PlayStation Development Network

Posted: **November 1st, 2012, 4:55 pm**

Alright so I've been playing around with some code and I can't figure out why my sprite eship (enemy ship) will move right across the screen but will not change directions. Written in C for PSXSDK.

Code: Select all

#include <stdio.h>
#include <psxgpu.h>
#include <psx.h>

GsDispEnv game_dispenv;
GsDrawEnv game_drawenv;

GsImage game_image;
GsSprite ship;
GsSprite shot;
GsSprite eship;

int refresh_needed=0;
int emove=true;

unsigned char file_buffer[0x30000];
unsigned int prim_list[4000];

int ship_coordinates[2];
int shot_coordinates[2];
int eship_coordinates[1];

void load_file_into_buffer(char *fname)
{
	FILE *f;
	int sz, fd;

	f = fopen(fname, "rb");

	fseek(f, 0, SEEK_END);	
	sz = ftell(f);

	fseek(f, 0, SEEK_SET);

	printf("%s (%d)\n", fname, sz);
	
	fread(file_buffer, sizeof(char), sz, f);
	
	fclose(f);
}

void InitializePSX (){
PSX_Init();
	
	GsInit();
	GsClearMem();
	GsSetVideoMode(320,240, VMODE_NTSC);
	
	game_dispenv.x=0;
	game_dispenv.y=0;
	
	GsSetDispEnv(&game_dispenv);
	
	game_drawenv.x=0;
	game_drawenv.y=0;
	
	game_drawenv.w=320;
	game_drawenv.h=240;
	
	game_drawenv.draw_on_display=1;
	game_drawenv.ignore_mask=0;
	game_drawenv.dither=0;
	game_drawenv.set_mask=0;
	
	GsSetDrawEnv(&game_drawenv);
	GsSetList(prim_list);
	
}
void ClearScreen(){
	
GsRectangle gs_rect;
gs_rect.x = 0;
	gs_rect.y = 0;
	gs_rect.w = 320;
	gs_rect.h = 240;
	gs_rect.r = 0;
	gs_rect.g = 0;
	gs_rect.b = 0;
	gs_rect.attribute = 0;	
	
	GsSortRectangle(&gs_rect);
	
	GsDrawList();
	while(GsIsDrawing());

}
void DoubleBuffering(){
if(game_dispenv.y == 0)
		{
			game_dispenv.y = 256;
			game_drawenv.y = 0;
		}
		else
		{
			game_dispenv.y = 0;
			game_drawenv.y = 256;
		}
			
		GsSetDispEnv(&game_dispenv);
		GsSetDrawEnv(&game_drawenv);
			
	}
void game_vblank_handler(){
	refresh_needed++;
}
void ShowFrameBuffer(int ShowIt){
	
	if (ShowIt==0)
	GsSetVideoMode(320,240, VMODE_NTSC);
	if (ShowIt==1)
	GsSetVideoMode(640,480, VMODE_NTSC);
}
void GamePadPlayerOneRead(){
	
	unsigned short pad1, pad2;
	
	PSX_ReadPad(&pad1, &pad2);
	
	if (pad1 & PAD_LEFT){
	if (ship_coordinates[0] > 6){
		ship_coordinates[0]-=3; 
		}else ;
	}
	if (pad1 & PAD_RIGHT){
	if (ship_coordinates[0] < 284){
		ship_coordinates[0]+=3;
		}else ;
	}
	if (pad1 & PAD_UP){
	if (ship_coordinates[1] > 6){
		ship_coordinates[1]-=3;
		}else;
	}
	if (pad1 & PAD_DOWN){
	if (ship_coordinates[1] < 194){
		ship_coordinates[1]+=3;
		}else;
	}
	if (pad1 & PAD_CROSS){
	
	if (shot_coordinates[1] < 0){
		shot_coordinates[0] = ship_coordinates[0]+11;
		shot_coordinates[1] = ship_coordinates[1]-17;
		}else;
	}
	
}

void GameDrawAllSprites(){
	
	ClearScreen();
		
		while(GsIsDrawing());
		
		ship.x=ship_coordinates[0];
		ship.y=ship_coordinates[1];
		shot.x=shot_coordinates[0];
		shot.y=shot_coordinates[1]-=6;
		if (emove=true){
		eship.x=eship_coordinates[0]+=1;
		}
		if (emove=false){
		eship.x=eship_coordinates[0]-=1;
		}
		if (eship.x > 208){
		emove=false;
		}else; emove=true;
		if (shot_coordinates[1] <= -15){
	shot_coordinates[1] = -50;
	}else;
		
		GsSortSprite(&ship);
		GsSortSprite(&shot);
		GsSortSprite(&eship);
	
		GsDrawList();
		while(GsIsDrawing());
		
		DoubleBuffering();
		
	}

int main(){

	InitializePSX();
	
	SetVBlankHandler(game_vblank_handler);
	
	ship_coordinates[0]=145;
    ship_coordinates[1]=155;
	shot_coordinates[0]=-50;
	shot_coordinates[1]=-50;
	eship_coordinates[0]=0;

	GsLoadFont(320, 240, 360, 240);
	
	load_file_into_buffer("cdrom:ship.TIM;1");
	GsImageFromTim(&game_image,file_buffer); 
	GsUploadImage(&game_image); 
	
	GsSpriteFromImage(&ship,&game_image,1);
	
	ship.x=ship_coordinates[0];
	ship.y=ship_coordinates[1];
	ship.w=30;
	ship.h=40;
	
	GsSortSprite(&ship);
	
	load_file_into_buffer("cdrom:shot.TIM;1");
	GsImageFromTim(&game_image,file_buffer); 
	GsUploadImage(&game_image); 
	
	GsSpriteFromImage(&shot,&game_image,1);
	
	shot.x=ship_coordinates[0]+=8;
	shot.y=ship_coordinates[1]-=-15;
	shot.w=7;
	shot.h=17;

	
	GsSortSprite(&shot);
	
	load_file_into_buffer("cdrom:eship.TIM;1");
	GsImageFromTim(&game_image,file_buffer);
	GsUploadImage(&game_image);
	
	GsSpriteFromImage(&eship,&game_image,1);
	
	eship.x=eship_coordinates[0];
	eship.y=0;
	eship.w=25;
	eship.h=35;
	
	GsSortSprite(&eship);
	
	GsDrawList();
	while(GsIsDrawing());
	
	while(1){
		while (refresh_needed){
			
		GamePadPlayerOneRead();
		
		GameDrawAllSprites();
		
	
	
		refresh_needed--;
		}
	}
}

Any help appreciated!

Posted: **November 1st, 2012, 9:02 pm**

Be careful using true and false values when writing in C, since they aren't supported natively. Instead, use 1 or 0, or write on the top of your source code:

Code: Select all

#define true 1
#define false 0

Apart from that, I've seen there are some syntax mistakes here:

Code: Select all

if (emove=true){
      eship.x=eship_coordinates[0]+=1;
      }
      if (emove=false){
      eship.x=eship_coordinates[0]-=1;
      }
      if (eship.x > 208){
      emove=false;
      }else; emove=true;

Comparing values in C needs a == symbol instead of a single =. Moreover, from what I've read, you want your enemy spaceship to change direction at x>208 setting emove to false to make it to go left. If you use an else condition, that means that, if x<=208 (just the opposite condition), emove will be set to true again. So that means your enemy spaceship will be stucked in x=208 forever, since emove will be changing value constantly. BTW, don't write "else" if there's no real need to.

Here is a corrected version of your code:

Code: Select all

#include <stdio.h>
#include <psxgpu.h>
#include <psx.h>

#define true 1
#define false 0

GsDispEnv game_dispenv;
GsDrawEnv game_drawenv;

GsImage game_image;
GsSprite ship;
GsSprite shot;
GsSprite eship;

int refresh_needed=0;
int emove=true;

unsigned char file_buffer[0x30000];
unsigned int prim_list[4000];

int ship_coordinates[2];
int shot_coordinates[2];
int eship_coordinates[1];

void load_file_into_buffer(char *fname)
{
   FILE *f;
   int sz, fd;

   f = fopen(fname, "rb");

   fseek(f, 0, SEEK_END);   
   sz = ftell(f);

   fseek(f, 0, SEEK_SET);

   printf("%s (%d)\n", fname, sz);
   
   fread(file_buffer, sizeof(char), sz, f);
   
   fclose(f);
}

void InitializePSX (){
PSX_Init();
   
   GsInit();
   GsClearMem();
   GsSetVideoMode(320,240, VMODE_NTSC);
   
   game_dispenv.x=0;
   game_dispenv.y=0;
   
   GsSetDispEnv(&game_dispenv);
   
   game_drawenv.x=0;
   game_drawenv.y=0;
   
   game_drawenv.w=320;
   game_drawenv.h=240;
   
   game_drawenv.draw_on_display=1;
   game_drawenv.ignore_mask=0;
   game_drawenv.dither=0;
   game_drawenv.set_mask=0;
   
   GsSetDrawEnv(&game_drawenv);
   GsSetList(prim_list);
   
}
void ClearScreen(){
   
GsRectangle gs_rect;
gs_rect.x = 0;
   gs_rect.y = 0;
   gs_rect.w = 320;
   gs_rect.h = 240;
   gs_rect.r = 0;
   gs_rect.g = 0;
   gs_rect.b = 0;
   gs_rect.attribute = 0;   
   
   GsSortRectangle(&gs_rect);

}

void DoubleBuffering(){
if(game_dispenv.y == 0)
      {
         game_dispenv.y = 256;
         game_drawenv.y = 0;
      }
      else
      {
         game_dispenv.y = 0;
         game_drawenv.y = 256;
      }
         
      GsSetDispEnv(&game_dispenv);
      GsSetDrawEnv(&game_drawenv);
         
   }
   
void game_vblank_handler(){
   refresh_needed=1;
}

void GamePadPlayerOneRead(){
   
   unsigned short pad1, pad2;
   
   PSX_ReadPad(&pad1, &pad2);
   
   if (pad1 & PAD_LEFT){
		if (ship_coordinates[0] > 6)
			ship_coordinates[0]-=3; 
   }
   
   if (pad1 & PAD_RIGHT){
		if (ship_coordinates[0] < 284)
			ship_coordinates[0]+=3;
   }
   
   if (pad1 & PAD_UP){
		if (ship_coordinates[1] > 6)
			ship_coordinates[1]-=3;
   }
   if (pad1 & PAD_DOWN){
		if (ship_coordinates[1] < 194)
			ship_coordinates[1]+=3;
   }
   
   if (pad1 & PAD_CROSS){
		if (shot_coordinates[1] < 0){
			shot_coordinates[0] = ship_coordinates[0]+11;
			shot_coordinates[1] = ship_coordinates[1]-17;
      }
   }
   
}

void GameDrawAllSprites(){
   
	  ClearScreen();
      
      ship.x=ship_coordinates[0];
      ship.y=ship_coordinates[1];
      shot.x=shot_coordinates[0];
      shot.y=shot_coordinates[1]-=6;
      
      if (emove==true)
      eship.x=eship_coordinates[0]+=1;
      
      if (emove==false)
      eship.x=eship_coordinates[0]-=1;
      
      if (eship.x > 208) //If x>208, the spaceship turns left
      emove = false;
     
	  if (eship.x <= 20) //If x<=20, the spaceship turns right
	  emove = true;
	  
	  
      if (shot_coordinates[1] <= -15)
		shot_coordinates[1] = -50;
      
      GsSortSprite(&ship);
      GsSortSprite(&shot);
      GsSortSprite(&eship);
   
      GsDrawList();
      while(GsIsDrawing());
          
      DoubleBuffering();
      
   }

int main(){

   InitializePSX();
   
   SetVBlankHandler(game_vblank_handler);
   
   ship_coordinates[0]=145;
    ship_coordinates[1]=155;
   shot_coordinates[0]=-50;
   shot_coordinates[1]=-50;
   eship_coordinates[0]=0;

   GsLoadFont(320, 240, 360, 240);
   
   load_file_into_buffer("cdrom:ship.TIM;1");
   GsImageFromTim(&game_image,file_buffer); 
   GsUploadImage(&game_image); 
   
   GsSpriteFromImage(&ship,&game_image,1);
   
   ship.x=ship_coordinates[0];
   ship.y=ship_coordinates[1];
   ship.w=30;
   ship.h=40;
   
   GsSortSprite(&ship);
   
   load_file_into_buffer("cdrom:shot.TIM;1");
   GsImageFromTim(&game_image,file_buffer); 
   GsUploadImage(&game_image); 
   
   GsSpriteFromImage(&shot,&game_image,1);
   
   shot.x=ship_coordinates[0]+=8;
   shot.y=ship_coordinates[1]-=-15;
   shot.w=7;
   shot.h=17;

   
   GsSortSprite(&shot);
   
   load_file_into_buffer("cdrom:eship.TIM;1");
   GsImageFromTim(&game_image,file_buffer);
   GsUploadImage(&game_image);
   
   GsSpriteFromImage(&eship,&game_image,1);
   
   eship.x=eship_coordinates[0];
   eship.y=0;
   eship.w=25;
   eship.h=35;
   
   GsSortSprite(&eship);
   
   GsDrawList();
   while(GsIsDrawing());
   
   while(1){
      while (refresh_needed){
         
      GamePadPlayerOneRead();
      
      GameDrawAllSprites();
   
      refresh_needed=0;
      }
   }
}

Some more considerations to take into account:

Â· The first example I sent you was very old, from the time I started writing with PSXSDK. That means functions such as ShowMeTheBuffer() are completely useless, so you can remove them.
Â· Instead of writing refresh_needed++, write refresh_needed = 1. Otherwise, if your game uses too many resources in a certain moment, this variable will increase a lot, so your game won't stop being refreshed until it becomes equal to zero again. It's already fixed in the code I've attached.
Â· Because of the same first reason, just use GsDrawList() and while(GsIsDrawing()) once all of your primitives (sprites, rectangles, whatever) are sorted. This reduces GPU load.
Â· Using arrays such as eship_coordinates[2] aren't really needed. I know they're used in my example, but, again, it was made when I was a newbie.

Posted: **November 2nd, 2012, 11:53 am**

That's alright. I'm a newbie right now as it is. Thanks for fixing up my code for me!

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