Re: [Plib-devel] directional lights

[Curtis L. O. <cu...@in...>]

Sam,

Thanks for the response.  I'm not sure if the specifics of what you
describe will work, but perhaps the general approach would.

The view direction doesn't really affect the choice I want to make.
The object position and view position produce one vector, but that
needs to be compared to a vector defining the optimal view direction
of the object.

Perhaps we would need to derive a new ssgSelector type class that
saves this directional vector and some tolerance and then does the
comparison when the scene graph is traversed.

Curt.


Sam Stickland writes:
> 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

--
Curtis Olson   Human Factors Research Lab       Flight Gear Project
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