Setting Graphics Mode

Hello. I'm new to the C++ programing game. But i'm slowly learning last week i whent over the basics now im moveing to visual. For some reason, anytime i try to compile a vga screen or a code that carrys lines the compiler wont reconize them no matter how I define them. I'm also looking for a demo script for changeing the screen to 320x200x256 so I can learn Pixels. If you have one feel free to post away. (Also anytime i try to switch to the screen the compiler wont let me)

What compiler are u using - Microsoft VC++ and some others only work under windows and so dont allow changing the screen to 13h (I think thats right) mode.

In MSVC you must use DirectX for graphics.

In others this will change the screen

union REGS regs;
regs.x.ax=0x13;
int86(0x10,& regs,& regs);

or

mov ax,013h
int 10h


For pixels you must get a pointer to video memory.

unsigned char *ptrScreen=(unsigned char *)MK_FP(0xa000,0);

paletteindex is a palette entry from 0 to 255 which corresponds to certain RGB values.
ptrScreen[y*320+x]=paletteindex;

For more information go to www.brackeen.com.

Quote:

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Originally posted by Bubba
ptrScreen[y*320+x]=paletteindex;

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To speed things up, you can use bitshifting. (y<<8) + (y<<6) is the same as y*(2^8) + y*(2^6) which is y*256 + y*64 which is y*(256+64) which is Y*320.

Doing this instead of the normal multiply 64000 times per frame (320*200=64000) will increase the update speed dramatically :).

I wouldn't say you have to use directX, you can use the windows api for small games i.e. my snake game.

Well thats all and well but with borland command line compiler it wont compile. it calls regs undefined along with .h.g ive looked it up and tryed that method.

Ive tried a few methods includeing:

#define GRAPHICS_MODE13 0x13
#define TEXT_MODE 0x03
#include <iostream>
#include <string>
#include <conio>
#include <stdlib>
#include <stdio>
using namespace std;
void Set_Graphics_Mode(int mode)
{
union REGS inregs,outregs;

inregs.h.ah = 0;
inregs.h.al = (unsigned char)mode;

_int86(0x10, &inregs, &outregs);
}
void main()
{
cout<<"Press any key to move to graphics mode..."endl;
getch();
Set_Graphics_Mode(GRAPHICS_MODE13);
}

And if you ask me borland compiler sucks because it will only do the most basic functions, if i try to compile anything found on this site it calls errors and wont compile. also i forgot the left shift in the ex above.

im going to work if you have any ideas on what may be going wroung email me at [email protected] thats also my msn name.

Look into SDL (www.libsdl.org). Other members might suggest Allegro. Both are APIs that take care of a great deal of the work for you so you can get started much quicker. If you're only going to do Windows programming then go with DirectX, but keep in mind it's more work to get started.

Is SDL compilable with the Borland command line compiler?

You must include <dos.h> to get int86(), int86x(), and geninterrupt().

Also the bit shifts should be in the final asm as most compilers should catch this and convert it to bit shifts. However, if you do no wish to rely on compiler optimizations then you can hard code the bit shifts in your code.

Yes, it is. There is a little tweaking involved to make the libraries work but all the resources are available so it's not difficult. Basically you'd need to run Borland's implib to create the appropiate libraries from the MSVC ones. An example can be found at the SDL website on how to do it.

I will say try a third party choice such as the OpenGL api and that will help you out tremendously besides Direc 3D is hard :(