Re: [Plib-devel] directional lights

[Sam S. <sa...@sp...>]

> Steve,
>
> Does plib provide any facilities for drawing or not drawing an object
> based on relative view angle?  I'm pondering how I might impliment
> directional lights such as VASI for runways ... lights that change
> color depending on your relative angle to them.

Hi, I'm not Steve but I think you could use the predraw callback to do this.
Something like:

int myCB ( ssgEntity *entity)
{
    /* Get the camera position */
    sgVec3 camPos ;
    ssgGetCurrentContext () -> getCameraPosition ( pos ) ;

    /* Get the objects position */
    sgVec3 objPos ;
    sgSetVec3 ( objPos, entity -> getBSphere () -> getCenter () ) ;

    /* Work out the angle between the two objects, and based on that either
change the colour of the light ... */

    sgVec4 *col = (ssgLeaf *) (entity) -> getColour ( blah) ;

    sgSetVec4 ( *col, 1.0f, 0.0f, 0.0f, 0.5f ) ;

    /* etc, you could also use getState() and alter that */

    /* Choose to draw the object by returning TRUE to FALSE */

    return TRUE;
}

Does that do the trick?

Sam