Code
class Vertex {
private double dx;
private double dy;
private double dz;
public double vx;
public double vy;
protected Vertex(double dx, double dy, double dz) {
this.dx = dx;
this.dy = dy;
this.dz = dz;
projectionTransformation();
}
private void projectionTransformation() {
double screenDistance = 500d;
double depth = 1000d;
double gz = dz + depth;
this.vx = screenDistance * dx / gz;
this.vy = screenDistance * dy / gz;
}
public void rotateTransformation(double kx, double ky, double kz) {
double x0 = dx * Math.cos(ky) - dz * Math.sin(ky);
double y0 = dy;
double z0 = dx * Math.sin(ky) + dz * Math.cos(ky);
double y1 = y0 * Math.cos(kx) - z0 * Math.sin(kx);
double z1 = y0 * Math.sin(kx) + z0 * Math.cos(kx);
this.dx = x0 * Math.cos(kz) - y1 * Math.sin(kz);
this.dy = x0 * Math.sin(kz) + y1 * Math.cos(kz);
this.dz = z1;
projectionTransformation();
}
}
// ...
List<Vertex> cube = new ArrayList<>(8);
double sideLength = 100;
cube.add(new Vertex(sideLength, sideLength, sideLength));
cube.add(new Vertex(sideLength, sideLength, -sideLength));
cube.add(new Vertex(-sideLength, sideLength, -sideLength));
cube.add(new Vertex(-sideLength, sideLength, sideLength));
cube.add(new Vertex(sideLength, -sideLength, sideLength));
cube.add(new Vertex(sideLength, -sideLength, -sideLength));
cube.add(new Vertex(-sideLength, -sideLength, -sideLength));
cube.add(new Vertex(-sideLength, -sideLength, sideLength));
// ...
// Projection transformation of each vertex of a regular hexahedron by moving the viewpoint to the origin, the distance to the screen to 500, and the z-axis coordinate value to the back of the screen to 1000.
// Draw a wireframe in the center of the JPanel by connecting the transformed vertex coordinates with Path2D
@Override protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(
RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
Path2D path = new Path2D.Double();
path.moveTo(cube.get(0).vx, cube.get(0).vy);
path.lineTo(cube.get(1).vx, cube.get(1).vy);
path.lineTo(cube.get(2).vx, cube.get(2).vy);
path.lineTo(cube.get(3).vx, cube.get(3).vy);
path.lineTo(cube.get(0).vx, cube.get(0).vy);
path.lineTo(cube.get(4).vx, cube.get(4).vy);
path.lineTo(cube.get(5).vx, cube.get(5).vy);
path.lineTo(cube.get(6).vx, cube.get(6).vy);
path.lineTo(cube.get(7).vx, cube.get(7).vy);
path.lineTo(cube.get(4).vx, cube.get(4).vy);
path.moveTo(cube.get(1).vx, cube.get(1).vy);
path.lineTo(cube.get(5).vx, cube.get(5).vy);
path.moveTo(cube.get(2).vx, cube.get(2).vy);
path.lineTo(cube.get(6).vx, cube.get(6).vy);
path.moveTo(cube.get(3).vx, cube.get(3).vy);
path.lineTo(cube.get(7).vx, cube.get(7).vy);
Rectangle r = SwingUtilities.calculateInnerArea(this, null);
g2.setPaint(Color.WHITE);
g2.fill(r);
g2.translate(r.getCenterX(), r.getCenterY());
g2.setPaint(Color.BLACK);
g2.draw(path);
g2.dispose();
}
// ...
// Add the following `MouseAdapter` to the `JPanel` that transforms and draws the projection of the regular hexahedron, and rotate each vertex in the space
private class DragRotateHandler extends MouseAdapter {
private final Cursor defCursor = Cursor.getDefaultCursor();
private final Cursor hndCursor = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR);
private final Point pp = new Point();
@Override public void mouseDragged(MouseEvent e) {
Point pt = e.getPoint();
double rotY = (pt.x - pp.x) * .03;
double rotX = (pt.y - pp.y) * .03;
double rotZ = 0d;
for (Vertex v : cube) {
v.rotateTransformation(rotX, rotY, rotZ);
}
pp.setLocation(pt);
e.getComponent().repaint();
}
@Override public void mousePressed(MouseEvent e) {
e.getComponent().setCursor(hndCursor);
pp.setLocation(e.getPoint());
}
@Override public void mouseReleased(MouseEvent e) {
e.getComponent().setCursor(defCursor);
}
}
References
- Draw a projection-transformed regular hexahedron wireframe in JPanel and rotate it in space by mouse dragging(Japanese)
- jdk-8-windows-x64-demos.zip\jdk1.8.0_341\demo\jfc\Java2D\src.zip\java2d\demos\Colors\Rotator3D.java
- APCS wiki - Perspective
