I've been having a bit of a problem with making the Y axis my up axis when exporting mesh and scenes from Blender. Both Blender and my export target use right handed transformation matrices. Z is the up axis in Blender while Y is the up axis in my target. The problem exists in 2 places though. The scene's transformations can't just be shifted on the X axis to fix this, because I also need to do the Y/Z switch for the vertices in the mesh (export as vertex.x, vertex.z, vertex.y). I need to have the actual Y and Z rotations switched, so that if the Y and Z rotations are the same, no change will occur (ie. identity). Thanks for your help in advance. Feel free to ask questions if I was not thorough enough.
Blender does two things different than the rest of the known world!
1. It uses Z axis for vertical (should be Y); Y axis for horizontal (should b X); and X axis for in and out (should b Z).
Very weird! Every high school graph since the beginning of time uses X for horizontal and Y for vertical.
It uses the right mouse button for selections.
U can change the selection btn in Preferences, but not the crazy axis arrangement!
no,
you do this
y=z
z=-y
no rotation of 90 degrees can make you go from left to right hand.
I ran into a similar issue when working with cinema4d and blender. In cinema4d Y is the up axis and rotations are heading,pitch and bank.
Blender's system looks like a right handed system, but rotated by 90 degrees on x axis.
I did the same thing for coordinates(exported as vertex.x,vertex.z,vertex.y). For rotations,
I think you should add 90 degrees(math.pi * 0.5) for rotations on X axis and the rest should be fine.
HTH
Have you tried just using Select All (the 'a' key) and then r x 90 to rotate everything 90 degrees around the X axis and the pivot point? (your pivot point is choosable in the menu bar of the 3D view if you need to control that).
You could do that, export, and then undo.
Just Download Wings3D. Export from Blender as .3ds and then Import this file in Wings3D.
Now you can just export it from Wings3D, again to .3ds. But instead of clicking directly on .3ds, click on the small icon in the right of the ".3ds" menu. now you can unchecked the Box Swap y und z axis and import the .3ds in another program.
There is no way that would be possible. Coordinate system was innately selected as hard coded from the blender source and there are no explicit option has been made in blender to switch it. It would also affected many of the hard coded functionality of any function blender was used or has been made by assume that coordinate
However, in theory, it would be possible to access blender source code and rebuild the blender to have it use another coordinate we would like. Albeit we need to carefully swap everything related to coordinate system
I too wish that left handed coordinate system (as of Unity3D) would be industrial standard and blender should at least have another version that work in left handed coordinate. People should just graduated from table coordinate to screen coordinate already
In blender, you could add empty plain axes, that will correct your orientation when exporting to unity, or try exporting as fbx file and change orientation in export options
Related
I am plotting meteor observation data from a sky camera, sometimes using right ascension and declination for my x and y axes, at other times azimuth and elevation. The problem I have in both cases is with the x axis when my observations span the 360 degree mark. Sometimes I get a batch of observations on the left of my plot (near zero degrees, and a batch on the right hand side (near 360 degrees), with a big expanse of nothing in the middle. Is there any easy way I can change the x axis so that the 360/0 degree wrap over is in the centre of the plot? I would still want to show the true azimuth (or right ascension) in the axis labels.
PS. Pointing the camera elsewhere is not an option ]1
PPS So in the image shown the plots on the left hand side should be to the right of those on the right hand side with x axis from 250 (via 360/0) to 100.
PPPS So the second image shows what I am after - but I got to that by doctoring the data - as is obvious from the scale of the x axis in this plot
I am building an augmented reality application and I have the yaw, pitch, and roll for the camera. I want to start placing objects in the 3D environment. I want to make it so that when the user clicks, a 3D point pops up right where the camera is pointed (center of the 2D screen) and when the user moves, the point moves accordingly in 3D space. The camera does not change position, only orientation. Is there a proper way to recover the 3D location of this point? We can assume that all points are equidistant from the camera location.
I am able to accomplish this independently for two axes (OpenGL default orientation). This works for changes in the vertical axis:
x = -sin(pitch)
y = cos(pitch)
z = 0
This also works for changes in the horizontal axis:
x = 0
y = -sin(yaw)
z = cos(yaw)
I was thinking that I should just make combine into:
x = -sin(pitch)
y = sin(yaw) * cos(pitch)
z = cos(yaw)
and that seems to be close, but not exactly correct. Any suggestions would be greatly appreciated!
It sounds like you just want to convert from a rotation vector (pitch,yaw,roll) to a rotation matrix. The conversion can bee seen on the Wikipedia article on rotation matrices. The idea is that once you have constructed your matrix, to transform any point simply.
final_pos = rot_mat*initial_pose
where final and initial pose are 3x1 vectors and rot_mat is a 3x3 matrix.
does anyone know the method or code to add a second x axis to a TGraph in CERN's ROOT program? Ive been searching the root website and its documentation almost always confuses me. What i need is just one plot of data, but a second X axis on top whose values are a function of the bottom x axis' values. Its basically so lazy people dont have to convert from the numbers of the bottom x axis to the top x axis.
For a simple example (if i wasnt clear)
Say you have a sine curve which is some function of theta. On the top x axis we could have degrees whereas on the bottom we could have radians with 360deg corresponding to 2pi rad...
Any help would be appreciated!
TGaxis is the class you are looking for to draw extra axes wherever you desire. Grabbing the world coordinate for your pad you can then superimpose like so. Replace low and high with the appropriate limits.
// your graph code here...
TGraph->Draw("AP");
TGaxis *axis = new TGaxis(gPad->GetUxmin(),gPad->GetUymax(),gPad->GetUxmax(),gPad->GetUymax(),low,high,510,"+L");
axis->Draw();
Check out TGaxis documentation for more examples.
(A previous answer I had was deleted as it was just a link to the site listed as a reference below. I hope this is more in line with the community guidelines.)
I think this might do what you want.
void axis2() {
TH1F *h = new TH1F("h","test",30,-3,3);
h->FillRandom("gaus",10000);
h->Draw();
TText t;
t.SetTextSize(0.02);
t.SetTextAlign(22);
Double_t yt = - h->GetMaximum()/15.;
for (Int_t i=1;i<=30;i++) t.DrawText(h->GetBinCenter(i),yt,Form("%d",i%10));
}
It doesn't create another taxis but shows you how to draw text at the same location of the axis. The answer comes from Rene Brun himself (one of the main authors of root) so I don't think you can have two x axes.
Source:
http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=7110
Here is an example showing how to proceed.
https://root.cern/doc/master/twoscales_8C.html
I am trying to plot a matrix in Gnuplot as I would using imshow in Matplotlib. That means I just want to plot the actual matrix values, not the interpolation between values. I have been able to do this by trying
splot "file.dat" u 1:2:3 ps 5 pt 5 palette
This way we are telling the program to use columns 1,2 and 3 in the file, use squares of size 5 and space the points with very narrow gaps. However the points in my dataset are not evenly spaced and hence I get discontinuities.
Anyone a method of plotting matrix values in gnuplot regardless of not evenly spaced in Xa and y axes?
Gnuplot doesn't need to have evenly space X and Y axes. ( see another one of my answers: https://stackoverflow.com/a/10690041/748858 ). I frequently deal with grids that look like x[i] = f_x(i) and y[j] = f_y(j). This is quite trivial to plot, the datafile just looks like:
#datafile.dat
x1 y1 z11
x1 y2 z12
...
x1 yN z1N
#<--- blank line (leave these comments out of your datafile ;)
x2 y1 z21
x2 y2 z22
...
x2 yN z2N
#<--- blank line
...
...
#<--- blank line
xN y1 zN1
...
xN yN zNN
(note the blank lines)
A datafile like that can be plotted as:
set view map
splot "datafile.dat" u 1:2:3 w pm3d
the option set pm3d corners2color can be used to fine tune which corner you want to color the rectangle created.
Also note that you could make essentially the same plot doing this:
set view map
plot "datafile.dat" u 1:2:3 w image
Although I don't use this one myself, so it might fail with a non-equally spaced rectangular grid (you'll need to try it).
Response to your comment
Yes, pm3d does generate (M-1)x(N-1) quadrilaterals as you've alluded to in your comment -- It takes the 4 corners and (by default) averages their value to assign a color. You seem to dislike this -- although (in most cases) I doubt you'd be able to tell a difference in the plot for reasonably large M and N (larger than 20). So, before we go on, you may want to ask yourself if it is really necessary to plot EVERY POINT.
That being said, with a little work, gnuplot can still do what you want. The solution is to specify that a particular corner is to be used to assign the color to the entire quadrilateral.
#specify that the first corner should be used for coloring the quadrilateral
set pm3d corners2color c1 #could also be c2,c3, or c4.
Then simply append the last row and last column of your matrix to plot it twice (making up an extra gridpoint to accommodate the larger dataset. You're not quite there yet, you still need to shift your grid values by half a cell so that your quadrilaterals are centered on the point in question -- which way you shift the cells depends on your choice of corner (c1,c2,c3,c4) -- You'll need to play around with it to figure out which one you want.
Note that the problem here isn't gnuplot. It's that there isn't enough information in the datafile to construct an MxN surface given MxN triples. At each point, you need to know it's position (x,y) it's value (z) and also the size of the quadrilateral to be draw there -- which is more information than you've packed into the file. Of course, you can guess the size in the interior points (just meet halfway), but there's no guessing on the exterior points. but why not just use the size of the next interior point?. That's a good question, and it would (typically) work well for rectangular grids, but that is only a special case (although a common one) -- which would (likely) fail miserably for many other grids. The point is that gnuplot decided that averaging the corners is typically "close enough", but then gives you the option to change it.
See the explanation for the input data here. You may have to change your data file's format accordingly.
I was asking myself if there are examples online which covers how you can for instance detect shapes in touch gestures.
for example a rectangle or a circle (or more complex a heart .. )
or determine the speed of swiping (over time ( like i'm swiping my iphone against 50mph ))
For very simple gestures (horizontal vs. vertical swipe), calculate the difference in x and y between two touches.
dy = abs(y2 - y1)
dx = abs(x2 - x1)
f = dy/dx
An f close to zero is a horizontal swipe. An f close to 1 is a diagonal swipe. And a very large f is a vertical swipe (keep in mind that dx could be zero, so the above won't yield valid results for all x and y).
If you're interested in speed, pythagoras can help. The length of the distance travelled between two touches is:
l = sqrt(dx*dx + dy*dy)
If the touches happened at times t1 and t2, the speed is:
tdiff = abs(t2 - t1)
s = l/tdiff
It's up to you to determine which value of s you interpret as fast or slow.
You can extend this approach for more complex figures, e.g. your square shape could be a horizontal/vertical/horizontal/vertical swipe with start/end points where the previous swipe stopped.
For more complex figures, it's probably better to work with an idealized shape. One could consider a polygon shape as the ideal, and check if a range of touches
don't have too high a distance to their closest point on the pologyon's outline, and
all touches follow the same direction along the polygon's outline.
You can refine things further from there.
There does exist other methods for detecting non-simple touches on a touchscreen. Check out the $1 unistroke gesture recognizer at the University of Washington. http://depts.washington.edu/aimgroup/proj/dollar/
It basically works like this:
Resample the recorded path into a fixed number of points that are evenly spaced along the path
Rotating the path so that the first point is directly to the right of the path’s center of mass
Scaling the path (non-uniformly) to a fixed height and width
For each reference path, calculating the average distance for the corresponding points in the input path. The path with the lowest average point distance is the match.
What’s great is that the output of steps 1-3 is a reference path that can be added to the array of known gestures. This makes it extremely easy to give your application gesture support and create your own set of custom gestures, as you see fit.
This has been ported to iOS by Adam Preble, repo on github:
http://github.com/preble/GLGestureRecognizer