3D Model Has Wrong Size After Import

[JGolden]

When I import a 3D model, the Model Size is correct, but after I click OK the model size changes.
The size went from 22.875in x 22.875in to 23.0419in x 23.0419in.
Why is this?

VCarve Pro - ShopBot Edition - 64 Bit
Version: 9.015 (Build 4048.3918.561)

[Adrian]

Could you attach the original model as well?

[tstuds]

I have this problem as well, Im trying to use imported DXF vectors for a profile path across the full sheet and at the same time take some 3D/2.5D features for an imported STL. Getting it all to line up is kicking my a*** partly because the imported 3D STL is slightly over or under size.

Not saying its a software issue as I still have a lot to learn in regards to VCarve but interesting to hear someone else with the same sort of issue.

[JGolden]

@Adrian

SketchUp 2019 Model: https://gofile.io/?c=vNk4cH

3DS File: https://gofile.io/?c=g8AhTN
DXF File: https://gofile.io/?c=ZLTp24
OBJ File: https://gofile.io/?c=rIhSR5
STL File: https://gofile.io/?c=OppPA7

[JGolden]

Also, when I move the 3D import (Anchor lower left) to Absolute 1.5Y 1.5X, and create a vector boundary, the boundary is at 1.6294Y 1.6294X (Anchor lower left).
And the vector boundary size is 22.8798in x 22.8798in

[Adrian]

Guessing it's because the component is pixel based rather than vector based so there will be an element of rounding. I remember there being an invisible border of 1 pixel around components as well but not sure if that is still the case. Hopefully someone who is a 3D expert will chime in.

[dealguy11]

As Adrian said, this is related to pixelation. Interestingly, if you choose the "Create vector boundary around selected components" and then measure the boundary, the boundary is only about .004" off from 22.875, so I think the extra size reported for the component is coming from an invisible pixel frame around the component. For positioning, I would create the boundary, select both the boundary and the component and move them both at the same time using the nodes from the boundary for positioning.

[JGolden]

Is there a way to import the 3D file as a 3D vector and not a 3D raster (pixles)?

[dealguy11]

No.

[TReischl]

Is there a way to import the 3D file as a 3D vector and not a 3D raster (pixles)?

You would not want to even if you could.

An STL usually contains tens of thousands of very small triangles. Each triangle has three sides. Each one of those sides is shared with the triangle next to it.

Besides all that Aspire is pixel based so it would not know what to do with all those vectors.

The stl models I have posted on this forum usually contain several hundred thousand triangles.

Aspire's ability to read an stl and then convert it into pixels is a good thing. It allows the software to work with models created in programs outside of Aspire. One of the things to remember is that the main focus of Vectric products started out as decorative/organic work. Those types of work rarely demand any real "precision". The vector portion of their products allow accurate mechanical work to be done easily.

[JGolden]

You would not want to even if you could.

An STL usually contains tens of thousands of very small triangles. Each triangle has three sides. Each one of those sides is shared with the triangle next to it.

Besides all that Aspire is pixel based so it would not know what to do with all those vectors.

The stl models I have posted on this forum usually contain several hundred thousand triangles.

Aspire's ability to read an stl and then convert it into pixels is a good thing. It allows the software to work with models created in programs outside of Aspire. One of the things to remember is that the main focus of Vectric products started out as decorative/organic work. Those types of work rarely demand any real "precision". The vector portion of their products allow accurate mechanical work to be done easily.

Interesting. This is the first CAM software I've used that couldn't keep 3D vectors.
Ok, what is the accuracy level / precision level of VCarve 3D pixels?

[mtylerfl]

You can try increasing your job resolution (if you haven’t already). “Pixel accuracy” varies due to job size in relation to the model size, as well as the job resolution setting you have chosen.

Just in case you don’t know, you access the higher resolution settings by holding down the Shift key whilst clicking on the “New” job icon. You can also change resolution after a job is created by holding Shift whilst clicking the Set Job Dimensions and Origin icon.

However, the model must be imported AFTER you set the new resolution. Otherwise the model is “stuck” at the previous resolution setting.

Another variable is the resolution of the model itself. If it was created/saved at a lower resolution, then higher job resolutions may not help much, if at all.

[JGolden]

You can try increasing your job resolution (if you haven’t already). “Pixel accuracy” varies due to job size in relation to the model size, as well as the job resolution setting you have chosen.

Just in case you don’t know, you access the higher resolution settings by holding down the Shift key whilst clicking on the “New” job icon. You can also change resolution after a job is created by holding Shift whilst clicking the Set Job Dimensions and Origin icon.

However, the model must be imported AFTER you set the new resolution. Otherwise the model is “stuck” at the previous resolution setting.

Another variable is the resolution of the model itself. If it was created/saved at a lower resolution, then higher job resolutions may not help much, if at all.

Thank you, I will try the higher resolutions.

For the 3D model, I'm using SketchUp and exporting as .STL, so not sure how to increase resolution.

[TReischl]

There are actually two resolutions that you are dealing with.

The first one occurs when exporting from another program, SketchUp in your case. I have not used SU in a long time so I have no idea if you can control the resolution. Someone else who uses it can chime in and let us know.

The next one occurs when importing an stl file. And stl is composed of triangles as I mentioned above. These represent the surface of a shape (think geodesic dome thingy). When I export from the one I am using it asks me how far the surface of one of those triangles can vary from the mathematical curve that is the true surface. Generally speaking I use .0001. Ok on to the importing. Those triangles are then fit into a digital matrix if you will. Think Rubics cube. X and Y are obvious, the shades of gray are the Z. Soooo, let's say just a small part of a triangle enters into the "cube". It will be ignored. That is losing resolution.

There is no way around it, period. Aspire is a pixel (I prefer the term voxel) based system.

Here is an example of what can happen. A CAD program outputs an stl file with low resolution which looks faceted. No matter how high you set the resolution in Aspire it will still look faceted. That is because the curves that defined the surface in the CAD program are not in the stl file, just those triangles.

[Adrian]

As an interesting aside Sketcjup isn't truly vector based either. It just gives the impression it is.

With Sketchup a lot of the resolution issues have to be handled by increasing segments on curves at design time rather than at export time otherwise you'll end up with large facets.

Also don't fall into the trap of thinking everything has to be done as a 3D object. With CNC a lot of things are more efficiently done as purely 2D with the toolpath itself handling the 3rd dimension or via a mixture of 2D and 3D toolpaths. With the advent of hobby level 3D printing I come across people all the time exporting very simple shapes as 3D as that's how they do it in their slicing software.