New GLator 16bpc oddity

Forum|Forum|7 years ago
November 26, 2018
1 reply
899 views

Hi. The 2017 GLator multiplies 16bpc by 1.99999 before doing processing then divides it by the same at the end. I'm confused why it does this, as 8bpc doesn't require any conversion. Thanks.

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S

shachar carmi

Community Expert

honest to god, i have no idea... i'm not even familiar with the problem...

On Mon, Nov 26, 2018 at 5:59 AM JamesWhiffin555 <forums_noreply@adobe.com>

J

JamesWhiffin555Author

Inspiring

The code is:

// in case of 16 bits, convert 32768->65535
colourOut = colourOut * multiplier16bit;

And at the end:

// finally handle 16 bits conversion (if applicable)
// in case of 16 bits, convert 65535->32768
colourOut = colourOut / multiplier16bit;

I guess you get double the precision but it's strange it's not done for 8bpc.

françois leroy

Inspiring

Hi guys!

OpenGL 16 bits is a bit weird... Or at least doesn't work like AE's 16 bits. So in the Glator sample, the 16 bits texture is just converted to "floats" (not really, cos' you can't have overbrights...) and then converted back to 16 bits when everything's done.

From what I can remember, texture is written as 'half-floats'.

That's why there's the 1.99999 multiplication, so it stays inside the 0 - 32768 range.

Cheers,

François

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