gistfile1.c

void generate_projection_matrix(GLfloat *matrix, double fovx, double aspect, double nearDist, double farDist)
{
    // Based on the gluPerspective implementation in java
    double deltaDist = farDist - nearDist;
    double cot = 1 / tan(fovx*M_PI / (2*aspect*180));

    // Column-major ordering, matrix[0*4 + 1] is right beneath matrix[0*4 + 0]
    matrix[0*4 + 0] = cot / aspect;
    matrix[0*4 + 1] = 0;
    matrix[0*4 + 2] = 0;
    matrix[0*4 + 3] = 0;

    matrix[1*4 + 0] = 0;
    matrix[1*4 + 1] = cot;
    matrix[1*4 + 2] = 0;
    matrix[1*4 + 3] = 0;

    matrix[2*4 + 0] = 0;
    matrix[2*4 + 1] = 0;
    matrix[2*4 + 2] = -(farDist + nearDist) / deltaDist;
    matrix[2*4 + 3] = -1;

    matrix[3*4 + 0] = 0;
    matrix[3*4 + 1] = 0;
    matrix[3*4 + 2] = -2 * nearDist * farDist / deltaDist;
    matrix[3*4 + 3] = 0;
}

void generate_view_matrix(GLfloat *matrix, point *cam_pos, point *cam_dir, point *up)
{
    printf("\n\nCam dir: (%f|%f|%f), |v| = %f", cam_dir->x, cam_dir->y, cam_dir->z, cam_dir->x*cam_dir->x + cam_dir->y*cam_dir->y + cam_dir->z*cam_dir->z);
    fflush(stdout);

    // Assumption: cam_dir is normalized
    // Side = cam_dir X up
    point side;
    cross(cam_dir, up, &side);

    // Rel up = side X cam_dir
    point relative_up;
    cross(&side, cam_dir, &relative_up);

    // Column-major ordering, matrix[0*4 + 1] is right beneath matrix[0*4 + 0]
    matrix[0*4 + 0] = side.x;
    matrix[0*4 + 1] = relative_up.x;
    matrix[0*4 + 2] = -cam_dir->x;
    matrix[0*4 + 3] = 0;

    matrix[1*4 + 0] = side.y;
    matrix[1*4 + 1] = relative_up.y;
    matrix[1*4 + 2] = -cam_dir->y;
    matrix[1*4 + 3] = 0;

    matrix[2*4 + 0] = side.z;
    matrix[2*4 + 1] = relative_up.z;
    matrix[2*4 + 2] = -cam_dir->z;
    matrix[2*4 + 3] = 0;

    matrix[3*4 + 0] = 0;
    matrix[3*4 + 1] = 0;
    matrix[3*4 + 2] = 0;
    matrix[3*4 + 3] = 1;
}