glFrustum() maths... are they correct?

sealfin

Moderator

Posts: 675
Joined: 2002.04

Post: #1

Dec 13, 2004 — 03:39 PM

As I'm becoming increasingly irritated by the limitations of gluPerspective(), I thought I'd code a quick function to set-up a perspective view...

Code:

void Perspective( const double p_halfWidth,

    const double p_halfHeight,

    const double p_angle,

    const double p_far,

    double *p_near )

{

  const double near = ( p_halfWidth / tan( p_angle * ( 3.141592654 / 180.0 )));

  glFrustum( -p_halfWidth, p_halfWidth,

    p_halfHeight, p_halfHeight,

    near, p_far );

  *p_near = near;

  return;

}

It's missing a lot of useful functionality (ensuring near < far, for a start), but I've quickly tested it, and it seems to return the results I'd expect (for example, for a 45Â° view, as the apparent dimensions of an object halve every time the distance from the near point doubles.)

But I just wondered whether a more knowledgable coder would take a look, point out any (inevitable?) errors in the maths

Mark Bishop

ThemsAllTook

Moderator

Posts: 1,552
Joined: 2003.10

Post: #2

Dec 13, 2004 — 08:00 PM

What on earth is wrong with using gluPerspective()?

- Alex Diener

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