Below is a slightly modified version of the physics demo, when you click on the wall bricks are removed instead of a cannonball being shot at it.
If the bricks are removed before the wall stops swaying the wall behaves as it should, and crumbles. if the wall stops moving before you remove a brick, the brick will happily defy gravity.
I get the feeling that this is just the work of an optimization, when motion stops physics stops and is only called again when there is a collision callback. Anyone know what’s up and how to fix it?
package jme3test.helloworld;
import com.jme3.app.SimpleApplication;
import com.jme3.asset.TextureKey;
import com.jme3.bullet.BulletAppState;
import com.jme3.bullet.control.RigidBodyControl;
import com.jme3.collision.CollisionResult;
import com.jme3.collision.CollisionResults;
import com.jme3.font.BitmapText;
import com.jme3.input.KeyInput;
import com.jme3.input.MouseInput;
import com.jme3.input.controls.ActionListener;
import com.jme3.input.controls.KeyTrigger;
import com.jme3.input.controls.MouseButtonTrigger;
import com.jme3.material.Material;
import com.jme3.math.Ray;
import com.jme3.math.Vector2f;
import com.jme3.math.Vector3f;
import com.jme3.scene.Geometry;
import com.jme3.scene.Node;
import com.jme3.scene.shape.Box;
import com.jme3.scene.shape.Sphere;
import com.jme3.scene.shape.Sphere.TextureMode;
import com.jme3.texture.Texture;
import com.jme3.texture.Texture.WrapMode;
/**
- Example 12 - how to give objects physical properties so they bounce and fall.
-
@author base code by double1984, updated by zathras
*/
class HelloPhysics extends SimpleApplication {
public static void main(String args[]) {
HelloPhysics app = new HelloPhysics();
app.start();
}
/** Prepare the Physics Application State (jBullet) */
private BulletAppState bulletAppState;
/** Prepare Materials */
Material wall_mat;
Material stone_mat;
Material floor_mat;
/** Prepare geometries and physical nodes for bricks and cannon balls. */
Node removables;
private RigidBodyControl brick_phy;
private static final Box box;
private RigidBodyControl ball_phy;
private static final Sphere sphere;
private RigidBodyControl floor_phy;
private static final Box floor;
/** dimensions used for bricks and wall */
private static final float brickLength = 0.48f;
private static final float brickWidth = 0.24f;
private static final float brickHeight = 0.12f;
static {
/** Initialize the cannon ball geometry /
sphere = new Sphere(32, 32, 0.4f, true, false);
sphere.setTextureMode(TextureMode.Projected);
/* Initialize the brick geometry /
box = new Box(Vector3f.ZERO, brickLength, brickHeight, brickWidth);
box.scaleTextureCoordinates(new Vector2f(1f, .5f));
/* Initialize the floor geometry */
floor = new Box(Vector3f.ZERO, 10f, 0.1f, 5f);
floor.scaleTextureCoordinates(new Vector2f(3, 6));
}
@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);
/** Add InputManager action: Left click triggers shooting. */
inputManager.addMapping("shoot",
new MouseButtonTrigger(MouseInput.BUTTON_LEFT));
inputManager.addListener(actionListener, "shoot");
removables = new Node("Removables");
rootNode.attachChild(removables);
/** Initialize the scene, materials, and physics space */
initMaterials();
initWall();
initFloor();
initKeys();
initCrossHairs();
}
/** Declaring the “Shoot” action and mapping to its triggers. /
private void initKeys() {
inputManager.addMapping(“Shoot”,
new KeyTrigger(KeyInput.KEY_SPACE), // trigger 1: spacebar
new MouseButtonTrigger(MouseInput.BUTTON_LEFT)); // trigger 2: left-button click
inputManager.addListener(actionListener, “Shoot”);
}
/* Initialize the materials used in this scene. */
public void initMaterials() {
wall_mat = new Material(assetManager, “Common/MatDefs/Misc/Unshaded.j3md”);
TextureKey key = new TextureKey(“Textures/Terrain/BrickWall/BrickWall.jpg”);
key.setGenerateMips(true);
Texture tex = assetManager.loadTexture(key);
wall_mat.setTexture(“ColorMap”, tex);
stone_mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
TextureKey key2 = new TextureKey("Textures/Terrain/Rock/Rock.PNG");
key2.setGenerateMips(true);
Texture tex2 = assetManager.loadTexture(key2);
stone_mat.setTexture("ColorMap", tex2);
floor_mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
TextureKey key3 = new TextureKey("Textures/Terrain/Pond/Pond.jpg");
key3.setGenerateMips(true);
Texture tex3 = assetManager.loadTexture(key3);
tex3.setWrap(WrapMode.Repeat);
floor_mat.setTexture("ColorMap", tex3);
}
/** 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() {
float startpt = brickLength / 4;
float height = 0;
for (int j = 0; j < 15; j++) {
for (int i = 0; i < 6; i++) {
Vector3f vt =
new Vector3f(i * brickLength * 2 + startpt, brickHeight + height, 0);
makeBrick(vt);
}
startpt = -startpt;
height += 2 * brickHeight;
}
}
/* This method creates one individual physical brick. /
public void makeBrick(Vector3f loc) {
/* Create a brick geometry and attach to scene graph. /
Geometry brick_geo = new Geometry(“brick”, box);
brick_geo.setMaterial(wall_mat);
/* Position the brick geometry /
brick_geo.setLocalTranslation(loc);
/* Make brick physical with a mass > 0.0f. */
brick_phy = new RigidBodyControl(2f);
/** Add physical brick to physics space. */
brick_geo.addControl(brick_phy);
bulletAppState.getPhysicsSpace().add(brick_phy);
removables.attachChild(brick_geo);
}
/** This method creates one individual physical cannon ball.
- By defaul, the ball is accelerated and flies
- from the camera position in the camera direction.*/
public void makeCannonBall() {
/** Create a cannon ball geometry and attach to scene graph. /
Geometry ball_geo = new Geometry(“cannon ball”, sphere);
ball_geo.setMaterial(stone_mat);
rootNode.attachChild(ball_geo);
/* Position the cannon ball /
ball_geo.setLocalTranslation(cam.getLocation());
/* Make the ball physcial with a mass > 0.0f /
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(cam.getDirection().mult(25));
}
private ActionListener actionListener = new ActionListener() {
public void onAction(String name, boolean keyPressed, float tpf) {
if (name.equals("Shoot") && !keyPressed) {
// 1. Reset results list.
CollisionResults results = new CollisionResults();
// 2. Aim the ray from cam loc to cam direction.
Ray ray = new Ray(cam.getLocation(), cam.getDirection());
// 3. Collect intersections between Ray and Shootables in results list.
removables.collideWith(ray, results);
// 4. Print the results
System.out.println("----- Collisions? " + results.size() + "-----");
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.");
}
// 5. Use the results (we mark the hit object)
if (results.size() > 0) {
// The closest collision point is what was truly hit:
Geometry closest = results.getClosestCollision().getGeometry();
// Let's interact - we mark the hit with a red dot.
bulletAppState.getPhysicsSpace().remove(closest.getControl(0));
removables.detachChild(closest);
bulletAppState.getPhysicsSpace().clearForces();
bulletAppState.getPhysicsSpace().applyGravity();
System.out.println("removing a "+closest.getName());
}
}
}
};
/** A plus sign used as crosshairs to help the player with aiming.*/
protected void initCrossHairs() {
guiNode.detachAllChildren();
guiFont = assetManager.loadFont(“Interface/Fonts/Default.fnt”);
BitmapText ch = new BitmapText(guiFont, false);
ch.setSize(guiFont.getCharSet().getRenderedSize() * 2);
ch.setText("+"); // fake crosshairs 
ch.setLocalTranslation( // center
settings.getWidth() / 2 - guiFont.getCharSet().getRenderedSize() / 3 * 2,
settings.getHeight() / 2 + ch.getLineHeight() / 2, 0);
guiNode.attachChild(ch);
}
}