Perspective

A perspective matrix is built from a field of view (typically in degrees), an aspect ratio, and near and far distances. It serves as an easy way to create a view frustum.

Implement the perspective function in mat4.cpp. Don't forget to add the function declaration to mat4.h:

mat4 perspective(float fov, float aspect, float n,float f){

    float ymax = n * tanf(fov * 3.14159265359f / 360.0f);

    float xmax = ymax * aspect;

    return frustum(-xmax, xmax, -ymax, ymax, n, f);

}

The perspective function will be used in almost all visual graphics demonstrations throughout the rest of this book. It's a really convenient way of creating a view frustum.