Posted: Wed Dec 05, 2007 11:20 pm Post subject:
Building a 3D scanner - real world objects into meshes
If I was to put a decent amount of time into writing an article, with plans, schematics and software, for producing your own cheap 3D scanner, would anyone be interested in building it for themselves?
The objective is being able to scan a real object (such as an apple, model car or a toy soldier) and produce it in 3DS (or similar) format on a computer. QUICK_EDIT
A homebrew make - a cheap alternative to people forking out 2 grand (but obviously won't be as good as the commercial make), and those that like hobby electronics. QUICK_EDIT
In the end, time and money spent building your own will be well over $2500.
I wasn't thinking of building one as good as the commercial scanners.
The princible is quite easy to understand, and shouldn't take too much work.
1.) Get a directed beam of light (say a Red LED or laser)
2.) Direct it at the object being scanned, but make sure it is parallel to the floor and has no slope in height.
3.) Have a camera directed at the object at a different angle to the incoming beam (but it can see where the beam hits the object).
4.) When the directed light hits the object (assuming a diffuse surface), the camera will see where it hits (a 'red' dot in the image). Write a function to find where the red dot in the image is (camera connected to the computer) and return the Top and Left coordinates where it was found in the image.
5.) We know the Y (height) and Z (depth) coordinates of the surface point from the light beam, but we need to find the X (width) coordinate. With the camera calibrated, you can create an unproject transform which turns the Top and Left coordinates in the image where the red dot was found, into the X (width) coordinate in 3D space, and whala, you have a reference point for the object's surface. (Similair to how cnc 3 turns your 2D mouse screen coordinates into 3D coordinates when you click on a building or unit).
6.) Reposition the light beam and / or object and get another point
Using inexpensive and readily available materials–a calibrated pair of cameras and a laser line projector–a 3D laser range scanner which requires no tracking is implemented in this paper. We introduce a planarity constraint for reconstruction, based on the fact that all points observed on a laser line in an image are on the same plane of laser light in 3D. This plane of laser light linearly parametrizes the homography between a pair of images of the same laser line, and this homography can be recovered from point correspondences derived from epipolar geometry. Points visible from multiple views can be reconstructed via triangulation and projected onto this plane, while points visible in only one view can be recovered via ray-plane intersection. The use of the planarity constraint during reconstruction increases the system’s accuracy, and using the planes for reconstruction increases the number of points recovered. Additionally, an interactive scanning environment is constructed, where incremental reconstruction is used to provide continuous visual feedback. Reconstructions with this method are shown to have higher accuracy than standard triangulation.
That may sound complicate, but it may give you some interesting ideas. QUICK_EDIT
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Building a 3D scanner - real world objects into meshes
