Hi All,
I am wondering if anyone knows how the 3D deep engraving reads grayscale and converts it to depth of cut because it does not seem to scale linearly. I understand black is 100% and white is 0%, but anything in between does not correlate linearly with engrave depth, a 50% grey does not cut half as deep compared to black but rather barely scratched the surface for me.
The same 3D grayscale image when converted to lithopane gave a perfect height profile.
So I am wondering if anyone knows how exactly does the grayscale correlate with cut depth, or if there is a setting anywhere to make the correlation linear? I asked live chat and they don’t seem to know either.
Here’s an example, as you can see, the engrave gave a relatively flat center of the flower compared to the lithopane (same dimension), the petals are also a lot flatter rather than having two obvious ridges.
What??? But your flower center actually looks well-rounded rather than mine is mostly flat. Are there any additional settings you change under the 3D deep engraving option?
I think you might be leaving the masking on. I at least run a score around the cut and remove the masking first. Anything white will not be touched even if you include extra so the result is worse. You can darken the white just a bit to make sure it is cut everywhere.
Edit: I also stretch the contrast to get the maximum range available. so I am using the whole 255 grays.
It looks like the center matches your template pretty exactly. From what I can tell the petals are lower than the entire center, so the lightest colour on the petal should be the same as the darkest colour on the center…does that match what you did?
Also, repeating the engrave will make everything deeper, so if you’re not happy where it is, you should run it again!
I eventually engraved all the way through a 1" thick piece of acrylic that way:
I generally go for much higher LPI than most folks and always full power, and then adjust the speed to get the maximum depth I want. If you are running at 30% power the machine is trying to divide that 30% into 255 levels where if it is full power each level will have a greater distance and be more distinct.
Working in acrylic I go to 1355LPI as anything less will leave ridges, and with full power, I may need even 2400 speed to not burn everything up.
Oh wow that is very impressive how you can carve through 1” acrylic!
I think the issue is somehow my machine is not scaling the grey linearly, almost takes exponentially darker to get twice the depth so more passes might only make it worse. I’ll probably just have to fiddle with the setting somehow.
That last picture doesn’t look like a true depth/height map. The reflection on it shows a couple of light sources at the upper left and lower right. There wouldn’t be a shine like that on a depth map. Look at the star image @deirdrebeth posted, straight gradient from top to bottom, no reflection.
Yeah the blue model was the image to lithopane tool I used to get an idea of what the result should look like https://3dp.rocks/lithophane/
This is the height map I used
I did some color measurements on the image and the website scales grayscale linearly, unlike my laser for whatever reason
I have done things like that. That lotus above is a good example as I wanted the center to stand high above the circle, and this would certainly do that, though I think the outer rim could use a bit more upper range as it could be higher on the outer edge and then dive low.
That would be disappointing… I am trying to create my own depth map and if % gray does not correspond to cut depth then there’s effectively no way of controlling the depth for anything that’s not strictly black and white.
It pretty much does exactly that. I have never tried to be specific (like 50% gray is a specific distance) as you have 250 possibilities and the low LPI you were using covered many levels in just the one level (I thought it was fabric at first it was so strong) you just need to be sure that darker = deeper. With that low LPI the difference between levels is harder to notice.
As you can see, it most definitely is not a linear relationship and depth increases significantly past 60% ish whereas 50% barely scratched the surface
I stopped during 2nd pass to showcase how more passes would only exacerbate the depth difference between different shades of gray, I would go through the entire material thickness before reaching actual 50% depth for 50% gray.
A better shot at the depth:
I made the input image using Procreate and saved it as JPEG then imported the image directly, unless this process somehow changed the grayscale, or Procreate, a professional drawing software, messed up their coloring scheme, I think this is the direct evidence that grayscale does not correlate linearly with 3D deep engraving depth.
