Peter Warren wrote:
> 
> Pardon me for my rudeness but...
> 
> What is your point?
> 
> Text Objects take a long time to render in Pov?
> 
> I cannot provide you with a technical explanation
> of this.

From a conversation with Ron Parker:

The text object is represented as a CSG union, with each glyph being a
separate object. A glyph is represented internally as a series of quadratic
curves (which require a large number of mathematical calculations).

To test for insideness, POV first makes sure the point is between the front
and back planes of the glyph, then makes sure the projection of the point
into X,Y space falls inside the glyph representation by counting crossings.

To intersect a ray, POV first finds the intersection points of the ray 
with the front and back planes.  Those points are projected onto the plane
and tested to make sure they're inside the glyph representation before
being pushed onto the intersection stack.  Finally, it projects the ray
itself into the plane (skipping the case where the ray is parallel to the
extrusion direction) and tests the projection of the ray against each curve
in the glyph representation.
--------------------

Now if we take what we learned above it becomes apparent that the text
object in it's own right requires quite a few calculations to represent
properly. If we now use the text object in a CSG operation we add greatly
to the number of ray intersection tests needed which consequently adds to
the render time of the scene it is used in.


-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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