OpenGL perspective matrix far plane

Question

The near plane clips at exactly the value I set just fine but instead of clipping at 1000 the far plane clips at 1.

Here is the code for the projection matrix:

public static Matrix4f perspective(Matrix4f dest, float fov, float aspectRatio, float near, float far) { if (dest == null) dest = new Matrix4f(); float tanHalfFOV = (float) Math.tan(fov / 2); float range = near - far; dest.m00 = 1.0f / (tanHalfFOV * aspectRatio); dest.m10 = 0; dest.m20 = 0; dest.m30 = 0; dest.m01 = 0; dest.m11 = 1.0f / tanHalfFOV; dest.m21 = 0; dest.m31 = 0; dest.m02 = 0; dest.m12 = 0; dest.m22 = (-near - far) / range; dest.m32 = 2 * far * near / range; dest.m03 = 0; dest.m13 = 0; dest.m23 = 1; dest.m33 = 0; return dest; }

The near plane is 0.1 and the far plane is supposed to be 1000.

Bálint · Accepted Answer · 2016-04-23 11:40:24Z

Your whole matrix is incorrect. For example, this is one of the ways it should look like:

So, in code:

dest.m00 = 1.0f / (tanHalfFOV * aspectRatio); dest.m10 = 0; dest.m20 = 0; dest.m30 = 0; dest.m01 = 0; dest.m11 = 1.0f / tanHalfFOV; dest.m21 = 0; dest.m31 = 0; dest.m02 = 0; dest.m12 = 0; dest.m22 = -(far + near) / range; dest.m32 = -2 * far * near / range; dest.m03 = 0; dest.m13 = 0; dest.m23 = -1; dest.m33 = 0;

And you calculate range the wrong way, it needs to be far - near, not near - far.

You were a bit rush when blamed the original matrix 'wrong'. It is correct. You can find it, for example here. — Grief
– Grief, Commented Jun 3, 2017 at 22:11

Bikush · Accepted Answer · 2016-03-23 15:13:32Z

As far as I can tell by comparing to GLM perspective matrix implementation, your range is computed negative and you are missing some negative signs. Below are the corrections.

float range = far - near; ... dest.m32 = - 2 * far * near / range; dest.m23 = - 1;

Check it out on their git. I am not sure just which matrix you need, this answer is for the RH one. Check the link for other implementations.

@minecraftwarlock perhaps a sign is wrong somewhere or the camera is positioned incorrectly — Bikush
– Bikush, Commented Mar 24, 2016 at 13:52

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