There is no silver bullet for making a high fidelity copy of a physical object in a digital modeling environment. Most processes take careful planning, understanding of technological constraints, and significant post processing to achieve suitable results. The following discusses relevant considerations and workflows for reverse engineering using Rhino’s modeling environment.
Rhino is a native NURBS surface modeler. This means that Rhino can very efficiently handle complex, free-form surfaces and smooth curvature. The majority of Rhino’s tools are oriented toward surface manipulation. Although Rhino can accommodate solid modeling with polygon meshes, its toolset in this regard is limited. This is important to consider when reverse engineering or preparing a file for rapid prototyping since many scanning and printing workflows generate or require high density polygon meshes. Because of this distinction, a significant part of the workflow requires knowing when and how to translate between NURBS Surfaces and Polygon Meshes in Rhino.
There are three main approaches to reverse engineering using Rhino and the resources available in the IDeATe Lab.
- Manual Reconstruction > Authors can build accurate reconstructions of physical objects using a combination of Rhino’s native commands. This workflow typically involves taking careful measurements of an object and importing scaled images to trace key information. There is usually a base layer of construction drawings that support the creation of 3D surfaces. Benefits to this workflow include full control of modeling accuracy and level of detail, ability to generate NURBS geometry directly. Drawbacks include time-consuming multi-step operations, limits to the level of complexity and surface detail one can realistically model.
- 3D Scanning > Authors can use a table top or hand-held 3D scanner to reconstruct an object. Benefits to this workflow include high-resolution mesh output (depending on the scanner), relatively low setup and processing times, the potential for minimal post-processing of mesh. Drawbacks include the need for expensive dedicated equipment, limitations in size and surface quality of scanned objects.
- Photogrammetry > Authors can use a series of overlapping photographic images to reconstruct a physical scene using software like Autodesk’s 123D Catch. Benefits to this workflow include the use of simple and accessible equipment (camera), relatively low capture times, the ability to capture irregular and complex geometries. Drawbacks include inability to capture reflective surfaces, need to extract objects from scene, often significant mesh post-processing.
I have uploaded a folder with example files that illustrates best practice and useful commands for reverse engineering using Rhino and 123D Catch.
- Rhino can import and export .obj and .stl files for mesh editing and rapid prototyping
- Use PictureFrame to import images into Rhino.
- Use CageEdit to apply custom global transformations to complex objects.
- Use Check to analyze mesh before printing.
123D Catch: A free app from Autodesk to create 3D scans using a camera.
Rhino Tools: A collection of resources related to reverse engineering in Rhino.
Rhino Reverse: A plugin for Rhino designed to aid Mesh to NURBS translation and handle high polygon count meshes.