"Chris B" <c_b### [at] btconnectcomnospam> wrote:
> "mine" <nomail@nomail> wrote in message
> news:web.4468ad3d4767bb90a533cc200@news.povray.org...
> > "Chris B" <c_b### [at] btconnectcomnospam> wrote:
> >> "mine" <nomail@nomail> wrote in message
> >> news:web.44687a797f9206dfa533cc200@news.povray.org...
> >> > I've made a basic macro (with the help of a tutorial)that randomly
> >> > places
> >> > objects (in this case spheres) in a given space. The trouble is the
> >> > tutorial didn't tell me how to stop the spheres from touching. Can
> >> > anyone
> >> > help? I've included the macro below.
> >> >
> >> ... snip ...
> >>
> >> Hi,
> >>
> >> You can declare an array of size 'floater_count', then each time round
> >> the
> >> current loop, do another loop to test whether the position of the centre
> >> of
> >> the sphere is closer than the diameter of floater to any of the existing
> >> positions (see the vlength() function, which you can use on the
> >> difference
> >> between each pair of positions).
> >>
> >> Then you can put the 'object' statement plus the line where you decrement
> >> 'floater_count' inside an #if clause along with a new line to add the new
> >> position into the array.
> >>
> >> If you're likely to want to increase float_count to where you get close
> >> to
> >> the limit where you can't find enough positions, then you should also add
> >> a
> >> way of breaking out of your existing loop to avoid that you loop
> >> indefinitely.
> >>
> >> I didn't post code because it sounds like you're trying to work stuff out
> >> for yourself, but if you want the answer, just say.
> >>
> >> Regards,
> >> Chris B.
> >
> > hi Chris B.
> > I tried figure it out but kept on getting lost. You better just give me
> > the
> > answer. I sort of understand what I was trying to do but I have no idea
> > how
> > to do it. Thanks for helping.
> >
> >
>
> Hi,
>
> I see Warp has posted a perfectly good solution, that does the same thing in
> a slightly different sequence. It collects the set of points into an array
> in the first loop, then draws the objects using those points in a second
> loop.
>
> Here's the approach I described using the code you posted as a starting
> point (I'd recommend you use uppercase letters to start each variable name
> as that helps avoid conflicts with any stuff added to future versions of
> POV-Ray). I also added the LoopLimit stuff that both Warp and I mentioned
> earlier to avoid infinite loops (so you probably want to set the
> Floater_count back to 20).
>
>
> camera {location <0, 0, -10> look_at  <3,3,0>}
> light_source { <0, 50, -400> color 1}
>
> #declare ObjectRadius = 1;
>
> #declare Floater = sphere{<0,.5,0>, ObjectRadius}
> #declare Thingy_red = <1,0,0>;
> #declare Floater_count = 200;
> #declare Locations = seed(1);
>
> #declare Positions = array[Floater_count];
> #declare FloaterQuantity = Floater_count;
> #declare LoopLimit = 1000;
> #declare CollisionCounter = 0;
>
> #while (Floater_count > 0 & CollisionCounter < LoopLimit)
>   #declare x_loc = rand(Locations)*7-1;
>   #declare y_loc = rand(Locations)*7-1;
>   #declare z_loc = rand(Locations)*7-1;
>   #declare I = FloaterQuantity - 1;
>   #declare TooClose = 0;
>   #while(I>Floater_count-1)
>     #if (vlength(<x_loc,y_loc,z_loc>-Positions[I])<ObjectRadius*2)
>       #declare TooClose = 1;
>     #end
>     #declare I = I - 1;
>   #end
>   #if (TooClose)
>     #declare CollisionCounter = CollisionCounter + 1;
>   #else
>     #declare CollisionCounter = 0;
>     object{Floater
>       pigment{color Thingy_red}
>       translate <x_loc,y_loc,z_loc>
>     }
>     #declare Floater_count = Floater_count - 1;
>     #declare Positions[Floater_count] = <x_loc,y_loc,z_loc>;
>   #end
> #end
>
> #if (CollisionCounter >= LoopLimit)
>   #debug "nnWARNING: Loop Limit Exceedednnn"
> #end
> .
>
> Regards,
> Chris B.

Thanks both for the help.

Chris B.
I never would have got that. This is the first time I've used these
#declare, #if, #while, etc. stuff. I really know hardly anything about this
macro stuff so I had trouble understanding what you where telling me to do.
Once I play around with this code I'm sure I'll have at least a bit easier
time of things. What's really needed is a series of good tutorials,
especially for new users of pov-ray, as the whole macro thing is very hard
to learn and understand. I'm sure with time I'll be fine.

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