TECHNOLOGY

CONVERTING REALITY INTO
VIRTUAL REALITY WITH 3D SCANNERS
Most people are familiar with 2D scanners, and there would hardly be any computer used for graphics that is not connected to one, directly or indirectly. What happens when you have a 3D object you need to work on in a 3D graphics or CAD package? Until recently, you could make some sketches and measurements and hit the extrude button.

Well, not any more. London based 3D Scanners Ltd. have developed a solution to this problem, and they can sell you a 3D scanner, or offer their 3DSource bureau service, to help you get the results you want, without the fuss of a week or more of serious modeling.

3D Scanners design their own hardware (laser scanners) and software to integrate into proprietary modeling and animation systems. Different productions and animation packages place different requirements on a 3D model. You may have noticed that the 3D models available from digital libraries rarely match exactly the user, needs. One of the major difficulties 3D Scanners had to face in developing their code was to provide tools to enable the 3D model to be created to precisely fulfill the purpose for which it is required.

THE SCANNER
The scanner is portable and can be carried in two smallish cases which contained the laser scanner and the digitizing arm. The digitizing arm is a Faro Bronze which clamps to a sturdy table. In standard form it can do point touch scanning by physically touching the subject, though on soft or fragile surfaces this can be undesirable. The arm can record a 1m x 1m x 0.75m subject without repositioning. However, by using datum balls (white spheres) on the object it can continually leapfrog around to cover larger objects.

The laser scanner is the top of the line model with a multi-power laser for scanning black or shiny objects and a camera for making colour texture maps. The laser is capable of scanning at an accuracy of 50 microns but not all projects would require this level of detail. Besides the control box which all parts plug in to, there is a footswitch for operation and a special DSP processor card to insert in the host computer.

THE SCANNING PROCESS
The process is like painting with a 2 inch (50mm) wide paintbrush. The laser sensor is pointed at the object and the scanning starts. The sensor is held about 100mm from the object. It projects a 50mm long laser stripe onto the object. It can be angled in any way so that 100 percent of the surface of the object may be scanned. The scanned image appears on the computer monitor in real time. The image is shiny and looks just like wet paint. As the image is built up, any missed areas are obvious and can be rescanned (touched up) immediately.

The accuracy of the scanner was verified by scanning a sphere of precisely known diameter. In this case, the difference between the actual and measured sphere diameters was 50 microns - about a hair’s breadth. The scanned data is stored as a collection of points (point cloud) measured over the surface of the object. On this particular scan the points were about 0.2mm apart.

The digitizing process is fairly speedy. You can finish simple objects in a few minutes. A large, complex dinosaur model might take up to two hours so as to faithfully scan all the details such as teeth and wrinkles into the point cloud. For a typical model about 30 percent of the time is spent scanning and the remaining 70 percent lies in the meshing of the point cloud data to create the desired model. For this task, 3D Scanners has developed a powerful and comprehensive suite of software algorithms.

THE SOFTWARE
The first stage of the meshing process is invariably the fusion of the point cloud to automatically produce a polygonal mesh of 100,000 to 3 million polygons. That is a lot of polygons. But for some high-end film/broadcast applications, a half million polygon model is what is required. Reducing it to 10,000 polys can be accomplished automatically using the decimation (polygon reduction) tools.

If you want a 200 polygon model for a real-time game, then 3D Scanners’ remeshing software tools enable you to quickly draw a new mesh on top of the large mesh which acts as a template. Alternatively, if NURBS are required you can construct a number of polylines using sectioning and drawing tools. These polylines can be imported into your NURBS modeling package in which your NURBS are created.

A detailed description of the full ModelMaker hardware and software system is beyond the scope of this review but more information on the technical specs and pricing can be found at 3D Scanners website - www.3dscanners.com.

Major customers include: REM Infographica in Spain, who use them for scanning models for their 3D model libraries, Codemasters, the UK games developer, where they scanned 3D models of the cars in their hit Christmas game: ’TOCA Touring Car Championship’ and most recently for an in-house facility at Framestore in Soho. Laser scanners and, perhaps more importantly, their accompanying model making software have undergone a long gestation. Now they have fulfilled their promise and are being used to produce high quality models by the market-leaders in 3D modeling and animation. And even for smaller projects, the 3D Source bureau service can save significant time and money.

ACCOMPANYING SOFTWARE FOR
CONVERTING 3D MODELS INTO POLYGON MESHES
ReMesh is a software from the same company that enables modelers to alter a 3D polygonal mesh as they wish. Featuring the world’s most powerful set of tools for patch-based remeshing, ReMesh can convert a mesh from a 3D scanner, digitizer, library or the web.

The software is highly versatile. Using ReMesh, artists can hone low polygon models by drawing new polygons on top of the original mesh. Engineers have tools to construct a network of patches for reverse engineering to produce high quality polygonal surfaces. There are tools for processing and aligning raw scanned/digitized meshes. ReMesh even allows the automatic generation of multiple LODs with smoothly flowing polygon meshes.

“ReMesh fills a gap in the market,” explains 3D Scanners President, Stephen Crampton. “3D models usually need changing - perhaps the polygon count is wrong, several LODs are required or the closest library model is not quite close enough - yet no mainstream 3D modeling package has a toolset for remeshing.”

“This is now possible with ReMesh. You simply input the mesh you have, remesh it and output the mesh you want.” ReMesh’s development team has been working with users in computer games, film and TV, virtual reality, multimedia and industrial styling. The software is expected to boost the already accelerated use of laser scanning services worldwide.

“For over a decade SIGGRAPH attendees have been waiting for laser scanners to fulfill their promise”, says the company chairman Crampton. “Now with ReMesh, the 3D modeling solution is complete. You just send your sculpted object off to a local scanning bureau, then Remesh the resulting 500,000+ polygon model to produce exactly what you want. With ReMesh, random polygon meshes and long, thin triangles are things of the past. Every remeshed model looks like a library model.”