Making a negative / mold from a complex shaped mesh

[infoPKJZY]

Hi!

I'm trying to 3D print a negative from a 3D scanned headlight cover in order to vacuum form spare headlight covers for a historic non-production race car.

The 3D scanned model is a complex mesh. I have already reduced the mesh to a resolution I can work with (4000 faces, the exact shape doesn't really matter and I can sand down the 3D print) and converted it to a body, and am now trying to extrude the bottom part of the body to the ground / XY plane. I cannot find a good way to do this for all faces at the same time. The only thing I can think of is doing a "sweep" using a line on the Z axis for every face, and then cut them all off on the XY plane, but I don't see how this could be the right way to do it.

Requirements:

- The top part of the model I'm trying to make needs to meet the bottom part of the headlight cover mesh / body

- When looking from above, the model I'm trying to make needs to have the same shape / outside perimeter as the headlight cover

Attached you can find the 3D scanned mesh, and the project I have so far.

Would greatly appreciate any help / tips on this!

Happy making!

[davebYYPCU · Accepted solution]

Top down mold, to the topside of the mesh?  Actually, on review, I realise, should be inside the mesh to your board.

Edit, kept the old photo, file updated.

Extrude the new material above the surface and use the surface with split body to remove the excess.

Might help....

[infoPKJZY]

Thank you so much for the help!

Looking at the design history I can understand exactly what you did, really helpful for my learning journey 😉

How you created the body from the mesh using the "create form" function is still a bit of dark magic for me. I will try to find some video's going more in depth on that feature, seems really cool!

Thanks again, really appreciate the help!

Have a great day!

[davebYYPCU]

I’m still learning how to be efficient with forms.

This might save you some time, couple of terms to help the research, 

Created a Quad ball, 2 panels, 

deleted bottom half.

Edit form - stretched and moved as required to get the bottom curved boundary and the height, close to matching the mesh body.

Then I subdivided the whole thing once.

Used the Pull Tool, selected all, and Auto.  

Then I extended the surface body with Ruled Tool to help the Split body, cut all the way.

Might help….