byRo
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...not a curve?
I was pretty comfortable with the idea that grey things are numbers, green things are images and blue things are curves. or, to Geekify, none, two and one dimensions But then I try to figure out why curve op's have a green input. Have a look at the attachment. The only information going to the gradient is a curve, but this little blue (curve) connection is carrying a whole greyscale image. Vladimir? onyXMaster? How does this stuff work?? Rô ![]() _________________________________
My favourite question is "Why?". My second favourite is "Why not?" |
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Posted: June 11, 2006 9:32 pm | ||||
onyXMaster
Posts: 350 |
Actually, while map components (green) are functions of two parameters (x and y), curves may appear to be functions of one parameter (called internally t). But practically, curves are functions of three parameters (t, x, and y). Curves which have map inputs ant therefore produce different values depending not only on t but also on x and/or y are called internally "mapped curves".
So the curve value depends not only on the value it remaps, but also on the x and y coordinates. In your case, the resulting curve value will different for every sample, since the "percentage" value is taken for each sample. Let's talk pixels instead of samples for simplicity: imagine that FF calculates the pixel X;Y of the "Profile Gradient" component. The profile gradient itself is a basic linear gradient, so the base t value for the curve is calculated using basic linear formula and yields the value T. After that, the value is remapped (since there's a Profile curve different from Linear pseudo-curve). So the Blend CurveOp is sampled with t=T1, x=X, y=Y. The Blend itself, samples input curves using the same t, x and y and gets the T'(sourceA) and T'(sourceB) values. Also, it samples the percentage map with x=X and y=Y, uses it's grayscale output V to control percentage and performs a blend between T'(sourceA) and T'(sourceB) using V. As you see, in this example, the value of V varies with change of X and Y, so you'll get different blend percentage for different input image. Hope that wasn't too technical ![]() |
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Posted: June 12, 2006 12:05 am | ||||
onyXMaster
Posts: 350 |
P.S. The preview of the mapped curve shows a finite number of curve shape approximations, with varied mapped coordinates -- it cannot and should not be used as a "median/average/statistical curve" for the image, just serve as a general preview.
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Posted: June 12, 2006 12:09 am | ||||
byRo
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Rô _________________________________
My favourite question is "Why?". My second favourite is "Why not?" |
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Posted: June 12, 2006 6:33 am | ||||
onyXMaster
Posts: 350 |
Sure, feel free to ask more if you need -- after all since we don't have detailed documentation, it's the only reliable way to get info (apart from experimenting of course
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Posted: June 12, 2006 7:48 am | ||||
Vladimir Golovin
Administrator |
Ahhh, you've discovered mapped curves ![]() When none of the green parameters of a curve component are mapped, the curve is same for every area of the filter. But when you connect a map component to one of the map inputs of a curve component, the curve can have different shape for every area of the filter. I admit, the idea of mapped curves is quite hard to digest, but it can lead to quite interesting results. I'm glad you've found this ![]() |
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Posted: June 12, 2006 12:53 pm | ||||
Vladimir Golovin
Administrator |
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Posted: June 12, 2006 1:08 pm | ||||
Kraellin
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i'd already discovered this from playing, but what limits it is that the blue curve outputs can only go into the blue inputs and if you use a tone curve then the curve only affects the tone and never the shape or anything else.
craig If wishes were horses... there'd be a whole lot of horse crap to clean up!
Craig |
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Posted: June 12, 2006 5:25 pm | ||||
xirja
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So from the recent Mountains at Sunset by Kochubey comes this attached image. Please explain and help me avoid the $300/hr. psychiatrist sir. ![]() _____________________________________________________
http://web.archive.org/web/2021062908...rjadesign/ _____________________________________________________ |
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Posted: November 30, 2015 7:01 pm | ||||
Ramlyn
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Good question. I'm curious too.
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Posted: November 30, 2015 9:55 pm | ||||
Betis
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The black and white values of the map turn into a different "slider" value at each sampled pixel.
In this example: Where the input is white, the bias curve has a high bias value, and the dark parts of the image change the curve (for those pixels only) to have a low bias. The curve preview you see has several different values that it displays to give you an idea of how the curve looks a different parts of the image (they're just stacked layers to give you an idea, they don't correspond to actual pixels) The reason the orange turns bright and dark is similar to how plugging in the orange to a Gamma node with the same black/white map would give you a similar effect (in fact I think the Gamma node is secretly a tone curve node with the gamma curve plugged in under the hood and only the Gamma parameter exposed). Kochubey decided to use a custom curve instead of a gamma curve, for whatever artistic reason. It might be fun to play around with this and plug in different curves like Noise, etc. Roses are #FF0000
Violets are #0000FF All my base are belong to you. |
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Posted: November 30, 2015 11:00 pm | ||||
xirja
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![]() ![]() _____________________________________________________
http://web.archive.org/web/2021062908...rjadesign/ _____________________________________________________ |
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Posted: December 1, 2015 10:12 am | ||||
Ramlyn
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Hummmm.... Interesting. Thanks Betis.
Changing Bias with other curves gives a wide variety of different results. They also don't look easy to control( at least for me ). |
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Posted: December 1, 2015 12:37 pm | ||||
xirja
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Truly, I thought I understood, but alas, a wrench in the works...
The results of the connected components should be the same AND what's with the B values in the first place! Argh! ![]() MaptoCurvePuzzle.ffxml _____________________________________________________
http://web.archive.org/web/2021062908...rjadesign/ _____________________________________________________ |
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Posted: December 1, 2015 12:43 pm | ||||
Betis
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That is very strange indeed. If you check "Preserve Colors" it does stay the same though.
Roses are #FF0000
Violets are #0000FF All my base are belong to you. |
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Posted: December 1, 2015 10:55 pm | ||||
Betis
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Posted: December 1, 2015 11:04 pm | ||||
xirja
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Oh thank goodness. D'oh! Yeah I was toying about, and I roughly understood. That good old difference test has been handy many a time.
![]() Maybe a tone curve without preserve color is the artistic reason Kochubey was hinting at? _____________________________________________________
http://web.archive.org/web/2021062908...rjadesign/ _____________________________________________________ |
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Posted: December 2, 2015 8:08 am |
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