[Solved]understanding zPos of cam.getWorldCoordinates(screenPos, zPos) jme3 r7243

Troubleshooting General Help
1

Hi! Can someone please explain what zPos does ?

I am looking in the following TestMousePick.java jme3 example, but I am confused,

pre type="java"
Vector3f origin = cam.getWorldCoordinates(inputManager.getCursorPosition(), 0.0f);


Vector3f direction = cam.getWorldCoordinates(inputManager.getCursorPosition(), 0.3f);
/pre

if 0.3f supposed to be the Z axis coord, if so being positive doesn’t it mean it’s behind camera and thus direction would be toward the camera? yet the ray goes in opposite direction from camera to scene

I looked but I’m not smart enough to understand its coding…

pre type="java"
/*

  • Copyright © 2009-2010 jMonkeyEngine

  • All rights reserved.


    *

  • Redistribution and use in source and binary forms, with or without

  • modification, are permitted provided that the following conditions are

  • met:


    *

    • Redistributions of source code must retain the above copyright

  • notice, this list of conditions and the following disclaimer.


    *

    • Redistributions in binary form must reproduce the above copyright

  • notice, this list of conditions and the following disclaimer in the

  • documentation and/or other materials provided with the distribution.


    *

    • Neither the name of ‘jMonkeyEngine’ nor the names of its contributors

  • may be used to endorse or promote products derived from this software

  • without specific prior written permission.


    *

  • THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

  • “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

  • TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

  • PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR

  • CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

  • EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

  • PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

  • PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

  • LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

  • NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

  • SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


    /





    package jme3test.collision;





    import com.jme3.app.SimpleApplication;


    import com.jme3.collision.CollisionResult;


    import com.jme3.collision.CollisionResults;


    import com.jme3.light.DirectionalLight;


    import com.jme3.material.Material;


    import com.jme3.math.ColorRGBA;


    import com.jme3.math.Quaternion;


    import com.jme3.math.Ray;


    import com.jme3.math.Vector3f;


    import com.jme3.scene.Geometry;


    import com.jme3.scene.Node;


    import com.jme3.scene.Spatial;


    import com.jme3.scene.debug.Arrow;


    import com.jme3.scene.shape.Box;


    import com.jme3.scene.shape.Sphere;





    public class TestMousePick extends SimpleApplication {





    public static void main(String[] args) {


    TestMousePick app = new TestMousePick();


    app.start();


    }





    Node shootables;


    Geometry mark;





    @Override


    public void simpleInitApp() {


    // flyCam.setEnabled(false);


    flyCam.setDragToRotate(true);


    flyCam.setMoveSpeed(10f);


    initMark(); // a red sphere to mark the hit





    /    * create four colored boxes and a floor to shoot at: */


    shootables = new Node(“Shootables”);


    rootNode.attachChild(shootables);


    shootables.attachChild(makeCube(“a Dragon”, -2f, 0f, 1f));


    shootables.attachChild(makeCube(“a tin can”, 1f, -2f, 0f));


    shootables.attachChild(makeCube(“the Sheriff”, 0f, 1f, -2f));


    shootables.attachChild(makeCube(“the Deputy”, 1f, 0f, -4f));


    shootables.attachChild(makeFloor());


    shootables.attachChild(makeCharacter());


    }





    @Override


    public void simpleUpdate(float tpf){


    Vector3f origin = cam.getWorldCoordinates(inputManager.getCursorPosition(), 0.0f);


    Vector3f direction = cam.getWorldCoordinates(inputManager.getCursorPosition(), 0.3f);


    System.out.println("origin : "+origin);


    System.out.println("direction: "+direction);


    direction.subtractLocal(origin).normalizeLocal();


    System.out.println("origin : "+origin);


    System.out.println("direction: “+direction);





    Ray ray = new Ray(origin, direction);


    CollisionResults results = new CollisionResults();


    shootables.collideWith(ray, 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).getWorldContactPoint();

// String hit = results.getCollision(i).getGeometry().getName();

// System.out.println("* Collision #" + i);

// System.out.println(" You shot " + hit + " at " + pt + ", " + dist + " wu away.");

// }

if (results.size() > 0) {

CollisionResult closest = results.getClosestCollision();

mark.setLocalTranslation(closest.getContactPoint());



Quaternion q = new Quaternion();

q.lookAt(closest.getContactNormal(), Vector3f.UNIT_Y);

mark.setLocalRotation(q);



rootNode.attachChild(mark);

} else {

rootNode.detachChild(mark);

}

}



/** A cube object for target practice */

protected Geometry makeCube(String name, float x, float y, float z) {

Box box = new Box(new Vector3f(x, y, z), 1, 1, 1);

Geometry cube = new Geometry(name, box);

Material mat1 = new Material(assetManager, "Common/MatDefs/Misc/SolidColor.j3md");

mat1.setColor("Color", ColorRGBA.randomColor());

cube.setMaterial(mat1);

return cube;

}



/** A floor to show that the "shot" can go through several objects. */

protected Geometry makeFloor() {

Box box = new Box(new Vector3f(0, -4, -5), 15, .2f, 15);

Geometry floor = new Geometry("the Floor", box);

Material mat1 = new Material(assetManager, "Common/MatDefs/Misc/SolidColor.j3md");

mat1.setColor("Color", ColorRGBA.Gray);

floor.setMaterial(mat1);

return floor;

}



/** A red ball that marks the last spot that was "hit" by the "shot". */

protected void initMark() {

Arrow arrow = new Arrow(Vector3f.UNIT_Z.mult(2f));

arrow.setLineWidth(3);



//Sphere sphere = new Sphere(30, 30, 0.2f);

mark = new Geometry("BOOM!", arrow);

//mark = new Geometry("BOOM!", sphere);

Material mark_mat = new Material(assetManager, "Common/MatDefs/Misc/SolidColor.j3md");

mark_mat.setColor("Color", ColorRGBA.Red);

mark.setMaterial(mark_mat);

}



protected Spatial makeCharacter() {

// load a character from jme3test-test-data

Spatial golem = assetManager.loadModel("Models/Oto/Oto.mesh.xml");

golem.scale(0.5f);

golem.setLocalTranslation(-1.0f, -1.5f, -0.6f);



// We must add a light to make the model visible

DirectionalLight sun = new DirectionalLight();

sun.setDirection(new Vector3f(-0.1f, -0.7f, -1.0f).normalizeLocal());

golem.addLight(sun);

return golem;

}

}


`/pre`
2

No, zPos is the z coord in view space (also called camera space), meaning, the space which origin is the camera. In this space positive Z go toward the screen.

1 Like