checking negative values in ACS

[msx2plus]

hey all; i've got an issue where this statement will turn up true the second the integer hits a negative value:

...
int playposz = round(GetActorZ (0));
if (playposz <= -440)
...

the values are returning properly rounded, but anything below 0 will trigger the if statement. interestingly, if i combine this with other checks via && (ex: if (playposz <= -440 && playposx <= -1336 && playposy >= 4480)), this alone will set off the entire thing. what on earth is going on?

Edited April 10, 2023 by msx2plus

[boris]

GetActorZ returns a fixed point value. That means you have to compare it to a fixed point value. The easiest way to do it is to add a ".0" to your integer values, i.e.

 

if (playposz <= -440.0)

 

[msx2plus]

that works perfectly! i was under the impression i wouldn't be able to store those as integers properly and that rounding/flooring them would work, but i guess not? thanks a bunch.

[Edward850]

3 hours ago, msx2plus said:

that works perfectly! i was under the impression i wouldn't be able to store those as integers properly and that rounding/flooring them would work, but i guess not? thanks a bunch.

Fixed point values are integers, in Doom they are 16.16. The upper 16 bits are basically treated as a signed word, while the lower 16 bits is the precision.

Basically,

if (playposz <= -440.0)

is no different from any of these

if (playposz <= (-440 << 16))
// --
if ((playposz >> 16) <= -440)
// -- This last one makes more sense if you chuck -28835840 into a programmer calculator set to DWORD to look at the bit arrangements, but it's basically what -440 << 16 equals to.
if (playposz <= -28835840)

 

Edited April 11, 2023 by Edward850

[msx2plus]

6 hours ago, Edward850 said:

Basically,

awesome clarification, thank you!