ref: 47f57bd42b9d8eb3ee5d9b34c4221c61cc161395
dir: /src/ztriangle_tried_openmp_backup.h/
/*
* An eXtReMeLy complicated, delicate, tuned triangle rasterizer
* Aight, so basically this is the most complicated code you'll ever read in your life.
* The lifetime of variables has been... SUPER Optimized, that's why there's so many random ass curly braces everywhere.
* Yes, it is necessary to do that. This code is extremely delicate
* and even a minor fuck-up is gonna tank the framerate
Before committing any changes, run gears, model, and texture on your changed code to make sure you didn't
fuck up!
Things to keep in mind:
1) Tight control of the lifetimes, scopes, and usage of variables lets us use registers more often and memory less
2) Doing the same operation on multiple items is faster than doing different things on different items, generally, because
they will be able to take advantage of any/all applicable SIMD/vector ops on your hardware.
3) Divide operations are vastly more expensive than add/sub/bitwise/etc
4) Bit shifting is your friend, it's the fast way to multiply or divide by 2.
5) Fixed point math is used for the depth "z" buffer
6) We're not just using floats for everything because this is still supposed to be fast on platforms without SSE2
7) Fewer variables is usually better
8) All variables that are used inside the rasterizer loop must exist irrespective of feature level at the language level,
because OpenMP needs to be able to declare them "private". The compiler will of course optimize out the unused ones.
*/
#define BEGIN_SEGMENT
{
//All these variables are safe to be shared.
//GLint dx1, dy1, dx2, dy2;
//these VAR VAR_min, and VAR_max must be private.
//#ifdef INTERP_Z
GLint dzdx, dzdy;
//#ifdef INTERP_RGB
GLint drdx, drdy;
GLint dgdx, dgdy;
GLint dbdx, dbdy;
GLint dsdx, dsdy;
GLint dtdx, dtdy;
GLfloat dszdx, dszdy;
GLfloat dtzdx, dtzdy; //Not the cause of our problem.
GLfloat fdzdx, fndzdx, ndszdx, ndtzdx;
/* we sort the vertex with increasing y */
if (p1->y < p0->y) {
ZBufferPoint *t = p0;
p0 = p1;
p1 = t;
}
if (p2->y < p0->y) {
ZBufferPoint *t = p2;
p2 = p1;
p1 = p0;
p0 = t;
} else if (p2->y < p1->y) {
ZBufferPoint *t = p1;
p1 = p2;
p2 = t;
}
GLfloat fz;
{GLfloat fdx1, fdx2, fdy1, fdy2;
/* we compute dXdx and dXdy for all GLinterpolated values */
fdx1 = p1->x - p0->x;//fdx1 first usage (VALUE_FDX1_USED)
fdy1 = p1->y - p0->y;//fdy1 first usage (VALUE_FDY1_USED)
fdx2 = p2->x - p0->x;
fdy2 = p2->y - p0->y;
fz = fdx1 * fdy2 - fdx2 * fdy1;//fz first usage
if (fz == 0)
return;
fz = 1.0 / fz; //value of fz is used (VALUE_FZ_USED)
//for these (VALUE_FZ_USED)
fdx1 *= fz;
fdy1 *= fz;
fdx2 *= fz;
fdy2 *= fz;
//and then
{
GLfloat d1, d2;
#ifdef INTERP_Z
{
d1 = p1->z - p0->z; //d1 first usage
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 zedzed;
zedzed = (GLfloat)p0->z;
p0->sz = (GLfloat)p0->s * zedzed;
p0->tz = (GLfloat)p0->t * zedzed;
zedzed = (GLfloat)p1->z;
p1->sz = (GLfloat)p1->s * zedzed;
p1->tz = (GLfloat)p1->t * zedzed;
zedzed = (GLfloat)p2->z;
p2->sz = (GLfloat)p2->s * zedzed;
p2->tz = (GLfloat)p2->t * zedzed;
}
{
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
}//EOF d1, d2 lifetimes.
}//eof fdx1 fdx2 fdy1 fdy2 lifetimes.
/* screen coordinates */
/*
pp1 = (PIXEL*)(zb->pbuf) + zb->xsize * p0->y; //pp1 first usage
#if TGL_FEATURE_POLYGON_STIPPLE == 1
the_y = p0->y;
#endif
pz1 = zb->zbuf + p0->y * zb->xsize;
*/
DRAW_INIT();
//Required reading:
//http://jakascorner.com/blog/2016/06/omp-data-sharing-attributes.html
//I'd also like to figure out if the main while() loop over raster lines can be OMP parallelized, but I suspect it isn't worth it.
#pragma omp parallel for num_threads(2)
for (GLint part = 0; part < 2; part++) {
//Variables specific to this part of the triangle.
#define ZEROASSN =0
//#define ZEROASSN /* a comment*/
GLint x1 ZEROASSN, dxdy_min ZEROASSN, dxdy_max ZEROASSN;
GLint z1 ZEROASSN, dzdl_min ZEROASSN, dzdl_max ZEROASSN;
GLint r1 ZEROASSN, drdl_min ZEROASSN, drdl_max ZEROASSN;
GLint g1 ZEROASSN, dgdl_min ZEROASSN, dgdl_max ZEROASSN;
GLint b1 ZEROASSN, dbdl_min ZEROASSN, dbdl_max ZEROASSN;
GLint s1 ZEROASSN, dsdl_min ZEROASSN, dsdl_max ZEROASSN;
GLint t1 ZEROASSN, dtdl_min ZEROASSN, dtdl_max ZEROASSN;
GLfloat sz1 ZEROASSN, dszdl_min ZEROASSN, dszdl_max ZEROASSN;
GLfloat tz1 ZEROASSN, dtzdl_min ZEROASSN, dtzdl_max ZEROASSN;
GLint nb_lines ZEROASSN;
GLushort* pz1 ZEROASSN;
PIXEL* pp1 ZEROASSN;
GLint error ZEROASSN, derror ZEROASSN;
GLfloat fzl = fz;
GLint dx1 ZEROASSN, dy1 ZEROASSN, dx2 ZEROASSN, dy2 ZEROASSN;
/* warning: x2 is multiplied by 2^16 */
GLint x2 ZEROASSN, dx2dy2 ZEROASSN;
#if TGL_FEATURE_POLYGON_STIPPLE == 1
GLushort the_y ZEROASSN;
#endif
{ZBufferPoint *pr1, *pr2, *l1, *l2; //BEGINNING OF LIFETIME FOR ZBUFFERPOINT VARS!!!
register GLint update_left, update_right; //update_left decl
if (part == 0) {
update_left = 1; //update_left first usage.
update_right = 1;
if (fzl > 0) { //Here! (VALUE_FZ_USED)
l1 = p0; //MARK l1 first usage
l2 = p2; //MARK l2 first usage
pr1 = p0; //MARK first usage of pr1
pr2 = p1; //MARK first usage pf pr2
} else {
l1 = p0;
l2 = p1;
pr1 = p0;
pr2 = p2;
}
pp1 = (PIXEL*)(zb->pbuf) + zb->xsize * p0->y; //pp1 first usage
#if TGL_FEATURE_POLYGON_STIPPLE == 1
the_y = p0->y;
#endif
pz1 = zb->zbuf + p0->y * zb->xsize;
nb_lines = p1->y - p0->y;
} else { //SECOND PART~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/* second part */
if (fzl > 0) { //fzl last usage (VALUE_FZ_USED)
update_left = 0;
update_right = 1;
pr1 = p1;
pr2 = p2;
} else {
update_left = 1;
update_right = 0;
l1 = p1;
l2 = p2;
}
pp1 = (PIXEL*)(zb->pbuf) + zb->xsize * p0->y + (zb->xsize * (p1->y - p0->y)); //pp1 update to second part.
#if TGL_FEATURE_POLYGON_STIPPLE == 1
the_y = p1->y;
#endif
pz1 = zb->zbuf + p0->y * zb->xsize + (zb->xsize * (p1->y - p0->y));
nb_lines = p2->y - p1->y + 1;
} //EOF SECOND PART
/* compute the values for the left edge */
//pr1 and pr2 are not used inside this area.
if (update_left)
//if (1)
{
{
register GLint tmp;
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
} //EOF update left
//Is l1 used after update_left?
/* compute values for the right edge */
if (update_right)
//if (1)
{ //Update right tested
dx2 = (pr2->x - pr1->x);
dy2 = (pr2->y - pr1->y); //LAST USAGE OF PR2
if (dy2 > 0)
dx2dy2 = (dx2 << 16) / dy2;
else
dx2dy2 = 0;
x2 = pr1->x << 16; //LAST USAGE OF PR1
} //EOF update right
} //End of lifetime for ZBufferpoints
/* we draw all the scan line of the part */
//TODO: omp parallel for
//for(GLint q = 0; q < nb_lines; q++)
//for(; nb_lines > 0; nb_lines--) //Replaces the while.
while(nb_lines>0)
{ nb_lines--; //Effectively matching the while.
#ifndef DRAW_LINE
/* generic draw line */
{
register PIXEL* pp;
register GLint n;
#ifdef INTERP_Z
register GLushort* pz;
register GLuint z;
#endif
#ifdef INTERP_RGB
register GLint or1, og1, ob1;
#endif
#ifdef INTERP_ST
register GLuint s, t;
#endif
#ifdef INTERP_STZ
//GLfloat sz, tz; //These variables go unused in this draw line function.
#endif
n = (x2 >> 16) - x1;
//pp = (PIXEL*)((GLbyte*)pp1 + x1 * PS_ZB);
pp = (PIXEL*)pp1 + x1;
#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; //What is SZ used for?
// tz = tz1; //What is TZ used for?
#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 * PS_ZB);
pp += 4;
n -= 4;
}
while (n >= 0) {
PUT_PIXEL(0); /*the_x++;*/
#ifdef INTERP_Z
//pz += 1;
pz++;
#endif
/*pp = (PIXEL*)((GLbyte*)pp + PS_ZB);*/
pp++;
n--;
}
}
#else
DRAW_LINE();
#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);
pp1 += zb->xsize;
#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