zdoom/qzdoom
0
0
Fork 0
mirror of https://github.com/ZDoom/qzdoom.git synced 2024-11-11 23:32:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

- Improve the 64 bit incompatibility patch.

Browse source 
- Reorder the operands. First the numerator, then the denominator :) .
- Add a comment regarding the motivations for this change.
This commit is contained in:
Edoardo Prezioso 2014-11-16 11:29:16 +01:00
parent 9ccb839ae2
commit 4b2af7074e
1 changed files with 11 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
src/p_map.cpp
View file

@ -736,8 +736,18 @@ bool PIT_CheckLine(line_t *ld, const FBoundingBox &box, FCheckPosition &tm)
else
{ // Find the point on the line closest to the actor's center, and use
// that to calculate openings
SQWORD r_den = (SQWORD(ld->dx)*ld->dx + SQWORD(ld->dy)*ld->dy) / (1 << 24);
// [EP] Use 64 bit integers in order to keep the exact result of the
// multiplication, because in the worst case, which is by the map limit
// (32767 units, which is 2147418112 in fixed_t notation), the result
// would occupy 62 bits (if I consider also the addition with another
// and possible 62 bit value, it's 63 bits).
// This privilege could not be available if the starting data would be
// 64 bit long.
// With this, the division is exact as the 32 bit float counterpart,
// though I don't know why I had to discard the first 24 bits from the
// divisor.
SQWORD r_num = ((SQWORD(tm.x - ld->v1->x)*ld->dx) + (SQWORD(tm.y - ld->v1->y)*ld->dy));
SQWORD r_den = (SQWORD(ld->dx)*ld->dx + SQWORD(ld->dy)*ld->dy) / (1 << 24);
fixed_t r = (fixed_t)(r_num / r_den);
/* Printf ("%d:%d: %d (%d %d %d %d) (%d %d %d %d)\n", level.time, ld-lines, r,
ld->frontsector->floorplane.a,