我正在使用 JMonkeyEngine 制作 Java 游戏，并且我按照他们网站上的教程在墙上射球（子弹）。我知道一切是如何工作的，但是当我增加子弹的速度时，它会直接穿过墙壁。
现在我知道发生这种情况的原因（因为子弹每帧移动太快而无法注册碰撞）。我也知道如何解决这个问题，我在他们的网站（JMonkeyEngine）上找到了以下方法。
setCcdMotionThreshold(0f)
但是谁能告诉我这是如何实现的，或者我在哪里可以找到使用它的人的样本？
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简介
连续碰撞检测(ccd) 处理子弹与纸张的问题。快速移动的物体在一个时间步长是薄物体的一侧，而在下一个时间步长是另一侧，导致物理引擎认为根本没有发生碰撞。另一方面，连续碰撞检测根本不使用时间步长。它在整个时间步长上创建一个扫描体积，并确定该扫描体积是否与任何物体发生碰撞。这既昂贵又不准确（因为为此使用了简单的圆形碰撞形状，而不是完整的碰撞形状）。
用法
连续碰撞检测设置在每个对象基础上，您可以同时拥有使用 ccd 的对象和不在同一场景中的对象，ccd 设置在物理对象上，如下所示
RigidBodyControl physicsObject = new RigidBodyControl(mass);
physicsObject.setCcdMotionThreshold(expectedWidthOfThinObject);
physicsObject.setCcdSweptSphereRadius(radiusOfSphereThatWillFullyContainObject);
- 您想将 expectedWidthOfThinObject 设置为可以逃脱的最高值；记住 ccd 既昂贵又不准确。将其设置为零将关闭 ccd
- 您希望将 radiusOfSphereThatWillFullyContainObject 设置得尽可能小，同时完全包含对象
完整示例
下面的源代码将显示使用连续碰撞检测和使用标准碰撞检测之间的区别。它发射两组球，一组快，一组慢，并以 5 秒的间隔打开和关闭 ccd。慢球总是与纸碰撞，快球只有在 ccd 开启时才会发生碰撞。
import com.jme3.app.SimpleApplication;
import com.jme3.bullet.BulletAppState;
import com.jme3.bullet.control.RigidBodyControl;
import com.jme3.font.BitmapText;
import com.jme3.material.Material;
import com.jme3.math.ColorRGBA;
import com.jme3.math.Vector3f;
import com.jme3.scene.Geometry;
import com.jme3.scene.shape.Box;
import com.jme3.scene.shape.Sphere;
public class BulletTest extends SimpleApplication {
public static void main(String args[]) {
BulletTest app = new BulletTest();
app.start();
}
/** Prepare the Physics Application State (jBullet) */
private BulletAppState bulletAppState;
/** Prepare Materials */
Material wall_mat;
Material slow_mat;
Material fast_mat;
Material floor_mat;
private RigidBodyControl brick_phy;
private static final Box box;
private static final Sphere sphere;
private RigidBodyControl floor_phy;
private static final Box floor;
/** dimensions used for wall */
private static final float brickLength = 2f;
private static final float brickWidth = 0.015f;
private static final float brickHeight = 1f;
static {
/** Initialize the cannon ball geometry */
sphere = new Sphere(32, 32, 0.1f, true, false);
/** Initialize the brick geometry */
box = new Box(brickWidth, brickHeight, brickLength);
/** Initialize the floor geometry */
floor = new Box(10f, 0.1f, 5f);
}
@Override
public void simpleInitApp() {
/** Set up Physics Game */
bulletAppState = new BulletAppState();
stateManager.attach(bulletAppState);
//bulletAppState.getPhysicsSpace().enableDebug(assetManager);
/** Configure cam to look at scene */
cam.setLocation(new Vector3f(0, 4f, 6f));
cam.lookAt(new Vector3f(2, 2, 0), Vector3f.UNIT_Y);
/** Initialize the scene, materials, and physics space */
initMaterials();
initWall();
initFloor();
setUpHUDText();
}
public static final float FIREPERIOD=0.5f;
double fireTimer=0;
public static final float SWEEPPERIOD=5f;
double sweepTimer=0;
boolean continuouslySweeping=true;
@Override
public void simpleUpdate(float tpf) {
fireTimer+=tpf;
sweepTimer+=tpf;
if (sweepTimer>SWEEPPERIOD){
sweepTimer=0;
continuouslySweeping=!continuouslySweeping;
}
hudText.setText("ContinouslySweeping=" + continuouslySweeping + "(" + (int)(SWEEPPERIOD-sweepTimer) + ")" );
if (fireTimer>FIREPERIOD){
fireTimer=0;
makeCannonBall(new Vector3f(-4,3,0),new Vector3f(6,4,0),slow_mat,continuouslySweeping); //slow arcing ball
makeCannonBall(new Vector3f(-4,3,-0.5f),new Vector3f(10,1,0),fast_mat,continuouslySweeping); //fast straight ball
}
}
public BitmapText hudText;
private void setUpHUDText(){
hudText = new BitmapText(guiFont, false);
hudText.setSize(guiFont.getCharSet().getRenderedSize()); // font size
hudText.setColor(ColorRGBA.White); // font color
hudText.setText("ContinouslySweeping=true"); // the text
hudText.setLocalTranslation(300, hudText.getLineHeight(), 0); // position
guiNode.attachChild(hudText);
}
/** Initialize the materials used in this scene. */
public void initMaterials() {
wall_mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
wall_mat.setColor("Color", ColorRGBA.Blue);
fast_mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
fast_mat.setColor("Color", ColorRGBA.Red);
slow_mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
slow_mat.setColor("Color", ColorRGBA.Green);
floor_mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
floor_mat.setColor("Color", ColorRGBA.Gray);
}
/** Make a solid floor and add it to the scene. */
public void initFloor() {
Geometry floor_geo = new Geometry("Floor", floor);
floor_geo.setMaterial(floor_mat);
floor_geo.setLocalTranslation(0, -0.1f, 0);
this.rootNode.attachChild(floor_geo);
/* Make the floor physical with mass 0.0f! */
floor_phy = new RigidBodyControl(0.0f);
floor_geo.addControl(floor_phy);
bulletAppState.getPhysicsSpace().add(floor_phy);
}
/** This loop builds a wall out of individual bricks. */
public void initWall() {
Vector3f location=new Vector3f(2,2,0);
Geometry brick_geo = new Geometry("brick", box);
brick_geo.setMaterial(wall_mat);
rootNode.attachChild(brick_geo);
/** Position the brick geometry */
brick_geo.setLocalTranslation(location);
//paper thin objects will fall down, mass 0 clamps it in position
brick_phy = new RigidBodyControl(0);
/** Add physical brick to physics space. */
brick_geo.addControl(brick_phy);
bulletAppState.getPhysicsSpace().add(brick_phy);
}
public void makeCannonBall(Vector3f startPoint, Vector3f initialVelocity, Material material, boolean continuouslySwept) {
/** Create a cannon ball geometry and attach to scene graph. */
Geometry ball_geo = new Geometry("cannon ball", sphere);
ball_geo.setMaterial(material);
rootNode.attachChild(ball_geo);
/** Position the cannon ball */
ball_geo.setLocalTranslation(startPoint);
/** Make the ball physcial with a mass > 0.0f */
RigidBodyControl ball_phy = new RigidBodyControl(1f);
/** Add physical ball to physics space. */
ball_geo.addControl(ball_phy);
bulletAppState.getPhysicsSpace().add(ball_phy);
/** Accelerate the physcial ball to shoot it. */
ball_phy.setLinearVelocity(initialVelocity);
if (continuouslySwept){
ball_phy.setCcdMotionThreshold(0.015f);
ball_phy.setCcdSweptSphereRadius(0.01f);
}
}
}
连续检测两组球的弹跳情况（球从左上角进入）：
随着连续检测快速球组（红色）穿过纸，就好像它不存在一样（偶尔慢球（绿色）也会穿过）：
于 2013-07-19T09:16:03.017 回答