• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
MARS_999

Bit mask math

12 posts in this topic

How can I combine this into one statement? 

 

I tried this but no luck

if(id &= ~(NX::COLLISION_ID_IsPickable | NX::COLLISION_ID_IsHighlightable) == 200)

//do something 

 

 

irr::s32 id = selectedNode->getID();
if(id &= ~NX::COLLISION_ID_IsPickable)
if(id &= ~NX::COLLISION_ID_IsHighlightable)
if(id == 200)
{
//do something
}
0

Share this post


Link to post
Share on other sites

Surely this is more readable?!:

id &= ~(NX::COLLISION_ID_IsPickable | NX::COLLISION_ID_IsHighlightable);
if (id == 200)
Edited by iMalc
1

Share this post


Link to post
Share on other sites

To elaborate on Sean's, I have to admit I have bought myself quite some peace of mind since I've restricted bitmask usage to serialization only. Just use structs.

auto props = selectedNode->getFlags();
if(props.canPick && props.canHilight) {
//do something
}

The profiler will tell you if code is hot or cold. Cold code has no point in not having maintainance and readability as priorities. Even if the code is hot, I would be careful in considering this an optimization.

0

Share this post


Link to post
Share on other sites

C++ wizardry like that drives me nuts, and is a clear sign of an inexperienced programmer. SeanMiddleditch is totally right.
Clarity always wins over a couple of cycles worth of optimization, especially in a team environment where you aren't the only one dealing with the code. Basically, if you're trying to reduce line counts for arbitrary reasons, then you're doing it wrong. Bit masking and bit shifting is almost always a sign of over-complication.
 

Edited by Scarabus2
0

Share this post


Link to post
Share on other sites

Bit fields might also help in this situation, since you can retain the packed nature of having bit-based data but instead accessing the data as C++ struct members for clarity.

0

Share this post


Link to post
Share on other sites

Bit fields might also help in this situation, since you can retain the packed nature of having bit-based data but instead accessing the data as C++ struct members for clarity.

 

One annoying detail to keep in mind: the order in which bits are assigned is not defined. Not an issue if everything is happening on one machine and within the same application.

 

Still, not knowing if setting a particular field will effectively result in 0x01 or in 0x80 is always making me nervous.

0

Share this post


Link to post
Share on other sites
Álvaro nice function. Like that...

 

The 200 isn't a permanent thing, it was more of a hurry up and post it!

 

I am using irrlicht and the id is a unsigned int and they are bit masking with the pipe | to do collision detection. So I am looking for ways to set and clear and change them without much headache...

 

Thanks!

0

Share this post


Link to post
Share on other sites

Although I share the concerns that everyone else has about the readability and maintainability of this code (I'd stick with something clear over something short)... it's also worth pointing out that pretty much every alternate form that people have posted does not have the same effect as the original code. If you do anything with id after the code that you posted, then the final value of id varies, depending on whether or not it had the Pickable flag set. (Highlighted is only cleared if id had any bit other than pickable). In fact, I'm beginning to seriously doubt that this code does what you think it does. What were you actually trying to do with this logic?

0

Share this post


Link to post
Share on other sites

Although I share the concerns that everyone else has about the readability and maintainability of this code (I'd stick with something clear over something short)... it's also worth pointing out that pretty much every alternate form that people have posted does not have the same effect as the original code. If you do anything with id after the code that you posted, then the final value of id varies, depending on whether or not it had the Pickable flag set. (Highlighted is only cleared if id had any bit other than pickable). In fact, I'm beginning to seriously doubt that this code does what you think it does. What were you actually trying to do with this logic?

I actually thought so too that the solutions are different, until I realized that the if-statements clears a bit but checks the entire value and not just that cleared bit. The only way to break on the first of the three if statements is if no bits at all are set in the original value. You are right that highlighted is only cleared if something other than pickable is set, but if nothing else is set then highlighted cannot be set either so there's nothing to clear in the first place (nor is there anything that can be equal to 200).

 

Whether you clear them all at the same time, as MARS and iMalc suggested in their solutions, or one at a time as MARS did in his original code actually makes no difference. All codes effectively clear both bits and checks the remaining value for 200. The net result is the same in all cases, and that includes whether the last if-statement (=200) is take or not, and what the final value of id is.

 

In Krohm's variant though it makes a difference since it doesn't modify anything at all. And, of course, like most other here I prefer a non-modifying variant.

Edited by Brother Bob
1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0