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Editorial Team
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Asked: 2026-06-14T21:29:57+00:00

I am building a simple Wavefront Obj file loader and renderer in Java, using

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I am building a simple Wavefront Obj file loader and renderer in Java, using JOGL. However, whenever I am loading a simple bunny test mesh, it’s rendering in a glitchy fashion, and I have no idea what could be causing it. I am just using geometry vertices and normals, no textures or materials.

the experienced glitch

another angle of that glitch

The following is the GL initialization code from the init() method:

gl.setSwapInterval(1);
gl.glClearColor(0.2f, 0.2f, 0.2f, 1.0f);        
gl.glEnable(GL2.GL_DEPTH_TEST);
gl.glDepthFunc(GL2.GL_LESS);
gl.glEnable(GL2.GL_CULL_FACE);
gl.glCullFace(GL2.GL_BACK);
gl.glShadeModel(GL2.GL_SMOOTH);
gl.glClearDepth(1.0d);

And this is the method that I’m using to render the model (fixed pipeline, for now):

 gl.glBegin(GL2.GL_TRIANGLES);
    for(Face face : master.faces) {
        for(int i = 0; i < face.points.length; i++) {
            gl.glNormal3f(face.normals[i].x, face.normals[i].y, face.normals[i].z);             
            gl.glVertex3f(face.points[i].x, face.points[i].y, face.points[i].z);
        }
    }
    gl.glEnd();

Where master is the main “group” that contains all the faces and vertices. I’ve checked – everything goes into the master group, and glNormal3f and glVertex3f get called for every needed vertex in every triangle.

Can anyone tell what could be causing those glitches?

Edit 1:

Here is the code I’m using to set the projection and modelview matrices up:

float aspect = (float) width / (float) height;

gl.glMatrixMode(GL2.GL_PROJECTION);
gl.glLoadIdentity();

glu.gluPerspective(60.0f, aspect, 0.01f, 100.0f);
glu.gluLookAt(2.0f, 1.0f, 1.5f,
        0.0f, 0.0f, 0.0f,
        0.0f, 1.0f, 0.0f);

gl.glMatrixMode(GL2.GL_MODELVIEW);
gl.glLoadIdentity();
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1 Answer

  1. Editorial Team

    Well, it seemed like this was being caused by a silly little bug in my object loader.
    When parsing my input vertices, it would chomp the first character of all the x coordinates of the geometry vertices. This didn’t affect the positive values, since they were all normalized and 0.43 = .43, but it messed up all negative values causing them to be interpreted as positive.

    It took me a while to figure that out, but I eventually found it and it just goes to show that the tiniest errors can be incredibly tricky to track down.

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