Billboard with lighting problem

Troubleshooting graphics
1

Hello,



First of I would like to show some code:

[java]

Quad q = new Quad(2, 2);

Geometry g = new Geometry(“Quad”, q);

Material mat = new Material(assetManager,

“Common/MatDefs/Light/Lighting.j3md”);

g.setMaterial(mat);

Texture tex = assetManager

.loadTexture(“Textures/Billboards/select_ring.png”);

mat.setTexture(“m_DiffuseMap”, tex);

mat.getAdditionalRenderState().setBlendMode(BlendMode.Alpha);



Node bb = new Node(“billboard”);

bb.addControl(new BillboardControl());

bb.attachChild(g);



rootNode.attachChild(bb);

DirectionalLight light= new DirectionalLight();

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

rootNode.addLight(light);

[/java]



The problem is that when I turn around directional light, I won’t see my billboard.

Or when I rotate around the billboard it dissapears.



Do you guys know what’s the problem here (I’m a beginner but the word normals sound related)?

2

To display both sides of the quad, use mat.getAdditionalRenderState().setFaceCullMode(FaceCullMode.FrontAndBack); (or something like that) For the directional light thing, we added AmbientLight in svn, if you are using alpha-3 you have to put a directional light on the opposite side as well as the directional light … well… is coming from one direction only :wink:

3

That hid it completely:

[java]

mat.getAdditionalRenderState().setFaceCullMode(FaceCullMode.FrontAndBack);

[/java]

Tried also:

[java]

mat.getAdditionalRenderState().setFaceCullMode(FaceCullMode.Off);//the same problem that in the beginnning

[/java]



Used ambient light only, then it is okay, as soon as I add a Directional light problem begins again.

[java]

public void simpleInitApp() {

flyCam.setMoveSpeed(10);



Quad q = new Quad(2, 2);

Geometry g = new Geometry("Quad", q);

Material mat = new Material(assetManager,

"Common/MatDefs/Light/Lighting.j3md");

g.setMaterial(mat);

Texture tex = assetManager

.loadTexture("Textures/Billboards/select_ring.png");

mat.setTexture("m_DiffuseMap", tex);

mat.getAdditionalRenderState().setBlendMode(BlendMode.Alpha);

mat.getAdditionalRenderState().setFaceCullMode(FaceCullMode.Off);

Node bb = new Node("billboard");

bb.addControl(new BillboardControl());

bb.attachChild(g);

AmbientLight amb = new AmbientLight();

rootNode.attachChild(bb);

DirectionalLight sun = new DirectionalLight();

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

rootNode.addLight(sun);

DirectionalLight sun2 = new DirectionalLight();

sun2.setDirection(new Vector3f(0.1f, 0.7f, 1.0f));

rootNode.addLight(sun2);

rootNode.addLight(amb);

}

[/java]

4

I tested it again, and actually it only dissapears at 1 point and then appears again.



Front all okay:





Side, all not okay:





It’s like some object is infront of it

5

And which is even more weird is what happens when I comment out blendmode and cullmode lines.



Now I move to the “side” - it is like 1 side is with alpha the other side is without alpha:





This is how it happens:

6

Here is the test case:







[java]

package test;



import com.jme3.app.SimpleApplication;

import com.jme3.light.AmbientLight;

import com.jme3.light.DirectionalLight;

import com.jme3.material.Material;

import com.jme3.math.Vector3f;

import com.jme3.scene.Geometry;

import com.jme3.scene.Node;

import com.jme3.scene.control.BillboardControl;

import com.jme3.scene.shape.Quad;

import com.jme3.texture.Texture;



public class TestBill extends SimpleApplication {



@Override

public void simpleInitApp() {

flyCam.setMoveSpeed(10);



Quad q = new Quad(2, 2);

Geometry g = new Geometry(“Quad”, q);

Material mat = new Material(assetManager,

“Common/MatDefs/Light/Lighting.j3md”);

g.setMaterial(mat);

Texture tex = assetManager

.loadTexture(“Textures/Billboards/select_ring.png”);

mat.setTexture(“m_DiffuseMap”, tex);

// mat.getAdditionalRenderState().setBlendMode(BlendMode.Alpha);

// mat.getAdditionalRenderState().setFaceCullMode(FaceCullMode.FrontAndBack);

Node bb = new Node(“billboard”);

bb.addControl(new BillboardControl());

bb.attachChild(g);

AmbientLight amb = new AmbientLight();

rootNode.attachChild(bb);

DirectionalLight sun = new DirectionalLight();

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

rootNode.addLight(sun);

DirectionalLight sun2 = new DirectionalLight();

sun2.setDirection(new Vector3f(0.1f, 0.7f, 1.0f));

rootNode.addLight(sun2);

rootNode.addLight(amb);

}



public static void main(String[] args) {

TestBill app = new TestBill();

app.start();

}

}

[/java]

7

Forgot to set m_Shininess? You have to set it on all lighting materials (REGARDLESS if you use specularity or not), otherwise NVIDIA cards won’t display it correctly.

8

Okay I switched to another material type which corrected that problem but now I can’t get the transparency right:

[java]

Quad q = new Quad(quadSize, quadSize);

Geometry g = new Geometry(“Quad”, q);

Material mat = new Material(assetManager,

“Common/MatDefs/Misc/SimpleTextured.j3md”);

g.setMaterial(mat);

Texture tex = assetManager

.loadTexture(“Textures/Billboards/select_ring.png”);

mat.setTexture(“ColorMap”, tex);

mat.getAdditionalRenderState().setBlendMode(BlendMode.Alpha);

[/java]

This doesn’t display transparency and I don’t know why not…



9

Try disabling zbuffer writes.

material.getAdditionalRenderState().setDepthWrite(false);

and see if it helps.



Alternatively, play with AlphaDiscardThreshold (set it to something like 0.5f for example).

10

Setting depth write false worked fine, can you explain me why? :slight_smile:

11

[java]

material.getAdditionalRenderState().setDepthWrite(false);

[/java]

That worked for transparency. But now I have the problem that the object that should be behind the billboard appears in front of it.

So I guess I need a better solution :frowning: