��������������������������������������������������������������������������� � � � ***** FadeCode ***** � � � � By Esak (Aug 19, 1994) � ���������������������������������������������������������������������������; �������������������������������������������������������������������������� A sad legal ***p I make no warranty whatsoever regarding this product. I assume no responsiblity for any malicious impact on you, your computer, your red blood cell production, or the sanity of the presidential candidate you supported during the last election, made by the use or misuse of this product. �������������������������������������������������������������������������� Hi there, I decided to release the code for a number of different palette effects. I will be the first to admit that it's not a Future Crew demo source code, or anything vaguely close to earth-shattering. But I belive this release may be useful to some beginning programmers. Learn from it if you can. Rip this off if you want. You may even include source in your own library as long as your library is a freeware as well. I won't ask for any credit. I am not overly proud for this release anyway. But if you find this useful, a postcard would be nice, though. �������������������������������������������������������������������������� Files �������������������������������������������������������������������������� FADE_C.C It contains higher level interface routines which calls some of the routines included in FADE.ASM. FADE.ASM This is the main module that contains a bunch of palette manipulating routines. *.OBJ OBJ files. Compiled for large model. MODEL.INC Include file for FADE.ASM Change this if you would like to compile under a different memory model. FADE.H Header file for C FADEDEMO.C FADEDEMO.PRJ FADEDEMO.EXE
A sample program demonstrating the use of the included functions. Link with FADE_C.C and FADE.ASM. Project file I used to link this program. The executable.
SCREEN.RAW PAL1.pal PAL2.pal
320*200 raw image file used by FADEDEMO palette file used by FADEDEMO palette file used by FADEDEMO
READMEOR.ELS README.1st
You are reading this. You read it before.
������������������������������������������������������������������������� A quick intro to VGA palette format (For a newbie) �������������������������������������������������������������������������� You (hopefully) know a VGA card can use 256 color at once. A VGA card needs three bytes of information for each color. One byte for red intensity. One byte for green intensity. And one byte for blue intensity. So data for a complete 256 color VGA color palette amounts to 768 bytes total. However, only six bit from each byte is used. So each byte can have a value between 0..63. Well, that's all I can and need to tell you now. �������������������������������������������������������������������������� Bresenham Algorithm �������������������������������������������������������������������������� One of the tricky problems that arise as you program palette fading is: SMOOTH TRANSITION FROM ONE COLOR TO ANOTHER Simulating fade in etc, requires smooth transition from one color to another. I have seen someone using floating point math to do this. For graphic coders, floating point math is an evil that must be avoided. So what's the solution? The famous/infamous Bresenham Algorithm. This is commonly known as line algorithm, but this algorithm pops up almost every corner in graphics programming world. Let's say you need to change the value of a byte from 2 to 23. And you must do changing 32 times. With floating math, it would be the_byte=0; loop 32 times begin the_byte=the_byte+43/23 loop end However, using Bresenham algorithm, it would be: the_byte=2 Decision_variable=0 loop 32 times begin Decision_variable=Decision_variable+(23-2) if Decision_variable<32 begin the_byte=the_byte+1 Decision_variable=Decision_variable-32 end loop end It may look more complicated. But using B-algorithm is a LOT faster than using floating point math. But as you can see, we need one more decision variable for each variable we want to change. Therefore, many of the routines included here use additional 768 bytes to implement smooth color transition.
�������������������������������������������������������������������������� Functions in FADE_C.C ��������������������������������������������������������������������������
void fade_screen(void far *pal) >it calls fade_once() 32 times. >the content of the palette array is not preserved. void fade_in_screen(void far *pal) >it calls fade_in_once() 32 times. >the content of the palette array is preserved. void bright_screen(void far *pal) >it calls bright_once() 32 times >the content of the palette array is not preserved. void bright_in_screen(void far *pal) >it calls bright_in_once() 32 times >the content of the palette array is preserved. void fade_between_screen(void far *pal,void far *pal_dest) >It call fade_between_once() 64 times >pal[] and pal_dest[] both have to be 768 bytes (chars) long >The content of neither palette array is preserved. However, the content of pal_dest[] will be moved to pal[]. Please look at FADEDEMO.C to get a better idea of how to use the routines in FADE_C.C.
�������������������������������������������������������������������������� Functions in FADE.ASM �������������������������������������������������������������������������� void setPal(void far *pal) >*pal points to an array of 768 bytes (chars) that contains void fill_pal(void far *pal,char red, char green,char blue); >Fills the palette array with the given color information void copy_pal(void far *pal,void far *pal_dest); >Copies one palette to another void rotate_pal(void far *pal,char index,char numCol, char displacement); >Note this carefully. >This routine DOES preserve the content of pal[] >Let me give you some examples to explain how this routine works. >rotate_pal(&pal,63,32,0); This routine will update palette number from 63-95. But no rotation will take place >rotate_pal(&pal,63,32,1); This routine will also update palette number from 63-95. But this time, the color #64 will replace the content of color #63 and color #65 will replace #66 etc. void sub_palette(void far *pal,void far *pal_dest); >Subtracts one palette from another. You have to call this function
>before calling fade_between_once() If you are not going to call >fade_between_once() directly, you have no business calling this >routine. In most cases, you WON'T have to call the following functions. I will explain when you have to use these functions. Please look at FADE_C.C. That would be the best way to learn how to use the following functions. void fade_out_once(void far *pal) >Changes the content of the palette array >Should be called 32 times to turn the screen completely black. void bright_out_once(void far *pal) >ditto void fade_in_once(void far *pal,void far *pal_dest) >ditto >*pal shoul point to an array of 768*2 *BLANK* chars, not 768 chars. >The second half of pal[768*2] will be used as decision variables for Bresenham algorithm. >After calling it 32 times, the content of pal[] will be identical to the content of pal_dest[] void fade_between_once(void far *pal,void far *pal_dest) >sub_palette() must be called before calling this function. >*pal shoul point to an array of 768*2 chars, not 768 chars. >The second half of pal[768*2] will be used as decision variables for Bresenham algorithm. >After calling it 32 times, the content of pal[] will be identical to the content of pal_dest[] You have to use a *something*_once() routines when you want to update palette while animating at the same time. What you do is something like this: n=32; do animate_sprite_or_whatever(); .... if(n>0) fade_once(&pal); n=n-1; .... while (not_finished)
�������������������������������������������������������������������������� What's to be done. �������������������������������������������������������������������������� First of all, all of the routines included in this file change entire 256 color palette. I didn't write routines which can be used to change a portion of palette. For most applications, you won't have to. (Especially since these routine run snow-free on every machine I tested so far.) But if you need to, I will leave this task for asn exercize for you. If
you are a half-way descent ASM programmer, it wouldn't be hard. Beside, that's what source code is for: to modify. Well, I admit that my assembly routines could use more documentation, though. If anyone ports these codes to 32bit Pmode, please let me know.
�������������������������������������������������������������������������� To fellow coders �������������������������������������������������������������������������� I have a very fast local bus VGA card. This toy allowed me to play _Strike Commander_ on my 486/25. The problem is that many games demos exhibit intolerable amount of snow when they change palette. I see strong evidences that many programmers are still sending palette data byte by byte. (out dx,al) I use this command instead. rep
outsb
This rep outsb command format has been around since 80286 came out. For Christssake, use it! I update 128 colors (384 bytes) at once and I get no snow on my video card. (Updating 256 color at once gave me little snow, though.) I am getting sick and tired of seeing snow on so many games and demos (Except for some exceptions like _Zone66_.) If you don't want to use my routine for palette fading, at least use rep outsb for updating palette.
�������������������������������������������������������������������������� About me �������������������������������������������������������������������������� I am a first year computer engineering student (will be a sophomore in a couple of weeks) attending Carnegie Mellon University, Pittsburgh, Pennsylvania, USA, North America, Earth, Solar System, Milky Way.. (DAMN, I hate that joke. But this stupid joke always keeps coming back to my mind..) Uh well. Anyways, the surest and fastest way to reach me would be through the Internet. My internet e-mail address is:
[email protected] Let me know if you have any problems, questions, comments, etc. I will do my best to reply, but don't get upset if you don't get any. Flames, outrageous requests, and questions like "I don't know C. What can I do?" etc, will most likely be ignored. If you need a coder or an artist, don't hesistate to contact me, especially if it's a paying job. |-) If you don't have an internet account, or would like to send me a postcard, a Lamborghini, a chunk of fissionable material, or an alien facehugger, use the following address. (Valid for 1994-95 school year) 1060 MOREWOOD AVE.
Box No. 1504 PITTSBURGH PA 15213 USA The alternate mailing address follows. It's the address of my uncle and aunt's home. Just make sure you use my real name (Hyun Yim) so they can forward the mails correctly. 37 Blanan Drive Chicopee, MA 01020-4803 USA
Excuse any spelling or grammatical or logical errors. English is not my first language and it's hard to think clearly at 5:00AM. Thanks to Draeden of VLA. I didn't use his routines. But his palette rotation code gave me the idea to code my own. What else... oh yeah, I used TC++3.0 and TASM 4.0. Use /m2 option when compiling with TASM. Well, that's it for now. Watch out for my first game which will be released sometime before the end of this millenium. Esak (aka Hyun Yim aka Attila the Hyun) ������������������������������������������������������������������������� My friends are toys. I make them. - JF Sebastian, from _BladeRunner_
My sister and I were driving along the other day when she asked me, what would I like for my computer. I thought long and hard about it, and came up with the following hypothesis. When a girl gets a Barbie doll, she then wants the extra ballgown for the doll, then the hairbrush, and the car, and the house, and the friends etc. When a guy gets a computer, he wants the extra memory, the bigger hard drive, the maths co-pro, the better motherboard, the latest software, and the bigger monitor etc. I told my sister all of this, and finished up with : "So as you can see, computers are Barbie dolls for MEN!" She called me a chauvinist. And hit me. Hard. - Grant Smith, aka DENTHOR of Asphyxia