Seams in engraving that is broken up into tiles

After searching the forums for how to address the fact that the Glowforge can’t handle very long running engraving jobs, I found that the recommended solution is to break the image into smaller engraving jobs. I found it frustrating that this was the official advice from Glowforge and that they didn’t have a built in way to do this, so I developed a tool to break any image up into tiles. I posted about the tool in the forum a few weeks ago.

The problem is that the Glowforge seems to introduce a seam into the engraving job, despite the tiles lining up perfectly. I had a suspicion about what was causing the seams and after closer investigation, it seems to be due to interpolation artifacts introduced by adding extra edge pixels.

If I’m correct, the simplest fix would be for the Glowforge to leverage the image-rendering property on the SVG image tag to switch between bilinear interpolation (“optimizeQuality”, the default) and nearest neighbor sampling (a valid implementation of “optimizeSpeed”, or the only valid implementation of the CSS option of “pixelated”).

A much more involved solution, but more versatile option, would be to implement SVG patterns.

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I’ll add, I believe this is why my engraves across passthrough steps all have what appears to be a “skipped” line, even though microscopic examination reveals the laser is indeed firing along those lines. Details of which have been posted in various passthrough threads, but I highlighted them again in the OPs post, linked above.

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Mine have the same issue. I usually just knock them down with a fingernail so they’re not as noticeable.

After searching the forums for how to address the fact that the Glowforge can’t handle very long running engraving jobs, I found that the recommended solution is to break the image into smaller engraving jobs.

I’m guessing you found some old posts from before January 2019. When we announced we solved that issue.

And here is the community post for that announcement.

In any case, that old limitation wouldn’t be causing the error you’re seeing.
image

I’d like to check out the logs from your unit to investigate that more.

  1. Reboot your Glowforge once more and wait about 30 seconds
  2. Hold down the button on your Glowforge for ten seconds, until it glows with a teal color
  3. Your Glowforge is now broadcasting a temporary Wi-Fi access point. Connect your computer to “Glowforge XXX-XXX” (from your Wi-Fi Settings)
  4. Visit the following URL in your browser: http://192.168.192.1:3000/logs/zip
  5. A .zip file should download to your computer
  6. Reconnect to your usual Wi-Fi network and email the .zip file to support@glowforge.com

Please let me know if you run into any difficulty with these steps. Thanks!

I appreciate the information. I’ll follow those steps and try another longer engraving as well as get the logs when I have a chance. I did find some older forum posts, as well as this document: https://support.glowforge.com/hc/en-us/articles/360033633694-File-Won-t-Print?mobile_site=true#design-includes-a-very-large-engrave

Even so, there may still be good reasons to break up an engraving and this doesn’t address the reported issue. Glowforge seems to introduce a seam into perfectly aligned raster images. Is this a know issue? Are there plans to address it?

Thanks for bringing that to my attention! I’m going to investigate if that page needs updating.

That doesn’t ring any bells.

I’d want to start by looking at some example prints.

There are a couple of different ways of aligning things. Can you say more about how the raster images were aligned? Are you referring to passthrough prints?

If you have example files you can share, or if you have prints that I could check into the logs, I’d be happy to take a look.

I can usually find what I’m looking for with an approximate date and time of the print, especially when I also have photos of the print result.

The clearest example I have is here: Simple tool for tiling any image to break up large engraving into smaller jobs

The raw SVG is provided in the linked post and discusses the issue (earlier in the post is a bit more discussion as well). There are 5 different versions of essentially the same image. If they were numbered 1-5 from left to right, the first, second and fourth are a 2 pixel x 2 pixel image with a simple black/white checker pattern. Each are embedded in the SVG with an image tag using a different image-rendering property (optimizeQuality, optimizeSpeed and pixelated). Glowforge treats them all the same and appears to use bilinear interpolation when sampling subpixel values.

The far right image is the same 2x2 pixel image, but represented with 4 separate 1 pixel images. You can see that the Glowforge engraves it very differently than the others due to the interpolation differences. This issue will affect any raster image that is broken up into tiles because the interpolation of the edge pixels on each tile will be engraved differently by the Glowforge. The linked case is particularly extreme because all 4 pixels are edge pixels and a single pixel is blown up to 1inch in size. In an image that is a normal size, this could present itself as a seam along the inner edges of the tiles. I don’t have a pass through slot, but if the process of splitting the image involves rasterizing into separate images, I imagine this would affect that as well.