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Re: [Public WebGL] Additional texture/vertex formats



It's necessary to touch the bytes though. Uploading raw data from a
file to OpenGL assumes that the endianness of the data in the file
matches that of the host architecture. I suppose that byte swapping
could be done with a Uint8Array without Float16 support in the typed
array spec.

Still, http://www.khronos.org/registry/webgl/extensions/OES_texture_half_float/
currently specifies that half-float textures can only accept data from
canvas, image and video elements -- and none of these widely support
high dynamic range content in browsers today. This effectively means
that they're only useful as render targets.

-Ken


On Mon, Jul 23, 2012 at 11:41 AM, Jeff Russell <jeffdr@gmail.com> wrote:
> Not a deal breaker. There is no "half" type in C either. One can just alias
> with Uint16 and some conversion functions I would guess if you really needed
> to manipulate the values in javascript. Mostly for IBL applications though
> you'd just be feeding bytes through from a file format without touching
> them.
>
> On Mon, Jul 23, 2012 at 2:37 PM, Kenneth Russell <kbr@google.com> wrote:
>>
>> Half float textures are spec'ed for WebGL in
>> http://www.khronos.org/registry/webgl/extensions/OES_texture_half_float/
>> . There's a big caveat currently that typed arrays can't be used to
>> upload data into them, since there's no Float16 typed array type (and
>> because it would be extremely inefficient, I do not foresee adding
>> one).
>>
>> Is that restriction a deal killer? Would the spec need to be amended
>> to support e.g. uploading from a Float32Array, with appropriate
>> truncation of the mantissa and exponent bits, in order to be useful
>> for image based lighting?
>>
>> -Ken
>>
>>
>> On Sun, Jul 22, 2012 at 6:49 PM, Mark Callow <callow_mark@hicorp.co.jp>
>> wrote:
>> >
>> > On 21/07/2012 03:42, Jeff Russell wrote:
>> >
>> > The bandwidth/memory savings are the main reason one would use them over
>> > float, and that's a big one. Not sure if it's still the case but in the
>> > desktop GPU world texture filtering was once easier to come by with half
>> > float instead of full precision float textures.
>> >
>> > I know less about mobile GPUs, but I understand bandwidth is if anything
>> > even more of an issue there.
>> >
>> > Bandwidth is indeed even more of an issue on mobile and it will almost
>> > certainly be the case that filtering will be more available for
>> > half-float
>> > than float for the same reasons it was once "easier to come by" on
>> > desktop.
>> >
>> > Regards
>> >
>> > -Mark
>> >
>> > --
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