I am trying to figure out how to use correctly body.applytorque(float torque, boolean wake) method on a body with a center of mass, to accelerate it's angular velocity. I want to apply an angular acceleration, in degrees per square second.
According to the libGDX doc, torque parameter uses Newton-meters. To set it, i'll use the formula :
𝛕 = I α
where 𝛕:torque[N-m], I:mass moment of inertia, α:acceleration
on the body :
// java
float acceleration = 120f; // deg/s²
float inertia = body.getInertia();
body.applyTorque(inertia * (float)Math.toRadians(acceleration), true);
but this leads to wrong acceleration, same thing with the mass.
What is the proper use of that method, in deg/s²?
Resolution : the problem came from the world editor UI i was using -
Overlap2D.
How to correct : multiply the torque by 2 in applytorque(...) .
The method i mentionned was used correctly in my example above, and so was the formula.
With Overlap2D software, I'm able to place all the bodies i want into a scene. When I then load the bodies and assets in my program, i load directly the world with. I use some convenience classes provided by ashley, e.g IteratingSystem, to compute directly every entity's behaviour at each rendering. This processing is affecting the forces, or at least torques. However i had no problems with angular impulses.
Thank to David Jeske and Louis Langholtz for having guided me.
Related
I'm trying to make a pleasing "spring" effect to scale a button and other components. In particular I want to scale them in when the view is created and shown, and I want to scale them down when a user taps a button, and if the user releases the button, I want them to scale back up to normal size with the spring effect.
The Facebook library "rebound" is a perfect example, see their demo here: https://facebook.github.io/rebound/.
I tried all the built in curves like bounceIn/Out and elasticIn/Out but they weren't springy enough (elastic is kind of springy).
Any help greatly appreciated!
As #Remi said, you can use the Curve class and override the transform method.
The difficult part is then figuring out the formula to use. I'd play around with something like this curve calculator to get a formula.
i.e. -(e^(-x/a) * cos(xw)) + 1 with a = 0.15 and w = 19.4.
Another alternative is to use existing curves together - since they all start at 0 and end at 1, you can simply multiply two different curves together in your overloaded curve method.
I'd take a look at the implementation of ElasticIn and ElasticOut to figure out how they did the math, but the dart math library should have everything you need.
You can create your own Curve by overriding transform.
As long a mycurve.transform(0) == 0 and mycurve.transform(1) == 1 you can do pretty much anything.
Better late than never:
you may find the package https://pub.dev/packages/sprung useful.
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.
I have an object - just cylinder (looks like chip) and I want to add to this object like Flip animation. When chip is flip - chip will go up and rotate in the air. Now I want to give a dynamic parameter determines Height for go up.
So right now I know 2 ways:
1) Is just in c# code write object.Rotate() with parameters
2) Write animation clip - and call in C# for Play - but here -I can't pass parameters (right or not?)
So please guys - just give me direction (links) for good Get started with unity3d. Sorry for my English - it's very bad I know ((
The best way to do it purely by script is definitely by using tweeners, I would suggest using this tool : https://www.assetstore.unity3d.com/en/#!/content/27676
Now after downloading this asset to your Unity just create a new script and include the asset
using DG.Tweening;
And here is simple method for doing the actual jump with dynamic parameters.
public Transform chip;
void JumpWithRotation(float heightOfJump, float timeForJump){
DOTween.Init(false, true, LogBehaviour.ErrorsOnly);
chip.DORotate (new Vector3 (0, 180f, 0), timeForJump).SetEase (Ease.InOutSine);
chip.DOMove (new Vector3 (0, heightOfJump, 0), timeForJump).SetEase (Ease.InOutSine);
}
The best thing about tweeners is that you can easily implement easing methods (making transition between two values (linear, sine, exponentional...)).
You can pass parameters to Animation - because animation is just file(it's not a code). So sure - if you want to pass dynamic parameters - you have only one options - by scripts. Just write 1 method who take GameObject and parameters for rotation and its done! good luck
I'm implementing in my program the gaussian blur effect. To do the job I need to render the first blur information (the one on Y axis) in a specific texture (let's call it tex_1) and use this same information contained in tex_1 as input information for a second render pass (for the X axis) to fill an other texture (let's call it tex_2) containing the final gaussian blur result.
A good practice should be to create 2 frame buffers (FBOs) with a texture attached for each of them and linked both to GL_COLOR_ATTACHMENT0 (for example). But I just wonder one thing:
Is it possible to fill these 2 textures using the same FBO ?
So I will have to enable GL_COLOR_ATTACHMENT0 and GL_COLOR_ATTACHMENT1 and bind the desired texture to the correct render pass as follow :
Pseudo code:
FrameBuffer->Bind()
{
FrameBuffer->GetTexture(GL_COLOR_ATTACHMENT0)->Bind(); //tex_1
{
//BIND external texture to blur
//DRAW code (Y axis blur pass) here...
//-> Write the result in texture COLOR_ATTACHEMENT0 (tex_1)
}
FrameBuffer->GetTexture(GL_COLOR_ATTACHMENT1)->Bind(); //tex_2
{
//BIND here first texture (tex_1) filled above in the first render pass
//Draw code (X axis blur pass) here...
//-> Use this texture in FS to compute the final result
//within COLOR_ATTACHEMENT1 (tex_2) -> The final result
}
}
FrameBuffer->Unbind()
But in my mind there is a problem because I need for each render pass to bind an external texture as an input in my fragment shader. Consequently, the first binding of the texture (the color_attachment) is lost!
So does it exist a way to solve my problem using one FBO or do I need to use 2 separate FBOs ?
I can think of at least 3 distinct options to do this. Where the 3rd one will actually not work in OpenGL ES, but I'll explain it anyway because you might be tempted to try it otherwise, and it is supported in desktop OpenGL.
I'm going to use pseudo-code as well to cut down on typing and improve readability.
2 FBOs, 1 attachment each
This is the most straightforward approach. You use a separate FBO for each texture. During setup, you would have:
attach(fbo1, ATTACHMENT0, tex1)
attach(fbo2, ATTACHMENT0, tex2)
Then for rendering:
bindFbo(fbo1)
render pass 1
bindFbo(fbo2)
bindTexture(tex1)
render pass 2
1 FBO, 1 attachment
In this approach, you use one FBO, and attach the texture you want to render to each time. During setup, you only create the FBO, without attaching anything yet.
Then for rendering:
bindFbo(fbo1)
attach(fbo1, ATTACHMENT0, tex1)
render pass 1
attach(fbo1, ATTACHMENT0, tex2)
bindTexture(tex1)
render pass 2
1 FBO, 2 attachments
This seems to be what you had in mind. You have one FBO, and attach both textures to different attachment points of this FBO. During setup:
attach(fbo1, ATTACHMENT0, tex1)
attach(fbo1, ATTACHMENT1, tex2)
Then for rendering:
bindFbo(fbo1)
drawBuffer(ATTACHMENT0)
render pass 1
drawBuffer(ATTACHMENT1)
bindTexture(tex1)
render pass 2
This renders to tex2 in pass 2 because it is attached to ATTACHMENT1, and we set the draw buffer to ATTACHMENT1.
The major caveat is that this does not work with OpenGL ES. In ES 2.0 (without using extensions) it's a non-starter because it only supports a single color buffer.
In ES 3.0/3.1, there is a more subtle restriction: They do not have the glDrawBuffer() call from full OpenGL, only glDrawBuffers(). The call you would try is:
GLenum bufs[1] = {GL_COLOR_ATTACHMENT1};
glDrawBuffers(bufs, 1);
This is totally valid in full OpenGL, but will produce an error in ES 3.0/3.1 because it violates the following constraint from the spec:
If the GL is bound to a draw framebuffer object, the ith buffer listed in bufs must be COLOR_ATTACHMENTi or NONE.
In other words, the only way to render to GL_COLOR_ATTACHMENT1 is to have at least two draw buffers. The following call is valid:
GLenum bufs[2] = {GL_NONE, GL_COLOR_ATTACHMENT1};
glDrawBuffers(bufs, 2);
But to make this actually work, you'll need a fragment shader that produces two outputs, where the first one will not be used. By now, you hopefully agree that this approach is not appealing for OpenGL ES.
Conclusion
For OpenGL ES, the first two approaches above will work, and are both absolutely fine to use. I don't think there's a very strong reason to choose one over the other. I would recommend the first approach, though.
You might think that using only one FBO would save resources. But keep in mind that FBOs are objects that contain only state, so they use very little memory. Creating an additional FBO is insignificant.
Most people would probably prefer the first approach. The thinking is that you can configure both FBOs during setup, and then only need glBindFramebuffer() calls to switch between them. Binding a different object is generally considered cheaper than modifying an existing object, which you need for the second approach.
Consequently, the first binding of the texture (the color_attachment)
is lost!
No, it isn't. Maybe your framebuffer class works that way, but then, it would be a very bad abstraction. The GL won't detach a texture from an FBO just because you bind this texture to some texture unit. You might get some undefined results if you create a feedback loop (rendering to a texture you are reading from).
EDIT
However, as #Reto Koradi pointed out in his excellent answer, (and his comment to this one), you can't simply render to a single color attachment in unextended GLES1/2, and need some tricks in GLES3. As a result, The fact I'm pointing out here is still true, but not really helpful for the ultimate goal you are trying to achieve.
I want to put/wrap images to 3D objects. To keep things simple and fast, instead of using(and learning) a 3D library I want to use mapping images. Mapping images are used in such a way:
So you generate the mapping images once for each object and use the same mapping for all images you want to wrap.
My question is how can I generate such mapping images (given the 3D model)? Since I don't know about the terminology my searches failed me. Sorry if I am using the wrong jargon.
Below you can see a description of the workflow.
I have the 3D model of the object and the input image, i want to generate mapping images that I can use to generate the textured image.
I don't even know where to start, any pointers are appreciated.
More info
My initial idea was to somehow wrap a identity mappings (see below) using an external program. I have generated horizontal and vertical gradient images in Photoshop just to see if mapping works using photoshop generated images. The result doesn't look good. I wasn't hopeful but it was worth a shot.
input
mappings (x and y), they just resize the image, they don't do anything fancy.
result
as you can see there are lots of artifacts. Custom mapping images I have generated by warping the gradients even looks worse.
Here is some more information on mappings: http://www.imagemagick.org/Usage/mapping/#distortion_maps
I am using OpenCV remap() function for mapping.
if i understand you right here, you want to do all of it in 2D ?
calling warpPerspective() for each of your cube surfaces will be much more successful, than using remap()
pseudocode outline:
// for each surface:
// get the desired src and dst polygon
// the src one is your texture-image, so that's:
vector<Point> p_src(4), p_dst(4);
p_src[0] = Point(0,0);
p_src[1] = Point(0,src.rows-1);
p_src[2] = Point(src.cols-1,0);
p_src[3] = Point(src.cols-1,src.rows-1);
// the dst poly is the one you want textured, a 3d->2d projection of the cube surface.
// sorry, you've got to do that on your own ;(
// let's say, you've come up with this for the cube - top:
p_dst[0] = Point(15,15);
p_dst[1] = Point(44,19);
p_dst[2] = Point(56,30);
p_dst[3] = Point(33,44);
// now you need the projection matrix to transform from one to another:
Mat proj = getPerspectiveTransform( p_src, p_dst );
// finally, you can warp your texture to the dst-polygon:
warpPerspective(src, dst, proj, dst.size());
if you can get hold of the 'Learning Opencv' book, it's described around p 170.
final word of warning, since youre complaining about artefacts, - yes, it'll all look pretty cheesy, 'real' 3d engines do a lot of work here, subpixel-uv mapping, filtering,
mipmapping, etc. if you want it to look nice, consider using the 'real' thing.
btw, there's nice opengl support built into opencv
To achieve what you are trying to do, you need to render the 3D-models UV to a texture. It will be easier to learn to render 3D than to do things this way. Especially since there are a lot of weaknesses in your aproach. difficult to to lighting and problems til the depth-buffer will be abundant.
Assuming all your objects shul ever only be viewed from one angle, you need to render each of them to 3 textures:
UV-map
Normal-map
Depth-map (to correct the depth-buffer)
You will still have to do shading in order to draw these to look like your object, and I don't even know how to do the depth-buffer-thing, I just know it can be done.
So in order to avoid learning 3D, your will have to learn all the difficult parts of 3D-rendering. Does not seem the easier route...