我怎样才能朝十字准线指向的方向拍摄？
使用JMonkey引擎，我正在创建一个游戏，我需要一艘船来射击其他船只。
因此，我根据用户输入创建了可以在屏幕上（向上，向下，向左，向右）移动的十字准线，因此用户可以瞄准某个地方。
现在我需要从我的船上射出一个大炮，朝着十字线的方向站立。
我怎样才能在十字准线指向的地方拍摄？
答案 0 :(得分：3)
您可以通过以下方式获取相机方向：
directionXYZ=cam.getDirection(); //Vector3f form
可以从以下位置获得职位：
positionXYZ=cam.getLocation(); //Vector3f
你可以进行光线投射：
Ray ray = new Ray(directionXYZ, positionXYZ);
然后可以收集碰撞数据：
shootables.collideWith(ray, results)
其中可拍摄的是“节点”。
最后，检查一下你想要的东西：
for (int i = 0; i < results.size(); i++) {
// For each hit, we know distance, impact point, name of geometry.
float dist = results.getCollision(i).getDistance();
Vector3f pt = results.getCollision(i).getContactPoint();
String hit = results.getCollision(i).getGeometry().getName();
System.out.println("* Collision #" + i);
System.out.println(" You shot " + hit + " at " + pt + ", " + dist + " wu away.");
}
答案 1 :(得分：1)
我对这个问题的解读是，目的不是拍摄相机所朝向的位置，而是光标（不在屏幕中央）指向的位置。
这可以使用cam.getWorldCoordinates(screenPosition, zDepth);命令来实现，这将返回空间中的3D点，该点将最终位于屏幕上的screenPosition点。因此，如果我们在zDepth为零时创建一个点，在zDepth为1时创建一个点，我们可以创建一个从光标位置向外传播的光线，这样就可以选择光标“过度”的任何东西。 screenPosition是从窗口左下角开始的像素
使用此技术的示例程序如下，基于hello picking的第二部分。
在我的例子中，使用键盘（H，J，K，U）移动光标，但也可以使用鼠标点击（但我使用鼠标环顾四周）
import com.jme3.app.SimpleApplication;
import com.jme3.collision.CollisionResults;
import com.jme3.font.BitmapText;
import com.jme3.input.KeyInput;
import com.jme3.material.Material;
import com.jme3.math.ColorRGBA;
import com.jme3.math.Ray;
import com.jme3.math.Vector2f;
import com.jme3.math.Vector3f;
import com.jme3.renderer.RenderManager;
import com.jme3.scene.Geometry;
import com.jme3.scene.Node;
import com.jme3.scene.shape.Box;
public class Main extends SimpleApplication {
public static KeyBindings keyBindings;
public Vector2f cursorPosition=new Vector2f(100,100);
public Node shootables=new Node();
public Node crossHairNode=new Node();
public static void main(String[] args) {
Main app = new Main();
app.start();
}
@Override
public void simpleInitApp() {
//bind keys to move cursor
keyBindings=new KeyBindings(inputManager); //for managing keystrokes
keyBindings.registerKeyBinding(KeyInput.KEY_SPACE, "fire");
keyBindings.registerKeyBinding(KeyInput.KEY_U, "up");
keyBindings.registerKeyBinding(KeyInput.KEY_J, "down");
keyBindings.registerKeyBinding(KeyInput.KEY_H, "left");
keyBindings.registerKeyBinding(KeyInput.KEY_K, "right");
initGui();
Box b = new Box(Vector3f.ZERO, 2, 2, 2);
Geometry geom = new Geometry("BigBox", b);
Box b2 = new Box(Vector3f.ZERO, 1, 1, 1);
Geometry geom2 = new Geometry("SmallBox", b2);
geom2.setLocalTranslation(3, 0, 3);
Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
mat.setColor("Color", ColorRGBA.Blue);
geom.setMaterial(mat);
geom2.setMaterial(mat);
rootNode.attachChild(shootables);
shootables.attachChild(geom);
shootables.attachChild(geom2);
}
@Override
public void simpleUpdate(float tpf) {
updateCrossHairs();
if (keyBindings.getBinding("fire").hasBecomeTrueSinceLastAccess()){
CollisionResults results = new CollisionResults();
Vector3f cursor3dLocation = cam.getWorldCoordinates(
new Vector2f(cursorPosition.x, cursorPosition.y), 0f).clone();
Vector3f dir = cam.getWorldCoordinates(
new Vector2f(cursorPosition.x, cursorPosition.y), 1f).subtractLocal(cursor3dLocation).normalizeLocal();
Ray ray = new Ray(cursor3dLocation, dir);
shootables.collideWith(ray, results);
if (results.size()>0){
resultsText.setText("Hit: " + results.getClosestCollision().getGeometry().getName());
resultsText.setLocalTranslation(settings.getWidth()-resultsText.getLineWidth(),resultsText.getLineHeight(), 0);
}else{
resultsText.setText("Missed");
resultsText.setLocalTranslation(settings.getWidth()-resultsText.getLineWidth(),resultsText.getLineHeight(), 0);
}
}
}
private void updateCrossHairs(){
if (keyBindings.getBinding("up").getValue()==true){
cursorPosition.y+=1;
}
if (keyBindings.getBinding("down").getValue()==true){
cursorPosition.y+=-1;
}
if (keyBindings.getBinding("left").getValue()==true){
cursorPosition.x+=-1;
}
if (keyBindings.getBinding("right").getValue()==true){
cursorPosition.x+=+1;
}
crossHairNode.setLocalTranslation(cursorPosition.x - crossHair.getLineWidth()/2,cursorPosition.y + crossHair.getLineHeight()/2, 0);
}
BitmapText crossHair;
BitmapText instructions;
BitmapText resultsText;
private void initGui() {
setDisplayStatView(false);
guiFont = assetManager.loadFont("Interface/Fonts/Default.fnt");
crossHair = new BitmapText(guiFont, false);
crossHair.setSize(guiFont.getCharSet().getRenderedSize() * 2);
crossHair.setText("+"); // crosshairs
crossHairNode.setLocalTranslation(cursorPosition.x - crossHair.getLineWidth()/2,cursorPosition.y + crossHair.getLineHeight()/2, 0);
guiNode.attachChild(crossHairNode);
crossHairNode.attachChild(crossHair);
instructions= new BitmapText(guiFont, false);
instructions.setSize(guiFont.getCharSet().getRenderedSize());
instructions.setText("Move cross hairs with U,H,J,K keys, fire with space \n (WSAD moves camera position and look with mouse)");
instructions.setLocalTranslation(0, settings.getHeight(), 0);
guiNode.attachChild(instructions);
resultsText= new BitmapText(guiFont, false);
resultsText.setSize(guiFont.getCharSet().getRenderedSize());
resultsText.setText("Press Space to fire");
resultsText.setLocalTranslation(settings.getWidth()-resultsText.getLineWidth(),resultsText.getLineHeight(), 0);
guiNode.attachChild(resultsText);
}
@Override
public void simpleRender(RenderManager rm) {
//TODO: add render code
}
}
键绑定，仅用于控制光标移动：
import com.jme3.input.InputManager;
import com.jme3.input.KeyInput;
import com.jme3.input.controls.ActionListener;
import com.jme3.input.controls.KeyTrigger;
import com.jme3.input.controls.MouseButtonTrigger;
import java.util.ArrayList;
import java.util.Locale;
public class KeyBindings implements ActionListener{
private InputManager inputManager;
private ArrayList<String> bindingString=new ArrayList<String>(100);
private ArrayList<KeyBinding> binding=new ArrayList<KeyBinding>(100);
public KeyBindings(InputManager inputManager){
this.inputManager=inputManager;
}
public void registerKeyBinding(int key,String bindingName){
bindingName=preprocess(bindingName);
inputManager.addMapping( bindingName, new KeyTrigger(key));
inputManager.addListener(this, bindingName);
binding.add(new KeyBinding());
bindingString.add(bindingName);
}
public void registerMouseBinding(int button,String bindingName){
bindingName=preprocess(bindingName);
inputManager.addMapping( bindingName, new MouseButtonTrigger(button));
inputManager.addListener(this, bindingName);
binding.add(new KeyBinding());
bindingString.add(bindingName);
}
public KeyBinding getBinding(String bindingName){
//get which binding we're after
bindingName=preprocess(bindingName);
int index=bindingString.indexOf(bindingName);
if (index!=-1){
return binding.get(index);
}else{
return null;
}
}
public void onAction(String bindingName, boolean isPressed, float tpf) {
bindingName=preprocess(bindingName);
//get which binding we're after
int index=bindingString.indexOf(bindingName);
if (index!=-1){
binding.get(index).setValue(isPressed);
}
}
private String preprocess(String string){
return string.toUpperCase();
}
}
public class KeyBinding {
private boolean value;
private boolean changedSinceLastAccess; //to avoid multiclicks etc
private boolean valueTrueSinceLastAccess;
public void setValue(boolean value){
this.value=value;
changedSinceLastAccess=true;
if (value==true){
valueTrueSinceLastAccess=true;
}
}
public boolean hasChangedSinceLastAccess(){
return changedSinceLastAccess;
}
public boolean hasBecomeTrueSinceLastAccess(){
//this collects any trues since the last access, is good for things like mouse clicks,
//which are instantaneous and you want then recorded on the next tick
if (valueTrueSinceLastAccess==true){
valueTrueSinceLastAccess=false;
return true;
}else{
return false;
}
}
public boolean getValue(){
changedSinceLastAccess=false;
valueTrueSinceLastAccess=false;
return value;
}
public boolean getValue_withoutNotifying(){
return value;
}
}