Quarter of a Circle

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Quarter of a Circle

CalcKid 06 Jan 2012 02:02

Does anybody know how to draw a 1/4 of a circle on the graphscreen?

Re: Quarter of a Circle

Weregoose 06 Jan 2012 04:47

A filled-in 90° arc positioned A pixels to the right of and B pixels above the origin, of pixel radius C, and with zero eccentricity regardless of the axes' aspect ratio, can be drawn with this variation on the midpoint circle algorithm:

:DelVar UC-1→V
:1-Ans→I
:-2V→J
:Repeat U>V
:ΔX(A+U:Line(Ans,BΔY,Ans,ΔY(B+V
:ΔY(B+U:Line(AΔX,Ans,ΔX(A+V),Ans
:I≥0→T
:I+JAns+(2U+3)not(Ans→I
:J+2T+2→J
:U+1→U
:V-T→V
:End

Re: Quarter of a Circle

Xeda Elnara 02 Feb 2012 20:02

Thanks, Weregoose, I can definitely apply this elsewhere! I am curious if you know of a way to draw arcs of arbitrary sizes using a similar algorithm?

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Z80 Assembly>English>TI-BASIC>Python>French>C>0

Re: Quarter of a Circle

blue_bear_94 06 Jan 2012 04:08

Maybe this can help:

For(I,0,.49π,.01π
Line(P+Rcos(I+A),Q+Rsin(I+A),P+Rcos(I+.01π+A),Q+Rsin(I+.01π+A
End

A is the rotation.

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Last edited on 10 Jan 2012 22:34 by blue_bear_94 Show more

Re: Quarter of a Circle

Weregoose 06 Jan 2012 05:05

On the initial visit of the graphscreen anytime after a ClrDraw, the Y variable reverts to zero.

Re: Quarter of a Circle

CalcKid 08 Jan 2012 17:01

I tried bluebear's program and all I got was a vertical line on Xmax; it didn't matter the window dimensions.

Re: Quarter of a Circle

blue_bear_94 10 Jan 2012 22:34

I edited it. See above.

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Sunrise 3 Progress: 30%
Size: around 20 KB, not including the save lists and in-game RAM.

Re: Quarter of a Circle

Timothy Foster 10 Jan 2012 23:17

Also make sure your calculator is set to radians, not degrees.

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Timothy Foster - @tfAuroratide
Auroratide.com - Go here if you're nerdy like me

Re: Quarter of a Circle

blue_bear_94 10 Jan 2012 23:40

Yay, a program for a filled circle now! Although it works only for no rotation…

For(I,Q,Q+R,ΔX
Line(P,I,P+R√((P-I)²-R²),I
End

This uses rotation:

For(I,0,.5π,K
Line(P,Q,P+Rcos(I+A),Q+Rsin(I+A
End

You need to specify a K small enough to draw a circle properly.

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Sunrise 3 Progress: 30%
Size: around 20 KB, not including the save lists and in-game RAM.

Last edited on 10 Jan 2012 23:41 by blue_bear_94 Show more