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Thread: strange artifacts from dry media tools

  1. #1
    Join Date
    Apr 2013
    Location
    Bandung, Jawa Barat, Indonesia.
    Posts
    12

    strange artifacts from dry media tools

    Hello guys,

    I wonder if any of you having this same strange artifacts when using dry media tools (chalk/wax, pencil and stiff oil brush) on a canvas with low roughness setting (below 5 %. 3% and 2% & are the most problematic).

    Here's how i can reproduce the issue in the screen shot:
    Set the canvas texture roughness to 3% and 2%, then I scribble using dry media tools.
    1. Using stiff oil brush: reset the oil brush tool to default value but set the stiffness to 90%
    2. Using Chalk/Wax: reset to default setting.
    3. Using pencil tool: reset to default setting.
    the artifact can also be reproduce using different settings, the settings above is what i use for testing.

    Click image for larger version. 

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    It may not be a big issue, as people who want to use very soft texture can set the roughness around 6% and not having this problem (as mentioned, the problem occur below 5%), while people who want to work very smoothly without texture can set the roughness to 0%. But still, if it's a bug then i don't think there's harm in fixing it.

    One more thing, in Artrage 1 the chalk and crayon fills the paper more realistically and the oils blend more evenly. It just feels right. How can i get the same look and feel in Artrage 4? I'm still fiddling and figuring out all the settings in AR4 (I'm new to artrage when it comes to changing and making custom settings).

    Click image for larger version. 

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  2. #2
    Join Date
    Nov 2011
    Posts
    937
    Well that is interesting.
    I can get the same as you but I have to have the tool pressure turned down as well to around 8%.
    This anomaly seems to be "vertical" in nature as you can see with the green crayon/chalk and the thinner green and blue pencil lines.
    Also of note is that a positive canvas % gave white "gaps" but a negative % gave the dark "blocks" as seen in the green lines.
    Also it was quite hard to persuade the oil brush into displaying this behavior (red line to the left) and then only with a low positive canvas %.
    Fortunately for me these are a combination of settings I've never needed to work with!
    Click image for larger version. 

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  3. #3
    Join Date
    Mar 2006
    Location
    New Zealand
    Posts
    3,140
    What you're seeing is the result of a decision made in the original ArtRage that means our paper grains are very low contrast images. To avoid custom images having huge gaps in them where the user generated too wide a range in contrast the grain system adjusts the grain image so that it's more likely to create a reasonable texture for painting. As a result, when roughness is down really low the grain almost completely disappears except for some sparse dots that were at the extreme points of the original grain image.

    Now for the complex technical bit: The grain image represents the highs and lows of the paper texture, but if all we did was say 'a brush only penetrates in to the deepest parts if pressure is above <x value>' then if your brush passed in to a wide area of 'deepest grain' and you were pressing lightly, you would get no paint, which isn't how it should work. For example, with a black canvas grain map you still get paint - If all we did was compare the grain value to the pressure you'd get no paint at all. To avoid this, instead of just comparing the grain at a point to the pressure value at the time, we sample the entire area around the brush head to determine the depths extents of the grain within that area and that gives us a potential range for paint application at any point of the stroke rendering process.

    So when the roughness is very low and the grain has almost entirely disappeared except for the extreme points the system can generate interactions as though the paper were entirely smooth, while in other places it sees a very small bump, to which we apply penetration parameters (which are a blend of pressure and other values in the settings block), resulting in a sudden change in paint application.

    We do try to interpolate the grain values in order to reduce this problem but there are points at which the small 'extreme' dots can create artifacts of the kind you're seeing. It's a problem with the historic model but it's something we have on our list to look at as we go forward. The challenge is how to avoid older paintings suddenly behaving oddly if we change how the grain interpolation works.

    I hope that sort of helps explain what's going on with it - The paint simulation is pretty complex internally and while we're looking at things we can do to improve it, there are some fringe cases where old models make it hard for the newer features we have added to reproduce earlier results.
    Matt
    ArtRage UI
    Ambient Design.

  4. #4
    Join Date
    Apr 2013
    Location
    Bandung, Jawa Barat, Indonesia.
    Posts
    12
    Quote Originally Posted by MattRage View Post
    ...
    We do try to interpolate the grain values in order to reduce this problem but there are points at which the small 'extreme' dots can create artifacts of the kind you're seeing. It's a problem with the historic model but it's something we have on our list to look at as we go forward. The challenge is how to avoid older paintings suddenly behaving oddly if we change how the grain interpolation works.

    I hope that sort of helps explain what's going on with it - The paint simulation is pretty complex internally and while we're looking at things we can do to improve it, there are some fringe cases where old models make it hard for the newer features we have added to reproduce earlier results.
    Okay. Thanks for replying with such depth. I get it now and more importantly, I'm reaally glad to know that the Ambient Design team is still actively looking to improve this already amazing digital painting software. I'm satisfied with the software as it is, but i know it can be a bit better still. Keep up the great work you guys!

  5. #5
    Join Date
    Feb 2011
    Location
    Maryland
    Posts
    142
    Has anyone discovered a work-around for this? I re-installed 3.5 Studio Pro hoping I could move a painting between programs so I could use my favorite preset without artifacts, but I have found different types of obstacles at each try. I got it to work (approximately) once, but now I don't know how to repeat that success.

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