Frustum

package frustum;

import org.lwjgl.util.vector.Matrix4f;
import org.lwjgl.util.vector.Vector3f;
import org.lwjgl.util.vector.Vector4f;

public class Frustum {

    private final Matrix4f projection;
    private final Vector4f[] coefficients = new Vector4f[6];

    public Frustum(final Matrix4f projection) {
        this.projection = projection;
    }

    public void update(final Matrix4f view) {
        Matrix4f a = Matrix4f.mul(projection, view, null);

        // left
        coefficients[0] = new Vector4f(a.m00 + a.m03, a.m10 + a.m13, a.m20 + a.m23, a.m30 + a.m33);
        // right
        coefficients[1] = new Vector4f(-a.m00 + a.m03, -a.m10 + a.m13, -a.m20 + a.m23, -a.m30 + a.m33);

        // bottom
        coefficients[2] = new Vector4f(a.m01 + a.m03, a.m11 + a.m13, a.m21 + a.m23, a.m31 + a.m33);
        // top
        coefficients[3] = new Vector4f(-a.m01 + a.m03, -a.m11 + a.m13, -a.m21 + a.m23, -a.m31 + a.m33);

        // near
        coefficients[4] = new Vector4f(a.m02 + a.m03, a.m12 + a.m13, a.m22 + a.m23, a.m32 + a.m33);
        // far
        coefficients[5] = new Vector4f(-a.m02 + a.m03, -a.m12 + a.m13, -a.m22 + a.m23, -a.m32 + a.m33);

        for (int i = 0; i < 6; i++) {
            coefficients[i].normalise();
        }
    }

    public boolean contains(final Vector3f v) {
        return contains(new Vector4f(v.x, v.y, v.z, 1));
    }

    public boolean contains(final Vector4f v) {
        for (int i = 0; i < 6; i++) {
            float value = Vector4f.dot(coefficients[i], v);
            if (value < 0.0f) {
                return false;
            }
        }

        return true;
    }

}