EnigmA Amiga Run 1995 November/EnigmA AMIGA RUN 02 (1995)(G.R. Edizioni)(IT)[!][issue 1995-11][Skylink CD].iso/earcd/program/amos/amoslist.lzh/AMOSLIST/[e-mail]_Tue Sep 26 11:50:33 1995.msg

Internet Message Format | 1995-10-02 | 4KB

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Date: Tue, 26 Sep 95 17:08:05 GMT
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In-Reply-To: <Pine.3.87.9509261038.A7411-0100000@tlti>
             (from Petri Hakkinen <[e-mail]>)
             (on Tue, 26 Sep 95 10:59:39)
Lines: 64
X-Mailer: ADMail 1.5 Copyright 1995 S.T.Brown
From: [e-mail] (Ben Wyatt)
To: [e-mail]
Subject: Re: Help me!
Status: RO
X-Status:

Greetings Petri, you wrote some text on the subject Re: Help me!, and now
I'm going to answer it.

PH> > M> Unfortunately, becouse of all the structure of the program, the screen is
PH> > M> in
PH> > M> Hi resolution, but you have just to use R/2 in the sin() part.

Opps, I missed that bit, but if it's in hires, wouldn't the cos have to be
R/2 or the sin be R*2 ?

PH> > M> But the biggest matter is that the 0 degree must be at 12 o'clock, 90
PH> > M> degrees at 3 o'clock and so on in clockwise (instead the trig functions
PH> > M> work
PH> > M> in the other direction.).
PH> > M> Finally, it must be fast enough, even if not just like the Circle command
PH> > M> (or Fcircle by Turbo extension!).
PH> >
PH> > This should do it:
PH> >
PH> > Procedure _PART_OF_CIRCLE[R,A,B,X,Y,STP]
PH> >    Gr Locate X+Sin(A)*R,Y-Cos(B)*R
PH> >    For N=A+STP To A+B Step STP
PH> >       Draw To X+Sin(N)*R,Y-Cos(N)*R
PH> >    Next N
PH> > EndProc
PH>
PH> If you want speed you should put Sin & Cos into arrays. Floating point
PH> calculations are really sssslllooooowwwwww.....
PH>
PH> Example:
PH>
PH> dim si(360),co(360)
PH> for t=0 to 360:si(t)=sin(t)*256:co(t)=cos(t)*256:next

I usually (virtually always) do

PH> and the draw part should be:
PH> Draw To X+(SI(N)*R)/256,Y-(CO(N)*R)/256
PH>
PH> the /256 is done with bitshifting so it don't take much of time,
PH> at least when compiled. Btw. isn't AMCAF's Turbo draw much faster?
PH> If you have AMCAF (or Turbo extension) use it instead of amos!

AMCAF can also be used for the precalculated Sines and Cosines (QSin, QCos)
It uses 0-1023 as 0-359 degrees, so triple (approx.) STP.

PH> Or even better, you can precalculate Sin(N)*R values with every possible
PH> N and R but it takes lots of memory... If you really want the speed...

Put it in a bank...

So, the revised version...

Procedure _PART_OF_CIRCLE[R,A,B,X,Y,STP]
   Gr Locate X+QSin(A,R),Y-QCos(B,R/2)
   For N=A+STP To A+B Step STP
      Turbo Draw To X+QSin(N,R),Y-QCos(N,R/2)
   Next N
End Proc

Bye  _________________________________
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