Learning Allegro with C++ :D :(

This is a discussion on Learning Allegro with C++ :D :( within the Game Programming forums, part of the General Programming Boards category; Hi, my first visit to the Games Programming thread, I guess it was inevitable. I have attached an assignment that ...

  1. #1
    The Dragon Reborn
    Join Date
    Nov 2009
    Location
    Dublin, Ireland
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    Learning Allegro with C++ :D :(

    Hi, my first visit to the Games Programming thread, I guess it was inevitable.
    I have attached an assignment that I have been working on in order to learn OOP style programming, and something is screwing me up. I haven't found the source for 24hrs.
    My first question- which has no relation to the problem is, what does clear_bitmap(BITMAP) do?
    From what I read and how I understood it is that clear_bitmap() function
    clears whatever drawing is on a bitmap(). But my world was thrown into confusion when my teacher uploaded his code online.
    He blitted a bitmap(which i call player) onto another bitmap(which i call backbuffer) which was then blitted (well draw_sprite() was used) on to the screen- double buffering which i understand.

    Now the player can draw itself. It has its own bitmap, a triangle is drawn on the bitmap, and this player bitmap is blitted to the backbuffer which was blitted to the screen.
    Before I saw my lecturers code. I didn't use the clear_bitmap(playerbuff) function.
    And because of that it appeared as if 2 individual bitmaps (for 2 players) were on the backbuffer, i checked everywhere to see if I could make the player bitmaps transparent to no avail.

    When I looked at my lecturers code I found i only needed one line of code! guess?
    clear_bitmap()!
    so I did
    Code:
    playerbuff = create_bitmap(100,200) ;
    clear_bitmap(playerbuff);
    draw_sprite(....) ;
    And that worked! it was as if there were 2 actual triangles on the screen and not 2 individual bitmaps if you get what I mean.
    but that confused me.
    how is it possible that after creating a bitmap, then clearing that bitmap
    I was still able to draw on the cleared bitmap and draw it on the backbuffer?

    2.
    I will post the code, that has made want to do a Padme Amidala
    Code:
    #include <allegro.h>								  
    #include "Player.h"
    #include "Vector2.h"  
    #include "Obstacle.h"
    
    #include "GameObjects.h"
     
    
    		GameObjects bullets[8] ;
    		
    void respondToKeyBoard(Player &,Player &) ;
    void updateBullets(Player &, BITMAP *) ;
    int oldspace  ;
    int spacedown ;
    			int count ;
    			
    void fireBullets(BITMAP *);
    volatile int ticks ;
    void timer()
    {
    	ticks++ ;
    }
    
    int main() 
    {
    		int oldticks;
    		count = 0 ;
    	spacedown = 0 ;
    	int x=0, y =0; 
    		
    		
    	if(!allegro_init())
    	{	 
    	
    		install_keyboard() ; 
    		install_mouse() ; 
    		install_timer();
    		
    		
    
    	
    		 Player playerOne(40.0f,50.0f) ; 
    		
    		 Player playerTwo(140.0f,50.0f) ; 
    
    		Obstacle SightBlinder(400.0f,100.0f);
    
    		Obstacle DarthVader(40, 350.0f);
    		
    	
    		  
    		BITMAP *backbuffer = create_bitmap(640,480) ;
    			 
    		
    			install_int_ex(timer,BPS_TO_TIMER(60)) ;
    			 srand(time(0)); 
    		if(!set_gfx_mode(GFX_AUTODETECT_WINDOWED, 640,480,0,0))
    		{  
    			
    			
    			while(!key[KEY_ESC])
    			{
    					clear_to_color(backbuffer,makecol(0,0,0)) ;
    				   	
    				   
    				
    					
    				while(ticks==0)
    				{
    					rest(1);
    				}
    				while(ticks>0)
    				{
    					 oldticks = ticks ;
    
    					 
    					 		
    				
    					ticks-- ; 
    
    				
    					if(oldticks<=ticks)
    					{
    						break ;
    					}  
    				}
    				respondToKeyBoard(playerOne, playerTwo)  ; 
    				
    				
    				  				fireBullets(backbuffer);
    								////textprintf(screen,font,320,0,makecol(255,0,0),"COunt: %d", count) ;
    				
    				playerOne.draw(backbuffer) ;
    				playerTwo.draw(backbuffer) ; 
    				
    				
    					SightBlinder.draw(backbuffer,40,30,100,110) ;
    				
    				 DarthVader.draw(backbuffer,40,30,100,110) ;
    			
    				
    				blit(backbuffer,screen,0,0,0,0,SCREEN_W,SCREEN_H) ; 
    				
    			}
    		}
    	}
    
    
    	return 0 ;
    }
    END_OF_MAIN() 
    
    
    void respondToKeyBoard(Player &playerOne, Player &playerTwo) 
    {
    
    	if(key[KEY_SPACE])
    				{
    					oldspace = 0 ; 
    					spacedown = 1 ;
    					if(!oldspace)
    					{
    				
    						for(int index =0;index<=7;index++)
    						{
    								
    								if(!bullets[index].isObjectAlive())
    								{
    									count++ ;
    									bullets[index].setMode(true) ;
    									bullets[index].pos.x = playerTwo.getPosX() ; 
    									bullets[index].pos.y = playerTwo.getPosY() ;
    									
    									
    									break ; 
    								}	
    								else
    								{
    									count =0 ;
    								}
    
    										
    										
    										
    										
    									
    								
    									
    						}
    					}		
    				}
    				else
    				{
    					spacedown = 0 ;
    					
    				}
    				
    
    				
    			
    				
    			    
    				if(key[KEY_A])
    				{
    					playerOne.strafe(-0.3f); 
    				}
    			
    				if(key[KEY_D])
    				{
    					playerOne.strafe(0.3f); 
    				}
    
    				if(key[KEY_W])
    				{
    					playerOne.walk(-0.3f); 
    				}
    			
    				if(key[KEY_S])
    				{
    					playerOne.walk(0.3f); 
    				}
    
    
    
    				
    				if(key[KEY_LEFT])
    				{
    					playerTwo.strafe(-0.3f); 
    				}
    			
    				if(key[KEY_RIGHT])
    				{
    					playerTwo.strafe(0.3f); 
    				}
    
    				if(key[KEY_UP])
    				{
    					playerTwo.walk(-0.3f); 
    				}
    			
    				if(key[KEY_DOWN])
    				{
    					playerTwo.walk(0.3f); 
    				}
    			
    				
    
    }
    
    void fireBullets(BITMAP *backbuffer)
    {
    	for(int i=0;i<8;i++)
    	{
    				 
    			
    							
    		if(bullets[i].isObjectAlive())
    		{
    					//	bullets[i].draw(backbuffer);
    					
    				
    						
    
    					circlefill(backbuffer,bullets[i].pos.x,bullets[i].pos.y,3,makecol(255,0,0)) ;
    
    						bullets[i].pos.y -= 1.0f;
    							  
    						 
    		}
    			if(bullets[i].getPosY()<0)
    			{
    				bullets[i].setMode(false) ; 
    			}
    				
    				
    					
    					 
    			
    						
    	}
    				
    }
    What I want to do is, if the user presses space draw a bullet on the screen.
    Another space input draw another bullet.
    But the thing is it appears to draw all 8 bullets at once. I tried using random velocities in an effort to separate them, no luck. I used random velocity plus timer
    and that doesn't work. Not only does it barely separates the bullets, it slows the 2 players down! which isn't fun .
    I have no idea what to do at this stage: I believe there is a bug in my code, so I hope one of you guys has experience with allegro and can help me with this please.

    I also want to inquire about the install_int (_ex)() function
    does it just call a function like every time seconds specified?
    like:
    Code:
    void timer()
    {
          ticks++ ;
    }
    install_int(timer, 60) ;
    what does that do? Does it call the function timer() every 60 seconds, thus incrementing ticks?

    wow, i'm a great story teller huh?
    Well thanks for any future suggestions, hints and answers.
    Attached Files Attached Files
    Last edited by Eman; 10-28-2010 at 05:15 PM.

  2. #2
    The Dragon Reborn
    Join Date
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    Location
    Dublin, Ireland
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    Remaining files:
    No need to create sprites! I am using vector graphics.
    Thanks for your help
    Attached Files Attached Files

  3. #3
    and the hat of wrongness Salem's Avatar
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    You should know about double posting by now.
    Learning Allegro with C++ :D :(
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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