ref: 3b961717be648d0810bb364e3cacbd4be8f7ce0b
dir: /src/ztriangle.h/
/*
* We draw a triangle with various GLinterpolations
*/
{
ZBufferPoint *t,*pr1,*pr2,*l1,*l2;
GLfloat fdx1, fdx2, fdy1, fdy2, fz, d1, d2;
unsigned short *pz1;
PIXEL *pp1;
GLint part,update_left,update_right;
GLint nb_lines,dx1,dy1,tmp,dx2,dy2;
#if TGL_FEATURE_POLYGON_STIPPLE
unsigned short the_y;
#endif
GLint error,derror;
GLint x1,dxdy_min,dxdy_max;
/* warning: x2 is multiplied by 2^16 */
GLint x2,dx2dy2;
#ifdef INTERP_Z
GLint z1,dzdx,dzdy,dzdl_min,dzdl_max;
#endif
#ifdef INTERP_RGB
GLint r1,drdx,drdy,drdl_min,drdl_max;
GLint g1,dgdx,dgdy,dgdl_min,dgdl_max;
GLint b1,dbdx,dbdy,dbdl_min,dbdl_max;
#endif
#ifdef INTERP_ST
GLint s1,dsdx,dsdy,dsdl_min,dsdl_max;
GLint t1,dtdx,dtdy,dtdl_min,dtdl_max;
#endif
#ifdef INTERP_STZ
GLfloat sz1,dszdx,dszdy,dszdl_min,dszdl_max;
GLfloat tz1,dtzdx,dtzdy,dtzdl_min,dtzdl_max;
#endif
/* we sort the vertex with increasing y */
if (p1->y < p0->y) {
t = p0;
p0 = p1;
p1 = t;
}
if (p2->y < p0->y) {
t = p2;
p2 = p1;
p1 = p0;
p0 = t;
} else if (p2->y < p1->y) {
t = p1;
p1 = p2;
p2 = t;
}
/* we compute dXdx and dXdy for all GLinterpolated values */
fdx1 = p1->x - p0->x;
fdy1 = p1->y - p0->y;
fdx2 = p2->x - p0->x;
fdy2 = p2->y - p0->y;
fz = fdx1 * fdy2 - fdx2 * fdy1;
if (fz == 0)
return;
fz = 1.0 / fz;
fdx1 *= fz;
fdy1 *= fz;
fdx2 *= fz;
fdy2 *= fz;
#ifdef INTERP_Z
d1 = p1->z - p0->z;
d2 = p2->z - p0->z;
dzdx = (GLint) (fdy2 * d1 - fdy1 * d2);
dzdy = (GLint) (fdx1 * d2 - fdx2 * d1);
#endif
#ifdef INTERP_RGB
d1 = p1->r - p0->r;
d2 = p2->r - p0->r;
drdx = (GLint) (fdy2 * d1 - fdy1 * d2);
drdy = (GLint) (fdx1 * d2 - fdx2 * d1);
d1 = p1->g - p0->g;
d2 = p2->g - p0->g;
dgdx = (GLint) (fdy2 * d1 - fdy1 * d2);
dgdy = (GLint) (fdx1 * d2 - fdx2 * d1);
d1 = p1->b - p0->b;
d2 = p2->b - p0->b;
dbdx = (GLint) (fdy2 * d1 - fdy1 * d2);
dbdy = (GLint) (fdx1 * d2 - fdx2 * d1);
#endif
#ifdef INTERP_ST
d1 = p1->s - p0->s;
d2 = p2->s - p0->s;
dsdx = (GLint) (fdy2 * d1 - fdy1 * d2);
dsdy = (GLint) (fdx1 * d2 - fdx2 * d1);
d1 = p1->t - p0->t;
d2 = p2->t - p0->t;
dtdx = (GLint) (fdy2 * d1 - fdy1 * d2);
dtdy = (GLint) (fdx1 * d2 - fdx2 * d1);
#endif
#ifdef INTERP_STZ
{
GLfloat zz;
zz=(GLfloat) p0->z;
p0->sz= (GLfloat) p0->s * zz;
p0->tz= (GLfloat) p0->t * zz;
zz=(GLfloat) p1->z;
p1->sz= (GLfloat) p1->s * zz;
p1->tz= (GLfloat) p1->t * zz;
zz=(GLfloat) p2->z;
p2->sz= (GLfloat) p2->s * zz;
p2->tz= (GLfloat) p2->t * zz;
d1 = p1->sz - p0->sz;
d2 = p2->sz - p0->sz;
dszdx = (fdy2 * d1 - fdy1 * d2);
dszdy = (fdx1 * d2 - fdx2 * d1);
d1 = p1->tz - p0->tz;
d2 = p2->tz - p0->tz;
dtzdx = (fdy2 * d1 - fdy1 * d2);
dtzdy = (fdx1 * d2 - fdx2 * d1);
}
#endif
/* screen coordinates */
pp1 = (PIXEL *) ((GLbyte *) zb->pbuf + zb->linesize * p0->y);
#if TGL_FEATURE_POLYGON_STIPPLE
the_y = p0->y;
#endif
pz1 = zb->zbuf + p0->y * zb->xsize;
DRAW_INIT();
for(part=0;part<2;part++) {
if (part == 0) {
if (fz > 0) {
update_left=1;
update_right=1;
l1=p0;
l2=p2;
pr1=p0;
pr2=p1;
} else {
update_left=1;
update_right=1;
l1=p0;
l2=p1;
pr1=p0;
pr2=p2;
}
nb_lines = p1->y - p0->y;
} else {
/* second part */
if (fz > 0) {
update_left=0;
update_right=1;
pr1=p1;
pr2=p2;
} else {
update_left=1;
update_right=0;
l1=p1;
l2=p2;
}
nb_lines = p2->y - p1->y + 1;
}
/* compute the values for the left edge */
if (update_left) {
dy1 = l2->y - l1->y;
dx1 = l2->x - l1->x;
if (dy1 > 0)
tmp = (dx1 << 16) / dy1;
else
tmp = 0;
x1 = l1->x;
error = 0;
derror = tmp & 0x0000ffff;
dxdy_min = tmp >> 16;
dxdy_max = dxdy_min + 1;
#ifdef INTERP_Z
z1=l1->z;
dzdl_min=(dzdy + dzdx * dxdy_min);
dzdl_max=dzdl_min + dzdx;
#endif
#ifdef INTERP_RGB
r1=l1->r;
drdl_min=(drdy + drdx * dxdy_min);
drdl_max=drdl_min + drdx;
g1=l1->g;
dgdl_min=(dgdy + dgdx * dxdy_min);
dgdl_max=dgdl_min + dgdx;
b1=l1->b;
dbdl_min=(dbdy + dbdx * dxdy_min);
dbdl_max=dbdl_min + dbdx;
#endif
#ifdef INTERP_ST
s1=l1->s;
dsdl_min=(dsdy + dsdx * dxdy_min);
dsdl_max=dsdl_min + dsdx;
t1=l1->t;
dtdl_min=(dtdy + dtdx * dxdy_min);
dtdl_max=dtdl_min + dtdx;
#endif
#ifdef INTERP_STZ
sz1=l1->sz;
dszdl_min=(dszdy + dszdx * dxdy_min);
dszdl_max=dszdl_min + dszdx;
tz1=l1->tz;
dtzdl_min=(dtzdy + dtzdx * dxdy_min);
dtzdl_max=dtzdl_min + dtzdx;
#endif
}
/* compute values for the right edge */
if (update_right) {
dx2 = (pr2->x - pr1->x);
dy2 = (pr2->y - pr1->y);
if (dy2>0)
dx2dy2 = ( dx2 << 16) / dy2;
else
dx2dy2 = 0;
x2 = pr1->x << 16;
}
/* we draw all the scan line of the part */
while (nb_lines>0) {
nb_lines--;
#ifndef DRAW_LINE
/* generic draw line */
{
register PIXEL *pp;
register GLint n;
#ifdef INTERP_Z
register unsigned short *pz;
register GLuint z,zz;
#endif
#ifdef INTERP_RGB
register GLuint or1,og1,ob1;
#endif
#ifdef INTERP_ST
register GLuint s,t;
#endif
#ifdef INTERP_STZ
GLfloat sz,tz;
#endif
n=(x2 >> 16) - x1;
/*the_x = x1; //Gek added this to make determining the X coordinate easier!*/
pp=(PIXEL *)((GLbyte *)pp1 + x1 * PSZB);
#ifdef INTERP_Z
pz=pz1+x1;
z=z1;
#endif
#ifdef INTERP_RGB
or1 = r1;
og1 = g1;
ob1 = b1;
#endif
#ifdef INTERP_ST
s=s1;
t=t1;
#endif
#ifdef INTERP_STZ
sz=sz1;
tz=tz1;
#endif
while (n>=3) {
PUT_PIXEL(0);/*the_x++;*/
PUT_PIXEL(1);/*the_x++;*/
PUT_PIXEL(2);/*the_x++;*/
PUT_PIXEL(3);/*the_x++;*/
#ifdef INTERP_Z
pz+=4;
#endif
pp=(PIXEL *)((GLbyte *)pp + 4 * PSZB);
n-=4;
}
while (n>=0) {
PUT_PIXEL(0);/*the_x++;*/
#ifdef INTERP_Z
pz+=1;
#endif
pp=(PIXEL *)((GLbyte *)pp + PSZB);
n-=1;
}
}
//the_y++;
#else
DRAW_LINE();//the_y++;
#endif
/* left edge */
error+=derror;
if (error > 0) {
error-=0x10000;
x1+=dxdy_max;
#ifdef INTERP_Z
z1+=dzdl_max;
#endif
#ifdef INTERP_RGB
r1+=drdl_max;
g1+=dgdl_max;
b1+=dbdl_max;
#endif
#ifdef INTERP_ST
s1+=dsdl_max;
t1+=dtdl_max;
#endif
#ifdef INTERP_STZ
sz1+=dszdl_max;
tz1+=dtzdl_max;
#endif
} else {
x1+=dxdy_min;
#ifdef INTERP_Z
z1+=dzdl_min;
#endif
#ifdef INTERP_RGB
r1+=drdl_min;
g1+=dgdl_min;
b1+=dbdl_min;
#endif
#ifdef INTERP_ST
s1+=dsdl_min;
t1+=dtdl_min;
#endif
#ifdef INTERP_STZ
sz1+=dszdl_min;
tz1+=dtzdl_min;
#endif
}
/* right edge */
x2+=dx2dy2;
/* screen coordinates */
pp1=(PIXEL *)((GLbyte *)pp1 + zb->linesize);
#if TGL_FEATURE_POLYGON_STIPPLE
the_y++;
#endif
pz1+=zb->xsize;
}
}
}
#undef INTERP_Z
#undef INTERP_RGB
#undef INTERP_ST
#undef INTERP_STZ
#undef DRAW_INIT
#undef DRAW_LINE
#undef PUT_PIXEL