Plot Node

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02 Feb, 2021 04:38 AM

This thread is a continuation of the discussion Floris and I started in the Image Node thread. We will examine new versions of the plot node, share plots made with it, and discuss possible improvements or variations.

Anyone else interested in developing ways of plotting pixel-based images using the image node is welcome to join us.

  1. Support Staff 1 Posted by john on 17 Feb, 2021 12:44 AM

    john's Avatar

    Attached is a demo with an improved version of the hatching node (v2).

    The node works just as before except that it zigzags its hatching lines (reverses direction in every other line) in order to reduce travel time when plotting.

    The example shows a circular hatching mask applied to an image and then plotted using our current plot node. In order to verify that the lines really are alternating direction, I made a "show_order" node which simply draws each connected line using a color gradient from bright red to dull gray. You can see the zigzagging effect.

    If I create new masking nodes in the future I will try to bake in this same plotting efficiency. The concentric circles mask is already plotter efficient since each circle starts and ends at the same position.

  2. 2 Posted by florisdejonge on 20 Feb, 2021 07:59 AM

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    Hi John,

    Thanks for your reply. I was first assuming the changes were contained within the show-order node, but later found it was the hatching node. So I meant to try to test whether the new version of the hatching node was increasing the speed of the plot. I’ve attached a screenshot of the image I plotted, containing 32 squiggly lines (120x120mm). The image on the left (with zigzag motion) took about 51 minutes to plot (at 70% speed), the one on the right (without zigzag) took around 54 minutes (at the same speed). I must admit I was a little underwhelmed, but the most time of moving is spent on travelling from point to point within the squiggly paths and not to travel from beginning to end of every row.

    So, I did a more simple test to check what kind of increase of speed this could lead to. This consists of 39 horizontal lines of 120mm length. The pattern with every 2nd line reversed took 8:23 minutes to draw, where the other (with every line drawn from left to right) took 14:52 minutes. So it does pay off to think about the order and direction of paths. Following your example of the node library, I’m trying to make more self-contained subnetworks of separate functions for easier use in other projects. The crosshatch-pattern provided here is such an attempt.


  3. Support Staff 3 Posted by john on 20 Feb, 2021 11:22 AM

    john's Avatar

    Attached is a general purpose posterize node.

    It takes in an image (pixel group) and spits out a posterized version with N levels of gray. The resulting image is automatically grouped into N regions, which could then be fed into a plot node with different textures for each region.

    (Render the posterize node to see the full image; stack the groups to see the regions separated.)

    The demo shows a comparison of Floris's original posterization algorithm which only works properly for 5 levels. His levels do not all cover the same subset of luma range and have custom gray levels. The first row shows the file regions broken out.

    The second row shows the output of my general purpose posterize node broken out. The results are roughly similar, but more evenly segregated than the Floris algorithm. Floris has fewer pixels in the first and last regions.

    With the regions separated like this, the posterize node acts a kind of mask. By feeding the output into Floris's crosshatch plot node, you could get a plot with a different texture for each region.

    Our next challenge is to make Floris's crosshatch node general purpose so that it could cope with something other than 5 regions. I will also try to simplify the original mask node inside Crosshatch to reduce render time.


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