Why does my depth test fail on Nvidia cards?

Question

I sent a test version of my in-development game to some friends, and they found out that the Depth Test in OpenGL does not work on Nvidia cards. I'm using LWJGL.

I use my own matrices and send them to the shader, and at the start of evey game loop I use

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); // clear the display

On an Nvidia card, you can see mountains through other mountains and stuff. On my Radeon HD 6650M it works perfectly fine. Any ideas?

I don't have anything special in the shaders—just some basic lighting calculations. I dont touch the gl_FragDepth.

Here's a screenshot (with placeholder textures):

I use these calculations for the Projection Matrix:

public Matrix4f getProjectionMatrix() {
    // Setup projection matrix
    Matrix4f projectionMatrix = new Matrix4f();
    float fieldOfView = 40.0f;
    float aspectRatio = (float)Display.getWidth() / (float)Display.getHeight();
    float near_plane = 0.1f;
    float far_plane = 1000f;

    float y_scale = coTangent((float) Math.toRadians(fieldOfView / 2f));
    float x_scale = y_scale / aspectRatio;
    float frustum_length = far_plane - near_plane;

    projectionMatrix.m00 = x_scale;
    projectionMatrix.m11 = y_scale;
    projectionMatrix.m22 = -((far_plane + near_plane) / frustum_length);
    projectionMatrix.m23 = -1;
    projectionMatrix.m32 = -((2 * near_plane * far_plane) / frustum_length);
    projectionMatrix.m33 = 0;
    return projectionMatrix;
}

Answer 1

Make sure you request a depth buffer from LWJGL by passing a PixelFormat to your call of Display.create. Like so:

Display.create(new PixelFormat(4,24,0,4));

The 24 indicates a 24 bit depth buffer.