Java 如何';获取';从仿射变换派生的形状对象的特定点
作为一个自我项目,我正在努力使游戏“小行星” 目前,我一直在试图找出如何使我的飞船发射的激光出现在飞船的顶端。到目前为止,我已经尝试使用Java 如何';获取';从仿射变换派生的形状对象的特定点,java,shape,affinetransform,Java,Shape,Affinetransform,作为一个自我项目,我正在努力使游戏“小行星” 目前,我一直在试图找出如何使我的飞船发射的激光出现在飞船的顶端。到目前为止,我已经尝试使用形状对象的.getBounds2D().getX()方法进行实验,但是由于getBounds2D()在多边形周围绘制了一个矩形,激光最终从我的多边形周围的假想“盒子”的一角出现ship 是否有一种从形状对象“获取”特定点的方法;其中,在这种情况下,该特定点是船的顶端 主要类别: public class AsteroidGame implements Acti
形状
对象的.getBounds2D().getX()
方法进行实验,但是由于getBounds2D()
在多边形周围绘制了一个矩形,激光最终从我的多边形周围的假想“盒子”的一角出现ship
是否有一种从形状对象“获取”特定点的方法;其中,在这种情况下,该特定点是船的顶端
主要类别:
public class AsteroidGame implements ActionListener, KeyListener{
public static AsteroidGame game;
public Renderer renderer;
public boolean keyDown = false;
public int playerAngle = 0;
public boolean left = false;
public boolean right = false;
public boolean go = false;
public boolean back = false;
public boolean still = true;
public double angle = 0;
public int turnRight = 5;
public int turnLeft = -5;
public Shape transformed;
public ArrayList<Laser> lasers;
public ArrayList<Shape> transformedLasers;
public final int WIDTH = 1400;
public final int HEIGHT = 800;
public Ship ship;
public Rectangle shipHead;
public Shape shipHeadTrans;
public Point headPoint;
public AffineTransform transform = new AffineTransform();
public AffineTransform lasTransform = new AffineTransform();
public AffineTransform headTransform = new AffineTransform();
public AsteroidGame(){
JFrame jframe = new JFrame();
Timer timer = new Timer(20, this);
renderer = new Renderer();
jframe.add(renderer);
jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jframe.setSize(WIDTH, HEIGHT);
jframe.setVisible(true);
jframe.addKeyListener(this);
jframe.setResizable(false);
int xPoints[] = {800, 780, 800, 820};
int yPoints[] = {400, 460, 440, 460};
//(800, 400) is the initial location of the 'tip' of the ship'.
headPoint = new Point(800, 400);
lasers = new ArrayList<Laser>();
transformedLasers = new ArrayList<Shape>();
ship = new Ship(xPoints, yPoints, 4, 0);
transformed = transform.createTransformedShape(ship);
shipHead = new Rectangle(headPoint);
shipHeadTrans = transform.createTransformedShape(shipHead);
//shipHeadTrans.getBounds2D().
timer.start();
}
public void repaint(Graphics g){
g.setColor(Color.BLACK);
g.fillRect(0, 0, WIDTH, HEIGHT);
Graphics2D g2d = (Graphics2D)g;
//drawing the ship
g2d.setColor(Color.WHITE);
g2d.draw(transformed);
//drawing lasers
g2d.setColor(Color.RED);
for (int i = 0; i < transformedLasers.size(); i++){
System.out.println(i);
g2d.draw(transformedLasers.get(i));
}
}
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
/*The for if and else if statements are just to send the ship
* to the other side of the canvas if it ever leaves the screen
*/
if (transformed.getBounds2D().getMinX() > WIDTH){
double tempAng = ship.getAng();
double diff = 90-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,WIDTH);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getX() < 0){
double tempAng = ship.getAng();
double diff = 90-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,-WIDTH);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getY() > HEIGHT){
double tempAng = ship.getAng();
double diff = 180-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,HEIGHT);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getY() < 0){
double tempAng = ship.getAng();
double diff = 180-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,-HEIGHT);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
if (right){
ship.right();
//rotating the ship
transform.rotate(Math.toRadians(turnRight), ship.getCenterX(), ship.getCenterY());
//rotating the 'tip' of the ship.
headTransform.rotate(Math.toRadians(turnRight), ship.getCenterX(), ship.getCenterY());
}
else if (left){
ship.left();
//rotating the ship
transform.rotate(Math.toRadians(turnLeft), ship.getCenterX(), ship.getCenterY());
//rotating the 'tip' of the ship
headTransform.rotate(Math.toRadians(turnLeft), ship.getCenterX(), ship.getCenterY());
}
if (go){
ship.go();
}
else if (back){
ship.reverse();
}
//moving and shaping each individual laser that had been shot
for (int i = 0; i < transformedLasers.size(); i++){
lasers.get(i).move();
lasTransform = new AffineTransform();
lasTransform.rotate(Math.toRadians(lasers.get(i).getAng()), transformed.getBounds2D().getX(), transformed.getBounds2D().getY());
transformedLasers.set(i, lasTransform.createTransformedShape(lasers.get(i)));
}
//moving the ship
ship.move();
//moving the 'tip'
shipHead.y -= ship.getSpeed();
transformed = transform.createTransformedShape(ship);
shipHeadTrans = headTransform.createTransformedShape(shipHead);
renderer.repaint();
}
//defining a new laser
public void fireLaser(){
Laser tempLaser = new Laser((int)transformed.getBounds2D().getX(), (int)transformed.getBounds2D().getY(), 5, 10, ship.getAng());
lasers.add(tempLaser);
lasTransform = new AffineTransform();
lasTransform.rotate(Math.toRadians(ship.getAng()), transformed.getBounds2D().getX(), transformed.getBounds2D().getY());
transformedLasers.add(lasTransform.createTransformedShape(tempLaser));
}
public static void main(String[] args){
game = new AsteroidGame();
}
@Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
if (e.getKeyCode() == KeyEvent.VK_RIGHT){
right = true;
keyDown = true;
}else if (e.getKeyCode() == KeyEvent.VK_LEFT){
left = true;
keyDown = true;
}
else if (e.getKeyCode() == KeyEvent.VK_UP){
go = true;
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN){
back = true;
}
//fire laser
if (e.getKeyCode() == KeyEvent.VK_SPACE){
fireLaser();
}
}
@Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
if (e.getKeyCode() == KeyEvent.VK_RIGHT){
right = false;
}
if (e.getKeyCode() == KeyEvent.VK_LEFT){
left = false;
}
if (e.getKeyCode() == KeyEvent.VK_UP){
go = false;
}
if (e.getKeyCode() == KeyEvent.VK_DOWN){
back = false;
}
still = true;
keyDown = false;
}
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
我在考虑将变形对象变换后的转换回多边形以获得点,但我不确定如何或是否可行。您可以使用它来变换多边形上的单个点
如果您不使用旋转变换来移动船舶,而是保留船舶所在位置的单个(x,y)
,事情会简单得多。您可以在move()
中移动船舶的位置,而不是尝试平移多边形。然后,当你想给船上漆时,例如:
// Optionally copying the Graphics so the
// transform doesn't affect later painting.
Graphics2D temp = (Graphics2D) g2d.create();
temp.translate(ship.locX, ship.locY);
temp.rotate(ship.angle);
temp.draw(ship);
要基于速度移动点,可以执行以下操作以查找移动向量:
double velX = speed * Math.cos(angle);
double velY = speed * Math.sin(angle);
locX += timeElapsed * velX;
locY += timeElapsed * velY;
这本质上是从极坐标到笛卡尔坐标的转换。x和y速度是斜边为速度
且已知角度为角度
的三角形的腿:
/|
/ |
/ |
/ |
speed / |
/ |
/ |velY
/ angle |
/)_______|
velX
在我的回答中有一个这样做的例子:
请注意:
你是说,与我的初始移动函数不同,只是为了让ship
保持一个点,因此我只会转换它
或多或少,是的。您仍然有一个多边形来保持船的形状,但是多边形上的点相对于(0,0)
假设以下定义:
- 多边形上的每个
(x,y)
点都是pi
。(换句话说,p0
、p1
、p2
和p3
中的一个)
- 平移的
(x,y)
坐标为T
然后,在翻译图形2d
后,每个pi
坐标变为面板上的pi+T
。因此,如果多边形点是相对于(0,0)
定义的,则转换到船舶的(locX,locY)
将多边形移动到相对于(locX,locY)
的位置
最简单的方法是将多边形顶端的点定义为(0,0)
,这样在平移后,船的顶端就是船的位置:
// Your original points:
int xPoints[] = {800, 780, 800, 820};
int yPoints[] = {400, 460, 440, 460};
// Become these points relative to (0,0):
int xPoints[] = {0, -20, 0, 20};
int yPoints[] = {0, 60, 40, 60};
例如,要在同一位置启动船舶,您需要将其位置初始化为(800400)
我又想了一遍,意识到旋转有点复杂,因为你可能不想绕着顶端旋转飞船。您可能希望围绕其中心旋转船舶
这里有一个MCVE演示如何完成所有这些
您仍然可以使用变换以这种方式进行计算,但依赖变换进行运动不会产生任何奇怪的结果。(在问题的代码中,例如,船舶仅沿y轴移动。明显的侧向移动是由于一系列旋转连接。)你是说,与我的初始移动功能不同,只是为了使船舶保持一个点,因此我只转换该点吗,我只是想知道如何才能找回飞船的“尖端”——我不一定需要翻译它。在画布上移动和转换的实例是变形的形状,
,但是没有任何方法可以让我获得船梢的特定坐标。一旦我得到了“提示”,我就可以改变激光发射的位置和方式的坐标。我意识到旋转有点复杂,所以我添加了一个MCVE,希望能有所帮助。好吧,我最终给出了你最初的建议/答案,效果很好,再次感谢。如果你想看看我最后做了什么,这里是我的github的链接:没问题!很乐意帮忙。
/|
/ |
/ |
/ |
speed / |
/ |
/ |velY
/ angle |
/)_______|
velX
// Your original points:
int xPoints[] = {800, 780, 800, 820};
int yPoints[] = {400, 460, 440, 460};
// Become these points relative to (0,0):
int xPoints[] = {0, -20, 0, 20};
int yPoints[] = {0, 60, 40, 60};
package mcve.game;
import javax.swing.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.Polygon;
import java.awt.RenderingHints;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.GraphicsConfiguration;
import java.util.Set;
import java.util.HashSet;
import java.util.List;
import java.util.ArrayList;
public class MovementExample implements ActionListener {
public static void main(String[] args) {
SwingUtilities.invokeLater(MovementExample::new);
}
final int fps = 60;
final int period = 1000 / fps;
final JFrame frame;
final GamePanel panel;
final Controls controls;
final Ship ship;
final List<Bullet> bullets = new ArrayList<>();
MovementExample() {
frame = new JFrame("Movement Example");
Dimension size = getMaximumWindowSize(frame);
size.width /= 2;
size.height /= 2;
frame.setPreferredSize(size);
panel = new GamePanel();
frame.setContentPane(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
controls = new Controls();
ship = new Ship(panel.getWidth() / 2,
panel.getHeight() / 2);
new Timer(period, this).start();
}
@Override
public void actionPerformed(ActionEvent e) {
double secondsElapsed = 1.0 / fps;
ship.update(secondsElapsed);
bullets.forEach(b -> b.update(secondsElapsed));
Rectangle bounds = panel.getBounds();
bullets.removeIf(b -> !bounds.contains(b.locX, b.locY));
panel.repaint();
}
class GamePanel extends JPanel {
GamePanel() {
setBackground(Color.WHITE);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
if (ship != null) {
ship.draw(g2);
}
bullets.forEach(b -> b.draw(g2));
g2.dispose();
}
}
abstract class AbstractGameObject {
double maxSpeed;
double rotationAngle;
double locX;
double locY;
double velX;
double velY;
AbstractGameObject(double initialX, double initialY) {
locX = initialX;
locY = initialY;
}
abstract void update(double secondsElapsed);
abstract void draw(Graphics2D g2);
}
class Ship extends AbstractGameObject {
Polygon shape;
double rotationRate;
Ship(double initialX, double initialY) {
super(initialX, initialY);
maxSpeed = 128; // pixels/second
rotationAngle = Math.PI * 3 / 2;
rotationRate = (2 * Math.PI) / 2; // radians/second
int xPoints[] = {0, -20, 0, 20};
int yPoints[] = {0, 60, 40, 60};
shape = new Polygon(xPoints, yPoints, 4);
}
Point2D.Double getTip() {
Point2D.Double center = getCenter();
// The tip is at (0,0) and it's already centered
// on the x-axis origin, so the distance from the
// tip to the center is just center.y.
double distance = center.y;
// Then find the location of the tip, relative
// to the center.
double tipX = distance * Math.cos(rotationAngle);
double tipY = distance * Math.sin(rotationAngle);
// Now find the actual location of the center.
center.x += locX;
center.y += locY;
// And return the actual location of the tip, relative
// to the actual location of the center.
return new Point2D.Double(tipX + center.x, tipY + center.y);
}
Point2D.Double getCenter() {
// Returns the center point of the ship,
// relative to (0,0).
Point2D.Double center = new Point2D.Double();
for (int i = 0; i < shape.npoints; ++i) {
center.x += shape.xpoints[i];
center.y += shape.ypoints[i];
}
center.x /= shape.npoints;
center.y /= shape.npoints;
return center;
}
@Override
void update(double secondsElapsed) {
// See my answer here: https://stackoverflow.com/a/43692434/2891664
// for a discussion of why this logic is the way it is.
double speed = 0;
if (controls.isUpHeld()) {
speed += maxSpeed;
}
if (controls.isDownHeld()) {
speed -= maxSpeed;
}
velX = speed * Math.cos(rotationAngle);
velY = speed * Math.sin(rotationAngle);
locX += secondsElapsed * velX;
locY += secondsElapsed * velY;
double rotation = 0;
if (controls.isLeftHeld()) {
rotation -= rotationRate;
}
if (controls.isRightHeld()) {
rotation += rotationRate;
}
rotationAngle += secondsElapsed * rotation;
// Cap the angle so it can never e.g. get so
// large that it loses precision.
if (rotationAngle > 2 * Math.PI) {
rotationAngle -= 2 * Math.PI;
}
if (controls.isFireHeld()) {
Point2D.Double tipLoc = getTip();
Bullet bullet = new Bullet(tipLoc.x, tipLoc.y, rotationAngle);
bullets.add(bullet);
}
}
@Override
void draw(Graphics2D g2) {
Graphics2D copy = (Graphics2D) g2.create();
copy.setColor(Color.RED);
// Translate to the ship's location.
copy.translate(locX, locY);
// Rotate the ship around its center.
Point2D.Double center = getCenter();
// The PI/2 offset is necessary because the
// polygon points are defined with the ship
// already vertical, i.e. at an angle of -PI/2.
copy.rotate(rotationAngle + (Math.PI / 2), center.x, center.y);
copy.fill(shape);
}
}
class Bullet extends AbstractGameObject {
Ellipse2D.Double shape = new Ellipse2D.Double();
Bullet(double initialX, double initialY, double initialRotation) {
super(initialX, initialY);
maxSpeed = 512;
rotationAngle = initialRotation;
velX = maxSpeed * Math.cos(rotationAngle);
velY = maxSpeed * Math.sin(rotationAngle);
double radius = 3;
shape.setFrame(-radius, -radius, 2 * radius, 2 * radius);
}
@Override
void update(double secondsElapsed) {
locX += secondsElapsed * velX;
locY += secondsElapsed * velY;
}
@Override
void draw(Graphics2D g2) {
Graphics2D copy = (Graphics2D) g2.create();
copy.setColor(Color.BLACK);
copy.translate(locX, locY);
copy.fill(shape);
}
}
// See https://docs.oracle.com/javase/tutorial/uiswing/misc/keybinding.html
class Controls {
final Set<Integer> keysHeld = new HashSet<>();
Controls() {
bind(KeyEvent.VK_A, "left");
bind(KeyEvent.VK_D, "right");
bind(KeyEvent.VK_W, "up");
bind(KeyEvent.VK_S, "down");
bind(KeyEvent.VK_SPACE, "fire");
}
boolean isLeftHeld() { return keysHeld.contains(KeyEvent.VK_A); }
boolean isRightHeld() { return keysHeld.contains(KeyEvent.VK_D); }
boolean isUpHeld() { return keysHeld.contains(KeyEvent.VK_W); }
boolean isDownHeld() { return keysHeld.contains(KeyEvent.VK_S); }
boolean isFireHeld() { return keysHeld.contains(KeyEvent.VK_SPACE); }
void bind(int keyCode, String name) {
bind(keyCode, name, true);
bind(keyCode, name, false);
}
void bind(int keyCode, String name, boolean isOnRelease) {
KeyStroke stroke = KeyStroke.getKeyStroke(keyCode, 0, isOnRelease);
name += isOnRelease ? ".released" : ".pressed";
panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)
.put(stroke, name);
panel.getActionMap()
.put(name, new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
if (isOnRelease) {
keysHeld.remove(keyCode);
} else {
keysHeld.add(keyCode);
}
}
});
}
}
// This returns the usable size of the display which
// the JFrame resides in, as described here:
// http://docs.oracle.com/javase/8/docs/api/java/awt/GraphicsEnvironment.html#getMaximumWindowBounds--
static Dimension getMaximumWindowSize(JFrame frame) {
GraphicsConfiguration config = frame.getGraphicsConfiguration();
Dimension size = config.getBounds().getSize();
Insets insets = Toolkit.getDefaultToolkit().getScreenInsets(config);
size.width -= insets.left + insets.right;
size.height -= insets.top + insets.bottom;
return size;
}
}
AffineTransform transform = new AffineTransform();
@Override
void update(double secondsElapsed) {
...
// Clear the previous translation and rotation.
transform.setToIdentity();
// Set to current.
transform.translate(locX, locY);
Point2D.Double center = getCenter();
transform.rotate(rotationAngle + (Math.PI / 2), center.x, center.y);
if (controls.isFireHeld()) {
Point2D.Double tip = new Point2D.Double(0, 0);
transform.transform(tip, tip);
Bullet bullet = new Bullet(tip.x, tip.y, rotationAngle);
bullets.add(bullet);
}
}