I want to write a program to simulate 5-axis cnc gcode with vpython and I need to rotate trail of the object that's moving. Any idea how that can be done?
It's difficult to know exactly what you need, but if instead of using "make_trail=True" simply create a curve object to which you append points. A curve object named "c" can be rotated using the usual way to rotate an object: c.rotate(.....).
Related
I'm trying to create a 3D mask model from the 3D coordinate points that are stored in the txt file. I use the Marching cubes algorithm. It looks like it´s not able to link individual points, and therefore holes are created in the model.
Steps: (by https://lorensen.github.io/VTKExamples/site/Cxx/Modelling/MarchingCubes/)
First, load 3D points from file as vtkPolyData.
Then, use vtkVoxelModeller
Put voxelModeller output to MC algorithm and finally visualize
visualization
Any ideas?
Thanks
The example takes a spherical mesh (a.k.a. a set of triangles forming a sealed 3D shape), converts it to a voxel representation (a 3D image where the voxels outside the mesh are black and those inside are not) then converts it back to a mesh using Marching Cubes algorithm. In practice the input and output of the example are very similar meshes.
In your case, you load the points and try to create a voxel representation of them. The problem is that your set of points is not sufficient to define a volume, they are not a sealed mesh, just a list of points.
In order to replicate the example you should do the following:
1) building a 3D mesh from your points (you gave no information of what the points are/represent so I can't help you much with this task). In other words you need to tell how these points are connected between then to form a 3D shape (vtkPolyData). VTK can't guess how your points are connected, you have to tell it.
2) once you have a mesh, if you need a voxel representation (vtkImageData) of it you can use vtkVoxelModeller or vtkImplicitModeller. At this point you can use vtk filters that need a vtkImageData as input.
3) finally in order to convert voxels back to a mesh (vtkPolyData) you can use vtkMarchingCubes (or better vtkFlyingEdges3D that is a very similar algorithm but much faster).
Edit:
It is not clear what the shape you want should be, but you can try to use vtkImageOpenClose3D so the steps are:
First, load 3D points from file as vtkPolyData.
Then, use vtkVoxelModeller
Put voxelModeller output to vtkImageOpenClose3D algorithm, then vtkImageOpenClose3D algorithm output to MC (change to vtkFlyingEdges3D) algorithm and finally visualize
Example for vtkImageOpenClose3D:
https://www.vtk.org/Wiki/VTK/Examples/Cxx/Images/ImageOpenClose3D
I am working on a simple game in Python 3 and I need to draw a rectangle rotated by a given angle and around a specific centre of rotation.
Is there a simple way of doing this?
As long as you are using the pygame library, the pygame.transform.rotate(*Surface*,*angle*) function may be worth a try.
Without a code sample it is hard to understand the context you are trying to apply this in.
I want to add zoom capability to an app, which at its core is a spf graph app. Now I currently have no zoom, but the ability to select/move, multi-select objects on the graph in the graph window. I started to write my own code to do scaling of the objects and then work out mouse co-ordinates to map clicks and redraws correctly. I didnt complete this as I found the Gdiplus::SetPageScale function, which scales the window fine but I cannot see any GDI function I can use to map the mouse click co-ordinates from the world co-ord's to the page co-ords. I tried TransformPoints(Gdiplus::CoordinateSpaceWorld, ::Gdiplus::CoordinateSpacePage, points, 2) but this does not convert the points and the returned points are (0,0).
So is this even possible with Gdiplus or do I need to write this mapping myself? Any advice appreciated!
You don't want to use Graphics::SetPageScale() in this case. The much more general way is to use the Matrix class instead. Its Scale, Translate and Rotate methods are handy to get the matrix you need. You'll want to use the Scale() method here, possibly Translate() to change the origin.
Before you start drawing, activate the matrix with the Graphics::SetTransform() method. Anything you draw will now automatically be scaled according to the arguments you passed to the Matrix::Scale() method. Mapping a mouse position is now exceedingly simple with Matrix::TransformPoints() method, the exact same transform that was used while drawing is now applied to the mouse coordinates. Even going back from graph coordinates to mouse coordinates is simple, use the Matrix::Invert() method to obtain the inverse transform.
When GDI+ draws, it applies a world transform (which is controlled by Graphics::SetTransform, ScaleTransform, etc.) followed by the page transform (which is controlled by Graphics::SetPageScale and Graphics::SetPageUnit) to transform the points to device coordinates.
So it normally goes like this: World coordinates --[World transform]--> Page coordinates --[Page transform]--> Device coordinates
You can use Graphics::TransformPoints the way you wanted, to map mouse coordinates to world coordinates, but you have to specify Device coordinates as the source space and World coordinates as the destination space.
However, there are good reasons to do it as Hans describes with a Matrix you store separately, most notably that you shouldn't be holding on to your Graphics object for long enough to process mouse input (nor should there be a need to create one then).
I got my country lat/long boundaries from koordinates.com. Now I want to fill in the interior with dots.
Since the file I have is KML, I was thinking of converting the coordinates to cartesian using the NetTopologySuite.
I do not want a polygon overlay. I want to generate dots/coordinates for the polygons interior - ideally at a density of my choosing.
I have seen algorithms like this one, http://alienryderflex.com/polygon_fill/. Is there a library that will do this for me? Alternatively, can someone share code?
Ultimately, I will convert the dot coordinates back to lat/long and populate a globe like this one
http://code.google.com/p/webgl-globe/
I'm affraid GIS isn't my area of expertise, but I've got two ideas:
Generate a set of random points. You can use a Point-In-Polygon function to determine if you're points are in the right place.
You can use a rectangle grid of points and use a 'resolution' to determine how many points there will be and how close. You can offset the grid positions to make them look more random if you need to. You'll check if the point inside the bounding rectangle of your polygon is inside the polygon or not.
Notice that the webgl-globe example uses a grid of points(similar to point(2)) converted to spherical coordinates.
Both ideas is kind of similar, only the points distribution differs.
You can find a roughly related implementation I did using actionscript here,
but I would also suggest asking on the GIS site.
I have a java applet that allows users to import a jpeg and world file from the local system. The user can then "click" draw lines on the image that was imported. Each endpoint of each line contains a set of X/Y and Lat/Long values. The XY is standard java coordinate space, the applet uses an affine transform calculation with the world file to determine the lat/long for every point on the canvas.
I have a requirement that allows a user to type a distance into a text field and use the arrow key to draw a line in a certain direction (Up, Down, Left, Right) from a single selected point on the screen. I know how to determine the lat/long of a point given a source lat/long, distance, and bearing.
So a user types "100" in the text field and presses the Right arrow key a line should be drawn 100 feet to the right from the currently selected point.
My issue is I don't know how to convert the distance( which is in feet ) into the distance in pixels. This would then tell my where to plot the point.
tcarobruce,
You are correct. The inverse transform algorithm is what I needed. Since I use java I was able to replace my "home made" transform algorithm with the java.awt.AffineTransform object which has an inverse transform function.
This seems to have solved my issue.
Thanks.
I guess you are certain your users are always uploading a raster image that is in the lat/lon wgs84 projection? Because in that case you can set a fixed coordinate transformation.
If you consider ever digitizing images from other sources with other projections, you might want to take a look at the open source geotools library: http://www.geotools.org/