this is very strange... um... it could be because of number of points, oh wait, i
know why...
The outside of my teeth are clipped by a cylinder to make them round, this uses a
difference, making it slower.
I bet i could make it faster by moving the clip to when i create the tooth, instead
of clipping all the teeth at once.

hmm... i also have a default texture built in, i would always set my texture using
gear_texture... it may be that having this set might cause povray to think there
are two textures over top of eachother if you made another in a object statement...

i don't use diametrical pitch because it's an imperial base messurement, i use
metric when ever i can... i'll add it to the next version.  mdl = 1/PD   (= mm of
pitch diameter per tooth)   :)
so, you could use gear_n_mdl (point, angle, n, 1/PD, th) if you want to call it
close to the same... or you could just add:
#macro Gear(NumTeeth, PD, FaceWidth) object {
gear_n_mdl (0,0,NumTeeth,1/PD,Face_Width) translate -Face_Width } #end
to the end of polar_gear.inc to make exactly the same call and pretty close to the
same output.

I added the center_point and rotangle because i didn't think you could use
gear(...) directly in an object... i thought you had to #declare it first... oops.

hmm... things that i notice your code lacking, but realy is just superfluous in
mine... solid gears(uses merge instead of union), adjustable quality, a problem
with realy large gears(see below), rounded outside, meshing code, adjustable
pressure angle.

the problem with realy large gears won't be noticed in your stuff... but i've added
the ability to leave the center out, speeding up spoked centers. If you have a very
large gear(many teeth) the base of the involute dips below the root circle, if you
have a thin ring holding the teeth, this will cause a spike into the center of the
ring... um... kinda not importaint most of the time... but i disliked that when i
did some tests.

things my code is still lacking: stub gears, backlash... um... i think that's it
other than helical, worm and bevel... and hypoid(i wonder how i'll do that...)

Since i haven't ever found any accual information on gears except in one book, i
didn't know the normal pa was 20... i'll make that a self-set variable in the next
version.

I'll also shuffle some of the other variables back into auto-setting stuff if i
can...

I did have a fully working bevel gear macro a bit back, but my hd crashed, taking
all of my work with it... i haven't gotten around to coding a new one.

I should be able to speed it up a bunch, and i think i will use the array method
next time, when i did this one, i didn't know how to use it. as well, this is just
a #macro'ised version of an earlier include i did...

This one is called polar_gear 'cause it is my middle step before making the bevel
gear one. polar coordinates are easier to convert into bevel gears...

      the Loial Raven

David Wilkinson wrote:

> On Sun, 04 Jun 2000 19:55:29 -0700, Loial Raven <Loi### [at] telusnet> wrote:
>
> >Ok... i just read the thread on looking for gears... i'll let my gear
> >stuff out :)
> >
> >I've been working on this for quite a while, it's still not finished,
> >and it won't be for quite a while yet. Right now i'm working on bevel
> >gears, as well as looking at making helical gears and helical bevels...
> >
>
> Loial,
>
> I think several of us in the POV community have had a go at gears.  Marc
> Schimmler and I have both posted macros for the generation of accurate involute
> gears.   Marc's gears are specified using the module of the gear and mine use
> the diametral pitch.
>
> Your macro seems to use the same technique as mine - a linear spline prism to
> define the tooth.  In my case I calculate an array of points on the tooth
> profile and then plug them into the prism, whilst you calculate them when
> defining the prism.  For the bevel gear I used a similar technique, but with a
> prism with a conic sweep.
>
> I did a comparitive test and rendered a 50 tooth gear of similar size using both
> your macro and mine, and yours took about 3.6 times as long as mine. I can't see
> why this should be, but perhaps you can find it.
>
> My macros and example programs for both types of gears are available for
> download on my website www.hamiltonite.com (The downloads also include flc
> animations.)
>
> Both Marc's macros and mine are intended to be simple to use.  In my case the
> pressure angle is assumed to be 20 degrees, a widely adopted engineering
> standard.  In the case of my spur gear macro, the user only needs to give the
> diametral pitch (dp), the number of teeth and the face width. The bevel gear
> macro is equally simple to use.
>
> I look forward to seeing your helical gears and spiral bevels.
>
> David
>
> dav### [at] hamiltonitecom
> http://www.hamiltonite.com/

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