Quake code sorcerery

bchip

bchip

Expert Member
Joined
Mar 12, 2013
Messages
1,324
Reaction score
418
Very interesting what these guys did

 
OMG, that was painful to watch. She is completely clueless about the history of that quake code. That idea loooong preceded quake. That code was copied from an existing reference implementation (not by ID software) with perhaps a change in the constant to better fit the range of inputs.

Also, anyone with a good understanding of floating point numbers and the Newton Raphson can see how it works.
 
cguy said:
OMG, that was painful to watch. She is completely clueless about the history of that quake code. That idea loooong preceded quake. That code was copied from an existing reference implementation (not by ID software) with perhaps a change in the constant to better fit the range of inputs.

Also, anyone with a good understanding of floating point numbers and the Newton Raphson can see how it works.
Click to expand...
Imagine if she has to do a vid on doom and how it was not 3d but "3d" and yes it was seriously bad hence the #2 cross...
 
ekske1 said:
@cguy brace yourself

"welcome to compchomp where we crack jokes in binary"


:ROFL::ROFL::ROFL:

+10 points if you make it to the end.
Click to expand...

At about 3 minutes in, she gets very confused about what the equal operator does.
 
There was some discussion about floating point approximations in Computerphile videos. Much better quality and informed presenters.

Floating point takes me back to the 1980s! All taken for granted nowadays, since the first Pentium series, and built in co-processors since the 486DX.
 
I always lol when people see the combination of C code and bit hacks and think it is mystical hacking.

Bit hacks are really squarely in the domain of mathematics and I think the reason it perplexes a lot of people is the base 2 aspect throws them.

ie> 55 << 1 = 110 (or vice versa, basically a comma shift but in base 2), wouldn't really seem strange to you if we used base 2 in every day. I mean if I took 55 and added a zero at the end and it gave me 550 you wouldn't think it was magic.
 
Gnome said:
I always lol when people see the combination of C code and bit hacks and think it is mystical hacking.

Bit hacks are really squarely in the domain of mathematics and I think the reason it perplexes a lot of people is the base 2 aspect throws them.

ie> 55 << 1 = 110 (or vice versa, basically a comma shift but in base 2), wouldn't really seem strange to you if we used base 2 in every day. I mean if I took 55 and added a zero at the end and it gave me 550 you wouldn't think it was magic.
Click to expand...

A comprehensive article on the hack is available on Wikipedia: https://en.wikipedia.org/wiki/Fast_inverse_square_root

Fast inverse square root, sometimes referred to as Fast InvSqrt() or by the hexadecimal constant 0x5F3759DF, is an algorithm that estimates 1⁄√x, the reciprocal (or multiplicative inverse) of the square root of a 32-bit floating-point number x in IEEE 754 floating-point format. This operation is used in digital signal processing to normalize a vector, i.e., scale it to length 1. For example, computer graphics programs use inverse square roots to compute angles of incidence and reflection for lighting and shading. The algorithm is best known for its implementation in 1999 in the source code of Quake III Arena, a first-person shooter video game that made heavy use of 3D graphics. The algorithm only started appearing on public forums such as Usenet in 2002 or 2003. At the time, it was generally computationally expensive to compute the reciprocal of a floating-point number, especially on a large scale; the fast inverse square root bypassed this step.
Click to expand...
 
I did tons of bit calculations in the assembly demo days, this woman is clueless and I got so dizzy from her shitty hand gestures.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X