From: Gavin Kistner <gavin@...>
Date: 2005-06-03T23:46:23+09:00
Subject: Re: [ANN] librend 0.0.1

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On Jun 3, 2005, at 12:26 AM, Ilmari Heikkinen wrote:
> There are also renderer "layers"; the renderer draws Views, which  
> have a
> viewlist. The viewlist is composed of [camera, scene, effects]-tuples,
> which the renderer draws in order, clearing the depth buffer between
> them. So it's possible to draw a perspective-projected scene first,
> followed by e.g. name markers, and then an ortho-projected HUD on top.

If the Text labels are positioned at the centroid of the object they  
are labeling, and the cameras for each views are matched to the same  
world space, this is an effective way of visually layering the  
content. However, the downside of this technique is that EVERY label  
is always visible, even if the part if fully occluded by other geometry.

Another (math-intensive) solution is to offset the pivot point of the  
text so that it rotates about the center of the object being  
labelled, but offset towards the camera the distance necessary for  
the billboarded bounding box of the text to fully clear the geometry  
of the object being labeled. As other objects move in front of the  
part/label, the label will be occluded along with the rest of the part.

Deriving the billboarding code, pivot offset/rotation, and box-on- 
geometry collision detection is left as an exercise to the reader ;)



--
"Contrary to what most people say, the most dangerous animal in the
world is not the lion or the tiger or even the elephant.  It's a shark
riding on an elephant's back, just trampling and eating everything they
see." -- Jack Handey



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