$PSDocId: Document Release 1.0 for Runtime Library Release 3.6$
$PSLibId: Runtime Library Release 3.6$

Sample program showing use of the Divide function

* The Divide function (of libgte) inhibits texture distortion caused 
  by polygon division.  


In this sample program, division is performed on the 
POLY_FT4 flat texture quadrilateral using the DivideFT4() function.  


* Control pad operation is as shown below.

	"Left cross key"		move up/down, left/right
	L1, L2				move front/back
	
	R1, R2				rotate
	"Right cross key"		rotate

	START + "Left cross key"	change number of divisions
	SELECT + "Left cross key"	change picture area

* Compiling the program

	> psymake all

* Loading the program

	> psymake load
	> run main

  The initial value for division depth is 2 (4 x 4 division) and the 
  initial size of the picture area is 540 (w) x 170 (h).


* Miscellaneous

To make the division process easy to understand, this sample program limits 
its operation to a region inside the screen, rather than using the full 
screen which is the normal picture area.  

In this example, the picture area is that area enclosed by the white line 
of the injector.  Division is not performed from outside this area up to 
the protruding section. 

Divided polygons are directly registered to the specified OT entry when 
the Divide function is called. They are registered to all of the same 
entries, independently of the otz, after division.  

The Divide function judges normal clipping only once before division.  
This means that large polygons that have approached a viewpoint are 
all clipped prior to divison.  This can produce situations where a 
section which is expected to be drawn is not. To prevent this from 
happening, use the RCpoly function instead of the Divide function as 
shown below.
 

u_long *DivideFT4(v0,v1,v2,v3,uv0,uv1,uv2,uv3,rgbc,s,ot,divp)
SVECTOR *v0,*v1,*v2,*v3;
u_long *uv0,*uv1,*uv2,*uv3;
CVECTOR *rgbc;
POLY_FT4 *s;
u_long *ot;
DIVPOLYGON4 *divp;  

{
    int i;
    u_short sz;
    long p,flag;
    RVECTOR *r0,*r1,*r2,*r3;
    

    r0= &divp->r0;
    r1= &divp->r1;
    r2= &divp->r2;
    r3= &divp->r3;
    divp->cr[0].r0 = r0;		
    divp->cr[0].r1 = r1;		
    divp->cr[0].r2 = r2;		
    divp->cr[0].r3 = r3;		
    r0->v = *v0;
    r1->v = *v1;
    r2->v = *v2;
    r3->v = *v3;

    if(RotAverageNclip4
       (
	&r0->v,&r1->v,&r2->v,&r3->v,
	&r0->sxy,&r1->sxy,&r2->sxy,&r3->sxy,
	&p,&sz,&flag)>0 )
	{
	    ReadSZfifo4(&r0->sz,&r1->sz,&r2->sz,&r3->sz);
	    divp->ot = ot;
	    divp->rgbc = *rgbc;
	    divp->clut = (*uv0)>>16;
	    divp->tpage = (*uv1)>>16;
	    *(u_long *)(r0->uv) = *uv0;
	    *(u_long *)(r1->uv) = *uv1;
	    *(u_long *)(r2->uv) = *uv2;
	    *(u_long *)(r3->uv) = *uv3;
	    s =(POLY_FT4 *)RCpolyFT4(s,divp);
	}
    return((u_long *)s);
}

			Copyright (C) 1995 Sony Computer Entertainment Inc.