Static Analysis

Last updated: 2020-12-23

Vision

Imagine designing a large bridge with LEGO(R) parts. Wouldn't it be useful if you could see whether your construction is robust before you order the parts? Depending on that, you might even find a better solution that is stronger, uses fewer parts, or looks better.

All that should be possible - if you have the right software. Unfortunately, there's currently no software capable of doing a physics analysis of a LEGO model.
BrickSim will change that.

Plan / Ideas

• The analysis model is just another object inside the element tree. The user can
  • hide it
  • delete it
  • enable automatic recomputing if his computer is fast enough or his model small enough
• If the element is visible, the bricks should be displayed in rainbow colors over the original bricks (red means high stress, green means low stress)

Technical Implementation

Part weight

The weight of all parts that consist only of normal ABS plastic can be calculated relatively easily. We can calculate the volume using the method described in this paper or use a library like the GNU Triangulated Surface Library.

We can get the weights of each brick directly using the BrickLink Catalog Download. This is the only way to get the correct volume for all parts which contain non-ABS materials.

Connections between parts

A lot of information about how the parts can be connected is already available in the LDraw parts library. All parts are composed of primitives. The Primitive Reference lists them all. Unfortunately not all connections can be derived from primitives. For example the underside stud of a 1x1 brick isn't made from primitives. Therefore, we need a list to add additional connections.

This component can later be reused for part snapping.

Data Structure

It's better to not use the element tree directly as the data structure. It should be simplified to a collection of parts because physics do not care about the part hierarchy of a model, and the code would just be unnecessarily complex.