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Use floats or doubles when writing mobile games
Use floats or doubles when writing mobile games
What's the largest “relative” level I can make using float?video card architectureIs “pure” OpenGL productive enough?How can I use allocators for different systems?When to use GameComponents?What are some gameplay cases where knowing the Z as a result of the raycasting is useful in a 2D setting?Can Mobile Games use Fragments instead of SurfaceViews?
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I know for shaders, floats should be used because they are the optimal choice for performance. Doubles are slow and use more memory which isn't ideal for shaders. While floats are less accurate and are prone to float overlflows, the tradeoff for speed is ideal on mobile hardware.
But what about everywhere else in the code base not related to the shader pipeline? I'm writing an engine and use doubles for the delta update tick and try to keep all units relative to that data type so there's lots of places using doubles. Should I be using floats on mobile in the engine as well?
The engine is written in C++ language
architecture memory-efficiency
asked 10 hours ago
DanDan
11911 bronze badges
$endgroup$
add a comment
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$begingroup$
I know for shaders, floats should be used because they are the optimal choice for performance. Doubles are slow and use more memory which isn't ideal for shaders. While floats are less accurate and are prone to float overlflows, the tradeoff for speed is ideal on mobile hardware.
But what about everywhere else in the code base not related to the shader pipeline? I'm writing an engine and use doubles for the delta update tick and try to keep all units relative to that data type so there's lots of places using doubles. Should I be using floats on mobile in the engine as well?
The engine is written in C++ language
architecture memory-efficiency
asked 10 hours ago
DanDan
11911 bronze badges
$endgroup$
$begingroup$
I'd imagine it largely depends on which language you're using.
$endgroup$
– DJ Spicy Deluxe
7 hours ago
$begingroup$
Added C++ in the description
$endgroup$
– Dan
4 hours ago
add a comment
|
$begingroup$
I know for shaders, floats should be used because they are the optimal choice for performance. Doubles are slow and use more memory which isn't ideal for shaders. While floats are less accurate and are prone to float overlflows, the tradeoff for speed is ideal on mobile hardware.
But what about everywhere else in the code base not related to the shader pipeline? I'm writing an engine and use doubles for the delta update tick and try to keep all units relative to that data type so there's lots of places using doubles. Should I be using floats on mobile in the engine as well?
The engine is written in C++ language
architecture memory-efficiency
asked 10 hours ago
DanDan
11911 bronze badges
$endgroup$
I know for shaders, floats should be used because they are the optimal choice for performance. Doubles are slow and use more memory which isn't ideal for shaders. While floats are less accurate and are prone to float overlflows, the tradeoff for speed is ideal on mobile hardware.
But what about everywhere else in the code base not related to the shader pipeline? I'm writing an engine and use doubles for the delta update tick and try to keep all units relative to that data type so there's lots of places using doubles. Should I be using floats on mobile in the engine as well?
The engine is written in C++ language
architecture memory-efficiency
architecture memory-efficiency
asked 10 hours ago
DanDan
11911 bronze badges
asked 10 hours ago
DanDan
11911 bronze badges
edited 4 hours ago
Dan
asked 10 hours ago
DanDan
11911 bronze badges
asked 10 hours ago
DanDan
11911 bronze badges
asked 10 hours ago
DanDan
11911 bronze badges
11911 bronze badges
$begingroup$
I'd imagine it largely depends on which language you're using.
$endgroup$
– DJ Spicy Deluxe
7 hours ago
$begingroup$
Added C++ in the description
$endgroup$
– Dan
4 hours ago
add a comment
|
$begingroup$
I'd imagine it largely depends on which language you're using.
$endgroup$
– DJ Spicy Deluxe
7 hours ago
$begingroup$
Added C++ in the description
$endgroup$
– Dan
4 hours ago
$begingroup$
I'd imagine it largely depends on which language you're using.
$endgroup$
– DJ Spicy Deluxe
7 hours ago
$begingroup$
I'd imagine it largely depends on which language you're using.
$endgroup$
– DJ Spicy Deluxe
7 hours ago
$begingroup$
Added C++ in the description
$endgroup$
– Dan
4 hours ago
$begingroup$
Added C++ in the description
$endgroup$
– Dan
4 hours ago
add a comment
|
1 Answer
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$begingroup$
You'd be hard pressed to find a mobile GPU that could use doubles even if you wanted to, so that choice is pretty much made for you.
There are only a few places where you might benefit from switching from single-precision floats in your game. Storing total elapsed time, or an absolute position several kilometers from the origin, are two examples of things you shouldn't try to store in a single-precision float, but that doesn't mean you need to use doubles necessarily. Integer types can handle these values just fine.
A delta time value will usually be on the order of 16 milliseconds, so storing it in a single precision float gives you precision to about $2^-29$, which is down to the level of nanoseconds — ie. probably higher precision than you can signal your threads or graphics refresh anyway. Adding more precision here with a double is unlikely to improve your game in any measurable way. So you can store your total elapsed at high precision or using an integer type, compute your delta and convert to single-precision float once per frame, then use floats happily form there on.
Similarly for positions. Even with a huge world, if you break it up into chunks less than 32 km across, then single precision floats can locate a position within a chunk to a precision of less than a millimetre. Relative offsets between objects (for computing headings and the like) are generally just fine to store in a float even out to immense distances. Your relative error stays in a controlled range.
So, there's not much reason to turn to doubles as a default. I'd consider that only if you have a very particular need, where you've computed the precision of floats won't cut it, and keep it contained to only the part of your game that actively needs it.
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
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$begingroup$
You'd be hard pressed to find a mobile GPU that could use doubles even if you wanted to, so that choice is pretty much made for you.
There are only a few places where you might benefit from switching from single-precision floats in your game. Storing total elapsed time, or an absolute position several kilometers from the origin, are two examples of things you shouldn't try to store in a single-precision float, but that doesn't mean you need to use doubles necessarily. Integer types can handle these values just fine.
A delta time value will usually be on the order of 16 milliseconds, so storing it in a single precision float gives you precision to about $2^-29$, which is down to the level of nanoseconds — ie. probably higher precision than you can signal your threads or graphics refresh anyway. Adding more precision here with a double is unlikely to improve your game in any measurable way. So you can store your total elapsed at high precision or using an integer type, compute your delta and convert to single-precision float once per frame, then use floats happily form there on.
Similarly for positions. Even with a huge world, if you break it up into chunks less than 32 km across, then single precision floats can locate a position within a chunk to a precision of less than a millimetre. Relative offsets between objects (for computing headings and the like) are generally just fine to store in a float even out to immense distances. Your relative error stays in a controlled range.
So, there's not much reason to turn to doubles as a default. I'd consider that only if you have a very particular need, where you've computed the precision of floats won't cut it, and keep it contained to only the part of your game that actively needs it.
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
$endgroup$
add a comment
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$begingroup$
You'd be hard pressed to find a mobile GPU that could use doubles even if you wanted to, so that choice is pretty much made for you.
There are only a few places where you might benefit from switching from single-precision floats in your game. Storing total elapsed time, or an absolute position several kilometers from the origin, are two examples of things you shouldn't try to store in a single-precision float, but that doesn't mean you need to use doubles necessarily. Integer types can handle these values just fine.
A delta time value will usually be on the order of 16 milliseconds, so storing it in a single precision float gives you precision to about $2^-29$, which is down to the level of nanoseconds — ie. probably higher precision than you can signal your threads or graphics refresh anyway. Adding more precision here with a double is unlikely to improve your game in any measurable way. So you can store your total elapsed at high precision or using an integer type, compute your delta and convert to single-precision float once per frame, then use floats happily form there on.
Similarly for positions. Even with a huge world, if you break it up into chunks less than 32 km across, then single precision floats can locate a position within a chunk to a precision of less than a millimetre. Relative offsets between objects (for computing headings and the like) are generally just fine to store in a float even out to immense distances. Your relative error stays in a controlled range.
So, there's not much reason to turn to doubles as a default. I'd consider that only if you have a very particular need, where you've computed the precision of floats won't cut it, and keep it contained to only the part of your game that actively needs it.
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
$endgroup$
add a comment
|
$begingroup$
You'd be hard pressed to find a mobile GPU that could use doubles even if you wanted to, so that choice is pretty much made for you.
There are only a few places where you might benefit from switching from single-precision floats in your game. Storing total elapsed time, or an absolute position several kilometers from the origin, are two examples of things you shouldn't try to store in a single-precision float, but that doesn't mean you need to use doubles necessarily. Integer types can handle these values just fine.
A delta time value will usually be on the order of 16 milliseconds, so storing it in a single precision float gives you precision to about $2^-29$, which is down to the level of nanoseconds — ie. probably higher precision than you can signal your threads or graphics refresh anyway. Adding more precision here with a double is unlikely to improve your game in any measurable way. So you can store your total elapsed at high precision or using an integer type, compute your delta and convert to single-precision float once per frame, then use floats happily form there on.
Similarly for positions. Even with a huge world, if you break it up into chunks less than 32 km across, then single precision floats can locate a position within a chunk to a precision of less than a millimetre. Relative offsets between objects (for computing headings and the like) are generally just fine to store in a float even out to immense distances. Your relative error stays in a controlled range.
So, there's not much reason to turn to doubles as a default. I'd consider that only if you have a very particular need, where you've computed the precision of floats won't cut it, and keep it contained to only the part of your game that actively needs it.
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
$endgroup$
You'd be hard pressed to find a mobile GPU that could use doubles even if you wanted to, so that choice is pretty much made for you.
There are only a few places where you might benefit from switching from single-precision floats in your game. Storing total elapsed time, or an absolute position several kilometers from the origin, are two examples of things you shouldn't try to store in a single-precision float, but that doesn't mean you need to use doubles necessarily. Integer types can handle these values just fine.
A delta time value will usually be on the order of 16 milliseconds, so storing it in a single precision float gives you precision to about $2^-29$, which is down to the level of nanoseconds — ie. probably higher precision than you can signal your threads or graphics refresh anyway. Adding more precision here with a double is unlikely to improve your game in any measurable way. So you can store your total elapsed at high precision or using an integer type, compute your delta and convert to single-precision float once per frame, then use floats happily form there on.
Similarly for positions. Even with a huge world, if you break it up into chunks less than 32 km across, then single precision floats can locate a position within a chunk to a precision of less than a millimetre. Relative offsets between objects (for computing headings and the like) are generally just fine to store in a float even out to immense distances. Your relative error stays in a controlled range.
So, there's not much reason to turn to doubles as a default. I'd consider that only if you have a very particular need, where you've computed the precision of floats won't cut it, and keep it contained to only the part of your game that actively needs it.
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
answered 7 hours ago
DMGregory♦DMGregory
72.8k16 gold badges128 silver badges204 bronze badges
72.8k16 gold badges128 silver badges204 bronze badges
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$begingroup$
I'd imagine it largely depends on which language you're using.
$endgroup$
– DJ Spicy Deluxe
7 hours ago
$begingroup$
Added C++ in the description
$endgroup$
– Dan
4 hours ago