Turning off VBO has no effect, other than the stack is slightly different (see below). 
I just tried running standalone outside of Eclipse, thought it was working at first but eventually it crashed in the same manner.

I've got multiple Object3Ds, I found that I have to disable compilation on most of them to avoid the crash.  Interestingly (or maybe not), I have a bunch of OBj3D's that are created via the Loader loadMD2()/load3DS() functions that seem to be ok if I leave them as compiled.

-Ed

[error occurred during error reporting (printing native stack), id 0xc0000005]

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
j  org.lwjgl.opengl.GL11.nglDrawElements(IIIJJ)V+0
j  org.lwjgl.opengl.GL11.glDrawElements(ILjava/nio/IntBuffer;)V+34
j  com.threed.jpct.CompiledInstance.compileToDL()V+294
J  com.threed.jpct.GLBase.compileDLOrVBO()V
J  com.threed.jpct.AWTGLRenderer.drawVertexArray(Lcom/threed/jpct/AWTDisplayList;I)V
J  com.threed.jpct.AWTJPCTCanvas.paintGL()V
j  org.lwjgl.opengl.AWTGLCanvas.paint(Ljava/awt/Graphics;)V+172
J  sun.awt.RepaintArea.paint(Ljava/lang/Object;Z)V
j  sun.awt.windows.WComponentPeer.handleEvent(Ljava/awt/AWTEvent;)V+107
J  java.awt.Component.dispatchEventImpl(Ljava/awt/AWTEvent;)V
J  java.awt.Component.dispatchEvent(Ljava/awt/AWTEvent;)V
j  java.awt.EventQueue.dispatchEvent(Ljava/awt/AWTEvent;)V+46
J  java.awt.EventDispatchThread.pumpOneEventForFilters(I)Z
j  java.awt.EventDispatchThread.pumpEventsForFilter(ILjava/awt/Conditional;Ljava/awt/EventFilter;)V+30
j  java.awt.EventDispatchThread.pumpEventsForHierarchy(ILjava/awt/Conditional;Ljava/awt/Component;)V+11
j  java.awt.EventDispatchThread.pumpEvents(ILjava/awt/Conditional;)V+4
j  java.awt.EventDispatchThread.pumpEvents(Ljava/awt/Conditional;)V+3
j  java.awt.EventDispatchThread.run()V+9
v  ~StubRoutines::call_stub


Hi,

First of all, thanks for your help previously with my earlier navigating-a-sphere questions.  I got it to work, the help I got from Egon and others on this board was very useful!

So, now I am playing around with .3ds models, and I loaded some low-poly trees into my world. they consist of a half-dozen or so quads, with an alpha 'leaf' texture applied to them (so only the leafy part shows), and a trunk, which is another low-poly mesh but with a standard, non-alpha texture applied to it.

To this point I have been using a variant of the model loader code from the JPCT wiki, that loads the sub-objects of the .3ds file and merges them into one Object3D.    The problem I've been having is that the leaves on the tree have z-ordering issues, where they pop in front of and in back of the tree trunks as you change camera perspective etc.  I have tried various values for sort depth and transparency, but since both the leaves and trunk are merged into a single object, I don't think it really solves the problem.

I suspect I might need to keep the leaves and trunk as separate objects, and apply different sort depths and transparency settings to each, but I wanted to see what people thought.  If I do that, it will double the number of tree-related objects, I don't know if that has a perf impact if there are a large number of trees.   I assume if I did that, I'd make one the child of the other or something so rotations/translations will move everything together ? (sorry,  im a bit of a newbie to 3D engine mechanics)

  I'm also assuming that I can't get away with setting sort order and transparency on the sub-objects before I merge them (ie, an Object3D can only have one value for each of these attributes.)  Along those lines, if there is some other kind of thing I should experiment with on the merged object to get my leaves to settle down, I'm interested! :-)

Thanks!

well I don't know how to get a particular sphere polygon below the camera, maybe there is a way to get it seeing I constructed it. I build the sphere just by iterating through the spherical coordinates at a given r and creating verticies/triangles by converting the coords back to cartesian:
for (float alt=-(float)Math.PI; alt < Math.PI; alt = alt+span) {
for (float az=-(float)Math.PI; az < Math.PI; az = az+span) {

surface.addTriangle(p2c(alt,az,varHt(alt,az,r)),
p2c(alt+span,az,r),
p2c(alt,az+span,r);

surface.addTriangle(p2c(alt,az+span,r),
p2c(alt+span,az,r),
p2c(alt+span,az+span,r));
}
}

         protected SimpleVector p2c (float a, float z, float r) {
SimpleVector v = new SimpleVector();
v.x = (float) (r * Math.cos(a) * Math.sin(z));
v.y = (float) (r * Math.sin(a) * Math.sin(z));
v.z = (float) (r * Math.cos(z));
return v;
}

There is probably a way to access the triangles in the mesh later but I'm pretty new to JPct/OpenGL programming, so I am not sure how.

The tangent on the sphere below the camera should in theory be easier to get.  The tangent plane to the point on the sphere should be orthogonal (normal?) to the camera's current position vector, then to select a particular tangent vector on that plane you would somehow take the camera's current direction into account? Some sort of vector addition/subtraction/math there but it's where I am fuzzy.

I assume though that the sphere itself doesn't enter into the calculations for the camera orientation, it can be derived solely based on the camera's position and current orientation.   I was thinking that maybe what I want is to set the camera's XZ plane to something orthogonal to it's position, and then somehow modify the x and y orientation of the camera based on the mouse-look deltas, but leave the z orientation as-is.  No idea how to do that though...


so the summary of what I have/what I need is:

have:
camera current position (== a vector that is normal to the polygon on the sphere below the current position I think)
camera current direction

need:
way to set camera Z orientation based on the above, leaving camera x and y orientation as-is.

Thanks for replying Egon, appreciate the  help.  This board seems pretty active and well run!
Ed