Decimating 3D Scan Data & Lossless Data Compression
Reducing the size of 3D Scan Data can be important. Most people familiar with 3D scan data are aware of this because scanners can generate a lot of redundant information in relation to actual useful information in the geometry.
Take, for example, a brick. It can be represented with a few dimensions (w x h x L, plus chamfer size if it’s a fancy brick). In CAD, a brick is light-weight and is composed of a few primitive pieces of geometry. But a 3D scanned brick can have millions of triangles.
Decimating scan data reduces the number of triangles, and a good decimation tool will keep track of the actual geometry and not try to deviate from the original geometry all that much.
Below is an example of a brick in (1) CAD, with an (2) Original Scan, and with a (3) Decimated Scan (note the scans are simulated). All of the shapes adequately represent the brick, and give a good idea about the heaviness of the different representations of the model
Decimation: Lossy Reduction
Rarely, however, are 3D Scanners used to scan simple shapes like bricks, and are better applied to complex shapes (with a lot of detail) or ones with complex forms. Below you’ll see a few examples of a free form shape being decimated. You can click to open the 3D view.
Click to view/rotate in 3D, you can also download the file here (http://bit.ly/Kxq2QG)
It is more clear in these samples the differences in decimation and that decimation can effect the geometry if it is over-applied. Clearly there is geometry loss when the data is decimated which can unacceptable in many situations.
Another way to reduce the size of data without changing the geometry is to store it in a more efficient format. Unfortunately for people moving heavy data around, it is common to see legacy data formats value a simple data structure rather than a compressed and more efficient format. An STL is a good example of this, as it an uncompressed and very heavy format which stores a lot of unnecessary and redundant information – it’s basically an extremely inefficient file format for storing 3d geometry. (An simple inefficient example of storing data would be storing an x-coordinate as 1.25 vs 1.25000, where the 000′s don’t contribute to the geometry and just take up extra file space).
One of the benefits of working and sharing 3D models on the cloud with TeamPlatform is that models are automatically compressed by TeamPlatform when they are uploaded. This means the the information (the 3d geometry) in the files can be loaded at a fraction of the time it would take to load the geometry had it not been compressed. Loading files on TeamPlatform is faster than downloading the original files because of the high (and lossless [no shape is lost]) compression. When this idea is taken a step further to viewing 3D models within TeamPlatform’s Design Review, the benefit of this compression can save a lot of time.
The video below shows a head to head comparison between launching and loading installed software vs. viewing data online in TeamPlatform (the software used is the very capable 3D scan data software Rapidform from INUS Technologies, www.rapidform.com)
The speed differences boil down to (1) compression of the 3D geometry makes loading the compressed file online much faster than downloading it, and (2) the file is accessed from the cloud and immediately loaded in the browser (which means you can skip the program launch and load times).
Viewing data obviously isn’t the end-all for 3D geometry. You might want to comment, or provide feedback, or send the data to someone else to process or review. When you really, really have to download the file, it’s good to have a fast internet connection on your side (download speeds typically max-out at a few MB’s per second), and a good software on your computer to handle the data.
Decimation and Compression both reduce the weight or filesize of geometry. Lossless Compression means that the filesize is reduced but the geometry is identical (100% exactly the same; no-loss; lossless). TeamPlatform uses lossless compression for it’s online viewer which means that you can view files in a fraction of the time they’d take to download and then reload into a viewer on your own PC.