Quote:Original post by pTymN
wtf?!

I remember

float 16 bits
double 32 bits
long double 64 bits (warning slow, not supported in hardware)

and i just found out that .net considers char a 2 byte size. What is the world coming to! Just cuz the space is there doesnt mean that we should use it so judiciously if the easy optimizations are so accessable, such as using only the memory that you need.

Nope,
float 32 bits
double 64 bits
long double 80 or 96 bits? (not sure, I've never needed them)
char = 8bits, unless maybe your project is set to unicode or something.

But hey, don't take my word for it. sizeof is your friend!

I too would be interested in a good 16-bit float class btw.

Quote:and i just found out that .net considers char a 2 byte size. What is the world coming to!

16-bit characters are to support Unicode. What the world is coming to is the realization that there are other languages than English and you can can miss out on a lot of revenue if you ignore that.

If you want a byte then use a byte type. The equivalence between chars and bytes is a C/C++ thing that likely won't be true in future languages.

just do this

float i = 4096.345232f

int s = i*2^17 = 536.916.162

i = s /2^17 = 4096.345230f

you see hardly a loss of precision who cares about 0.000002

if your player for example is 72 units high float height = 72.0f

would you care if his position varies 0.01f ?

i wouldn t

s = i*2^7 = 524.332

i = s/2^7 = 4096.34375 is a difference of 0.002 who cares about such a less of precision since you update the player position by the server all over again anyways

so on a +-4096 units map you only need 19 bits to represent a float
or 20

for angles id only send the part infront of the comma no need to wast a lot of bandwidth since angles change pretty fast so precision doesn t matter

do you mind explaining a little bit how that works, Basisor? 4096 seems like a pretty small map though. also, an int is 4 bytes as well, did you mean to make it a short?

thanks for any help.

no all i do is i multiply by 2^7 to get atleast 0.01f precision


and yes +-4096 are small maps as in most quake engines
you could of course increase it by adding another few bits


and no i don t mean convertion to short or what ever

i just use as many bits as i need to represent the information

you don t have to use 16 bits to send 256 over the net

i guess you understood how i saved the first 2 decimals

just take a calculator and try it

Basisor, i guess i just dont understand exactly how this all works. i mean, the whole XOR thing confuses me really.

also, if your not using all the bits in that integer, how do you convert the integer to something that is N bits big, for sending over the wire?

btw: i thought a UDP packet minimum was 28 bytes?

Basisor used "^" to mean "power", not XOR.

However, I don't understand what he wants to show. A 16-bit floating-point number has 10 bits of mantissa, so at size +/- 4000 units, the precision would be +/1 2 units -- certainly way too little precision to use.

Quote:Original post by graveyard filla
Basisor, i guess i just dont understand exactly how this all works. i mean, the whole XOR thing confuses me really.

also, if your not using all the bits in that integer, how do you convert the integer to something that is N bits big, for sending over the wire?

btw: i thought a UDP packet minimum was 28 bytes?

as hplus said i use ^ as power not as XOR

well the server and the client define a format for a vector


lets say

DELTA_FLOAT_VECTOR (7,N)

where N is the number of bits the integer uses and 7 is the exponent which you use to multiply a float with

2^7 = 128

so you multiply a float with 128 and move the decimal 2 positions to the right

ab,cd*128 = ab,cd*100 + ab,cd*28 >abcd,00

so on the server and on the client you know the number of bits of the integer and the exponent to use to convert the abcd->ab,cd *rounding error: loss of precision*

HL1 does this btw

now i think you wanted to know how to pack a 20 integer into a buffer right?

ok i have a gamestate class which sums up all the variables i send and get the number of bits needed to create a buffer

iBits = getBitsNeeded();
iBytes = iBits / 8;
if(iSpace = iBits%8){//modulo 8
++iBytes; //add one byte to reach >= iBits size
}

ok now we have got a buffer large enought to write the variables to
now you need a routine to write x bits of a variable to the buffer

i don t have my code on this computer now, but i think it shouldn t be too difficult to figure out the rest on your own


my routine is approximately 8-10 lines of code but still unoptimized

if you wish ill post it here but you should try it on your own its a nice practise :)