SDK LOD produce more triangles than it was before

Yolo. I am trying to generate LOD via sdk. However, it generates LOD levels but creates MORE triangles that it was by default
Before generating LODs:

After generating LODs:

I converted models directly from blenders without any modificators. Does anybody know how to fix this issue and is it any solution exists? It happens with every model. Starting with human and ending with plants.

It happens both with Reduction and Constant.

Yes , I noticed that too.

I did test it both with blender importer and xbuf importer.
This just happens for models imported with blender importer.
And actually it does not create MORE triangles after creating LOD but it shows wrong numbers (it shows less) before creating LOD. I do not know what really goes wrong.

So for example I have a model, when i import it with xbuf importer the number is for example 100 triangles , but when i import it with blender importer the number is 10 triangles.
Then after i generate LOD for model imported with xbuf the number of triangles are 100 again , but after i generate LOD for model imported with blender importer now it shows 100 for triangle numbers.

Can you please try it with Ogre to see what is the result ?

I used OGRE, converted the model to j3o and successfully added LODs.

So number of triangles are the same before and after adding LOD ?

Edit: No, number of triangles isn’t the same after adding LODs, you are right!

Okay

Just tested with HoverTank model from jme-testdata

with blender importer :
before adding LOD : 9692 triangles
after adding LOD ( on lod 0) : 29076 triangles

with ogre : it is the same before and after adding LOD
before adding LOD : 9692 triangles
after adding LOD ( on lod 0) : 9692 triangles

@CoreDevelopers please help

Idk what are the internals of Blender and xbuf loaders, but yeah it usually works with ogre.

Ogre usually works well for me too. Anyway maintainers of XBuf/Blender internals might be interested in this.

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Once i also reported an issue with JME LOD generator which was not working correctly on xbuf models but it is not fixed yet unfortunately.
But JME always allows you to find your own solution and this is what i love about JME.:slight_smile:
I am using Blender LOD generator instead (which has better result) and a modified version of LODControl. (by updating mesh on model)

Blender LOD Generator

It even works on Animated models

If you needed any help with using this i will be glad to help.

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Cool. So you get meshes from Blender with different count of vertices. And then just swapping these meshes depending on distance?

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Yes
And swapping is done by JME’s LodControl and i just modified a few lines of it to work with this.

Could you share please these lines?

Yes

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package com.overthemoon.gamecore.optimization.control;
import com.jme3.bounding.BoundingVolume;
import com.jme3.export.InputCapsule;
import com.jme3.export.JmeExporter;
import com.jme3.export.JmeImporter;
import com.jme3.export.OutputCapsule;
import com.jme3.math.FastMath;
import com.jme3.renderer.Camera;
import com.jme3.renderer.RenderManager;
import com.jme3.renderer.ViewPort;
import com.jme3.scene.Geometry;
import com.jme3.scene.Mesh;
import com.jme3.scene.Spatial;
import com.jme3.scene.control.AbstractControl;
import com.jme3.scene.control.AreaUtils;
import com.jme3.scene.control.Control;
import java.io.IOException;

/**
 * Determines what Level of Detail a spatial should be, based on how many pixels
 * on the screen the spatial is taking up. The more pixels covered, the more
 * detailed the spatial should be. It calculates the area of the screen that the
 * spatial covers by using its bounding box. When initializing, it will ask the
 * spatial for how many triangles it has for each LOD. It then uses that, along
 * with the trisPerPixel value to determine what LOD it should be at. It
 * requires the camera to do this. The controlRender method is called each frame
 * and will update the spatial's LOD if the camera has moved by a specified
 * amount.
 */
public class CustomeLodControl extends AbstractControl{

    private float trisPerPixel = 0.5f;
    private float distTolerance = 1f;
    private float lastDistance = 0f;
    private int lastLevel = 0;
    private int numLevels;
    private int[] numTris;
    private Mesh[] lodMeshes;
   
    /**
     * Creates a new
     * <code>LodControl</code>.
     */
    public CustomeLodControl() {
    }

    /**
     * Returns the distance tolerance for changing LOD.
     *
     * @return the distance tolerance for changing LOD.
     *
     * @see #setDistTolerance(float)
     */
    public float getDistTolerance() {
        return distTolerance;
    }

    /**
     * Specifies the distance tolerance for changing the LOD level on the
     * geometry. The LOD level will only get changed if the geometry has moved
     * this distance beyond the current LOD level.
     *
     * @param distTolerance distance tolerance for changing LOD
     */
    public void setDistTolerance(float distTolerance) {
        this.distTolerance = distTolerance;
    }

    /**
     * Returns the triangles per pixel value.
     *
     * @return the triangles per pixel value.
     *
     * @see #setTrisPerPixel(float)
     */
    public float getTrisPerPixel() {
        return trisPerPixel;
    }

    /**
     * Sets the triangles per pixel value. The
     * <code>LodControl</code> will use this value as an error metric to
     * determine which LOD level to use based on the geometry's area on the
     * screen.
     *
     * @param trisPerPixel triangles per pixel
     */
    public void setTrisPerPixel(float trisPerPixel) {
        this.trisPerPixel = trisPerPixel;
    }

    @Override
    public void setSpatial(Spatial spatial) {
        if (!(spatial instanceof Geometry)) {
            throw new IllegalArgumentException("LodControl can only be attached to Geometry!");
        }

        super.setSpatial(spatial);
        for(int i=0;i<lodMeshes.length;i++)
            lodMeshes[i].prepareForAnim(false);
        numLevels =  lodMeshes.length;
        numTris = new int[numLevels];
        for (int i = numLevels - 1; i >= 0; i--) {
            numTris[i] = lodMeshes[i].getTriangleCount();
        }
    }

    @Override
    public Control cloneForSpatial(Spatial spatial) {
        CustomeLodControl clone = (CustomeLodControl) super.cloneForSpatial(spatial);
        clone.lastDistance = 0;
        clone.lastLevel = 0;
        clone.numTris = numTris != null ? numTris.clone() : null;
        return clone;

    }

    @Override
    public Object jmeClone() {
        CustomeLodControl clone = (CustomeLodControl)super.jmeClone(); 
        clone.lastDistance = 0;
        clone.lastLevel = 0;
        clone.numTris = numTris != null ? numTris.clone() : null;
        return clone;
    }     
    
    @Override
    protected void controlUpdate(float tpf) {
    }

    protected void controlRender(RenderManager rm, ViewPort vp) {
        BoundingVolume bv = spatial.getWorldBound();

        Camera cam = vp.getCamera();
        float atanNH = FastMath.atan(cam.getFrustumNear() * cam.getFrustumTop());
        float ratio = (FastMath.PI / (8f * atanNH));
        float newDistance = bv.distanceTo(vp.getCamera().getLocation()) / ratio;
        int level;

        if (Math.abs(newDistance - lastDistance) <= distTolerance) {
            level = lastLevel; // we haven't moved relative to the model, send the old measurement back.
        } else if (lastDistance > newDistance && lastLevel == 0) {
            level = lastLevel; // we're already at the lowest setting and we just got closer to the model, no need to keep trying.
        } else if (lastDistance < newDistance && lastLevel == numLevels - 1) {
            level = lastLevel; // we're already at the highest setting and we just got further from the model, no need to keep trying.
        } else {
            lastDistance = newDistance;

            // estimate area of polygon via bounding volume
            float area = AreaUtils.calcScreenArea(bv, lastDistance, cam.getWidth());
            float trisToDraw = area * trisPerPixel;
            level = numLevels - 1;
            for (int i = numLevels; --i >= 0;) {
                if (trisToDraw - numTris[i] < 0) {
                    break;
                }
                level = i;
            }
            lastLevel = level;
        }

        ((Geometry)spatial).setMesh(lodMeshes[level]);
    }

    @Override
    public void write(JmeExporter ex) throws IOException {
        super.write(ex);
        OutputCapsule oc = ex.getCapsule(this);
        oc.write(trisPerPixel, "trisPerPixel", 1f);
        oc.write(distTolerance, "distTolerance", 1f);
        oc.write(numLevels, "numLevels", 0);
        oc.write(numTris, "numTris", null);
    }

    @Override
    public void read(JmeImporter im) throws IOException {
        super.read(im);
        InputCapsule ic = im.getCapsule(this);
        trisPerPixel = ic.readFloat("trisPerPixel", 1f);
        distTolerance = ic.readFloat("distTolerance", 1f);
        numLevels = ic.readInt("numLevels", 0);
        numTris = ic.readIntArray("numTris", null);
    }
    
    public void setLODs(Mesh[] lodMeshes){
        this.lodMeshes=lodMeshes;
    }

    public Mesh[] getLODs() {
        return lodMeshes;
    }
    
}

You set LODs in form of mesh array to method setLODs(Mesh[] lodMeshes) then you add control to your geometry. (Note you should add it to a Geometry not a Node)

Note that lodMeshes[0] should reference to models original mesh.

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Wow, thanks for sharing!

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Thanks!

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