MAMEWorld Forums - EmuChat - Re: Star Wars Arcade (SEGA, 1993): fixing model1 emulation

Got it!!! Collision, it's working!

It turns out f60 (int_point) needs to output either (+/-1,0,0), (0,+/-1,0), or (0,0,+/-1), and that's where your mystery three-value integer comes in play. Let me explain with the code, f24_swa (intercept) function:

Code:


// store that number in Qunk variable
//		adr++; // 0, 1 or 2...
		Qunk= tgp_data[adr++];


// replace x1,y1,z1 with x2,y2,z2
// think it works better for f57 (int_normal)
// which uses these coordinates for bounce translation 
		ix = x2 + dx*t;
		iy = y2 + dy*t;
		iz = z2 + dz*t;

// this is the main part here
		if(cp == 0 || cp == 4) 
		{
			m_tgp_int_px = ix;
			m_tgp_int_py = iy;
			m_tgp_int_pz = iz;

			collX=collY=collZ= 0;

			if(Qunk == 0)
			{
				if(dx<0)
					collX= 1;
				else
					collX= -1;

				m_tgp_int_px+= 900*collX;
			}
			else  
			if(Qunk == 1)
			{
				if(dy<0)
					collY= 1;
				else
					collY= -1;

				m_tgp_int_py+= 900*collY;
			}
			else 
			if(Qunk == 2)
			{
				if(dz<0)
					collZ= 1;
				else
					collZ= -1;

				m_tgp_int_pz+= 900*collZ;
			}


			ret = 0;
			adr -= 17;
			break;
		}

I only show differences. So if Qunk is 0 (plane perpendicular to x-axis), then f60 (int_point) function should output either (-1,0,0) or (1,0,0). If Qunk is 1 (plane perpendicular to y-axis), then f60 (int_point) function should output either (0,-1,0) or (0,1,0). And if Qunk is 2 (plane perpendicular to z-axis), then f60 (int_point) function should output either (0,0,-1) or (0,0,1). I also increase m_tgp_int_px/py/pz for 900 units to increase bounce distance, although the whole bounce reaction is likely handled some other way, but for now that works well enough.

f60 (int_point) and f57 (int_normal):

Code:


static void f60(void)
{
	fifoout_push_f(collX);
	fifoout_push_f(collY);
	fifoout_push_f(collZ);

	next_fn();
}

static void f57(void)
{
	fifoout_push_f(m_tgp_int_px);
	fifoout_push_f(m_tgp_int_py);
	fifoout_push_f(m_tgp_int_pz);	

	next_fn(); 
}

Now, there are still some little problems. For stage 2 I had to make collZ positive for both dz<0 and dz>0 or the ship would collide with something at the very entrance of stage 2 when autopilot disengages, possibly the wall behind. But after the ship moves a bit from the starting point then it's all good. Another problem is with asteroids, sometimes collision triggers only after the ship has already went through it. Also, sometimes the ship manages to go through walls despite the bounce, which can be helped by increasing bounce distance, however large bounce distance is not good for narrow corridors and tunnels in the final stage as it can bounce the ship outside through the opposite wall.