• September 19, 2021, 12:34:33 AM

Author Topic: (Problem) What is this blue grainy stuff doing here?  (Read 268 times)

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Offline Uma410

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(Problem) What is this blue grainy stuff doing here?
« on: September 14, 2021, 04:04:32 PM »
As you can see, KF generates this blue grainy stuff on top of the fractal. The problem here is that zooming in scales the blue grainy stuff with the camera and it isn't rotationally symmetric when I am in an area that is rotationally symmetric so I don't think it's actually part of the fractal. If it is, please tell me, if it isn't then this is wierd.

Linkback: https://fractalforums.org/index.php?topic=4405.0

Offline claude

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Re: What is this blue grainy stuff doing here?
« Reply #1 on: September 14, 2021, 06:01:53 PM »
can you share KFR?  probably an artifact of numerical differences based distance estimation / slopes, try enabling derivatives in the Formula dialog and choosing Analytic in the differences dropdown (probably initialized to Diagonal 2x2; Analytic is at the end) bottom left of Color dialog.

Offline Uma410

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Re: What is this blue grainy stuff doing here?
« Reply #2 on: September 14, 2021, 06:44:16 PM »
Here is the KFR.

Offline Uma410

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Re: What is this blue grainy stuff doing here?
« Reply #3 on: September 14, 2021, 06:46:11 PM »
With derivatives and analytic in the color dialog it looks like this. Is it supposed to look like this?

Offline claude

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Re: What is this blue grainy stuff doing here?
« Reply #4 on: September 14, 2021, 07:56:41 PM »
this location is so extremely dense that any DE-based colouring (including slopes) will have lots of noise and need lots of supersampling.  recommend finding somewhere else to explore, supersampling a lot, or changing the palette to a different scheme

Offline Zhuoran

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Re: What is this blue grainy stuff doing here?
« Reply #5 on: September 16, 2021, 08:27:46 AM »
It can be rendererd correctly with OpenGL disabled.

Offline claude

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Re: What is this blue grainy stuff doing here?
« Reply #6 on: September 16, 2021, 01:00:07 PM »
Oh, interesting.  I just tried it here (sorry for not trying before) and it looks fine both with OpenGL and without OpenGL (though the colours from slopes are different, which is a separate bug).

What graphics hardware and driver version are you using?

Offline Zhuoran

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Re: What is this blue grainy stuff doing here?
« Reply #7 on: September 16, 2021, 01:20:38 PM »
What graphics hardware and driver version are you using?

Intel Iris Xe Graphics, driver version 27.20.100.9168
NVIDIA GeForce RTX 3070 Laptop GPU, driver version 30.0.14.7141
Both have this problem.

Offline Uma410

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Re: What is this blue grainy stuff doing here?
« Reply #8 on: September 16, 2021, 02:17:39 PM »
Just to clear this up, what exactly did you do to get rid of the noise? I don't quite follow and would still like to get rid of it myself.

Offline claude

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Re: What is this blue grainy stuff doing here?
« Reply #9 on: September 16, 2021, 07:09:22 PM »
I have no noise, with AMD Radeon RX 580 with AMDGPU/Mesa driver on Linux.  You could try disabling OpenGL in KF (uncheck "enable" in Colors -> OpenGL dialog).  Chances are there is something not quite right in KF's OpenGL implementation or your graphics drivers, probably the blue corresponds to some infinity or not a number somewhere?  you could try something like
Code: [Select]
vec3 c = KF_Colour(); return isnan(c.r+c.g+c.b) ? vec3(1,0,0) : isinf(c.r+c.g+c.b) ? vec3(0,1,0) : c; and seeing if the blue noise turns to bright red or bright green noise...
« Last Edit: September 16, 2021, 10:42:33 PM by claude, Reason: Typo »


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