Is it possible to update the texture coordinates on an existing object at runtime?

In producing a real terrain I now have an issue with sheer volume of data. After reading a few posts, it appears the way to reduce creation time and memory overhead on Android is to pre-create models, serialize them and then load on the mobile device.
The issue I have with this approach is that I want to change the texture (and texture size) on the model dynamically once it is loaded. i.e.  I have a 200x200 quad plane as a serialize'd model which, once loaded, I can assign either one 200x200 texture to it, or 4 x 100 or 16 x 50 texture's etc.

Is this possible, or do I have to stick with creating the plane dynamically at runtime as well?!

Thanks.

In terms of the original question, is object creation and texture loading thread-safe?

I am creating objects and loading textures in a separate thread and then passing the objects to a Handler in the renderer which adds them to the world from a Stack in onDrawFrame(). Randomly these objects are not being displayed (incidentally all the objects are map tiles - 2 triangles with one texture).

Logcat reports that 9 textures are loaded, 9 objects are added to the world/ compiled, but potentially only 4 will actually be displayed.

Should texture's be loaded and/ or objects created in the render thread as well as adding?

Hi all !
I'm trying to implement two things at the moment, and after three days its still driving me nuts!

Firstly, and most importantly, I'm trying to automatically 'clamp' objects to the ground....yes that old chestnut! I've read many a post here, but I just can't get a catch all that works for .obj models and in-built primitives (like a cube, which I seem to have fixed now incidentally)

In the app I either create a primitive, such as a cube, or load an .obj model and then add it to the scene through the following method;

public void addObjectsToWorld(A_Object3D[] objects) {

if (objects==null || sceneOrientation==null) return;
SimpleVector frontAxis = sceneOrientation.front.normalize();
SimpleVector upAxis = sceneOrientation.up.normalize();

// Align our object axis to the ECEF axis
for (A_Object3D obj : objects) {
if (obj.requiresOrientation) {
obj.setOrientation(frontAxis, upAxis);
}
obj.applyStyleRotations();
obj.build();
}

// Add...
theWorld.addObjects(objects);

// Now clamp objects to the floor if flagged to do so...
SimpleVector trans = new SimpleVector();

for (A_Object3D obj : objects) {
if (!obj.clampToGround) continue;

float dist = plane.calcMinDistance( obj.getTransformedCenter(), upAxis );

// Move object above plane by 20m and try again
if (dist==Object3D.COLLISION_NONE) {
trans.set( upAxis );
trans.scalarMul( -20f );
obj.translate( trans );

dist = plane.calcMinDistance( obj.getTransformedCenter(), upAxis );

// Couldn't collide, move to original position
if (dist==Object3D.COLLISION_NONE) {
trans.set( upAxis );
trans.scalarMul( 20f );
obj.translate( trans );
}
}

// Do the clamping...
if (dist!=Object3D.COLLISION_NONE) {
float htAdjust = obj.isPlane ? 0f : -obj.getMesh().getBoundingBox()[3];

Log.i(LOG_TAG, "Obj: "+obj.getParentFeatureID()+" Dist: "+(dist+htAdjust));
trans.set( upAxis );
trans.scalarMul( dist-obj.heightOffset+htAdjust );

// (paulscode) Grab a handle to the Object3D's world transformation matrix:
Matrix m = new Matrix( obj.getWorldTransformation() );
// Turn that into a rotation matrix:
float[] dm = m.getDump();
for( int i = 12; i < 15; i++ ) dm[i] = 0;
dm[15] = 1;
m.setDump( dm );
// Apply this rotation matrix to the translation vector:
trans.matMul( m );

obj.translate( trans );
}
}

The plane object is a transparent plane sat 2m below the camera position.
Adding additional planes (map tiles) through the above method works; adding cubes works, but .obj models (and an arrow which I'll get to in the minute) does not. The links should hopefully illustrate;

Screen1: Primitive models sat on ground, but .obj model floating


Screen2: Model the same size and axis alignment, but sat below plane (the rotating arrow is sat below the overlay).



It should be noted that the models (not mine!) are exported from Sketch-up with the swap YZ axis option enabled. To then align the axis to jPCT I use the following;

if (shapeName.endsWith(".obj") || shapeName.endsWith(".3ds")) {
ret = getShapeFromAssets(shapeName);
/* jPCT axis are rotated 180 around X axis,
* contrary to most graphics systems, so we rotate and then
* replace the matrix so this rotation is ignored in later
* translations and rotations */
ret.obj.rotateZ(PI);// Why Z, not X ??? (Is Z so North is aligned)
ret.obj.rotateMesh();
ret.obj.setRotationMatrix( new Matrix() );
ret.obj.getMesh().setLocked(true);
}

I can seem to get a decent value from calcMinDistance, one model is 0.09m, whereas the other is 19.4m. ??

As a secondary issue, I'm trying display an arrow permanently in front of the camera, at a fixed distance, but also clamped to the ground. I suspect a very similar problem as, again, the arrow is loaded from an .obj, added to as a child to a dummyObject at the camera position and then translated to be in front of the camera. With the arrow being 8m in front of the camera, calcMinDistance is returning 6.9 metres from the plane!!??

Many, many thanks to the person who tells me what stupid thing I'm doing!

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Hi Egon.
Thought I would post here as a general query.

Within my application I (can) re-use an object, such as a cube or arrow, many times... To save re-creation, memory and time I load each object type that is required into a HashMap with a name (like CUBE1) - if the same object is needed again, it is got from the Map and a new Object3D created from it via the Object3D( 'object_a' ) constructor (which I believe clones the original object).

This process also clones the textures assigned to object 'a' on object 'b' - which is fine except I want a different texture on object 'b' than 'a'. I set object 'b's texture to my newly required texture through obj.setTexture(), but it just <i>adds</i> a reference to the new texture, compared to replacing it. This would be fine, but I cannot remove/ change the reference to the original texture, therefore object 'b' now has two textures.

How can I re-use an object many times, whilst minimising replication, but keep changing the texture  - is there a way of doing obj.removeTexture(), obj.deleteTexture() or obj.replaceTexture() ?

Many thanks...

Hi.

I'm trying to remove objects from the world during runtime but keep getting a concurrent thread modification error.
I've searched the forum but it seems no-one else is getting this issue?!

I have extended the Object3D class to add a 'allow remove' flag. Every 30seconds within the onDrawFrame method the code below is called, which checks for the flag and calls theWorld.removeObject(o); In the second iteration of the while loop I get the exception and no items are removed from the world - This causes memory issues after some time as more and more objects are added to the world, with none of the old ones being removed.

Enumeration<Object3D> e = theWorld.getObjects();
int i = 0;
try {
while (e.hasMoreElements()) {
A_Object3D o = (A_Object3D) e.nextElement();
if (o.isRemoved()) {
theWorld.removeObject(o);
o=null;
i++;
}
}
} catch (Exception err) {
Log.w(LOG_TAG, "Failed during object removal: "+err.getMessage() );
}


I'll admit I'm not too surprised to get this error, but don't know how to safely remove objects from the world that are no longer required.
Does anyone have any suggestions - i.e. can this only be done within the renderer onPause() event??

Many thanks.

Hi.
I am trying to draw a basic grid of 100m size tiles at floor/ ground level within my scene (think '80s Tron!)
I thought the new Polyline() class would be idea for this but it doesn't get rendered at all. Would Polyline be the right choice for this, or should I be creating something with Plane() ? Incidentally I want to be able to switch it on and off, but I can't see a method for removing/ changing the visibility of poylines on World().
public static Polyline testPolyLine(SimpleVector origin) {
SimpleVector o = origin;

SimpleVector[] points = new SimpleVector[4];
points[0] = new SimpleVector(o.x,o.y,o.z-100);
points[1] = new SimpleVector(o.x,o.y,o.z+100);
points[2] = new SimpleVector(o.x,o.y-100,o.z);
points[3] = new SimpleVector(o.x,o.y+100,o.z);

return new Polyline(points, new RGBColor(130, 130, 130));

}
And at start-up (when a position is known)
getRenderer().getTheWorld().addPolyline( Utilities.testPolyLine( gridOrigin ) );

As a note; the java doc doesn't include the Polyline() class...

Many thanks in advance.

Hi,
Last week I implemented jPCT-AE within my AR application instead of using my own OpenGL renderer; and first-off let me say that it is excellent, providing many more features than I could possibly code myself!

Like many others, I have some issues with rotations, but I did previously have this working (along with GPS location updates) very well. Due to the the various coordinate systems in play, I am generating vectors to describe the direction the camera should be facing in ECEF coordinates. These vectors were fed to the renderer as below;

private float[] mLookMatrix = new float[16];

    public void setCameraPosition(CamPosition newCamera) {
    Matrix.setLookAtM(mLookMatrix, 0,
    newCamera.eyeX,
    newCamera.eyeY,
    newCamera.eyeZ,
    newCamera.frontX + newCamera.eyeX,
    newCamera.frontY + newCamera.eyeY,
    newCamera.frontZ + newCamera.eyeZ,
    newCamera.upX,
    newCamera.upY,
    newCamera.upZ);
   }

with the following function being called on each DrawFrame();

private void setViewAndProjection() {
        float[] modelMatrix = new float[16]; // model matrix (identity)
        Matrix.setIdentityM(modelMatrix, 0);
        Matrix.translateM(modelMatrix, 0, 0, 0, 0);

        // calculating the current model-view-projection matrix
        Matrix.frustumM(mProjMatrix, 0,
        -fSize, fSize,
        -fSize / ratio, fSize / ratio,
        zNear, viewRange);

        // multiply matrices
        Matrix.multiplyMM(mWorldMatrix, 0, mProjMatrix, 0, mLookMatrix, 0);
        Matrix.multiplyMM(modelViewProjectionMatrix, 0, mWorldMatrix, 0, modelMatrix, 0);
       
        GLES20.glUniformMatrix4fv(muMVPMatrixHandle, 1, false, modelViewProjectionMatrix, 0);
}

Obviously a lot of this is no longer needed, but my issue is finding a suitable replacement for the Matrix.setLookAt() function within jPCT-AE.

The issue I have is that using
    public void setCameraPosition(CamPosition newCamera) {
    SimpleVector dir = new SimpleVector(
    newCamera.frontX + newCamera.eyeX,
    newCamera.frontY + newCamera.eyeY,
    newCamera.frontZ + newCamera.eyeZ
    );
    SimpleVector up = new SimpleVector(
    newCamera.upX,
    newCamera.upY,
    newCamera.upZ);

    worldCamera.setOrientation(dir, up);
    worldCamera.setPosition(newCamera.eyeX, newCamera.eyeY, newCamera.eyeZ);
    }

...results in some very strange results! Initially 'the world' is viewed as before, but after a randomly short period of time, during movement of the device the axis of rotation get screwed up (x,y or z are inverted or switched) or just point in  another direction to the one I am facing.

I have tried getting and setting the camera matrix directly, but with no benefit. Additionally I have searched the forum, but the various code snippets didn't help either, due to angles not being used.

Could anyone suggest either what is wrong, or how I can set the lookAt vectors in jPCT-AE as is done in OpenGL ??

Many thanks in advance.