R: [Plib-users] scenegraph structure

[Paolo L. <p.l...@ci...>]

-----Messaggio originale-----
Da: pli...@li...
[mailto:pli...@li...] Per conto di deepha sv
Inviato: sabato 3 dicembre 2005 6.37
A: pli...@li...
Oggetto: [Plib-users] scenegraph structure

> hi,
>     I am using a simulation software ,as we are reading the data file =
and
storing into a scenegraph tree structure=20
>=20
> 1. how are we actually taking the data from the scenegraph and placing =
it
in frustrum.

By means of the camera positioning and actual drawing.

  sgCoord camera;  // has xyz (camera position) and hpr (camera =
orientation)
fields
  // ...
  // set camera.xyz and camera.hpr as your camera motion model
  // ...
  ssgSetCamera( &camera );
  ssgCullAndDraw( scene );  // scene is your scene graph root

Anyway there are other camera placement approaches in SSG, e.g. by 4x4
camera matrix, or by a LookAt approach (the one showed is somehow a =
LookFrom
instead).

> 2. how and where , are we  placing the frustum in scenegraph

Where: at window resize time (i.e. within the resize callback if you're
using Glut)
How:
  ssgSetFOV( fov_x_deg, fov_y_deg );  // frustum hor & vert =
field-of-view
  ssgSetNearFar( nnear, ffar );       // frustum near, far
Or, if you need an explicit frustum control (calculating frustum params =
it's
up to you):
  ssgSetFrustum( left, right, bottom, top, near_clip, far_clip );

Modern SSG syntax want frustum things to be set as methods of a =
ssgContext,
and set it as current context.

> 3. how the data from the frustum are rendered.

The actual drawing occurs at the ssgCullAndDraw call.

> for preparing scenegraph and rendering i am using plib library.

Welcome on board.

As usual with apparently simple questions I hope to have interpreted =
your
questions in the intended meaning.

Greetings -

Paolo Leoncini