I'm working on camera calibration and pose estimation.Do you know any software for producing synthetic data? I want to put my camera and my calibration object in the scene and move the calibration object. I want the simulator to give me the positions of calibration object in world's coordinate system and camera's coordinate system and some info like this...
Do you know such a thing?
You can have a look at Blender: you specify the positions of camera and objects in the scene by means of 3D coordinates; then with the render command you get the image for the camera.
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Hi I am an undergraduate student working on a graduate project, and a beginner to computer vision.
After I went through the tutorial "Camera Calibration and 3D Reconstruction" provided by OpenCV (link) : https://docs.opencv.org/master/d9/db7...
I failed to see the connections between the second part to the final part. What I understand here is :
The intrinsic and extrinsic parameters of a camera is required to
estimate the position of the camera and the captured object
To reconstruct a 3D model multiple point clouds are needed, and to
generate a point cloud a disparity map is required.
What I do not understand is :
The importance of estimating the position of the camera or the object to compute the epiline or epipole in either image planes.
The importance of epipolar geometry, and finding out the location of epiline and epipole to compute the disparity map.
As far as I am aware, the code below generate a disparity map
stereo = cv2.createStereoBM(numDisparities=16, blockSize=15)
disparity = stereo.compute(imgL,imgR)
and the input includes a pair of stereo images, minDisparities, numDisparities and blockSize, but not the position of the camera nor the epiline/epipole.
Any help would be greatly appreciated.
I'm currently rendering a 3D model (Wavefront .obj format) in my Qt program. Right now, I'm rendering the model using Scene3D in QML, and I'm able to get it to display in the viewing area. What I would like to do is have a user click on the model and generate a 2D cross section of the slice that I would like to plot on a different window. I'm quite new to 3D rendering, and a lot of Qt documentation isn't very descriptive. I've been reading Qt documentation, experimenting, and searching online with no luck. How can I create 2D slices of a 3D object Model in Qt 3D, preferably in QML? What Qt libraries or classes can I use to achieve this?
Unfortunately, the fact that models are stored as a set of surfaces makes this hard. QT probably doesn't have a built in method for this.
Consider, for example, that a model made of faces might be missing a face. What now? can you interpolate across that gap consistently from different angles? What about the fact that a cross-section probably won't contain any vertices?
But, of course, it can be solved. First, just don't allow un-closed surfaces (meshes with holes). Second, for finding the vertices of your cross-section, perform an intersection between every edge in your model and the plane you're using, and if there's an intersection, there's a point there. Third, to find the edges, look at the list of vertices, and any two that are from an edge on the same polygon in the mesh should be connected by an edge in the cross section. To find which direction the edge should go, project the normal of the polygon onto the plane your using. For filling, I don't really know what to do. I guess that's whatever you want it to be.
I am working with disparity maps (1024 x 768) obtained via stereo and I am able to get point clouds with XYZRGB pcl::Points. However not all pixels from the disparity map are valid depth hence there will never be 1024x768 = 786432 XYZRGB points. Fortunately I am able to save the point clouds unorganized (i.e. height=1). Unfortunately, some normal estimation methods etc, are tailored for organized pointclouds. How can I create organised pointclouds from this ?
I believe that this is not possible.
First of all unorganized point cloud (PC) is just list of points in random order written in file
On the other hand organized PC carries information of in which order orginal points were obtained by depth camera and some other information. This information is stored in lets call it grid.
Once you destroy this grid omiting some points theres no algorithm that can put it back together as it originally was
You can use other methods which provides PCL that doesnt take OPC as an argument. Result will be same as if you would use organized point cloud only little bit slower (depends on size of your input cloud)
I assume that you do have the calibration parameters that are necessary to transform the image points and their depth into 3D points, right?
In this case, you simply create a 2D point cloud and do the following for each pixel of the disparity map:
If the point is valid:
set the corresponding point in the point cloud to the 3D point
else:
set the corresponding point in the cloud to NaN (i.e. a 3D point with NaN as coordinates)
My question is similar to 3D Scene Panning in perspective projection (OpenGL) except I don't know how to compute the direction in which to move the mesh.
I have a program in which various meshes can be selected. Once a mesh is selected I want it to translate when click-dragging the cursor. When the cursor moves up, I want the mesh to move up, and so on for the appropriate direction. In other words, I want the mesh to translate in directions along the plane that is perpendicular to the viewing direction.
I have the Vector2 for the Delta (x,y) in cursor postion, and I have the Vector3 viewDirection of the camera and the center of the mesh. How can I figure out which way to translate the mesh in 3d space with the Delta and viewDirection? Will I need other information in order to to this calculation (such as the up, or eye)?
It doesn't matter if if the scale of the translation is off, I'm just trying to figure out the direction right now.
EDIT: for some reason I had a confusion about getting the up direction. Clearly it can be calculated by applying the camera rotation to the specified perspective up vector.
You'll need an additional vector, upDirection, which is the unit vector pointing "up" from your camera. You can now cross-product viewDirection and upDirection to get rightDirection, the vector pointing "right" from your camera.
You want to map y deltas to motion along upDirection (or -upDirection) and x deltas to motion in rightDirection. These vectors are in world-space.
You may want to scale the translation speed to match the mouse speed. If you are using perspective projection you'll want to scale the translation speed with your model's depth with respect to your camera (The further the object is from your camera, the faster you will need to move it if you want it to match the mouse.)
Where would you use a vector projection in game development. I know that it projects one vector to another, but I don't know where would I use that.
Regards
Here are a few examples:
Vector projection is common in computer graphics, which many games depend on.
In 3D games, during the rendering process the renderer has access to the 3D coordinates of every vertex of every mesh in the game world. These vertices need to be mapped onto a 2D rectangle that's the same shape as your screen. A projection matrix coincidentally called the Projection Matrix does this.
Sometimes projection matrices are used make objects cast shadows onto the surfaces of other objects.
Or suppose you're making a homing missile with a 60-degree field of view. You could say that the missile sees the world through a circular screen, and it loses track of its target if its target goes off the screen. You could use a projection matrix to map the 3D position of the target onto the homing missile's screen, and then decide whether the missile can see the target.