This is an extract from my main game program. For the matter of simplicity i have created a sample program. There are two sprites namely Sprite_Red and Sprite_Yellow. ''Sprite_Red'' moves over a Yellow Stick and ''Sprite_Yellow'' moves over a Red Stick from top to bottom and vice versa, without disturbing the background. Things are OK as long as I enable only one Sprite lets say ''Sprite_Red'' or `Sprite_Yellow''. On enabling both the sprites, the background image of both the sprites in the array clashes. Both the sprites are using different array for storing their respective backgrounds. i don''t know why the arrays are clashing even though i am using different arrays. in no way i am able to understand what is wrong in my program. I am using Turbo C 3.0 DOS compiler. Pls. compile this and see the sample first. The main functions are: 1. Backg_Image_Capture() - Capture the background for both sprites. 2. DrawSprites() - Draws both sprites. 3. EraseSprites() - Erases both sprites using the background captured. I have commented `Sprite_Yellow'' portions in the above three functions by default so that `Sprite_Red'' works. I am listing below the full source code. pls. help as early as possible because i cannot go ahead unless i fix this bug. #include <stdlib.h> #include <conio.h> #include <alloc.h> #include <memory.h> #include <dos.h> #define SCREEN_WIDTH 320 #define SCREEN_HEIGHT 200 #define SCREEN_SEGMENT 0xA000 #define IMAGE_WIDTH 14 #define IMAGE_HEIGHT 14 #define INPUT_STATUS 0x03da #define VRETRACE 0x08 #define NUM_GHOSTS 1 char Sprite_Red[] = { 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12, }; char Sprite_Yellow[] = { 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,14,14,14,14,14,14,14, }; //for storing the backgrounds. char Sprite_Red_Backg_Array[196]; char Sprite_Yellow_Backg_Array[196]; typedef unsigned char byte; byte *On_Screen=(byte *)MK_FP(0xA000,0); int Sprite_Red_X=126, Sprite_Red_Y=0, Sprite_Yellow_X=226, Sprite_Yellow_Y=0, ydir= 1; //---------------------------- Screen Codes Begins -------------------------- void EnterMode13H(void) {union REGS regs;regs.x.ax = 0x0013;int86(0x10, &regs, &regs);} void LeaveMode13H(void) {union REGS regs;regs.x.ax = 0x0003;int86(0x10, &regs, &regs);} //------------------------------------------------------------------------------------------ //------------------------- Plot-Read Pixels Begins ------------------------- void PlotPixel (unsigned int x, unsigned int y, unsigned char c) { if ((x < 320) && (y < 200)) { On_Screen[(y << 8) + (y << 6) + x] = c; } } unsigned char ReadPixel(unsigned int x, unsigned int y) { if((x < 320) && (y < 200)) { return (On_Screen[(y << 8) + (y << 6) + x]); } else { return(0); } } //------------------------------------------------------------------------------------------ //------------------------- Vertical Retrace Begins ------------------------- void wait_for_retrace(void) { while ((inp(INPUT_STATUS) & VRETRACE)) {}; while (!(inp(INPUT_STATUS) & VRETRACE)) {}; } //------------------------------------------------------------------------------------------ //--------------------------- DrawLine Begins -------------------------------- void DrawLine(int x, int y, int x1, int y1, unsigned char c) { int i, dx=0, dy=0, length; if (x==x1) { length = (y1-y); dy=1; } else { length = (x1-x); dx=1; } for (i=0; i<=(length); i++) { PlotPixel(x,y,c);x = x+dx; y = y+dy; } } //------------------------------------------------------------------------------------------ //------------------------------- IMAGE CAPTURE BEGINS ---------------------------------- Backg_Image_Capture() { int h, w, c; // sprite X, Y values - you can skip this if (Sprite_Red_Y == 186) {ydir=-1;} if (Sprite_Yellow_Y == 186) {ydir=-1;} if (Sprite_Red_Y == 1) {ydir=1;} if (Sprite_Yellow_Y == 1) {ydir=1;} Sprite_Red_Y = Sprite_Red_Y + ydir; Sprite_Yellow_Y = Sprite_Yellow_Y + ydir; //-------------------------- SPRITE RED BACKGROUND CAPTURE ------------------------------- c=0; for (h=0; h<= IMAGE_HEIGHT; h++) { for (w=0; w<= IMAGE_WIDTH; w++) { Sprite_Red_Backg_Array[c++] = ReadPixel(Sprite_Red_X+w, Sprite_Red_Y+h); } } //------------------------ SPRITE YELLOW BACKGROUND CAPTURE ------------------------------- /* c=0; for (h=0; h<= IMAGE_HEIGHT; h++) { for (w=0; w<= IMAGE_WIDTH; w++) { Sprite_Yellow_Backg_Array[c++] = ReadPixel(Sprite_Yellow_X+w, Sprite_Yellow_Y+h); } } */ } //--------------------------------- CAPTURE ENDS ------------------------------- //------------------------- Draw Sprites Begins ----------------------------- void DrawSprites() { int h, w; char far *Sprite_Red_RowPtr; char far *Sprite_Red_BufferPtr; char far *Sprite_Red_ImagePtr; char far *Sprite_Yellow_RowPtr; char far *Sprite_Yellow_BufferPtr; char far *Sprite_Yellow_ImagePtr; //--------------------------- DRAW SPRITE_RED ------------------------------- Sprite_Red_RowPtr = On_Screen+(Sprite_Red_Y * SCREEN_WIDTH) + Sprite_Red_X; Sprite_Red_ImagePtr = Sprite_Red; for (h = 0; h < IMAGE_HEIGHT; h++) { for (w=0, Sprite_Red_BufferPtr = Sprite_Red_RowPtr; w < IMAGE_WIDTH; w++) { *Sprite_Red_BufferPtr++ = *Sprite_Red_ImagePtr++; } Sprite_Red_RowPtr += SCREEN_WIDTH; } //------------------------------------------------------------------------------------------ //--------------------------- DRAW SPRITE_YELLOW ------------------------------- /* Sprite_Yellow_RowPtr = On_Screen+(Sprite_Yellow_Y * SCREEN_WIDTH) + Sprite_Yellow_X; Sprite_Yellow_ImagePtr = Sprite_Yellow; for (h = 0; h < IMAGE_HEIGHT; h++) { for (w=0, Sprite_Yellow_BufferPtr = Sprite_Yellow_RowPtr; w < IMAGE_WIDTH; w++) { *Sprite_Yellow_BufferPtr++ = *Sprite_Yellow_ImagePtr++; } Sprite_Yellow_RowPtr += SCREEN_WIDTH; } */ //------------------------------------------------------------------------------------------ } //----------------------- Erase Sprites Begins ----------------------------- void EraseSprites() { int h, w, c; char far *Sprite_Red_RowPtr; char far *Sprite_Red_BufferPtr; char far *Sprite_Yellow_RowPtr; char far *Sprite_Yellow_BufferPtr; Sprite_Red_RowPtr = On_Screen+(Sprite_Red_Y * SCREEN_WIDTH) + Sprite_Red_X; Sprite_Yellow_RowPtr = On_Screen+(Sprite_Yellow_Y * SCREEN_WIDTH) + Sprite_Yellow_X; //------------------------- ERASE SPRITE_RED --------------------------------------- c=0; for (h = 0; h <= IMAGE_HEIGHT; h++) { for (w=0, Sprite_Red_BufferPtr = Sprite_Red_RowPtr; w <= IMAGE_WIDTH; w++) { *Sprite_Red_BufferPtr++ = Sprite_Red_Backg_Array[c++]; } Sprite_Red_RowPtr += SCREEN_WIDTH; } //------------------------- ERASE SPRITE_YELLOW --------------------------------------- /* c=0; for (h = 0; h <= IMAGE_HEIGHT; h++) { for (w=0, Sprite_Yellow_BufferPtr = Sprite_Yellow_RowPtr; w <= IMAGE_WIDTH; w++) { *Sprite_Yellow_BufferPtr++ = Sprite_Yellow_Backg_Array[c++]; } Sprite_Yellow_RowPtr += SCREEN_WIDTH; } */ } //------------------------------------------------------------------------------------------ //--------------------------- Draw Red & Yellow Stics -------------------------------- DrawSticks() { int i, rsx=130, ysx=230; for (i = 0; i <= 5; i++) { DrawLine(rsx,1,rsx,199,14); rsx++; } for (i = 0; i <= 5; i++) { DrawLine(ysx,1,ysx,199,12); ysx++; } } //------------------------------------------------------------------------------------------ void main() { EnterMode13H(); DrawSticks(); do { Backg_Image_Capture(); DrawSprites(); wait_for_retrace(); //getch(); EraseSprites(); } while (!kbhit()); getch(); LeaveMode13H(); }

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