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If l want to draw a circle.How to do it?


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#1 bluepig.man   Members   -  Reputation: 388

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Posted 30 October 2012 - 07:05 PM

l need draw many point for a circle,or have some simple ways?

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#2 Nik02   Crossbones+   -  Reputation: 2654

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Posted 31 October 2012 - 02:56 AM

Everything you draw on a computer (other than a single point) ends up as many points.

Search for "Bresenham circle" for a discrete approach; alternatively, you can tessellate (or subdivide) your circle into line segments that approximate the circle and draw those with a line algorithm.

Niko Suni


#3 skytiger   Members   -  Reputation: 258

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Posted 31 October 2012 - 08:34 AM

Or you can draw a quad and decide whether each pixel should be on or off based on an equation
which will give you scalable resolution for only 4 verts ...

#4 slayemin   Members   -  Reputation: 2053

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Posted 01 November 2012 - 01:58 PM

Every point on a circle can be calculated by:

x = radius * cos(theta);
y = radius * sin(theta);

Where, theta is all values between 0 and 2PI, and radius is greater than zero.

So, to draw a circle, you can could either plot a bunch of pixels to the screen at the X,Y coordinates as you loop through every value of theta...
or you could draw line segments between each of the X/Y value pairs for all values of theta.

Eric Nevala

Currently a self-employed indie game dev


#5 phil67rpg   Members   -  Reputation: 767

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Posted 01 November 2012 - 05:25 PM

you might want to search this site I have found quite a few threads that might help.




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