# Depth camera 3d reconstruction

This is a 3 part series, here are the links for Part 2 and Part 3. It has come to my attention that most 3D reconstruction tutorials out there are a bit lacking. Worse yet they use specialized datasets like Tsukuba and this is a bit of a problem when it comes to using the algorithms for anything outside those datasets because of parameter tuning.

This tutorial is a humble attempt to help you recreate your own world using the power of OpenCV. From Perceptron to Deep Neural Nets. Neural networks for solving differential equations.

Turn your Raspberry Pi into homemade Google Home. To avoid writing a very long article, this tutorial is divided in 3 parts. Part 1 theory and requirements : covers a very very brief overview of the steps required for stereo 3D reconstruction. You are here. Part 2 Camera calibration : Covers the basics on calibrating your own camera with code. Part 3 Disparity map and point cloud : Covers the basics on reconstructing pictures taken with the camera previously calibrated with code.

There are many ways to reconstruct the world around but it all reduces down to getting an actual depth map. A depth map is a picture where every pixel has depth information instead of color information. It is normally represented like a grayscale picture. As mentioned before there are different ways to obtain a depth map and these depend on the sensor being used.

A type of sensor could be a simple camera from now on called RGB camera in this text but it is possible to use others like LiDAR or infrared or a combination. The type of sensor will determine the accuracy of the depth map. Depth maps can also be colorized to better visualize depth. Depending on the kind of sensor used, theres more or less steps required to actually get the depth map.

The Kinect camera for example uses infrared sensors combined with RGB cameras and as such you get a depth map right away because it is the information processed by the infrared sensor. In this case you need to do stereo reconstruction. Stereo reconstruction uses the same principle your brain and eyes use to actually understand depth. The gist of it consists in looking at the same picture from two different angles, look for the same thing in both pictures and infer depth from the difference in position.

This is called stereo matching. In order to do stereo matching it is important to have both pictures have the exact same characteristics. This is a problem because the lens in most cameras causes distortion. This means that in order to accurately do stereo matching one needs to know the optical centers and focal length of the camera.

In most cases this information will be unknown especially for your phone camera and this is why stereo 3D reconstruction requires the following steps:. Step 1 only needs to be executed once unless you change cameras. Steps 2—5 are required every time you take a new pair of pictures…and that is pretty much it.

The actual mathematical theory the why is much more complicated but it will be easier to tackle after this tutorial since you will have a working example that you can experiment with by the end of it. In the next part we will explore how to actually calibrate a phone camera, and some best practices for calibration, see you then. Sign in. Part I. Omar Padierna Follow. Trending AI Articles: 1.In fact, this TOF camera, initially adopted by XBox Kinect machine, can be used to develop a real time depth scanner to reconstruct models real time!

Since I had a difficult time understanding the mathematics of the original paper KinectFusion link at the end that proposed such method, I wanted to share an overview on the entire pipeline and method of this 3D reconstruction algorithm. Note: No code snippets are presented in this article. The implementation of the mathematics for the entire KinectFusion may be long and daunting, so I believe introducing the mathematical concepts and insights on the data structures would be much better for understanding.

Actual code on Github is provided at the end. Its ultimate goal is to create 3D models based on multiple images, where these images could be RGB or depth-based. KinectFusion is one of the older traditional methods developed in that attempts to use depth images — images where the the value of depth is given instead of the RGB values for every pixel — as the only inputs to generate an entire 3D model.

This is going to be the my attempt of explaining the methods of KinectFusion in the most straightforward and simplified way possible. Nonetheless, a little background in matrix algebra such as matrix addition and multiplication will come in handy for faster and better understanding. Here are the two essential linear algebra concepts required:. Matrix Transformation.

### 3D Scene Reconstruction from Depth Camera Data

Imagine a 2D plane with x- axis and y- axis, a point can be represented in a Cartesian form x, y. We can therefore use matrix computation to represent a translation. Similarly, a rotation can also be represented through matrices can also be presented through a rotation matrix. By combining the rotation matrix with the translation matrix, we will be able to deduct a matrix equation that transforms any point to its new coordinate after the transformation. One thing to note is that this equation performs the rotation first and then the translation.

The same idea can be applied to the three dimensional space; the matrices will be more complex but the concept is quite similar. Matrix Projection. A projection of a real-world object onto the camera image can be viewed in the following way:. The pixel on the image plane with coordinate u, v corresponds to the point x, y, z on the 3D object, and can be found through a projection like this using the concept of similar shapes:. Therefore, we can also represent such computation in terms of matrix, which is the widely known as the camera intrinsic matrix K :.

The projected pixel coordinate u, v can then be calculated by:. With these two concepts in mind we can dive into the 4 procedures of real time 3D reconstruction. Assuming we have acquired the depth map of the object in front.

**Color Map Optimization for 3D Reconstruction with Consumer Depth Cameras**

The first thing is to compute a vertex map and a normal map by converting every pixel in the depth map back to its corresponding point in the 3 dimensional world.

This can be done through the inverse property of multiplication in matrices applied to every pixel point:. The normal vector of a point can then be retrieved by computing the cross product of two neighboring vertices, since cross product gives us a vector that is orthogonal to both vertices.Three-dimensional geometrical models with incorporated surface temperature data provide important information for various applications such as medical imaging, energy auditing, and intelligent robots.

In this paper we present a robust method for mobile and real-time 3D thermographic reconstruction through depth and thermal sensor fusion. A multimodal imaging device consisting of a thermal camera and a RGB-D sensor is calibrated geometrically and used for data capturing. Based on the underlying principle that temperature information remains robust against illumination and viewpoint changes, we present a Thermal-guided Iterative Closest Point T-ICP methodology to facilitate reliable 3D thermal scanning applications.

The pose of sensing device is initially estimated using correspondences found through maximizing the thermal consistency between consecutive infrared images. The coarse pose estimate is further refined by finding the motion parameters that minimize a combined geometric and thermographic loss function.

Experimental results demonstrate that complimentary information captured by multimodal sensors can be utilized to improve performance of 3D thermographic reconstruction. Through effective fusion of thermal and depth data, the proposed approach generates more accurate 3D thermal models using significantly less scanning data.This tutorial shows how to use the mental ray Depth-of-Field render effect to increase the realism of your renderings.

Depth of field is a technique used to focus on a fixed point in a scene, called a focal plane. The area of the focal plane remains in focus, while objects closer than the focal plane, and farther from it, are blurred.

This is how real-world cameras work, and using Depth of Field can make it appear as if the rendering were a photograph. Skill level: Intermediate. Time to complete: 45 minutes. Set up the lesson:.

## 3D reconstruction from multiple images

Measure distances:. You will use the Tape helper to determine the distance between the camera and three objects in the scene: a chair, a flower pot, and a corner of the building. The location of each object will become a focal plane, or region where the scene is in the sharpest focus.

On the Parameters rollout, the Length field displays the distance between the two objects as roughly 2. The Length field displays a length of about 20 meters. The Length field displays a length of about 28 meters. Now that you know the distances, you will use the chair in the foreground as the focal plane for the first rendering. Adjust the f-stop and focus plane:.

The depth-of-field render effect works only in Perspective viewports, so now you need to change the viewport view. The lower the aperture, or f-stop setting, the larger the aperture and the more blurred the out-of-focus regions become.

The focal plane, which is set to the chair in the foreground, is in the sharpest focus, while the background becomes progressively more blurred.

Use the other two focal planes to create renderings:. The area in sharpest focus is now the flower pot and the plant in it. All objects in the foreground and, to a lesser extent, the background are blurred. All objects in the foreground are blurred, while the house is mainly in focus. One last adjustment remains. You will now adjust the f-Stop to make the foreground less out of focus.

### Can I Perform 3D Scanning with the Intel® RealSense™ Depth Camera D400 Series?

Use the f-stop setting to control the depth-of-field effect:. The foreground is much more defined than in the previous rendering. Above: f2. Below: f5. Save your work:. The Depth-of-Field camera effect is an easy way to make it appear as if your rendering was taken by a real-world camera. See Where to Find Tutorial Files. Note: You can also sharpen the foreground image by dragging the Image Precision Antialiasing slider in the Rendered Frame Window to the right, but this option greatly increases render time.

Summary The Depth-of-Field camera effect is an easy way to make it appear as if your rendering was taken by a real-world camera. Parent topic: Rendering Tutorials.Specifically, as a new user, I struggle with placing nodes together.

I would be happy to start here if there is any documentation I can distill down. If you can point me to documentation I can do some work here.

A list of papers and datasets about point cloud analysis processing. Update the documentation on how to use the library as 3rd party, only modern cmake approach is supported ie using imported targets. Please Make the changes mentioned above so that it becomes clear that the path where vcglib is downloaded maybe anywhere on the system.

The result looks like this, and I can't tell if this is what it should look like:. Could you please add it there for the sake of completeness. Algorithm to texture 3D reconstructions from multi-view stereo images. LiveScan3D is a system designed for real time 3D reconstruction using multiple Kinect v2 depth sensors simultaneously at real time speed.

Lotayou a. Here's the result:. The network's structure contains max pooling immediately followed by upsampling. Maybe I'm missing something but it doesn't seem to make any sense. And just removing it should improved results. Implementation of Newcombe et al. Add a description, image, and links to the 3d-reconstruction topic page so that developers can more easily learn about it. Curate this topic.

To associate your repository with the 3d-reconstruction topic, visit your repo's landing page and select "manage topics. Learn more. Skip to content. Here are public repositories matching this topic Language: All Filter by language. Sort options. Star 5k. Code Issues Pull requests. A resource repository for 3D machine learning.Playing with stereo 3D reconstruction using one camera and rotating the object, but I can't seem to get proper Z mapping.

Take left and right images by rotating the object: fixed camera, the object rotates on itself on the Y axis the background is green screen I remove. I get the disparity map with StereoBM. I use a Rotation matrix which I built using Rodrigues on a rotation vector. My rotation is only along the Y axis, so the rotation vector is [0, angle, 0] angle being the angle by which the object was rotated. The Rotation matrix seems right as far as I can tell: I tried with trivial angles and I get what is expected.

I also need the translation vector, so I used [cos angle0, sin angle ] since I rotate only along Y, I then have a unit-less translation of the camera by the arc of the rotation. From my reading Rotation and Translation matrices are unit-less. I use stereoRectify with the same camera matrix and distortion for both cameras since it is the same camera.

## Depth and thermal sensor fusion to enhance 3D thermographic reconstruction.

When i reprojectImageTo3D with Q and the disparity mapI get a result that looks OK in Meshlab when looking at the right angle, but the depth seems way off when I move around i. If I need to account somewhere for the distance from the camera to the center of rotation of the object: as I mentioned I tried to apply that factor to the translation vector but it only seems to scale the whole thing.

I wonder also if it may be a problem with the application of the colors: I use one of the 2 images to get the colors, because I wasn't sure how I could use both. I am not sure how the disparity map maps to the original images: does it map to Left or Right or neither? I could see that if color assignment to the disparity map is wrong, the I don't understand " Take left and right images by rotating the object"? Well, it's all relative, right? The camera rotate around the object or the object rotates in front of the camera.

I use a green screen to remove background, so effectively I rotate the object on itself, but in fact it is as if the camera moved around the object, by the same angle, at a given distance from the object.

I have only used 2 images right now. I understand that if I wanted to move around the object degrees I would need to move each frame by the exact same angle, but would be the same if I was to move the camera. But with 2 images, I only need to know one angle. My question really is: is 2 frame enough to get reasonable Z, or am I supposed to go around? If I have to take multiple frames, how am I supposed to match the Z from one reprojection to another? Are you sure your translation vector between the camera at frame 1 and the camera at frame 2 is OK?

From what I have been reading, the rotation and translation matrices are unit-less. Correct me if I am wrong. So the distance to the object is constant, yes, and unit 1. I did try adding a multiplication factor to account for the distance to the object, but all that seems to do is change the scale in x,y and z not change the z depth.In last session, we saw basic concepts like epipolar constraints and other related terms.

We also saw that if we have two images of same scene, we can get depth information from that in an intuitive way. Below is an image and some simple mathematical formulas which proves that intuition. Image Courtesy :. The above diagram contains equivalent triangles. Writing their equivalent equations will yield us following result:. So in short, above equation says that the depth of a point in a scene is inversely proportional to the difference in distance of corresponding image points and their camera centers.

So with this information, we can derive the depth of all pixels in an image.

So it finds corresponding matches between two images. We have already seen how epiline constraint make this operation faster and accurate. Once it finds matches, it finds the disparity. Below image contains the original image left and its disparity map right.

As you can see, result is contaminated with high degree of noise. By adjusting the values of numDisparities and blockSize, you can get better results. OpenCV-Python Tutorials latest. Note More details to be added.

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