> can someone explain to me some of the notation in the pov-ray help files. I
> looked in the help for how to make a prism and it gave this:
> 
> PRISM:
>  { [PRISM_ITEMS] F_HEIGHT1, F_HEIGHT2, I_NUM_POINTS, POINT_LIST [open]
> [PRISM_MODIFIERS] }
F_HEIGHT1, F_HEIGHT2 determine the vertical extent of the prism. They 
must be different. Their use is very simple for linear_sweep. It can be 
tricky when you use a conical_sweep (normaly, you also need to use some 
scaling).
I_NUM_POINTS is the number of points needed to define the shape of the 
prism. It includes the actual points plus any controll points.
POINT_LIST is a list of the actual 2D doordinates of all the points 
defining the shape of the prism. It MUST match the value of I_NUM_POINTS.

> PRISM_ITEMS:
> [PRISM_SPLINE_TYPE] & [PRISM_SWEEP_TYPE]
Those are optional parameters with default values.

> PRISM_SPLINE_TYPE:
> linear_spline | quadratic_spline | cubic_spline | bezier_spline
linear_spline means that the points are connected by straight lines. NO 
controll point. (default spline type used if not defined)
All others can have curved shapes and need at least 2 controll points.
bezier_spline use: point, control_point, control_point, point, 
control_point,....(2 control points between each actual points pair)

> PRISM_SWEEP_TYPE:
> linear_sweep | conic_sweep
linear = sides that are parallel (default value that will be used if you 
don't provide that parameter)
conic = sides that converge to a single point.
You must use one or the other, but never both.

> PRISM_MODIFIERS:
> [sturm [BOOL]] & [OBJECT_MODIFIERS]
Optional parameters.
strum use an alternate, more precise but slower, algorythm to trace the 
prism. If strum is absent, it's means "strun off". It's presence alone 
means "strum on".
The object modifiers are things like rotation, scalling and 
translations. Can also include any pigment, texture or material.

> 
> what do the F/I and in other areas V terms mean? I can't work out how to do a
> prism from this information
> 
> Please help
> 
> Thanks
> 
> 
"F" is for a float numerical value: 1.2345, pi, 1/3, sin(0.1), ...
"I" is for an integer numerical value: 1
"V" is for a vector like: <1,2>, <1,2,3>,... If needed, a single float 
or integer can be used if you want a vector where all elements have the 
same value. In that case, the value provided will be promoted to a 
vector. 1 can become <1,1,1>

A simple prism:
prism{0,1, 4 0,<1,1>,<1,0>,0}
Create a triangular prism one unit high. The sides are straight and 
vertical.


Alain

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