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This article is confusingly written. Its explanations sound silly to anyone even a little familiar with 3d, since it spends the first half of the article explai
by edanm 9y ago
This article is confusingly written. Its explanations sound silly to anyone even a little familiar with 3d, since it spends the first half of the article explaining that this "breakthrough" is "computationally clever and forehead-slappingly simple", the breakthrough being that you can represent things as surface-models instead of voxels.
Well, surface rendering is how almost all 3d work is done already, that's definitely not a breakthrough. You can probably spend an entire career never dealing with voxels.
What this article never mentions (surprisingly) is that this paper is about neural networks. I'm not an expert, but as I understand the article, voxel representations have been the standard specifically when building neural networks to turn 2d images into 3d. The main idea is that you can build a network that only renders high-resolution voxels when close to the surface of the model, and renders very low-resolution voxels everywhere else (say, on the inside of the model). This means you can both represent much larger models memory-wise, but also that you're not having to run the NN computations on voxels that are not likely to change, since everything "inside" of the model you probably guessed correctly pretty quickly.
Here's the paper's abstract, much better at explaining itself than the article:
"Recently, Convolutional Neural Networks have shown
promising results for 3D geometry prediction. They can
make predictions from very little input data such as for example
a single color image, depth map or a partial 3D volume.
A major limitation of such approaches is that they only
predict a coarse resolution voxel grid, which does not capture
the surface of the objects well. We propose a general
framework, called hierarchical surface prediction (HSP),
which facilitates prediction of high resolution voxel grids.
The main insight is that it is sufficient to predict high resolution
voxels around the predicted surfaces. The exterior and
interior of the objects can be represented with coarse resolution
voxels. This allows us to predict significantly higher
resolution voxel grids around the surface, from which triangle
meshes can be extracted. Our approach is general
and not dependent on a specific input type. In our experiments
we show results for geometry prediction from color
images, depth images and shape completion from partial
voxel grids. Our analysis shows that the network is able to
predict the surface more accurately than a low resolution
prediction."
- xg15 9y agoI was stumped by that as well. It spends half the text explaining the well-known parts (surface models) and then mentions the actual contribution completely in passing: > So first his system renders a 3D reconstruction of the 2D image in very low resolution [...] Next, do a higher-resolution render of the area you kept. Where apparently the author seems to think producing a 3D reconstruction of a 2D object is trivial even though that's what the paper is about.
- deleted 9y ago[deleted]
- averagewall 9y agoThat's not what the paper is about. The abstract quoted by the GP shows that it has been done before. Probably only very recently so it's going to be a surprise to a lot of readers, but perhaps old news measured in machine learning years.
- dahauns 9y agoIt was actually astonishing for me how old a lot of the machine learning methods and algorithms are - quite often stuff I worked with on university almost 20 years ago. The main difference being that you have more computation power and memory by orders of magnitude. You can throw datasets at the NN that would have been prohibitive in size back then. Stuff I had to reserve time for on the uni "super-"computer probably runs on your phone nowadays. Oh my god, I sound like my father.