Re: [Algorithms] Draw & fill regular polygon?

[Martin G. <mgl...@gm...>]

There are also a number of line rasterizing algorithms that do 2, even 3
pixels per iteration, i.e. with them you will be able to fill the arrays
faster. Lookup for double-step rasterizing algorithms.

Also, in my experience the extrema arrays are not needed: for convex
polygons there are only two active edges at a time, therefore you just need
to traverse the poly in clockwise and anti-clockwise order to switch the
active edges until they meet at the maximum Y coordinate.

Hope that helps further.

Cheers,
Martin

On Wed, Aug 10, 2011 at 6:29 PM, Graham Rhodes ARA/SED <gr...@ar...>wrote:

> Some helpful Google search terms are "polygon rasterization" and "polygon
> scan conversion." Someone else mentioned the Foley/van Dam book/et al. book,
> which is a good reference that describes the classic algorithm. The book
> Graphics Gems I also has a discussion, though it is brief. You can also find
> this stuff online, for free. For example, two sets of lecture slides from
> University of Virginia that look good:
>
>
> http://www.cs.virginia.edu/~gfx/courses/2004/Intro.Fall.04/handouts/11-polyscan.pdf
> www.cs.virginia.edu/~asb/teaching/cs445-fall06/slides/09-rasterization.ppt<http://www.cs.virginia.edu/%7Easb/teaching/cs445-fall06/slides/09-rasterization.ppt>
>
> I even found this YouTube video:
>
> http://www.youtube.com/watch?v=TNbkX5bYrtE
>
> Graham
>
> -----Original Message-----
> From: Joel B [mailto:one...@ea...]
> Sent: Wednesday, August 10, 2011 7:49 AM
> To: Game Development Algorithms
> Subject: [Algorithms] Draw & fill regular polygon?
>
> I should know how to do this, but i don't. I only have the ability in my
> system to draw lines (x1,y1,x2,y2)' to a bitmap, or write to the bitmap as a
> byte array. Can someone tell me the stepwise procedure to draw a polygon of
> n sides and then fill it? Having trouble finding anything online that
> doesn't use pre-existing primitives or libraries.
>
> Thanks,
>
> Joel
> Sent from my iPhone
>
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