[Solved] If I lookAt() a geometry… the geometry desappear!

Troubleshooting General Help
1

Hy,



I have an geometry “charge” that is a sphere



[java]

Sphere sphereCharge = new Sphere(10, 10, 2f);

charge = new Geometry(“tete”, sphereCharge);

charge.setMaterial(mat);

[/java]



and in the method simpleUpdate, when i look at “Charge”, Charge desapear. (but the camera look at Charge)



[java]

cam.lookAt(charge.getWorldTranslation(), Vector3f.UNIT_Y);

[/java]



Should i do something different ? should i create another Node who ll be at the same position than “charge” ?



Just wondering the best way to do it :wink:



thanks

2

No, it should work. I guess it might have to do with the “local updates” that @Momoko_Fan built in when you use getWorldXXX without calling rootNode.updateGeometricState() before… Try adding rootNode.updateGeometricState() at the beginning of your update method.

Cheers,

Normen

3

no sorry rootNode.updateGeometricState() at the beginning of simpleupdate don t solve the problem

4

in fact, i just discover that "charge didn t desappear, but returned to 0,0,0 local coordinates…

5

If that happens when you do the rootNode.updateGeometricState() still the problem is most likely in your code.

6

Hy Normen,



I created an exemple to show the problem



[java]package jme3test.helloworld;



import com.jme3.app.SimpleApplication;

import com.jme3.material.Material;

import com.jme3.math.ColorRGBA;

import com.jme3.math.FastMath;

import com.jme3.math.Vector3f;

import com.jme3.scene.Geometry;

import com.jme3.scene.shape.Box;

import com.jme3.scene.shape.Sphere;

import com.jme3.system.AppSettings;



public class HelloLookAtMe extends SimpleApplication{



private Geometry charge;

int cpt = 0;



public static void main(String[] args){

HelloLookAtMe app = new HelloLookAtMe();

AppSettings settings = new AppSettings(true);

settings.setResolution(1280, 720);

settings.setFrameRate(60);

app.setSettings(settings);

app.setShowSettings(false);

app.start();

}



@Override

public void simpleInitApp() {

Material mat = new Material(assetManager, “Common/MatDefs/Misc/WireColor.j3md”);

mat.setColor(“m_Color”, ColorRGBA.Blue);



Box boxBase = new Box(Vector3f.ZERO, 2, 2, 2);

Geometry base = new Geometry(“Box”, boxBase);

base.setMaterial(mat);



Sphere sphereCharge = new Sphere(10, 10, 2f);

charge = new Geometry(“tete”, sphereCharge);

charge.setMaterial(mat);



rootNode.attachChild(base);

rootNode.attachChild(charge);



cam.setLocation(new Vector3f(0, 0, 30f));

cam.lookAt(Vector3f.ZERO, new Vector3f(0, 1, 0));

cam.setFrustumFar(500);

}



public void simpleUpdate(float tpf) {

rootNode.updateGeometricState();// ?

charge.setLocalTranslation(0, 10*FastMath.sin(cpt++/100.0f), 0);

cam.lookAt(charge.getWorldTranslation(), Vector3f.UNIT_Y);

}

}[/java]



if you comment the last line [java]am.lookAt(charge.getWorldTranslation(), Vector3f.UNIT_Y);[/java], you ll see the ball moving (and camera don t)



if you don t comment it, you ll see the camera folowing the movement of the ball, but the ball stay a the origin point.



What do you think ?

7

Try to switch lines 50&51 so that updateGeometric() is called after you modified the spatial. If that works the problem lies in the “local updates” as I suspected earlier.

8

So yeah if updateGeometric() is called after having made the move of the geometry it works well :slight_smile: (sorry i only tried before as sou said)



Thanks for this help, That was very helpfull



Zoff

9

is there a way to say “solved” for a topic ?

10

Seems like @Momoko_Fan has to fix something in the local updates then… You can add [solved] before the topic title if you want…

Thanks for the feedback!

Normen