Re: Draw & fill regular polygon?

Hi Joel,

Maybe what you're looking for is something like this:

http://www.dpfiles.com/dpfileswiki/index.php?title=Tricks_of_the_Windows_Game_Programming_Gurus%2C_Chapter_8:_Vector_Rasterization_and_2D_Transformations#Solid_Filled_Polygons

it's from an old book of Andre LaMothe, in this chapter he described how to
rasterize poligons with just a pointer to vram.

check it out.

hope it's usefull. ;)


*"It's not that I'm insane, it just happens that I'm very creative with my
own sanity"*


On Wed, Aug 10, 2011 at 8:21 AM, Richard Fabian <[email protected]> wrote:

> On 10 August 2011 12:49, Joel B <[email protected]> wrote:
> > 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
>
> if you already have a line drawing function, then use the code from
> that to update a pair of arrays of min/max on the x axis:
>
> int xmin[SCREEN_HEIGHT] = { SCREEN_WIDTH... }
> int xmax[SCREEN_HEIGHT] = { -1... }
>
> then for each step of your line drawing function update the min/max:
>
> replace your: put_pixel(x,y,colour)
> with: xmin[y] = min(x,xmin[y]); xmax[y] = max(x,xmax[y]);
>
> Once you have the arrays, it's a simple case of iterating over them
> and rendering all pixels between the min and max where the difference
> is positive.
>
> foreach y in SCREEN_HEIGHT:
>  if( xmax[y] > xmin[y] )
>    foreach( x in range( xmin[y], xmax[y] ):
>      put_pixel( x,y, colour )
>
> and you have an untextured triangle.
> if you want it textured, don't forget to store only UV values when the
> max/min is updated.
>
> --
> fabs();
> Just because the world is full of people that think just like you,
> doesn't mean the other ones can't be right.
>
>
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