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.
