Not sure if the question is already answered. I am working with tethedral mesh (medit mesh) file with CGAL. I need to find out the faces around the vertices in this mesh. So it will be a vertex-face iterator. Does anyone know if CGAL has this kind of iterator?
You can use the function finite_incident_cells and test whether the cells are in the complex using is_in_complex.
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I've been successfully testing CGAL Efficient RANSAC using this provided example to detect planes in a point cloud. The only piece missing from the CGAL Efficient RANSAC examples is a way to write the detected planes into a mesh (something like what polyfit offers at the end of this example)
I've noted that I can use the planes() method from Efficient_RANSAC to get an iterator of Plane but I'm a bit lost after that. Do I need to read all points from each plane and try and manually create a mesh from it ?
Thanks in advance for any help
I'm trying to use Polygonal Surface Reconstruction with building point cloud to create simplified building models.
I did first tests with this CGAL code example and got first promising results.
As an example, I used this point cloud with vertex normals correctly oriented and got the following result from PSR. Some faces are clearly inverted (dark faces with normals pointing inside the watertight mesh and therefore not visible).
I was wondering if there a way to fix this face orientation error. I've noticed orientation methods on Polygon mesh but I don't really know to apply them to the resulting PSR surface mesh. As far as logic is concerned making normal point outwards should not be too complicated I guess.
Thanks in advance for any help
You can use the function reverse_face_orientations in the Polygon mesh processing package.
Note that this package has several functions that can help you to correct/modify your mesh.
Is there a way to make a z-stack of 2-D images, at the isometric view in 3-D, of points in each 2-D image projecting downwards to the next slice of 2-D images? I am certain there is a technical term for this, but I just don't have the vocabulary to find the most pertinent answer. Would someone be able to point me in the right direction?
Below, I've drawn an "idea" of what this looks like. I'd love to know if this is possible without re-inventing wheels for matplotlib or other Python plotting libraries.
The original question was posed for doing so in Python. After many months of searching, I found a way to do so in TikZ. I cannot consider this my original work, it is largely based on Pascal Seppecher's interaction diagram found here.
To reconstitute my question above, one can use the above template to define:
Agents of different shapes, specify fills
The frame (plane)
which they reside in
Flows of directed edges that communicate
how agents interact with each other in each plane
Inter-plane
interaction flows
https://texample.net/tikz/examples/interaction-diagram/
I am trying to extract rotation matrix and translation matrix from essential matrix.
I took these answers as reference:
Correct way to extract Translation from Essential Matrix through SVD
Extract Translation and Rotation from Fundamental Matrix
Now I've done the above steps applying SVD to essential matrix, but here comes the problem. According to my understanding about this subject, both R and T has two answers, which leads to 4 possible solutions of [R|T]. However only one of the solutions would fit in the physical situation.
My question is how can I determine which one of the 4 solutions is the correct one?
I am just a beginner on studying camera position. So if possible, please make the answer be as clear (but simple) as possible. Any suggestion would be appreciated, thanks.
The simplest is testing a point 3D position using the possible solution, that is, a reconstructed point will be in front of both cameras in only one of the possible 4 solutions.
So assuming one camera matrix is P = [I|0], you have 4 options for the other camera, but only one of the pairs will place such point in front them.
More details in Hartley and Zisserman's multiple view geometry (page 259)
If you can use Opencv (version 3.0+), you count with a function called "recoverPose", this function will do that job for you.
Ref: OpenCV documentation, http://docs.opencv.org/trunk/modules/calib3d/doc/calib3d.html
I am looking for an algorithm that receives a 3d surface mesh (i.e comprised of 3d triangles that are a discretization of some manifold) and generates tetrahedra inside the mesh's volume.
i.e, I want the 3d equivalent to this 2d problem: given a closed curve, triangulate it's interior.
I am sorry if this is unclear, it's the best way I could think of explaining it.
For the 2d case there's Triangle. For a 3d case I could find none.
pygalmesh (a project of mine based on CGAL) can do just that.
pygalmesh-volume-from-surface elephant.vtu out.vtk --cell-size 1.0 --odt
https://github.com/nschloe/pygalmesh/#volume-meshes-from-surface-meshes
I found GRUMMP which seems to answer all the needs mentioned in the question, and more...
I haven't had any experience using GRUMMP, but as far as a 3D version of triangle there is tetgen. If you know the triangle switches it is built to resemble it. It also has fairly decent documentation and a python wrapper for it and triangle.
http://wias-berlin.de/software/tetgen/
http://mathema.tician.de/software/meshpy/