From:	Peter Danielsson <e96pd AT efd DOT lth DOT se>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: fast depth buffer
Date:	Wed, 24 Nov 1999 01:23:00 +0100
Organization:	Student
Lines:	81
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References:	<81eth3$95r$2 AT gxsn DOT com>
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To:	djgpp AT delorie DOT com
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I have written some code that you perhaps would like. It is inside a program,
but I could cut it out for you. It is written in assembler and C/C++ and is
fast. It has a 640*480 integer Z-buffer and can scale an image in 256 colors
with the width 128 (easy modified to any power of 2) on another bitmap (ie.
unsigned char *). Of course it sets Z-buffer to newlength if it is closer. Is
ths something for you?

/Peter

Anthony Graham wrote:

> Anyone good with speeding up code?
>
> I need to code a Z-Buffer Manually (Can't use a library as it makes it too
> easy and so i'd not get the grade i need in my A-Level).... This is how it
> works, not the actual code, in DJGPP and ALLEGRO:
>
> int THEZBUFFER[640][480];
> BITMAP *SCREEN_BUFFER;
>
> void ClearZBuffer()
> {
>  int xrun;
>  int yrun;
>  for (yrun=0;yrun<480;yrun++)
>  {
>  for (xrun=0;xrun<640;xrun++)
>  {
>   THEZBUFFER[yrun][xrun]=1000000;
>  }
>  }
>
> }
>
> void drawpixel(int x, int y, int z)
> {
> if (z<THEZBUFFER[y][x])
> {
> THEZBUFFER[y][x]=z;
> {draw the pixel}
> }
>
> my first thoughts were to make an int BLANK_ZBUFFER[640][480] and clear that
> and use the normal zbuffer and instead of clearing it:
> THEZBUFFER=BLANK_ZBUFFER but i get an error about incompatable types!! even
> though they're the exact same!!
>
> any ideas?
>
> I'll try upgrading to the latest versions of djgpp and allegro.
>
> some libs use a bitmap??!! but they can only have 256 levels of depth as
> they store chars not ints,
>
> unfortunatly i can't follow the code in these libs, nor can i use them, If
> anyone could explain how to use bitmaps as zbuffers i'd be very grateful.
>
> Please use C not C++ as i don't understand C++
> Please e mail me suggestions to the address below
>
> Thanks in advance:
>
> - Anthony
> Anthony AT fonzyco DOT co DOT uk
>
> My Engine Stats:
>
> 500 small persp correct textured triangles per scene:
>
> both still check the zbuffer even though they don't clear it, this makes
> them useless but it demonstrates how slow the clear of the zbuffer is:
>
> with zbufferclear @640,480: 13.88 FPS
> without zbufferclear @640,480: 24.9 FPS
> with zbufferclear @320,240: 50 FPS
> without zbufferclear @320,240: 100 FPS
>
> This is without any game code, the triangles are hardcoded (and repeated
> many times), there is no other things happening, like key checks animation
> or anything!!!

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