I’m filling engraves with resin and the ability to have the area of the engrave would make calculating the volume of resin require a lot easier(and accurate).
Cheers,
Chrome
The Measurement tool will give you the area of a shape. However, this doesn’t work with multiple shapes at a time. So given the complexity of the design you’re trying to engrave this may or may not be practical for what you’re trying to do.
There’s the old standby trick of weighing cardboard:
- Cut out a 10×10 cm = 100 cm² square of cardboard
- Weigh it (in grams, not USA-ian ounces)
- Change the
Filllayer (the one you engrave) to aCutlayer - Cut out those pieces from the same type of cardboard
- Weigh them
The ratio between those two weights gives you the area in units of
100 cm².
For example, if the cardboard square weighs 7.2 g and the cutouts weigh 25 g, then the ratio is 3.5 and the area is 350 cm² = 3.5 × 100 cm².
Multiply by the depth to fill (in cm) and that’s the volume.
Perhaps Automatic Jack might use a trick like that, somewhere in Gibson’s Sprawl. 
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Thanks for the reply.
I understand the math but I don’t get the relationship between the weight of the cardboard and area. I’m not doubting I just like to understand the concepts I’m working with.
Nice catch on the reference. Mollys got your back.
I think the answer is no.
You’re talking about a 3d volume metric.
There is no way, that I know of, for it to tell you how much it has removed, area wise. Even if you know the depth for volume computation purposes…
There might be some relationship between the distance it travels lasing compared to just traveling between cuts. That’s the closes thing I can think of. This is in the bottom of the preview screen… There are still a bunch of unknowns…
Good luck
IF you can get the linear outline path surrounding the area you want to measure, you can get the “circumference” in mm of the area from the Preview window. It does not matter the shape of the outline as long as it is a closed loop,.
Then use the formula Area = (Circumference squared) divided by (4 times Pie). That result times the depth gives you the volume. You then get cubic mm which can be converted to mL as needed.
Will this get you close enuff so you don’t mix too much resin?
Are you willing to upload your LB file here to have a play with?
Edit:
Ok, does this work for you?
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Select all shapes and duplicate them.
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Move the duplicate(s) off to one side.
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Right-click the duplicate(s) and select “Convert to Bitmap”.
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Select then right-click the bitmap and select “Trace Image”.
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Use the Measure tool to measure the area of the resulting trace.
It’s absurdly simple after you see it, but it does require an “Ah-ha!” moment.
Just in case anybody else is wondering, here’s how it goes:
Cut out one reference cardboard square: 10×10 cm. Label it “A”.
Cut out three cardboard rectangles and label them:
- X = 20×10 cm
- Y = 30×10 cm
- Z = 20×20 cm
Which produces this assortment:
You can see:
- X has twice the area of A
- Y has three times the area
- Z has four times the area
Weigh them:
- A = 7 g (your piece will be different)
- X = 14 g
- Y = 21 g
- Z = 28 g
So:
- X has twice the area of A and weighs twice as much
- Y has three times … and weighs three …
- Z has four … you get the idea
Now cut out the perimeter of the layout you want to engrave, perhaps an oddly shaped lake called S:
The S shape weighs 11 g, so it has more area than A at 7 g and 100 cm², but less than X at 14 g and 200 cm².
Its area is proportional to its weight with respect to A:
157 cm² = (11 g / 7 g) × 100 cm²
You can use any piece of cardboard, like X or Z, that you know the weight and area of:
157 cm² = (11 g / 14 g) × 200 cm²
157 cm² = (11 g / 28 g) × 400 cm²
Knowing the area of S, multiply by the depth of the engraving to get the volume of epoxy and fill 'er up. If the lake should be 0.5 cm deep, you need:
78.5 cm³ = 0.5 cm × 157 cm² of epoxy
Not as easy as having LightBurn figure the area, but comes with free tactile feedback: you can see the cardboard shape, lay it out on the tabletop, and make sure it fits.
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Export a DXF, and import into the free 2D version of Solid Edge 2021 - works pretty good, but it is out of LB
Darn you ednisley! That made perfect sense and I had to learn something new!
An elegant solution…
Good mind expanding concept.
Unfortunately Lightburn doesn’t do this for you… 
A great suggestion for feature suggestions?
A cardboard calculator?
I thought of doing something like this in Inkscape. I did a test but because of the ‘unique’ way that LB deals with overlapping objects regarding fill I couldn’t find a practical way of getting a total the lasered area as it would be in LB, hence my solution. Obviously we haven’t seen @Burningchrome’s design so we’re guessing a bit but does the Solid Edge method work like LB does with multiple and partially overlapping shapes?
Not sure if this is what you are looking for, but I could do multiple clicks within overlapping areas, and it updated the area,
That’s good and is a solution if the design is quite simple. However, like I said: we haven’t seen @Burningchrome’s design yet and I’m not sure it would be very practical for a complex design with many regions.
Hey all, Thanks for the replies. This design is little complex for some of the options. @RalphU I tried SE2023 but it seems to crash every time I open the measure tool. @ednisley It took me a bit but I see the relationship. I’ll be working with larger engraves at some point, my machine is 600*400 but I assume I could shrink the size of the design by a factor of 5,cut it and solve for area then multiply by 5 for the final area.
breadshed sign.lbrn2 (274.4 KB)
I can’t see any filled areas in your design. What regions do you want to know the areas of?
Apologies. I was futzing around experimenting and I saved the wrong element. This is the right file
breadshed sign.lbrn2 (427.4 KB)
Ok, no problem. My original method doesn’t seem to work on your file 
However this does seem to work:
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Export from LB as SVG
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Open SVG in Inkscape
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Select all and convert to Path
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Select Path|Combine
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Select 'Extensions|Visualise Path|Measure Path
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Make sure you’ve selected your combined graphic and you’ve selected ‘Area’ in the drop-down. Click the ‘Apply’ button.
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You should now see the total area of all the filled areas.
I haven’t done a thorough check yet but it looks good so far.
Hope this helps.
I thought I’d do a bit of a sanity check by using part of my original suggestion (convert to bitmap then trace) then exporting that to Inkscape. There’s something odd going on because I get a very different value for the area:
It’s probably something obvious I’m missing but I’ve not got to the bottom of why there’s such a large discrepancy yet, I’ll see what I can find…