Creating a high quality model of a physical shape

[rshawiii]

I’m trying to get to a high quality model of a hull form for which I have an actual physical “plug” or master. The way in which I have been working towards the end goal is via a process known as photogrammetry, where many pictures are taken and are resolved ultimately into a mesh. Ultimately I want the sketchup model to be accurate to < 1mm of what the true physical shape is. The sketchup model will be used for conceptualizing and generating other models for other parts (oar mounts/rigging, seat mounts and sliding systems, accessory brackets, etc.) For these other smaller parts I hope to be able to 3D print or have machined masters that can be surfaced and molds made from, in which actual composite parts will be formed in carbon fiber/epoxy, etc.

For the photogrammetry tool I have been using something called RealityCapture. I have been able to get it to generate a triangle mesh that is rough but does represent the geometries. This program is very difficult to use and the documentation and youtube how to videos are horrific. The advantage of Reality Capture is they offer a pay-as-you-go model. This is attractive as this is a one time effort. I don’t plan on doing these type of scans in the future, and this category of software tends to be pricey.

I have gotten Reality Capture to produce an approximately 1 million triangle mesh model of the part. I have been able to import this into sketchup, scale it, verify that the geometries are roughly correct and have done a little form tracing with FredoSpline. It is however a “dirty” model and is a long way from the end goal. Also sketchup is at the point of choking on this size mesh, even on a farily fast gaming grade machine. Through some more effort I’m sure I can get Reality Capture to produce a better mesh, but it will not ever be at the level of accuracy I’m looking for.

So after researching the forums, etc. I’ve got a number of questions and issues I’m trying to resolve. I’m looking for input from the Sketchup community that will help get me to the end goal and not waste a lot of time going into dead ends.

Here they are:

Given that sketchup is struggling with the mesh editing (because of size I presume), should I be looking at doing some of this in a tool such as MeshLab. The cost of this to me is the learning curve.

My thinking is that with a reasonably accurate mesh, I should be able to loft the shape using splines and create a new organic surface with one of the various surfacing tools such as curviloft.

What tools/extensions to sketchup are recommended? Obviously Thom Thom’s Vertex2. FredoSpline, etc. (I’ve installed most of Aaron’s recommended top 10 extensions as well as a few others. There are other mesh/organic modeling extensions out there: Artisan (looks like they aren’t updating) and even Trimble Scan Essentials for Sketchup (again not cheap and not sure is appropriate for this use case).

What about quads? I’ve been reading about quad meshes. Do I need to be getting this model into a quad format? Outside of sketchup or inside? Using what?

Thanks for any help or insight out there.

[john_mcclenahan]

If you still have physical access to the hull mould, I’d be inclined to take a number of key measurements off the mould you have, and redraw the hull lines using Bezier curves.

Typically, full size hulls are drawn from an astonishingly small number of profile lines and cross sections - often, not more than half a dozen to ten of each, so it shouldn’t take too long.

Then ‘skin’ it with Curviloft.

That way you can get a smooth model without too many polygons in your mesh.

[rshawiii]

that is what i’ll probably do if I can’t get the mesh to work. I’ve got 20+ foam board templates that I made to help fair the plug (fixing problems that were in the original mold that sat in a backyard for years). Taking measurements of these organic shapes is not as easy as it seems. I’d still like to see the higher tech method work. only with less roadblocks. seems like we should be there in 2021.

[mihai.s]

Import your Reality Capture scan (OBJ, FBX file) with Universal Importer, Skimp or Transmutr, all of them been able for geometry simplification (polygon reducer).

I used for exemplification (rough example) a sailboat hull scanned model of Seth Hamer, downloaded from sketchfab.com

instead of Curvizard, you could use FredoSpline for a better profile

[rshawiii]

So I’ve got a hull shape generated from curviloft. As in your hull form there are some adjustments I need to make as well as merging several non-contiguous surfaces. Does any one know if there are any limitations to using vertex tools on these surfaces (what appear to be groups of faces and edges - psuedo quads?) I’ve got vertex tools 2.0.4 and am not sure if it is working correctly or is having a problem with the curviloft surfaces. I’m thinking these are user (my knowledge understanding) problems, but not sure.

[pbacot]

You have to use Vertex tools directly on the mesh geometry, not on closed groups. If you want to work on surfaces that should be contiguous, you need to put them in the same group and open (“edit”) the group (or you can work on ungrouped geometry–preferably in a file that has no other ungrouped geometry). I don’t know of limitations. It seems pretty robust.

Curviloft makes groups of the results. you don’t have to leave them in the groups, but you may want to keep your mesh separate from the curves that you started with, using groups for each or removing the original curves from the area or file.