ref: 3c2622aa007b32a3c1e11ea6532c42c2481aca3f
dir: /src/ztriangle.h/
/*
* We draw a triangle with various GLinterpolations
*/
{
ZBufferPoint *pr1, *pr2, *l1, *l2;
GLfloat fdx1, fdx2, fdy1, fdy2, fz, d1, d2;
GLushort* pz1;
PIXEL* pp1;
GLint part, update_left, update_right;
GLint nb_lines, dx1, dy1, tmp, dx2, dy2;
#if TGL_FEATURE_POLYGON_STIPPLE == 1
GLushort 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 */
{
ZBufferPoint *t;
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 == 1
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 GLushort* 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;
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 == 1
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