È una prospettiva corretta Matrix Fov?

Question

Ho una prospettiva fov, ma quando ruota, non è "guarda" correttamente - oggetti più vicini attraversati più velocemente di oggetti più stretti, passandoli nel mezzo dello schermo.

Allora: è corretto?Utilizzando le coordinate destrimane, se questo è importante?

    public static Matrix4x4 PerspectiveFOV(float fov, float aspect, float near, float far)
    {
        float yScale = 1.0F / (float)Math.Tan(fov / 2);
        float xScale = yScale / aspect;
        float farmnear = far - near;
        return new Matrix4x4(
            xScale, 0, 0, 0,
            0, yScale, 0, 0,
            0, 0, far / (farmnear), 1,
            0, 0, -near * (far / (farmnear)), 1
            );
    }

.

Grazie.

Answer 1

I see a couple of problems. First, the argument to tan() should be converted from degrees to radians.

Second, the formula for perspective projection in OpenGL is a little different from yours. As specified here, it uses 'near - far' in the denominator instead of your 'far - near'. The numerator terms are also different. Modifying your function slightly and converting from Java to C, I produced a projection matrix identical to the one given by gluPerspective() with the following:

static void my_PerspectiveFOV(double fov, double aspect, double near, double far, double* mret) {
    double D2R = M_PI / 180.0;
    double yScale = 1.0 / tan(D2R * fov / 2);
    double xScale = yScale / aspect;
    double nearmfar = near - far;
    double m[] = {
        xScale, 0, 0, 0,
        0, yScale, 0, 0,
        0, 0, (far + near) / nearmfar, -1,
        0, 0, 2*far*near / nearmfar, 0 
    };
    geom_matrix4_copy(m, mret);
}

Answer 2

For questions such as this one I would suggest an excellent resources: https://www.scratchapixel.com/lessons/3d-basic-rendering/perspective-and-orthographic-projection-matrix It really goes in the detail of the projection matrix. They are more lessons on the topic of camera, constructing camera rays, etc. You will need to do some digging.