enter image description here
I use Adobe Animate, I'm not a basic coder.
I am creating an animation to understand the effect of the moon on the tide.
I manage to run:
-The earth on itself indefinitely.
-The moon around the earth AND at the same time on itself (we only have the same side of the moon).
For example, I use these functions:
createjs.Ticker.addEventListener("tick", revolution_moon);
function revolution_moon(){
_this.moon_bon.rotation+=-0.009164222874;
}
Per frame the moon rotates by -0.009164222874°
I would like, on the same principle, to evolve an object which goes up and down according to the number of frames. (Rise during so many frames until y=? then go down during so many frames until y=?-1 ).
Anyone have an idea?
According to the link that I posted in the comments and assuming that the "waving" will be somehow synchronized with the rotation you can try something like this:
createjs.Ticker.addEventListener("tick", revolution_moon);
function revolution_moon(){
_this.moon_bon.rotation+=-0.009164222874;
_this.mov_obj.y = Math.sin(2 * Math.PI * _this.moon_bon.rotation / 360) * 204 + 204;
}
If you need more help, please add a minimal reproducible example of your code.
Related
I just cannot figure out how to make an a point with a given velocity move around in cartesian space in my visualization while staying around a sphere (planet).
The input:
Many points with:
A Vector3 position in XYZ (lat/lon coordinates transformed with spherical function below).
A Vector3 velocity (eg. 1.0 m/s eastward, 0.0 m/s elevation change, 2.0 m/s northward).
Note these are not degrees, just meters/second which are similar to my world space units.
Just adding the velocities to the point location will make the points fly of the sphere, which makes sense. Therefore the velocities need to be transformed so stay around the sphere.
Goal: The goal is to create some flowlines around a sphere, for example like this:
Example image of vectors around a globe
So, I have been trying variations on the basic idea of: Taking the normal to center of my sphere, get a perpendicular vector and multiply that again to get a tangent:
// Sphere is always at (0,0,0); but just to indicate for completeness:
float3 normal = objectposition - float3(0,0,0);
// Get perpendicular vector of our velocity.
float3 tangent = cross(normal,velocity);
// Calculate final vector by multiplying this with our original normal
float3 newVector = cross(normal, tangent);
// And then multiplying this with length (magnitude) of the velocity such that the speed is part of the velocity again.
float final_velocity = normalize(newVector) * length(velocity);
However, this only works for an area of the data, it looks like it only works on the half of the western hemisphere (say, USA). To get it (partially) working at the east-southern area (say, South-Africa) I had to switch U and V components.
The XYZ coordinates of the sphere are created using spherical coordinates:
x = radius * Math.Cos(lat) * Math.Cos(lon);
y = radius * Math.Sin(lat);
z = radius * Math.Cos(lat) * Math.Sin(lon);
Of course I have also tried all kinds of variations with multiplying different "Up/Right" vectors like float3(0,1,0) or float3(0,0,1), switching around U/V/W components, etc. to transform the velocity in something that works well. But after about 30 hours of making no progress, I hope that someone can help me with this and point me in the right direction. The problem is basically that only a part of the sphere is correct.
Considering that a part of the data visualizes just fine, I think it should be possible by cross and dot products. As performance is really important here I am trying to stay away from 'expensive' trigonometry operations - if possible.
I have tried switching the velocity components, and in all cases one area/hemisphere works fine, and others don't. For example, switching U and V around (ignoring W for a while) makes both Africa and the US work well. But starting halfway the US, things go wrong again.
To illustrate the issue a bit better, a couple of images. The large purple image has been generated using QGIS3, and shows how it should be:
Unfortunately I have a new SO account and cannot post images yet. Therefore a link, sorry.
Correct: Good result
Incorrect: Bad result
Really hope that someone can shed some light on this issue. Do I need a rotation matrix to rotate the velocity vector? Or multiplying with (a correct) normal/tangent is enough? It looks like that to me, except for these strange oddities and somehow I have the feeling I am overlooking something trivial.
However, math is really not my thing and deciphering formula's are quite a challenge for me. So please bear with me and try to keep the language relative simple (Vector function names are much easier for me than scientific math notation). That I got this far is already quite an achievement for myself.
I tried to be as clear as possible, but if things are unclear, I am happy to elaborate them more.
After quite some frustration I managed to get it done, and just posting the key information that was needed to solve this, after weeks of reading and trying things.
The most important thing is to convert the velocity using rotation matrix no. 6 from ECEF to ENU coordinates. I tried to copy the matrix from the site; but it does not really paste well. So, some code instead:
Matrix3x3:
-sinLon, cosLon, 0,
-cosLon * sinLat, -sinLon * sinLat, cosLat,
cosLon * cosLat, sinLon * cosLat, sinLat
Lon/Lat has to be acquired through a Cartesian to polar coordinate conversion function for the given location where your velocity applies.
Would have preferred a method which required no sin/cos functions but I am not sure if that is possible after all.
I have this code:
SACSegmentation<PointXYZ> seg;
seg.setAxis(Vector3f(0, 0, 1));
seg.setEpsAngle(0.5 * M_PI / 180.0);
seg.setModelType(SACMODEL_PLANE);
seg.setMethodType(SAC_RANSAC);
seg.setDistanceThreshold(0.2);
// then set the input cloud and filter..
The axis and epsAngle seem to do nothing at all-- the point cloud still picks up walls when the sensor gets close enough to them that the wall has more points than the ground. I construct the point cloud explicitly from xyz point data, and so PointCloud member variables like sensor_origin_ and sensor_orientation_ are likely not set (unless PointCloud defaults them to something). Could this be the root of my problem? Or am I doing something else wrong?
Other posts I've seen on this problem all suggest setting the eps angle, which I'm already doing. I appreciate your help!
I sniffed around on the PCL docs and found the answer. They don't make it abundantly clear in the documentation, but only SOME of the models are affected by setAxis() and setEpsAngle(). For my application, that model was SACMODEL_PARALLEL_PLANE. You can find the others here: http://docs.pointclouds.org/1.7.0/group__sample__consensus.html.
For a university project I need to implement a computer graphics paper that has been relased a couple of years ago. At one point, I need to triangulate the results I get from my simulation. I guess its easier to explain what I need looking at a picture contained within the paper:
Let's say I already have got all the information it takes to reconstruct the contour lines that you can see in the second thumbnail. Using those I need to do some triangulation using those siluettes as constrains. I have searched the internet for triangulation libraries like CGAL, VTK, Triangle, Triangle++, ... but I always ended up throwing my hands up in horror. I am not a good programmer and it seems impossible to me to get into one of those APIs before the deadline of this project passes.
I would appreciate any kind of help like code snipplets, tips, etc...
I know that the algorithms need segments (pairs of points) as input, so let's say I have got one std::vector containing all pairs of points defining the siluette as well as the left and right side of the rectangle.
Can you somehow give me a code snipplet for i.e. CGAL that I could use for my purpose? First of all I just want to achieve the state of the third thumbnail. Lateron I will have to do some displacement within the "cracks" and finally write the information into a VBO for OpenGL rendering.
I have started working it out with CGAL. One simple problem still drives me crazy:
It is possible to attach informations (like ints) to points before adding them up to the triangulator object. I do this since I need on the one hand an int-flag that I use lateron to define my texture coordinates and on the other hand an index which I use so that I can create a indexed VBO.
http://doc.cgal.org/latest/Triangulation_2/Triangulation_2_2info_insert_with_pair_iterator_2_8cpp-example.html
But instead of points I only want to insert constraint-edges. If I insert both CGAL returns strange results since points have been fed into two times (once as point and once as point of a constrained edge).
http://doc.cgal.org/latest/Triangulation_2/Triangulation_2_2constrained_8cpp-example.html
Is it possible to connect in the same way as with points information to "Constraints" so that I can only use this function cdt.insert_constraint( Point(j,0), Point(j,6)); before I iterate over the resulting faces?
Lateron when I loop over the triangles I need some way to access the int-flags that I defined before. Like this but not on acutal points but the "ends" defined by the constraint edges:
for(CDT::Finite_faces_iterator fit = m_cdt.finite_faces_begin(); fit != m_cdt.finite_faces_end(); ++fit, ++k) {
int j = k*3;
for(int i=0; i < 3; i++) {
indices[j+i] = fit->vertex(i)->info().first;
}
}
The best example of what I am trying to achieve is on this youtube video
http://www.youtube.com/watch?v=53Tk-oGL2Uo
The letters that make up the word 'Atari' fly in from the edges of the screen spinning and then line up to make the word at the end.
I know how to make an object move across the screen, but how do I calculate the spinning so that when the object gets to its end position it's facing the correct direction?
The trick is to actually have the object(s) in the right position for a specific time (say t=5.0 seconds) and then calculate backwards for the previous frames.
i.e. before 5.0 seconds you rotate the object(s) by [angular velocity] * (5.0 - t) and translate by [velocity] * (5.0 - t)
If you do this, then it will look like the objects fly together and line up perfectly. But what you've actually done is blown them apart in random directions and played the animation backwards in time :-)
The CORRECT way of doing this is using keyframes. You can create the keyframes in any 3D editor (I use MAX, but you could use Blender). You don't necessarily need to use the actual characters, even a cuboid would suffice. You will then need to export those animation frames (again, in MAX I would use ASE - COLLADA would work with Blender) and either load them up at runtime or transform them to code.
Then it's a simple matter of running that animation based on the current time.
Here's a sample from my own library that illustrates this technique. Doing this once will last you far longer and give you more benefits in the long run than figuring out how to do this procedurally.
i am playing around with the rotationX/Y/Z properties available in flashplayer since version 10. for testing purpose i created a cube and put canvas objects on three sides of it (top, front, bottom) and created a tween to get the values required for turing by 90 deg. turning the cube (a canvas) using rotationX = xx works well when the three side-canvas objects are small and filled with a not-to-complex element hierarchy. when using larger and more complex content it slows down. the next idea was to remove the canvas elements content and replace it by a snapshotimage of the content instead before starting the turn, after the turn is performed the original content is put back on the sides again. this results in a good perfomance increase. using a tween the last step of rotation is done in the function that is called as the tweenEnd handler. in this function also the process of copying the canvases content back is performed. unfortunately this results in a short hang of the cube right in that last rotation step, the reason for which is that rotation and copying back takes place at the same time.
so i could wait for some time after having called cube.rotationX = endValue by using a timer or setTimeout(func, 500), but this is ugly.
so my question is: after having called cube.rotationX = endValue a period of time is required to calculate data for the rotation and do the rotation itself. is there a way to find out the point in time when the rotation has ended, so that then the copying can be started ?
thank you in advance
tyler
There's no any default event, dispatching when rotation is completed. But I think of using callLater() function to copy back content. Try it.
that is exactly the point, there is not an event indicating the end of the rotation. the solution using callLater() instead of using setTimeout() appears to be an improvement however since waiting for a certain amount of time is always invloving some 'hope it works on machine x'. thank you very much for the hint !
greetings
tyler