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Why do I need to clamp elevation?

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Zoltan Erdokovy

Posts: 204
Filters: 24
When using an elevation gradient, I apparently need to clamp the elevation data to 0.9999 otherwise the gradient starts to repeat: full white pixels get the color meant for full blacks.

Is this intentional?

I was also wondering if there is a dedicated clamp node planned.
Posted: April 24, 2010 12:25 pm   Details E-Mail
Zoltan Erdokovy

Posts: 204
Filters: 24
Here is an example setup:



You can see the problem on the bottom part of the lifesaver: the green spot in the
middle of the red area. It appears where the input is 1.0 bright.
Clipping it to 0.9999 fixes the issue.

In FF v1.x (using the same setup) the green won't creep in at highlights.

EDIT: Bigger image.
Posted: April 27, 2010 1:27 am   Details E-Mail
tigerAspect
Posts: 222
Filters: 9
Wow, that's definitely a bug. It only happens with the External Image, it seems to be incorrectly setting the white level at about 1.0000001 brightness, even when passed through a non-HDR blend.
Posted: April 27, 2010 10:06 am   Details E-Mail
Zoltan Erdokovy

Posts: 204
Filters: 24
For me, the bug appears for noises as well. (Hmm, could it be system dependent?)
The cool new color picker shows that the highlights are indeed 1.0 (at least on the surface).
Clamping to 1.0 doesn't help, it needs to be <1.0 of brightness.

I'm on Win7 x64, Q6600.
Posted: April 27, 2010 10:16 am   Details E-Mail
tigerAspect
Posts: 222
Filters: 9
Oh, whoops, I was using my "corrected" gradient to test the Noise node. Ok, so what it loks like is that all Gradients are actually offset by about -0.0000001, even Free Gradient. Wierd.
Posted: April 27, 2010 11:33 am   Details E-Mail
CorvusCroax
CorvusCroax

Posts: 1227
Filters: 18
Quote
Zoltan Erdokovy wrote:
I was also wondering if there is a dedicated clamp node planned.


Vlad has mentioned about adding some math nodes which would effectively do that.

http://www.filterforge.com/forum/read...&PAGEN_1=2

Quote
Vladimir Golovin wrote:

We'll add a couple of simple tonemappers (Clip and Knee) in the next beta.

Posted: April 27, 2010 2:13 pm   Details E-Mail
Vladimir Golovin
Administrator
Posts: 3446
Filters: 55
Haven't checked it yet, but it's on the list.

(Sorry, too busy.)
Posted: May 4, 2010 3:12 am   Details E-Mail

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