Sketching on a surface not on a plane

When double tapping on a 3 D model to start sketching can we make the drawing on the surface of the 3 D object instead of the created straight plane?

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Don’t double-tap. Just single-tap on the face where you want to start a sketch.

I think what @zsurgeon is asking for is for the ability to sketch directly on the model surface and not on a plane.
Double tapping, single tapping, however many tapping wasn’t the point… Single tapping the face of a model highlights the face but when you select the pen tool the face rotates and a separate plane is generated ready to sketch on.
It is then necessary to project the sketch onto the object. There are obvious advantages to this method but it would still be nice to have the option (maybe shift-tap? @Istvan_CEO_Shapr3D) to draw directly onto the surface of an object if preferred.

@zsurgeon Please correct me if I’ve mis-understood.

It is always possible to start a sketch on any planar face after double-tapping on it or hovering over the mouse and pressing space. In these cases, it is not necessary to create a dedicated construction plane, Shapr3D will recognize the planar faces automatically.

Sketching on curved surfaces, however, is not possible.

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Whichever way I do it, (hover/spacebar, click/spacebar, double-click/spacebar), as soon as I begin to sketch a sketch plane is created which means I then have to project the sketch onto the surface once my sketch is completed.
It would be nice to be able to circumvent that process when necessary and simply sketch directly on to the surface.

You can sketch directly on a surface provided it is a flat planar surface. No sketch plane is created.

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I can’t seem to be able to do it without invoking a sketch plane :flushed:
I’m using a MacBook Air M1.
I use either the trackpad or my One by Wacom.
As soon as I start to sketch, a sketch plane is invoked in the sidebar and that is what I am sketching on.

Note the double tap with my fingers (red dots).

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And these sketches are actually part of the body and not on a sketch plane?

Sketching on a surface ‘auto creates’ a sketch plane. You don’t need to create a plane to start with.

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Ah, I think there has been a total misunderstanding here.

I’m aware that it automatically creates a sketch plane which is why I commented that a sketch plane is invoked as soon as I start to sketch.

However, this means the sketch is on the sketch plane and not the model. To apply the sketch to the model one would have to then project the sketch onto the model.

In my original comment to the OP I expressed a wish to actually sketch onto the model without these steps.

Oh, I see! Those are different modeling elements called edges. They cannot be sketched directly, but a projection will do the trick just make sure to have the Edge option selected:

Please note that these edges can be transformed with the Move/Rotate tool which makes them a powerful deforming tool.

If you project a sketch onto a planar face, you have an option to select the result should be either another sketch or an edge. This option is only available if you project to planar faces. If the target face is curved, the result can only be an edge.

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Yes. I frequently project onto surfaces (edges) and have deformed models on occasion by pushing/pulling those surfaces.

I guess my original comment (and what I think the OP was tying to ask) could be taken as a Feature Request - It would be really handy to be able to skip the projection step and draw directly without invoking a sketch plane.

I believe welshsteve got the idea and I think it would be an important addition to the software regarding my field which is designing a patient specific implants as all the tissues whether bones or soft tissues have a curved surface. And when I try to use other softwares to adapt it on the curved surface it deforms. When I tried to project it on the target mesh it deforms as well


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That is an interesting topic and a bit different than simple projections I think as mesh models arrived at the party. Even if mesh models look smooth and curved, they do not have any curves just small planar polygons all around. If a mesh looks smooth, that is the result of a huge number of tiny polygons - and regularly a significant file size.

Projecting a perfectly curved spline to a mesh would result in a polyline with dozens or even hundreds of segments depending on the areas of the polygons the spline is projected onto. That would be a nightmare to work with and simplifying the projected curve would differ from the projected one.

If you are working with scanned data in a CAD software without reverse engineering, the workflow may strongly rely on the boolean tools. In this case, I’d scale up a copy of the scanned data big enough to have a gap between the original and the scaled mesh. The gap will define the thickness of the implant. Then create an extrusion from the spline that is way longer than it should be, the goal is to extrude it through both the original and the scaled meshes. If a Subtract is applied to this composition where the tool bodies are the meshes and the target body is the extruded body, you will have an implant that follows the shape of the scanned mesh.


Dear KPeter. I did what you suggested and gave a 10% expansion for the mandible. After subtracting the bone

plate from the original mandible and intersecting the result from the scaled up mandible I had a result that I have some observations on
1- the direction of the bone plate arm and holes are not perpendicular to the original mandible
2- I cannot change it to be thinner or thicker while keeping its adaptation to the surface of the original mandible
3- the scaling gave thickness in some areas more than other areas so the plate does not have uniform thickness
4- because the inside of the mandible is not solid like it’s outer surface there are some areas not intersected well. The bone does have some spongy bone from inside so there are some gaps that were not intersected
5- I do not have edges to bevel nor sculpting brushes to smooth the edges

May I ask you to share the model with us? you can upload it here or feel free to share it with me in PM, there are some tweaks that I’d like to show.

Apart from those, the difference in CAD-mesh properties is a challenge in this kind of project that requires some workaround. The boolean between the CAD and mesh models should be applied as late as it is possible because the CAD will be automatically converted to mesh to make sure the boolean can be finished. After converting to mesh, it will not be possible to make the body thinner/thicker or fillet the edges.

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I will add the file to my reply. If it failed to load I will email it to you

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Hello KPeter

The file could not be uploaded in the forum. Here is a link to download it and if you want to post it on the forum or anywhere go ahead

(Attachment mandible.stl is missing)