Model loading without rendering

Troubleshooting graphics
1

Hi folks,



I noticed a misbehavior in the model conversion code. It is not possible to convert a stored model (in my case an .obj file model) without having the GL display created.

The following class will fail with a NullPointerException even if the URL stuff is set up correctly:

import com.jme.math.Vector3f;
import com.jme.scene.Node;
import com.jme.scene.Spatial;
import com.jme.util.export.binary.BinaryImporter;
import com.jmex.model.converters.ObjToJme;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.URL;

public class FailedGeomLoad {

    public FailedGeomLoad() {
        loadGeom();
    }
   
    public static void main(String[] args){
        FailedGeomLoad l = new FailedGeomLoad();
    }

    public void loadGeom() {
        ObjToJme conv = new ObjToJme();
        conv.setProperty("mtllib", GeomLoad.class.getClassLoader().getResource("loadtest/"));

        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        URL url = GeomLoad.class.getClassLoader().getResource("loadtest/ear1.obj");
        Node loadedNode = new Node();
        loadedNode.setLocalTranslation(new Vector3f(2, 0, 0));

        InputStream is = null;
        try {
            is = url.openStream();
        } catch (Exception err) {
            System.out.println("Could not open Model file: " + err);
        }

        try {

            // Converts the file into a jme usable file
            conv.convert(is, bout);

            // Used to convert the jme usable file to a TriMesh
            BinaryImporter binaryImporter = new BinaryImporter();
            ByteArrayInputStream in = new ByteArrayInputStream(bout.toByteArray());

            //importer returns a Loadable, cast to Node
            Spatial geom = (Spatial) binaryImporter.load(in);

        } catch (Exception err) {
            System.out.println("Error loading obj model:" + err);
            err.printStackTrace();
        }
    }
}





If you put the identical code in a subclass of SimpleGame it will work:

public class GeomLoad extends SimpleGame{

    public static void main(String[] args) {
        GeomLoad l = new GeomLoad();
        l.setDialogBehaviour(ALWAYS_SHOW_PROPS_DIALOG);
        l.start();
    }

    public void loadGeom() {
        ObjToJme conv = new ObjToJme();
        conv.setProperty("mtllib", GeomLoad.class.getClassLoader().getResource("loadtest/"));
       
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        URL url = GeomLoad.class.getClassLoader().getResource("loadtest/ear1.obj");
        Node loadedNode = new Node();
        loadedNode.setLocalTranslation(new Vector3f(2,0,0));
       
        InputStream is = null;
        try {
            is = url.openStream();
        } catch (Exception err) {
            System.out.println("Could not open Model file: " + err);
        }

        try {

            // Converts the file into a jme usable file
            conv.convert(is, bout);

            // Used to convert the jme usable file to a TriMesh
            BinaryImporter binaryImporter = new BinaryImporter();
            ByteArrayInputStream in = new ByteArrayInputStream(bout.toByteArray());

            //importer returns a Loadable, cast to Node
            Spatial geom = (Spatial) binaryImporter.load(in);
            loadedNode.attachChild(geom);
            rootNode.attachChild(loadedNode);
           
        } catch (Exception err) {
            System.out.println("Error loading obj model:" + err);
            err.printStackTrace();
        }

    }
 
    @Override
    protected void simpleInitGame() {
         loadGeom();
       
}



Notice that this class will convert the wavefront model without problems. For my case this is a highly inconvenient behavior, because my application does not all the time keeps open the rendering window.
Is there a way to load the spatial prior to opening the rendering window?

Greetings,
Marcus
2

You can use a DummyDisplaySystem instead.  I know that will work fine for loading most models without a display.  I've never tried switching back and forth though, so not sure how well that will work.

3

Thanks,

could you give a short code snippet, how to "use" the DummyDisplaySystem? Because the display system stuff seems to be done in the model conversion classes. Is there a way to tell them to use the DummyDisplaySystem?

4

You can just create the DummyDisplaySystem before using them…  see the main method in most of the FormatConverter classes.

5

Thanks, this works.

But one drawback of this approach is, that if you later render the models loaded via DummyDisplaySystem, they will not have any color / material settings. I guess this is because DummyDisplaySystem somehow overrides the RenderingStates during the import process.

Personally I can live with this behavior, but one should eventually think about if this is a bug or a feature?



Thanks again,

Marcus