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PO3D coordinate rotation lacking Precision in perspective 2D
 

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  1. PO3D coordinate rotation lacking Precision in perspective 2D
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    <p>So I wrote a Program to draw and display a 3D cube, using these simple conversion formula's as used in isometric graphs:</p> <p><code>x2 = x*cos(30) - y*cos(30)</code><br> <code>y2 = x*sin(30) + y*sin(30) + z</code></p> <p>The coordinate conversion is fine and everything comes out in perspective.</p> <p>The Issue is rotating, Large degree rotations messes up all the coordinates and gives me an entire shape. And rotating at small degrees many many times, (ie 1000 1degree rotation or more) reduces the size of the cube.</p> <pre><code>public void rotateX(double dg) //cube is shrinking along y and z { y = (y*Math.cos(dg)-z*Math.sin(dg)); z = (y*Math.sin(dg)+z*Math.cos(dg)); } public void rotateY(double dg) //cube is shrinking along x and z { x = x*Math.cos(dg)-z*Math.sin(dg); z = x*Math.sin(dg)+z*Math.cos(dg); } public void rotateZ(double dg) //cube is shrinking along x and y { x = x*Math.cos(dg)-y*Math.sin(dg); y = x*Math.sin(dg)+y*Math.cos(dg); } </code></pre> <p>How can i solve this lack of precision of cos and sin after multiple uses??</p> <p>Here's the entire code written in 3 seperat classes:<br> Main class:</p> <pre><code>import java.awt.*; import javax.swing.*; import java.util.Random; public class Frame extends JFrame { private Random rnd = new Random(); private cubeGUI cube; public Frame() { super(); } public void paint(Graphics g) { cube = new cubeGUI(75,300.0,300.0); cube.convertall(); double dg = 0.5; // The Smaller the degree, the less the error after long rotations. int sl = 5; int turns, axe; while (1 == 1) { turns = rnd.nextInt(200)-100; axe = rnd.nextInt(3); for(int i = 0; i&lt;turns; i++) { switch (axe) { case 0: cube.rotatx(dg); break; case 1: cube.rotaty(dg); break; case 2: cube.rotatz(dg); break; } g.clearRect(0,0,600,600); g.drawLine(cube.a.x2,cube.a.y2,cube.b.x2,cube.b.y2); g.drawLine(cube.a.x2,cube.a.y2,cube.c.x2,cube.c.y2); g.drawLine(cube.c.x2,cube.c.y2,cube.d.x2,cube.d.y2); g.drawLine(cube.b.x2,cube.b.y2,cube.d.x2,cube.d.y2); g.drawLine(cube.e.x2,cube.e.y2,cube.f.x2,cube.f.y2); g.drawLine(cube.e.x2,cube.e.y2,cube.g.x2,cube.g.y2); g.drawLine(cube.g.x2,cube.g.y2,cube.h.x2,cube.h.y2); g.drawLine(cube.f.x2,cube.f.y2,cube.h.x2,cube.h.y2); g.drawLine(cube.a.x2,cube.a.y2,cube.e.x2,cube.e.y2); g.drawLine(cube.b.x2,cube.b.y2,cube.f.x2,cube.f.y2); g.drawLine(cube.c.x2,cube.c.y2,cube.g.x2,cube.g.y2); g.drawLine(cube.d.x2,cube.d.y2,cube.h.x2,cube.h.y2); try { Thread.sleep(sl); //Rotation Speed, In relation with Angle of rotation. } catch(InterruptedException ex) { Thread.currentThread().interrupt(); } } } } public static void main(String[] args) { Frame cube = new Frame(); cube.setSize(600,600); cube.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); cube.setVisible(true); } } </code></pre> <p>cube class:</p> <pre><code>public class cubeGUI { public Point center,a,b,c,d,e,f,g,h; private double x, y; public cubeGUI(int m, double x, double y) { this.x = x; this.y = y; a = new Point(-m,-m,-m); b = new Point(m,-m,-m); c = new Point(-m,m,-m); d = new Point(m,m,-m); e = new Point(-m,-m,m); f = new Point(m,-m,m); g = new Point(-m,m,m); h = new Point(m,m,m); } public void rotatx(double dg) { a.rotateX(Math.toRadians(dg)); b.rotateX(Math.toRadians(dg)); c.rotateX(Math.toRadians(dg)); d.rotateX(Math.toRadians(dg)); e.rotateX(Math.toRadians(dg)); f.rotateX(Math.toRadians(dg)); g.rotateX(Math.toRadians(dg)); h.rotateX(Math.toRadians(dg)); convertall(); } public void rotaty(double dg) { a.rotateY(Math.toRadians(dg)); b.rotateY(Math.toRadians(dg)); c.rotateY(Math.toRadians(dg)); d.rotateY(Math.toRadians(dg)); e.rotateY(Math.toRadians(dg)); f.rotateY(Math.toRadians(dg)); g.rotateY(Math.toRadians(dg)); h.rotateY(Math.toRadians(dg)); convertall(); } public void rotatz(double dg) { a.rotateZ(Math.toRadians(dg)); b.rotateZ(Math.toRadians(dg)); c.rotateZ(Math.toRadians(dg)); d.rotateZ(Math.toRadians(dg)); e.rotateZ(Math.toRadians(dg)); f.rotateZ(Math.toRadians(dg)); g.rotateZ(Math.toRadians(dg)); h.rotateZ(Math.toRadians(dg)); convertall(); } public void convertall() { a.convert(x,y); b.convert(x,y); c.convert(x,y); d.convert(x,y); e.convert(x,y); f.convert(x,y); g.convert(x,y); h.convert(x,y); } } </code></pre> <p>Point class (this calculates all coordinates):</p> <pre><code>public class Point { private double x, y, z, F; public int x2, y2; public Point(double a, double b, double c) { x = a; y = b; z = c; } public int getX() { return (int)x; } public int getY() { return (int)y; } public int getZ() { return (int)z; } public void rotateX(double dg) //cube is shrinking along y and z { y = (y*Math.cos(dg)-z*Math.sin(dg)); z = (y*Math.sin(dg)+z*Math.cos(dg)); } public void rotateY(double dg) //cube is shrinking along x and z { x = x*Math.cos(dg)-z*Math.sin(dg); z = x*Math.sin(dg)+z*Math.cos(dg); } public void rotateZ(double dg) //cube is shrinking along x and y { x = x*Math.cos(dg)-y*Math.sin(dg); y = x*Math.sin(dg)+y*Math.cos(dg); } public void convert(double xx, double yy) { x2 = (int)(-(Math.cos(Math.toRadians(30))*x - Math.cos(Math.toRadians(30))*y) + xx); y2 = (int)(-(Math.sin(Math.toRadians(30))*x + Math.sin(Math.toRadians(30))*y + z) + yy); } public String toString() { return ("Y = " + y + ", Z = " + z); } } </code></pre>
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    1. USThaBomb
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    1. COHave you tried using `BigDecimal`?
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    2. COWell i didn't want to go with BigDecimal because it would just waste memory, and only reduce the problem, not remove it. All i would have to do is continue rotating until BigDecimal numbers are not nearly enough to get rid of the error encountered by cos/sin as they give lots of irrational numbers with infinite digits.
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      1. PO3D coordinate rotation lacking Precision in perspective 2D
      1. USThaBomb
 

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