> Thomas de Groot <tho### [at] degrootorg> wrote:
>
>>
>> Just out of curiosity, what would the advantage be of this trick? I
>> assume that calling such a macro would increase parsing time, even if by
>> only a tiny, tiny bit ;-)
>>
>
> When I was designing my 'animation blurring' scheme several years ago (i.e.,
> averaging 10 or more frames to create motion blur), I was trying to come up with
> a way to easily tell my code what type of image files I was going to use (.bmp,
> ..png, .jpeg), without having to do that in the body of the code (in the pigment
> statement itself) but rather at the beginning of the scene. That's where I like
> to add all of my 'switches,' to set up parameters, turn things on and off, etc.
> So I worked out a scheme that uses strings for *part* of what I wanted to do,
> but not all. Here's an example code snippet, buried way down in my code:
>
> image_map{jpeg "my_image" once} // inside a #while loop, using a pigment_map
> // to average lots of images together to get blur
>
> For the 'my_image' part, I built a string construction that automatically takes
> the 'real' image name (along with its included number in the animation
> sequence), adds a period, then adds 'jpeg' after it, then it is all #declared as
> my_image. (Same for the other file types, using a rather ugly #switch
> statement.) So it's mostly automatic; all I have to do at the beginning of the
> file is to specify what the real file name is, and the file type-- both as
> #declared strings.
>
> But I didn't know how to likewise create the 'file type' that comes immediately
> after image_map{   as it's a KEYWORD. I've basically been looking for a more
> 'elegant' way of doing that. ;-) So now, with Alain's #macro idea, I can
> automate that small bit of the process as well!
>
> In a bigger context, it seems to me that this particular kind of macro use might
> be a way to #declare things that are not normally declare-able. Keywords might
> be just *one* example-- although I can't think of any others right now.
>
>
>
>
>
>
For the task of motion blur, you should try the experimental uberpov 
"blink" feature.
It does the averaging for you using only a single rendering step.

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