Shadow3D ver.2 - accurate 3D scanning with gadgets you already have

prusaprinters

Simple but precise 3D scanner which uses the shape of shadow. You will get precise 3D model with gadgets you may already have. You need only a digital camera, LED flashlight, tripod and straight stick. Contrary to photogrammetry, it can measure smooth surface without texture. It has higher resolution than depth sensor on iPhone. It uses a reference object to calibrate the system. You will get metric 3D reconstruction results (undistorted 3D models with correct scale). 3D reconstruction process is done in web browser (Google chrome is recommended). Versatile flashlight holder is provided. After recording videos, 3D reconstruction can be done at in English : https://shiura.com/html5/3d2.html in Japanese : https://shiura.com/html5/3d2j.html Video Description Taking a movie of the object Use a camera with manual exposure and focus. If the camera automatically adjusts focus or exposure, the shadow detection will fail. Place the flashlight at the right side of the camera. The software assumes that the shadow is cast from right to left. Use a flashlight with single but bright LED. The size of the light emitting area matters to cast sharp shadow onto the object. Cover the entire field of view with a white and flat background. The Shadow on the background is a reference of the shadow position, so the distortion of the background affects to the shape of the object. Do not cover the top and bottom edge of the field of view by the object. The position of the shadow is measured at the top and bottom edges. Therefore, if some object touches the edges, the shape measurement result will be damaged. I rotated the camera 90deg CCW to place the object on the floor (in this case, right and left long edges should be clear). Please take a look at the imave above, or video. To acquire sufficiently dense point cloud, take a movie for one minutes. Long measurement time will improve the quality of the measured shape by averaging effect. If you want to recover the shape in high resolution, long measurement is necessary or the shape will have many holes. Software Your data is processed in your computer. Nothing is uploaded to the server, and your privacy is completely kept. You can download the program to your computer for offline use. For that case, Please download "opencv.js", "math.js" and "math.js.map". If you want to measure larger object, scale the reference object. The default value in the software coincides to the size of the reference object provided as a STL file. You can change the values, but it is easier to scale the measured 3D shape afterwards. Google chrome browser is recommended. Automatic calibration needs dense shape reconstruction result of the reference object. All 5 sides of the reference object should be clearly measured. Calibration data (3D homography matrix) can be downloaded for future use. Flashlight holder The flashlight holder is versatile. It assumes that the diameter of the cylinder to be clamped is 30mm, so scale them to fit to your flashlight and tripod. (For example, I scaled one set to 90% to fit to my flashlight with 27mm diameter. Another part is 83% for 25mm diameter pipe of the tripod.) To connect two holders to attach the flashlight to the tripod, use a tapping screw with 3mm diameter. Print the parts with the posture as supplied STL files for smooth operation. Theory Shadow-based 3D measurement has a long history in computer vision society. The most similar method was presented in ICCV98, 3D Photography on your desk Jean-Yves Bouguet and Pietro Perona http://www.vision.caltech.edu/bouguetj/ICCV98/ which uses the disparity of the shadow between the background and the object. However, at that time, "projective reconstruction" theory is not so popular and they assumed that all equipments should be calibrated in prior. Contrary, in my system, I used 3D homography which transforms distorted shape from uncalibrated system to the right shape. Category: Gadgets