SFML community forums
Help => System => Topic started by: N1ghtly on May 03, 2012, 06:00:25 pm
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Hello,
I'm designing an AnimatedSprite class for my sprite engine and I've run into a little issue.
I'm thinking of overriding the draw() function to draw the sprite AND automatically update the frame.
Now I'm thinking, is it madness to have an sf::Clock for every AnimatedSprite?
Because it would be very easy if you don't have to worry about updating the time for every AnimatedSprite.
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No it's not, sf::Clock is internally just a Int64 and a system call.
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I'm thinking of overriding the draw() function to draw the sprite AND automatically update the frame.
That's not a good idea, drawing shouldn't alter the object, for example one might draw it multiple times (maybe to different places). This is also expressed in code; sf::Drawable::draw() is const.
Now I'm thinking, is it madness to have an sf::Clock for every AnimatedSprite?
Not because of performances, but it strongly limits the use cases. With clocks, you cannot interrupt the animation, that is a game pause is not possible.
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Ahh didn't think about that!
void update(sf::Time frameTime)it is then!
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Ahh didn't think about that!
void update(sf::Time frameTime)it is then!
I don't know how big (in memory) is the sf::Time class, I think this is small but prefer a reference or a const reference since I'm sure this is smaller =)
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Nop: it's only a Int64, so even if it's bigger than a pointer on 32-bits systems, it's still faster to pass by value (no dereferencing, etc.).
N1ghtly just followed SFML, which passes all its sf::Time instances by value.
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Nop: it's only a Int64, so even if it's bigger than a pointer on 32-bits systems, it's still faster to pass by value (no dereferencing, etc.).
N1ghtly just followed SFML, which passes all its sf::Time instances by value.
Really ? To pass a 64bit value is faster than 32 reference ?
I need better C++ courses oO
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Well, this conclusion is not obvious, in fact it depends on many parameters.
This article is very interesting and detailed:
http://www.macieira.org/blog/2012/02/the-value-of-passing-by-value/
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Do not forget that -- although you don't see it in code -- references need to be dereferenced, which also has a cost.
In fact, sf::Vector2f should also be passed by value :P
(It also makes the syntax nicer and prevents API changes, for example if a returned const sf::Vector2f& that refers to a member is replaced by a copy to a local object).
Side note: Already with the old standard, yet more with C++11, some situations encourage to pass even big objects by value.
C++Next: Want speed? Pass by value (http://www.google.ch/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CIoBEBYwAA&url=http%3A%2F%2Fcpp-next.com%2Farchive%2F2009%2F08%2Fwant-speed-pass-by-value%2F&ei=Av6jT7OPEKjj4QTjgN3ICA&usg=AFQjCNGRt8Wkv5etdt1JkREH-MyS0rdSiQ&sig2=DMpRTV567OfjoL6hTqW2Tg)