[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]
Re: [pygame] fast sqrt? and profiling
Oh, I guess they are pretty much equivalent, even though Casey seems
to say complex have better performance than euclid.
I just use complex because it's available out of the box with Python
:) (and because I didn't know about Euclid; maybe I'll use it if I do
3D)
On Thu, Jan 22, 2009 at 11:58 PM, Jake b <ninmonkeys@xxxxxxxxx> wrote:
> Still confused on the difference between complex and euclid.Vector2 [ doc:
> http://www.partiallydisassembled.net/euclid/vector-classes.html ]
>
> On Wed, Jan 21, 2009 at 9:24 PM, Casey Duncan <casey@xxxxxxxxxxx> wrote:
>>
>> Here's some example code with some commonly used functions. Addition and
>> subtraction are built into the complex type and work as expected (I use the
>> real part
>
> So far, this looks like euclid.Vector2. Are you doing the same thing, only
> using 'real as the x component, and 'imag' as y? ( Meaning you are using
> complex instead of tuple, equivalent to using vector2 instead of tuple ? )
>
> Or, I think i'm missing something. What is the advantage to to use this over
> euclid.Vector2? [ more below ]
>
>> for x and the imaginary part for y). complex multiply can be used to
>> rotate vectors:
>
> Does complex multiply behind the scenes do something like this?
>
> def rad2v(rad,mag=1.): # convert radians to vector with magnitude
> return mag*Vector2(cos(rad), sin(rad))
>
> def v2rad(v): return atan2(v.y, v.x) # convert vector to radians
>
> def mod_angle(v,rad): # add radians to vector's orientation
> r = v2rad(v)
> r+=rad
> return rad2v( r, v.magnitude() )
>
> >>> v = rad2v( radians(142.8),2.5)
> # now equals: deg=142.8, mag=2.5, v=Vector2(-1.99, 1.51)
> >>> v = mod_angle( v, radians(3.))
> # now equals: deg=145.8, mag=2.5, v=Vector2(-2.07, 1.41)
>
>>
>> # 2D vectors using python complex numbers
>>
>> def radians(vector):
>> return atan2(vector.imag, vector.real)
>>
>> def unit(radians):
>> return cmath.exp(radians * 1j)
>>
>> def normal(vector):
>> L = length(vector)
>> if L == 0:
>> return vector2()
>> else:
>> return vector / L
>>
>> def clamp(vector, max_length):
>> L = length(vector)
>> if L > max_length:
>> return vector * (max_length / L)
>> else:
>> return vector
>
> At first, this code looks the same, except there are new functions:
> .radians(v) and unit(r). Radians looks like a 'convert vector to euler
> radians angle'.
>
> But whatis .unit()? I'm guessing it's to create a new unit vector in the
> angle of 'radians.' But calling it with a few values, I'm not getting what I
> was expecting.
>
> Is it the equivalent of rad2v(r) for Vector2, but unit(r) does the same for
> complex numbers?
>
>>
>> def distance(vector1, vector2):
>> return length(vector1 - vector2)
>> This is good if the list may change during iteration. If you do this
>> repeatedly in a given frame, it might be better to create a custom class
>> (perhaps subclass set) that contains a stable set of the actors. When you
>> add or remove, these are stored in ancillary sets rather than changing the
>> stable set immediately. An update method called at the beginning of each
>> frame adds and removes the items from the ancillary sets to update the
>> stable set. These ancillary sets are then cleared. This mean less memory
>> allocation/cleanup and work copying the lists
>>
>> class StableSet(set):
>
> I'll try it out.
>
> @emile: ( continued from above ), I'm trying to understand how/why complex
> numbers are used.
>
> Here is my Vector2 equivalent to your code.
>
> It looks like you treat complex same way I treat euclid.Vector2 ? Am I
> missing something?
>
> from euclid import Vector2
> class Spaceship():
> def __init__(self, pos=Vector2(0,0), max_accel=100):
> self.pos = pos
> self.vel = Vector2(0, 0) # or'speed'. changed named to not be
> confused as Scalar
> self.accel = Vector2(0, 1.) # or 'direction'
> self.boosters_on = False
> self.max_accel = max_accel
>
> def update(self, dt):
> if self.boosters_on:
> self.vel += self.accel * self.max_accel * dt
> self.pos += self.vel * dt
> --
> Jake
>