I am trying to make a dartboard game with a moving dartboard. I have animated the dartboard but it flickers like hell. I have been facing this problem from the day i started to animate objects. Can someone please suggest a solution for minimising the flickering without going overboard in Assembly and VGA programming(cos I am still learning Assembly).

Check out the following code in Turbo C++ to animate the dartboard(which flickers)

#include<conio.h>
#include<graphics.h>
#include<stdlib.h>
#include<dos.h>

void driver()
{
int gdriver = DETECT, gmode, errorcode;
initgraph(&gdriver, &gmode, "c:\\tc\\bgi");
errorcode = graphresult();
if (errorcode != grOk) exit(1);
}

void DrawBoard(int x,int y)
{
setfillstyle(1,14);
bar(x,y-5,x+5,y+5);
setfillstyle(1,13);
bar(x+5,y-10,x+15,y+10);
setfillstyle(1,12);
bar(x+15,y-20,x+25,y+20);
setfillstyle(1,7);
bar(x+25,y-30,x+35,y+30);
}

void EraseBoard(int x,int y)
{
setfillstyle(1,0);
bar(x,y-30,x+40,y+30);
}

void MoveBoard()
{
int y=240;
DrawBoard(450,y);
getch();
EraseBoard(450,y);
while(!kbhit())
{
static flag=1;
DrawBoard(450,y);
EraseBoard(450,y);
delay(10);
y+=flag;
if(y==400) flag*=-1;
if(y==100) flag*=-1;
}
}

void main()
{
driver();
//setcolor(10);
MoveBoard();
getch();
}

The secret to removing flickering from amimation is to use virtual screens. Instead of writing directly to the screen, write to a buffer, the copy this to the screen

declare buffers as follows

// declare a pointer to the offset of VGA memory
unsigned char *vga = (unsigned char *) MK_FP(0xA000, 0);
// declare a pointer to the offset of virtual screen.
unsigned char *vscreen = (unsigned char *) MK_FP(0x6000 , 0);


Now in the drawing functions, write to the vscreen

eg.
void ghline(int x1,int x2,int y,unsigned char colour)
{
memset (vscreen+(y*320)+x1, colour, x2-x1+1);
}

instead of

void ghline(int x1,int x2,int y,unsigned char colour)
{
memset (vga+(y*320)+x1, colour, x2-x1+1);
}

When you have all the drawing of one frame complete, copy this to the screen

void memtoscreen()
{
memcpy(vga,vscreen,size_t(6400*10));
}

Hope this helps. If not just ask again.

Ciaran

Make use << & >> for * and /, they are faster. With BGI, assembly's vertical blanking doesn't work I think.

: The secret to removing flickering from amimation is to use virtual screens. Instead of writing directly to the screen, write to a buffer, the copy this to the screen
:
: declare buffers as follows
:
: // declare a pointer to the offset of VGA memory
: unsigned char *vga = (unsigned char *) MK_FP(0xA000, 0);
: // declare a pointer to the offset of virtual screen.
: unsigned char *vscreen = (unsigned char *) MK_FP(0x6000 , 0);
:
:
: Now in the drawing functions, write to the vscreen
:
: eg.
: void ghline(int x1,int x2,int y,unsigned char colour)
: {
: memset (vscreen+(y*320)+x1, colour, x2-x1+1);
: }
:
: instead of
:
: void ghline(int x1,int x2,int y,unsigned char colour)
: {
: memset (vga+(y*320)+x1, colour, x2-x1+1);
: }
:
: When you have all the drawing of one frame complete, copy this to the screen
:
: void memtoscreen()
: {
: memcpy(vga,vscreen,size_t(6400*10));
: }
:
: Hope this helps. If not just ask again.
:
: Ciaran
: