Semantic Shape Editing | Hacker News Reader

Semantic Shape Editing

meyumer.com

41 pointsstokedmartin13 comments

Reminds me of this scene from Star Trek https://www.youtube.com/watch?v=d0qGXPDJ19c&feature=youtu.be... where the characters try to recreate their memories using the Holodeck. When I first saw it I thought that scene was ridiculously unrealistic -- but I suppose that's what I get for betting against technology.

It seems like defining how the semantic sliders behave would be much more work than having an artist do the 3d modelling. And either way, you're going to need that 3d artist in the first place. Am I missing something?

I didn't read the paper (so I might be full of shit) but I think the idea is that the semantic sliders represent vectors in a vector space that is learned by a machine learning model, based on a sample set of examples. So the idea would be to take a bunch of examples (made by a 3D artist, taken from existing work, scanned in from real objects, etc) and first rate them in each category (which is subjective, and does still take a fair amount of human work)... but then you use an algorithm to train a model that can generate new examples in that vector space. Then, the sliders just modify the values of the different components of a vector representing a new, generated example. I doubt that the behavior of the semantic sliders is hard-coded - instead, there's a general algorithm for coming up with new sets of semantic sliders. So - ideally, for problems this model works well for, you would ideally be able to dramatically reduce the number of 3D models you need to characterize a whole space of parametrized variants.

EDIT:

Just actually went and read the paper. It's not machine learning, it's crowd-sourced. So it really needs a lot of people working on it... so I think that your concerns are totally well placed).

(Maybe we'll see the machine-learning version of this in the near future!)

I think so. You don't need a 3D artist -- models can also be created with a 3D scanner.

I also don't think (I haven't read the paper, yet!) you need to do anything to get the semantic sliders other than to label existing data. If you're going to design a single chair, it's probably more time efficient to have an artist make a 3D model to your specifications. On the other hand, if you're going to design something like a customized biomedical part with variations that depend upon the patient, then this could easily be a net win. Not to mention if you'd like to automate that design, you now have a much smaller dimensional parameter space to play with.

> You don't need a 3D artist -- models can also be created with a 3D scanner

As someone who creates 3D models from scanned objects... hah haha hahahahaa. <sob> It's so freaking hard. I wish it weren't so, but it's so frustrating, it is probably the aspect of my job that I enjoy the least. I use a Faro CMM arm with a laser line scanner and polyworks (IIRC that whole package costs about $90k), and you can get decent scans of certain objects without much effort, but it's really hard to get good definition in small details, and some surfaces (shiny ones, transparent ones, ones where light scatters slightly below the surface) and some details (holes, crevices, small protrusions) are really hard to capture. And even still, the resulting model has high complexity... If you want a smooth mesh without holes or other aberrations, that's another layer of work. And if you need to convert it to proper NURBS surfaces, that is yet another layer of work (and one that takes an entirely separate skill set).

I know these technologies are getting better all the time, but that one's still a really hard problem that's waiting for a better solution.

Oh I agree with you on all those points. That's one of the main thrusts of my work as well. It's hard, but doable, and if you've gone through the effort then you might as well leverage it with a technique such as this.

It means someone can take an existing model and modify it in a simple way.

Example: Download a toy plane model from thingiverse. Decide you want it to look "stealthier", this can modify it. The plane model was not one in the original training set.

The process appears to take a bunch of example models, then asks people to score them on various parameters. The algorithm then works out how to use that knowledge to modify shapes in those directions.

This looks fantastic.

Before Google axed it, there was 'Google Sets', which expanded a few basis terms into a longer list of related phrases.

To be sure, this seems to be more powerful than that. The ability to eek out a 3D model by simply playing around with five or so intuitive parameters could be enough to get millions of people to use 3D modelling for many casual purposes in the first place (whereas traditional tools require orders of magnitude more deliberate thought, and therefore cannot be justified for non-critical drawings).

I haven't read the paper, but from the video this kind of feels like blend shapes to me which are definitely not a new thing. Custom facial rigs often have blending between different expressions, controlled by 2d sliders. Another issue is probably the fact that the meshes need to be composed of the exact same amount of vertices to blend correctly, so no scanned 3d models. Would be cool if they blended on an underlying voxel representation though.

> Another issue is probably the fact that the meshes need to be composed of the exact same amount of vertices to blend correctly

These examples don't require the same topology, in fact they seem to use really quite different ones.

This should allow them to take new, unseen shapes and modify them in a similar way. I think that's what they're doing anyway but haven't read all the paper yet.

I like this a lot! One big challenge in 3d today is making the jump from data to content: The jump we made for 2d in the late 80s when Photoshop changed the perception from pixels to images. But what is the equivalent to a histogram or a brightness/contrast filter in 3d?

I was thinking about EXACTLY the same idea before I went to sleep last night!

This is not an idea, it's an implementation.

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