  
        backLayer.childList[key].setAngle(a,b);  
        backLayer.childList[key].draw(backLayer);  
   }  
}

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