Segmentation fault when drawing an MD3 model with vertex arrays

[pureza]

Hi,

I have written an md3 parser and I'm trying to display the resulting mesh using opengl vertex arrays. This is what I am doing:

for (Mesh mesh : model.getMeshes()) {
    Frame currentFrame = mesh.getFrames()[0 /* Get the first frame*/];

    GL11.glEnableClientState(GL11.GL_VERTEX_ARRAY);
    GL11.glVertexPointer(3, 0, currentFrame.getVertices());
    GL11.glDrawElements(GL11.GL_TRIANGLES, mesh.getTriangles());
}

currentFrame.getVertices() is a FloatBuffer containing the <x, y, z> coordinates of each vertice in that frame.
mesh.getTriangles() returns an IntBuffer containing the indices of the vertices of each triangle.

When I run this code I obtain a segmentation fault:

SIGSEGV (0xb) at pc=0x7b3759f8, pid=7246, tid=3084782480
#
# Java VM: Java HotSpot(TM) Server VM (10.0-b19 mixed mode linux-x86)
# Problematic frame:
# C  [fglrx_dri.so+0x2809f8]

I think it's unlikely that the error is with the vertices FloatBuffer or the triangles IntBuffer, because if I render each triangle individually, everything works fine. Also, even though it seems to crash while executing graphics card driver code, it happened on another computer with a different graphics card model and driver.

I'm using lwjgl-1.1.4 with java version "1.6.0_04", on a Linux machine.

Can you find any error on my code? Thanks in advance,

Luís Pureza

[Fool Running]

Have you flip()ed the IntBuffer and FloatBuffer after you put the data in them?

[pureza]

Have you flip()ed the IntBuffer and FloatBuffer after you put the data in them?

Yes:

// in is a RandomAccessFile
// header contains the mesh's header that contains info like the number of frames, triangles, etc.

IntBuffer triangles = ByteBuffer.allocateDirect(header.getNumTriangles()  * 3 * 4).asIntBuffer();

for (int i = 0; i < triangles.capacity(); i++) {
    triangles.put(in.readInt());
}

triangles.flip();

I do the same for the vertices buffer.

Thanks,

Luis Pureza

[pureza]

Hi,

I've written simple test case in C using real data extracted from an md3 mesh and using vertex arrays and everything worked fine.

Then, I ported it to Java with lwjgl and I got the segmentation fault again. As I was unable to get any help on this issue, I'm thinking this might be a bug in lwjgl. I've uploaded the simple test case so that you can try it and confirm my results. It is at:

http://student.dei.uc.pt/~pureza/Main.java

If you uncomment the code between glBegin/glEnd inside the render() method, you should see a white backpack.

Can you confirm that it is a bug in LWJGL? Or is it just the fact that I'm a complete n00b in opengl? :-)

Thanks,

Luís Pureza

[pureza]

Problem solved! I was not doing .order(ByteOrder.nativeOrder()) on buffer creation!

Special thanks to void256 who diagnosed the problem.