ref: d74a2542f79ae3b033311fe6ddcbbc2f1fa475f9
parent: faf04e4acad1607b7eedf3ea1e15f8b3cb302808
author: Fabien Sanglard <fabien.sanglard@gmail.com>
date: Fri Dec 14 04:31:55 EST 2012
Added comments to sectorscan and iinside
--- a/Engine/src/engine.c
+++ b/Engine/src/engine.c
@@ -349,22 +349,30 @@
wal2 = &wall[wal->point2];
// In camera space the center is the player.
- // Make the camrea the center of the world: Wall coordinates
- x1 = wal->x-globalposx; y1 = wal->y-globalposy;
- x2 = wal2->x-globalposx; y2 = wal2->y-globalposy;
+ // Make the camera the center of the world for the 2 Wall endpoints (x,y)
+ x1 = wal->x-globalposx;
+ y1 = wal->y-globalposy;
+
+ x2 = wal2->x-globalposx;
+ y2 = wal2->y-globalposy;
// If this is a portal...
if ((nextsectnum >= 0) && ((wal->cstat&32) == 0))
- //If this portal has not been visited.
+ //If this portal has not been visited yet.
if ((gotsector[nextsectnum>>3]&pow2char[nextsectnum&7]) == 0)
{+ //Cross product -> Z component
tempint = x1*y2-x2*y1;
// Using cross product, determine if the portal is facing us or not.
// If it is: Add it to the stack and bump the stack counter.
+ // This line is equivalent to tempint < 0x40000
if (((unsigned)tempint+262144) < 524288)
+ {+ //(x2-x1)*(x2-x1)+(y2-y1)*(y2-y1) is the squared length of the wall
if (mulscale5(tempint,tempint) <= (x2-x1)*(x2-x1)+(y2-y1)*(y2-y1))
sectorborder[sectorbordercnt++] = nextsectnum;
+ }
}
// Rotate the wall endpoint position according to the player orientation.
@@ -371,7 +379,7 @@
// This is a regular rotation matrix using [29.3] fixed point.
if ((z == startwall) || (wall[z-1].point2 != z))
{- //If this is the first endpoint of the bunch, rotate
+ //If this is the first endpoint of the bunch, rotate: This is a standard cos sin 2D rotation matrix projection
xp1 = dmulscale6(y1,cosglobalang,-x1,singlobalang);
yp1 = dmulscale6(x1,cosviewingrangeglobalang,y1,sinviewingrangeglobalang);
}
@@ -381,11 +389,13 @@
xp1 = xp2;
yp1 = yp2;
}
- xp2 = dmulscale6(y2,cosglobalang,-x2,singlobalang);
- yp2 = dmulscale6(x2,cosviewingrangeglobalang,y2,sinviewingrangeglobalang);
+ // Rotate: This is a standard cos sin 2D rotation matrix projection
+ xp2 = dmulscale6(y2,cosglobalang,-x2,singlobalang);
+ yp2 = dmulscale6(x2,cosviewingrangeglobalang,y2,sinviewingrangeglobalang);
+
// No idea what this is.
if ((yp1 < 256) && (yp2 < 256)) goto skipitaddwall;
@@ -396,21 +406,31 @@
if (xp1 >= -yp1)
{- if ((xp1 > yp1) || (yp1 == 0)) goto skipitaddwall;
+ if ((xp1 > yp1) || (yp1 == 0))
+ goto skipitaddwall;
+
xb1[numscans] = halfxdimen + scale(xp1,halfxdimen,yp1);
- if (xp1 >= 0) xb1[numscans]++; /* Fix for SIGNED divide */
- if (xb1[numscans] >= xdimen) xb1[numscans] = xdimen-1;
+ if (xp1 >= 0)
+ xb1[numscans]++; /* Fix for SIGNED divide */
+
+ if (xb1[numscans] >= xdimen)
+ xb1[numscans] = xdimen-1;
+
yb1[numscans] = yp1;
}
else
{- if (xp2 < -yp2) goto skipitaddwall;
+ if (xp2 < -yp2)
+ goto skipitaddwall;
+
xb1[numscans] = 0;
tempint = yp1-yp2+xp1-xp2;
- if (tempint == 0) goto skipitaddwall;
+ if (tempint == 0)
+ goto skipitaddwall;
yb1[numscans] = yp1 + scale(yp2-yp1,xp1+yp1,tempint);
}
- if (yb1[numscans] < 256) goto skipitaddwall;
+ if (yb1[numscans] < 256)
+ goto skipitaddwall;
if (xp2 <= yp2)
{@@ -451,7 +471,7 @@
}
}
- //FCS: TODO rename this p2[]. This name is an abomination
+ //FCS: TODO rename this p2[] to bunchList[] or something like that. This name is an abomination
for(z=numscansbefore;z<numscans;z++)
{if ((wall[thewall[z]].point2 != thewall[p2[z]]) || (xb2[z] >= xb1[p2[z]]))
@@ -3874,7 +3894,7 @@
int32_t i, x1, y1, x2, y2;
uint32_t cnt;
- //Quick check if the sector ID is valide.
+ //Quick check if the sector ID is valid.
if ((sectnum < 0) || (sectnum >= numsectors)) return(-1);
cnt = 0;
@@ -3894,9 +3914,15 @@
//Again, compare the sign of x1 and x2. If (x1^x2) >= 0 then x is on the left or the right of both wal->x and wall[wal->point2].x.
if ((x1^x2) >= 0)
+ {+ // Euh...je ne sais pas.....
cnt ^= x1;
+ }
else
+ {+ //Cross-Product WTF ?
cnt ^= (x1*y2-x2*y1)^y2;
+ }
}
wal++;
@@ -3904,6 +3930,7 @@
} while (i);
+ //Just return the sign.
return(cnt>>31);
}