Problems in Safari iOS on mediump #25
Comments
gregtatum
changed the title
|
This random codepen I found seems to exhibit the behavior: https://codepen.io/ykob/pen/qbwLaY I'm not sure if it's the exact latest version of the shader in this repo. Steps to reproduce:
|
|
Yes, high precision is required for the functions to work in WebGL. All
functions require it, and it's not easy to fix, because the code that
requires high precision is not the floating point computations, but the
integers for the hashing. This is not a bug, it's simply a requirement for
the algorithm to work. I will add it to the documentation to make this more
clear.
|
|
The wiki page still says
suggesting that |
|
I don't agree that this suggests mediump support, but I will clarify that
passage.
The functions worked on my then-current Samsung Note 1 smartphone which had
a GPU inferior to anything you would find even in budget smartphones today,
and it ran fine on my contemporary generation of the Raspberry Pi, also a
stone age GPU with modern measures. That was the frame of reference I had
when I wrote that passage some time in 2015 or so.
Which platforms are you working on that still don't have highp support? My
experience is almost exclusively with desktop/laptop hardware, various
Samsung smartphones I have owned myself and my wife's iPhones of various
older, company-issued models. (Her employer is not a cheapskate, but their
security certification of new hardware takes longer than the generation
changes, which is a major nuisance.)
Den fre 25 mars 2022 22:10Tomasz Grajewski ***@***.***> skrev:
… The wiki page <https://github.com/ashima/webgl-noise/wiki> still says
NOTE: You do not need a super fast GPU to use these functions. They are
useful even on low end hardware, old hardware and embedded OpenGL ES
hardware with low performance.
suggesting that mediump would be supported, which is not true.
—
Reply to this email directly, view it on GitHub
<#25 (comment)>,
or unsubscribe
<https://github.com/notifications/unsubscribe-auth/AAFGK2VCGOUTAOWWBKN63CTVBYTTPANCNFSM5DXIAJ2A>
.
You are receiving this because you commented.Message ID:
***@***.***>
|
|
Thanks, would be great if I'm working on games and targeting mostly mobile devices. From my experience even if a smartphone supports |
|
Sounds like I have a task, then: create some noise functions that work with
mediump ! :)
Do these devices have integer support (WebGL 2)? I suppose integer
precision is specified separately from float precision, and then the
changes required are minimal, provided that integer operations have
reasonable performance. (The first desktop GPUs with integer support were
dead slow with integer math, so I am not taking this for granted.)
I could probably restrict the code to work with only 16-bit half-floats and
no integers, although it will probably require some workarounds that might
be slow. I have no clear plan on how to do this, but I'm pretty sure it
*can* be done.
And, not least importantly, how would you suggest I test this? My current
Samsung S21 seems to use "highp" no matter what I specify for the
precision, but I might be doing my testing wrong. My experience with mobile
devices is limited, and I have access only to two smartphones: my own
Samsung S21 and my wife's somewhat dated iPhone. Could I perhaps persuade
you to provide some assistance in testing? I would be happy to add you as a
developer to a Github repo for this purpose.
|
|
Hey, awesome! Yes, I'm in :) Here is a list of some devices that do not support
Unfortunately I don't own any of them, but I have some devices with |
|
I got "mediump" working just now on my Samsung S21 (classic stupid mistake:
I just needed to wait for the server refresh of the HTML test file I
edited), so I will get back to you about testing once I get something
working on this one device. So far, I have only broken the function by
putting "precision mediump float" at the top, but now I can at least see
for myself when (if) I fix it.
Let me just repeat my question from before: is WebGL 2 with a mix of mostly
floats and a few integers a reasonable target? That should be relatively
quick and easy, while a WebGL 1 compatible version with half-floats only
would require more thought.
Also, reading the letter of the WebGL 2 spec it says that "mediump float"
could actually be the 10-bit kind-of-floats that I can't see how they could
handle anything beyond simple color blending, and "highp float" could be
the one that maps to 16-bit "half float". Is that a thing, or can I assume
that "mediump" means 16-bit floats? On my Samsung S21, "highp" seems to
give me 32-bit "proper" floats in fragment shaders, and with very
reasonable performance, and "mediump" seems to be 16-bit half-floats.
|
|
WebGL 2 is not good, too low adoption, it needs few more years. Regarding float precision for |
|
OK. The feature gap between WebGL 1 and 2 (GLSL ES 1.00 vs. GLSL ES 3.00)
is a rather wide one, while the differences between GLSL ES 3.00 and the
upcoming WGSL are mostly syntactic in nature. For the next few years I
guess there will be a need to support two versions of GLSL as well as WGSL.
Oh, well. It's not as if "the Web" has ever been a well defined and easy
platform to target.
To get a more clear picture of where we stand, I made a test page. When/if
you have the time and opportunity, you could check this out:
https://stegu.github.io/psrdnoise/test/showprecision.html
There's no hurry with this, absolutely no obligations, and in any case I
don't expect you to give me more than a general hunch, but thanks in
advance for any help!
To me, the important information would be whether you see any important
devices/platforms that report *less* than 16 bits for "mediump float", and
whether the "int" type has support even where WebGL 2 is reported as "not
supported", which would imply that the *device* is WebGL2 ready even though
the browser is not.
It would be interesting to know also if any device supports 32-bit integers
but not 32-bit floats. I suppose that's not the case, but I'm just
guessing. Actual field testing on real devices is infinitely more useful
than guesswork and reading formal specs.
|
|
A first attempt at mediump-tolerant 2D noise, in the recently
published "psrdnoise" style:
https://stegu.github.io/psrdnoise/test/psrdnoise2-mediump.html
It seems to work, but using "mediump" precision has some nasty side
effects: mediump texture coordinates makes the pattern blocky if you
try to evaluate noise too far from the origin, and when you leave the
page running for a few minutes the "time" uniform parameter for
animation starts to stair-step and make the animation of "alpha"
visibly jumpy. There might be more errors and flaws in there, this is
a first attempt.
To avoid overflow in the half-float hash, the repeat tile is smaller,
49x98 units, and the pattern might not be as good looking, because the
restrictions for what I could use for the hash function was tight.
This is not the final word on the hash, but there are now a lot fewer
options to try to improve the "random look" of the pattern. On top of
that, the hash function needs a ton of intermediate mod() operations
to prevent overflow and truncation in the "half-float-integer" math.
Therefore, this is not obviously faster than a highp version, but it
might be, and it does work in mediump. Unless you find a way to break
it, in which case I will gladly try to fix it. That's what "help with
testing" means, after all.
For reference, this is the 32-bit highp version with the "psrdnoise"
that is oficially published on that github repo:
https://stegu.github.io/psrdnoise/test/psrdnoise2-highp.html
|
|
This is what I get for:
|
|
Interesting that compared to that older A9, my reasonably fresh Samsung A21
has added lower precisions (16-bit for both lowp and mediump int *and*
float) to the vertex stage.
I have bothered friends and family with checking the test page as well, and
they all report that WebGL2 *is* supported for both IOS and Android, and
that mediump 16-bit floats and highp 32-bit floats are both available for
fragment shaders. It's only a sample of a half dozen devices, but I will
try putting together a WebGL2-only noise with an integer hash as well.
Because it won't need all the mod() operations, it might be considerably
faster.
I noticed that the hash in 2D mpsrdnoise needs tweaking for the rotation
--- there are too many instances of adjacent gradients pointing in more or
less the same direction, and that creates ugly streaks in the pattern.
Other than that, do you see any problems with the function?
|
|
I mean, of course, S21. All these numbers...
|
|
Main obstacle for WebGL 2 is older Safari on iOS devices. Yes, new Safari supports WebGL 2, but from my experience many people still use older Safari v10, v11, etc., without WebGL 2 support. |
|
I thought Safari updates were more or less mandatory on MacOS and iOS
devices. So much for "the benefits of a unified ecosystem for developers"...
Updated the hash to improve the look of the 2D mediump-compatible noise.
Let me know whether you find it good enough for use.
Moving on to the 3D noise now, but that could be a bit more tricky. The 3D
grid transforms and their inverses are more sensitive to low precision. 3D
simplex noise might not be a good match for mediump. We'll see.
|
|
Benchmarking the 2D mediump noise on a few desktop GPUs, where
"mediump" has no effect on speed or precision, it's 15-20% slower
because of the extra mod() operations. I'm really not the right person
to guess how this translates to mobile GPU performance, but unless
mediump and highp are the same speed, I would say the mediump version
is quite likely to be faster. Any real world data on this would be
appreciated. :)
|
|
I can do some benchmarks on the devices I have, but give me few days. |
|
No hurry, no obligations, just: thanks a lot!
|
|
I've tested the page
|
|
Well, that pattern should not be difficult even on a fairly weak mobile GPU
-- it's just one noise value per fragment. If you want to benchmark by
frame rate, I should make a considerably more taxing test page with a sum
of several noise components to make the frame rate drop below the 60 FPS
cap.
(Better do it right away, or I will forget)
There. This computes 10 noise values per pixel and sums them up to display
a slowly changing cloud-like fractal pattern:
https://stegu.github.io/psrdnoise/test/noisebench-mediump.html
The shader is a lot more complicated than it needs to be for that
particular pattern, it's written only to require a lot of work for the GPU.
My Samsung S21 displays that animation at 60 FPS as well, but we are
primarily looking for the phones that struggle with this, which would be
3D-capable budget phones or older phone models. Perhaps we need to increase
the workload even more to get any useful results?
Benchmarking is cumbersome if we have to measure it by frame rate. Isn't
there any profiling tool that can report on how hard the GPU is working? If
not, tell me what you would like to see in terms of benchmarks to give you
the information you need as a developer. (If you have any ideas, that is.
If not, don't sweat it.)
|
|
I again get 60 FPS on this updated benchmark on the same phone. |
|
Hmm. Okay, 10 noise values per fragment, on a 600x600 pixels canvas at 60
FPS, that's still "only" 216 million noise values per second. Most modern
GPUs are probably not hitting the limit on that test. I won't dig deeper
into this for now, but you can make your own copy of the HTML file (note
that an included JS file is required as well, but that's it), and increase
the number of repeats for the loop and/or the size of the canvas, to see
where a certain piece of hardware hits the limit and drops below 60 FPS.
Looking at the raw specs, I think a reasonably modern mobile GPU should be
able to compute 1 billion noise values per second, probably more. For
comparison, the current top performing desktop GPUs can compute 100 billion
2D noise values per second, in 32-bit precision, which is kind of crazy.
Still working on the 3D mediump noise. The 49-element hash I used for 2D is
not quite good enough for a nice "random look" in 3D, at least not without
some tweaks I haven't found yet. I think I need to let this simmer on the
back burner for a while, and see if I get any better ideas.
Have you tried using the noise for anything yet? It could prove a bit
tricky to program procedural patterns that look good if all variables are
restricted to mediump. Any stories of real world experiences with this,
good or bad, would be useful.
|
|
I get 25 FPS on my Galaxy A9 when I modify the canvas to be full screen. I don't yet have use of simplex/perlin noise, but used white noise found somewhere on the Internet for some shaders. |
|
White noise is certainly useful for some purposes, but band limited, smooth
looking pseudo-random noise ("Perlin noise") is great for generating
patterns and motion that are quite unlike what we usually mean by "noise":
Dirt, wear, fade, scratches, specks, clouds, waves, terrain, fire, smoke,
flicker, wind, wrinkles, roughness etc.
I'm hoping to see more uses of noise in real time content soon. In offline
rendering, it has been used extensively for all the purposes mentioned
above, and more, for the past 30 years, and there's a lot of great
examples to learn from as GPU hardware gets up to the task of rendering
procedural content.
|
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
It seems like
snoise(vec3)and maybe others are only working usingprecision highp float;on Safari in iOS. I spent a bit of time debugging some older shaders of mine that aren't working anymore and this appeared to fix it.The text was updated successfully, but these errors were encountered: