Smooth animation of three shapes in SciLab - animation

This answer provides a nice way to make smooth animations in SciLab. I now have to write a simulation of a body attached to two strings (and therefore its movement regarding some additional forces).
The code in the link works well to render movement of a single point and, unfortunately, I didn't manage to make an animation of a point + two lines using this method. If someone is curious, I tried this code to do it:
frametime=(tk-t0)/Nt//defining the waitnig time
plot(Y(1,1),Y(2,1),"o")//plotting the point
plot([0;Y(1,1)],[0;Y(2,1)],style=1)
plot([D;Y(1,1)],[0;Y(2,1)],style=1)//plotting the two initial lines
h1_compound = gce();
h_point=h1_compound.children
h_point.mark_size = 20;
h_point.mark_background = 2;
h_line1=h_compound.children
h_line2=h_compound.children
//h_axes = gca();
//h_axes.data_bounds = [0,-1;10,1];
realtimeinit(frametime);
for i=1:Nt//my vectors have Nt points
realtime(i);//wait "frametime" seconds before drawing the new position
h_point.data=[Y(1,i),Y(2,i)];
h_line1.data=[[0;Y(1,i)],[0;Y(2,i)]]
h_line2.data=[[D;Y(1,i)],[0;Y(2,i)]]
end
The question is: is there any way to make an animation of three shapes without making axes blink (as it is with the window refreshment) or other wierd stuff?

Since you didn't create a MCVE I can't reproduce your exact problem. But you may try to add drawlater(); before, and drawnow(); after your data modification to see if it does help with blinking or not.
Or you may get much better looking result by saving your plots in every round with xs2gif and assemble the animation with another gifmaker progam (there are free online sites to do this, however with some limitations). If you need to present your result, you should do this step anyway.

Related

why is computeBoundingBox() working differently if switching to another browser tab during loading?

I’m working on a complex project in threejs.
Trying to cut the corner:
I have to load an obj, create some pivot point to use as parent of the mesh inside this obj, let the user move and rotate the pivots.
It takes somewhere about 10 to 15 seconds to load due to its complexity.
My problem is that it is working flawlessly if I load the page and don’t change the focus, but if I change the browser tab or collapse the browser window I got a very specific problem:
geometry.computeBoundingBox() gives different results.
Is there someone who can help me figure out what’s happening?
To help you better understand the situation: at loading time I have to rotate the obj to -90° on the X axis (inverting Y and Z as a consequence); I think it’s relevant because the boundingBox calculation somehow inverts Y and Z and changes its min and max also, but as I said only if I switch tab or collapse the browser.
p.s. No matter the OS nor the browser. It’s a super consistent bug
Ok, I somehow solved the issue, but take it with a grain of salt:
the problem can be tracked back to the execution stack of javascript:
the first function computes the bounding box, the second uses this computation, but if the first function is somehow slower to execute, the second could not have what it needs.
What I did is to force javascript to execute functions in a given order and only when the previous is finished.
The problem occurred only when changing the tab because browsers optimize resources of non visible tabs, but the code I wrote was anyway too much entropic to work properly.
I hope what I found will be understandable and useful to someone else in future.

Inconsistent transparency, looking like render order issue

I am using r82.
I have a mesh with multiple materials. I can change their opacity just fine, but how they are rendered is what I would call "splotchy". I have been using ThreeJs for a while, and EDIT: was able to get the transparency working in a past version (r67) with the same model in a significantly more consistent way. So I was wondering if there is something that now I need to set that I didn't need to set before or if I am just overlooking something. Upon revisiting my older code and testing it again, I found that the same transparency issues were present. It was simply a matter of there not being as obvious "splotches" (and not testing enough, I'm sure). Here is a screenshot.
Here are a few more pictures I took that highlight the issue a bit better. I have the outside wall in a light grey and the floors a dark grey in the model and can toggle the outside walls to be visible or not. In these pictures I have one face of the outside wall purple and a face of the floor in the room on the other side of the wall green.
Based on the angle of the camera, it makes part of the green floor face invisible even though there is only one face between the camera and it.
The materials are all double sided already and there is no sign of this until the transparency is on. I found a similar question that suggested changing the mesh.setFaceCulling (or something similar) but that seemed to be from an older version and wasn't in r82.
Thanks for any help in advance!
EDIT:
I started looking into the old version of threeJS and the current version's source code to see what is done differently regarding transparency. I found transparentObjects, which is an array of the objects (I believe faces) that are going to be rendered and are in sorted based on "reversePainterSortStable". There is another list of objects (I believe for the materials objects, maybe?) called opaqueObjects that uses "painterSortStable". So to see if changing the sort order would change the outcome of how things are looking when transparent I changed it so that transparentObjects got sorted by "painterSortStable" and it did change how things showed up significantly (granted it didn't fix my problem since it just removed some problem spots and created new ones).
So the short version, it looks like it is an issue with the renderOrder of the faces.
That being said, I tried finding how the r67 version of the code handled the "renderOrder" of the faces since it wasn't something that (to my knowledge) could be set in that version and just did it automatically. But I have had no such luck tracking down how it was done as of yet.
So I see two possibilities. 1) find out how the past version correctly did transparency (at least for my purposes) and change the logic in the current version to use that. Or 2) find how to properly set the renderOrder of the faces based on the camera position in the scene. Will look into the second option first, but figured it would be good to document this for others looking to help answer or that have a similar problem.
EDIT 2:
So digging through the source code for threeJs and noticed something about the transparentObjects array I mentioned in the previous edit. The first, that I cannot for the life of me figure out how it gets populated since it doesn't seem like it is added to anywhere in the code. The second is that I think it is being populated with duplicates of the entire building object/mesh (see screenshot below).
The z indexes all seem to be the same. as well as the ids and the objects are all of type "mesh" (of the ones I looked through, granted, since there are a few thousand). So I was going to figure out why its adding what is being added to the array, but that is when I stumbled across the issue of not finding where in the code that the transparentObjects array actually get populated.
EDIT 3:
WestLangley, I tried setting the depth test for the outer wall material to false and got this. Like I said in my response comment, even if it did work it wouldn't fix the issues experienced with the camera inside the building, but wanted to follow up none the less (see snapshot below).

Javafx : setRotate and setTranslate in a for loop

I'm new to JavaFX and encountered a problem with the rotating animation while trying to write a Rubik's cube solving program.
I know JavaFX provides some classes for the animation ,but instead of using them, I wanted to try my own approach initially.
Following is the rough idea of my code :
for(90 times)
{
cube.setRotate(cube.getRotate() + 1);
try{Thread.sleep(100);}
catch{InterruptedException e) {Thread.currentThread().interrupt();}
}
By rotating the cube only one degree at a time and using time delay and loop appropriately, I expected to see something similar to rotating animation.
But the result I get is that the cube in the screen doesn't change with each setRotate() in the for loop, it only changes after the loop is over and therefore it changes 90 degrees at one time after 90*100 milliseconds.
I'm wondering if there is a method that can refresh the output in the screen each time using the setRotate() method.
Why do you want to avoid the mechanisms which are designed to make animations. Don't you think there is a reason that they exist?
With your code you are blocking the JavaFX application thread and the resulting behaviour is described in all documents dealing with this issue.

Three.js - Under what conditions are THREE.Lines frustum-culled?

I'm drawing a handful of lines (THREE.Line). Under some conditions, the line suddenly disappears from the screen. This happens frequently when one endpoint is far outside the camera's field of view, but the other one is definitely within the field of view. This also happens when the line crosses the camera's field of view, but both endpoints are far outside it.
I can temporarily fix it by setting frustumCulled to false for each line, but this isn't optimal since I might have thousands of lines in the scene.
Is this working as expected?
BTW, I'm using r68. I haven't had time to refactor my app to work with r69. I'm using the WebGLRenderer.
I needed avoiding lines to dissapear too.
Following Justin idea of frustumCulled I had to do
line.frustumCulled = false;
I thought it was
line.geometry.frustumCulled = false;
but I was wrong, you've to apply it on the line not on its geometry.
This works for me on version 0.70

Qt Animation: Appearing & Disappearing Objects

I'm writing a video annotation application with Qt4 in which users need to be able to seek to various points in a video, putting markers on various objects and then setting keypoints for those markers so that they stay on the objects in the video as they move around. QGraphicsItemAnimation seems like a great place to start for these markers, however they need to be able to appear and disappear at specific times, which I can't figure out how to do with the QGraphicsItemAnimation. I could set the scale at 0 to make the objects disappear, but that seems like a pretty hacky solution, and I'm guessing that the paint engine would still waste cpu cycles trying to draw those invisible objects. Does anyone have a better solution than this? I'm using Qt 4.5.3 right now, but I'm willing to upgrade to 4.6 if it makes things easier. Thanks!!
It seems like the functionality you want of showing/hiding QGraphicsItem objects is beyond the scope of the simple "tweening" that the animation class performs. It is only for one object at a time, and any appearance or disappearance you have to write yourself.
You still might get some mileage out of QGraphicsItemAnimation (although the fact that it uses its own timer instead of being locked to the frame clock of your video is a little dodgy).
Neglecting "seeking" for a moment, there is a QTimeLine::finished() signal. If you let the end of an annotation's active animation timeline represent the point where you want it to disappear, you can trigger QGraphicsItem::hide() at that point. When it comes time to turn it back on, you would construct a new QGraphicsItemAnimation (based on the next run of keyframe data for that object) and call QGraphicsItem::show().
Note that one of the headlining features of Qt 4.6 is the QtAnimation framework, which is more sophisticated but also rather complex. I've not used it yet, but looking over the examples it seems like you might be able to "animate" a visibility or opacity property.

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