ref: c99b80721b808a9475068a8eafde9b7c3cac679e
dir: /src/zline.h/
{
GLint n, dx, dy, sx, pp_inc_1, pp_inc_2;
register GLint a;
register PIXEL *pp;
#if defined(INTERP_RGB) || TGL_FEATURE_RENDER_BITS == 24
register GLuint r, g, b;
#endif
#ifdef INTERP_RGB
register GLuint rinc, ginc, binc;
#endif
#ifdef INTERP_Z
register GLushort *pz;
GLint zinc;
register GLint z, zz;
#endif
if (p1->y > p2->y || (p1->y == p2->y && p1->x > p2->x)) {
ZBufferPoint *tmp;
tmp = p1;
p1 = p2;
p2 = tmp;
}
sx = zb->xsize;
pp = (PIXEL *) ((GLbyte *) zb->pbuf + zb->linesize * p1->y + p1->x * PSZB);
#ifdef INTERP_Z
pz = zb->zbuf + (p1->y * sx + p1->x);
z = p1->z;
#endif
dx = p2->x - p1->x;
dy = p2->y - p1->y;
#ifdef INTERP_RGB
r = p2->r << 8;
g = p2->g << 8;
b = p2->b << 8;
#elif TGL_FEATURE_RENDER_BITS == 24
/* for 24 bits, we store the colors in different variables */
r = p2->r >> 8;
g = p2->g >> 8;
b = p2->b >> 8;
#endif
#ifdef INTERP_RGB
#define RGB(x) x
#if TGL_FEATURE_RENDER_BITS == 24
#define RGBPIXEL pp[0] = r >> 16, pp[1] = g >> 16, pp[2] = b >> 16
#else
#define RGBPIXEL *pp = RGB_TO_PIXEL(r >> 8,g >> 8,b >> 8)
#endif
#else /* INTERP_RGB */
#define RGB(x)
#if TGL_FEATURE_RENDER_BITS == 24
#define RGBPIXEL pp[0] = r, pp[1] = g, pp[2] = b
#else
#define RGBPIXEL *pp = color
#endif
#endif /* INTERP_RGB */
#ifdef INTERP_Z
#define ZZ(x) x
#define PUTPIXEL() \
{ \
zz=z >> ZB_POINT_Z_FRAC_BITS; \
if (ZCMP(zz,*pz)) { \
RGBPIXEL; \
*pz=zz; \
} \
}
#else /* INTERP_Z */
#define ZZ(x)
#define PUTPIXEL() RGBPIXEL
#endif /* INTERP_Z */
#define DRAWLINE(dx,dy,inc_1,inc_2) \
n=dx;\
ZZ(zinc=(p2->z-p1->z)/n);\
RGB(rinc=((p2->r-p1->r) << 8)/n;\
ginc=((p2->g-p1->g) << 8)/n;\
binc=((p2->b-p1->b) << 8)/n);\
a=2*dy-dx;\
dy=2*dy;\
dx=2*dx-dy;\
pp_inc_1 = (inc_1) * PSZB;\
pp_inc_2 = (inc_2) * PSZB;\
do {\
PUTPIXEL();\
ZZ(z+=zinc);\
RGB(r+=rinc;g+=ginc;b+=binc);\
if (a>0) { pp=(PIXEL *)((GLbyte *)pp + pp_inc_1); ZZ(pz+=(inc_1)); a-=dx; }\
else { pp=(PIXEL *)((GLbyte *)pp + pp_inc_2); ZZ(pz+=(inc_2)); a+=dy; }\
} while (--n >= 0);
/* fin macro */
if (dx == 0 && dy == 0) {
PUTPIXEL();
} else if (dx > 0) {
if (dx >= dy) {
DRAWLINE(dx, dy, sx + 1, 1);
} else {
DRAWLINE(dy, dx, sx + 1, sx);
}
} else {
dx = -dx;
if (dx >= dy) {
DRAWLINE(dx, dy, sx - 1, -1);
} else {
DRAWLINE(dy, dx, sx - 1, sx);
}
}
}
#undef INTERP_Z
#undef INTERP_RGB
/* GLinternal defines */
#undef DRAWLINE
#undef PUTPIXEL
#undef ZZ
#undef RGB
#undef RGBPIXEL