I am a very novice programmer and I have hit a wall with a side project I am working on. I am trying to set-up a loop to repeatedly get a translation array from movement across the leap motion. I found in the leap motion documentation this code for python:
linear_frame_movement = frame.translation(start_frame)
which by definition sounds like exactly what I need, but when I attempt to use this command in a very basic code, I'm not exactly understanding how to define the initial frame nor the reference frame. below is the section of code I am trying to get the frame.translation to be printed:
position = hand.palm_position
L = frame.translation(position, start_frame)
y = position
print "position: %s" % (L)
print "position1: %s" % (position)
This reports back with an error like "L = frame.translation(position, start_frame), more than 2 arguments listed".
Does this mean that only a start frame needed to be initialized then the command will determine translation arrays on its own, or do the 2 arguments need to be defined in a completely different way?
My coding background is in matlab, so python has be quiet foreign to me. My apologizes if this is a very straight forward question I am just missing. Any input would be greatly appreciated.
reading from the documentation, the translation method only requires one input which is the inital frame that the translation will be referenced from (hence, start_frame variable name). This will be a valid frame obtained before the current frame.
you do not have to reference the current frame as the translation method is within the current frame object - frame.translation().
the return is 0 if either the current frame or start_frame is invalid
(this is checked using the attribute frame.is_valid which returns a Boolean).
Otherwise, the return is a vector class. The vector class will give the translations of objects in the x and y direction (which can be obtained using the attributes vector.x and vector.y), in reference to the current frame. Therefore, a previous objects position could be determined by translating the current objects position using the return vector.
This can simply be done by taking away the x and y values of the translation vector from the current objects position x and y values. This can be done also in reverse. I havent tested this out, so im unsure if it is the right method.
Hope this helps!
Related
So this question has been asked a few times, but I think my C++ skills are too deficient to really appreciate the answers. What I need is a way to start with an HEVC encoded video and end with CSV that has all the motion vectors. So far, I've compiled and run the reference decoder, everything seems to be working fine. I'm not sure if this matters, but I'm interested in the motion vectors as a convenient way to analyze motion in a video. My plan at first is to average the MVs in each frame to just get a value expressing something about the average amount of movement in that frame.
The discussion here tells me about the TComDataCU class methods I need to interact with to get the MVs and talks about how to iterate over CTUs. But I still don't really understand the following:
1) what information is returned by these MV methods and in what format? With my limited knowledge, I assume that there are going to be something like 7 values associated with the MV: the frame number, an index identifying a macroblock in that frame, the size of the macroblock, the x coordinate of the macroblock (probably the top left corner?), the y coordinate of the macroblock, the x coordinate of the vector, and the y coordinate of the vector.
2) where in the code do I need to put new statements that save the data? I thought there must be some spot in TComDataCU.cpp where I can put lines in that print the data I want to a file, but I'm confused when the values are actually determined and what they are. The variable declarations look like this:
// create motion vector fields
m_pCtuAboveLeft = NULL;
m_pCtuAboveRight = NULL;
m_pCtuAbove = NULL;
m_pCtuLeft = NULL;
But I can't make much sense of those names. AboveLeft, AboveRight, Above, and Left seem like an asymmetric mix of directions?
Any help would be great! I think I would most benefit from seeing some example code. An explanation of the variables I need to pay attention to would also be very helpful.
At TEncSlice.cpp, you can access every CTU in loop
for( UInt ctuTsAddr = startCtuTsAddr; ctuTsAddr < boundingCtuTsAddr; ++ctuTsAddr )
then you can choose exact CTU by using address of CTU.
pCtu(TComDataCU class)->getCtuRsAddr().
After that,
pCtu->getCUMvField()
will return CTU's motion vector field. You can extract MV of CTU in that object.
For example,
TComMvField->getMv(g_auiRasterToZscan[y * 16 + x])->getHor()
returns specific 4x4 block MV's Horizontal element.
You can save these data after m_pcCuEncoder->compressCtu( pCtu ) because compressCtu determines all data of CTU such as CU partition and motion estimation, etc.
I hope this information helps you and other people!
To summarize the problem(s):
I have two bodies in my world so far, one being the ground, the other one being a falling box called "fallingStar".
1) I do not understand why my bullet world is not aligned with my drawn world unless I set an offset of btVector3(2,2,2) to the (btDefault)MotionState.
There is no fancy magic going on anywhere in the code that would explain the offset. Or at least I could not find any reason, not in the shaders, not anywhere.
2) I expected to be able to use multiple instances of btDefaultMotionState, to be precise, I wanted to use one instance for the falling entity and place it somewhere above the ground and then create another instance for the ground that should simply be aligned with my graphics-ground, ever unmoving.
What I am experiencing in regards to 2) is that for whatever reason the btDefaultMotionState instance for the falling entity is always also influencing the one for the ground, without any reference.
Now to the code:
Creation of the fallingBox:
btCollisionShape *fallingBoxShape = new btBoxShape(btVector3(1,1,1));
btScalar fallingBoxMass = 1;
btVector3 fallingBoxInertia(0,0,0);
fallingBoxShape->calculateLocalInertia(fallingBoxMass, fallingBoxInertia);
// TODO this state somehow defines where exactly _ALL_ of the physicsWorld is...
btDefaultMotionState *fallMotionState = new btDefaultMotionState(btTransform(btQuaternion(0,0,0,1), btVector3(2,2,2)));
//btDefaultMotionState *fallMotionState = new btDefaultMotionState();
btRigidBody::btRigidBodyConstructionInfo fallingBoxBodyCI(fallingBoxMass, fallMotionState, fallingBoxShape, fallingBoxInertia);
/*btTransform initialTransform;
initialTransform.setOrigin(btVector3(0,5,0));*/
this->fallingBoxBody = new btRigidBody(fallingBoxBodyCI);
/*fallMotionState->setWorldTransform(initialTransform);
this->fallingBoxBody->setWorldTransform(initialTransform);*/
this->physicsWorld->addBody(*fallingBoxBody);
Now the interesting parts to me are the necessary offset of btVector3(2,2,2) to align it with my drawn world and this:
btTransform initialTransform;
initialTransform.setOrigin(btVector3(0,5,0));
this->fallingStarBody = new btRigidBody(fallingStarBodyCI);
fallMotionState->setWorldTransform(initialTransform);
If I reenable this part of the code ALL the bodies again show an offset, but NOT just 5 up, which I could somehow comprehend if for whatever reason the worldTransform would effect every entity, but about 2,2,2 off... which I cannot grasp at all.
I guess that this line is useless:
fallMotionState->setWorldTransform(initialTransform); as it does not change anything whether it's there or not.
Now to the code of the ground creation:
btCompoundShape *shape = new btCompoundShape();
... just some logic, nothing to do with bullet
btTransform transform;
transform.setIdentity();
transform.setOrigin(btVector3(x + (this->x * Ground::width),
y + (this->y * Ground::height),
z + (this->z * Ground::depth)));
btBoxShape *boxShape = new btBoxShape(btVector3(1,0,1)); // flat surface, no box
shape->addChildShape(transform, boxShape);
(this portion just creates a compoundshape for each surface tile :)
btRigidBody::btRigidBodyConstructionInfo info(0, nullptr, shape);
return new btRigidBody(info);
Here I purposely set the motionstate to nullptr, but this doesn't change anything.
Now I really am curious... I thought maybe the implementation of btDefaultMotionState is a singleton, but it doesn't look so, so... why the hell is setting the motionState of one body affecting the whole world?
Bullet is a good library but only few dedicate time to write good documentation.
To set position of a btRigidBody, try this :-
btTransform transform = body -> getCenterOfMassTransform();
transform.setOrigin(aNewPosition); //<- set orientation / position that you like
body -> setCenterOfMassTransform(transform);
If your code is wrong only at the set transformation part (that is what I guess from skimming your code), it should be solved.
Note that this snippet works only for dynamic body, not static body.
About CompoundBody:-
If it is a compound body, e.g. shape B contains shape C.
Setting transformation of B would work (set body of B), but not work for C.
(because C is just a shape, transformation support only body.)
If I want to change relative transformation of C to B, I would create a whole new compound shape and a new rigid body. Don't forget to remove old body & shape.
That is a library limitation.
P.S.
I can't answer some of your doubt/questions, these information are what I gathered after stalking in Bullet forum for a while, and tested by myself.
(I am also coding game + game library from scratch, using Bullet and other open sources.)
Edit: (about the new problem)
it just slowly falls down (along with the ground itself, which should
not move as I gave it a mass of 0)
I would try to solve it in this order.
Idea A
Set to the compound mass = 0 instead, because setting a child shape's mass has no meaning.
Idea B
First check -> getCenterOfMassTransform() every time-step , is it really falling?
If it is actually falling, to be sure, try dynamicsWorld->setGravity(btVector3(0,0,0));.
If still not work, try with very simple world (1 simple object, no compound) and see.
Idea C (now I start to be desperate)
Ensure your camera position is constant.
If the problem is still alive, I think you now can create a simple test-case and post it in Bullet forum without too much effort.
Lower amounts of lines of code = better feedback
What you are describing is not normal bullet behavior. Your understanding of the library is correct.
What you are most likely dealing with is either a buffer overrun or a dangling pointer. The code you have posted does not have an obvious one of either, so it would be coming from somewhere else in your codebase. You might be able to track that down using a well-placed memory breakpoint.
You "might" be dealing with a header/binary version inconsistency issue, but that's less likely as you would probably be seeing other major issues.
Just had the exact same type of behavior with the DebugDrawer suspended on top of the world. Solved it by passing to Bullet Physics the projectionview matrix alone, without the model matrix that he has and multiplies with already:
glUseProgram(shaderID);
m_MVP = m_camera->getProjectionViewMatrix();
glUniformMatrix4fv(shaderIDMVP, 1, GL_FALSE, &m_MVP[0][0]);
if (m_dynamicWorld) m_dynamicWorld->debugDrawWorld();
So I'm working on a project for a class and I'm still trying to figure out how to go about doing something.
I am making a game where there is a board of squares or hexagons, they are either black or white, each being a state of being "Flipped", and when you click one square/hexagon, it flips all the adjacent shapes too.
Here is an image of what I am aiming to create.
Assignment images
I have gotten it running with squares, but now I need to do it with Hexagons. With the squares I registered a mouseclick as being within a square parameters of the x and y location of the click, and the state changes are assigned to a list of values assigned similarly to how the shapes were assigned within a list.
I will include a quick recording of the square program running in a folder I'm going to link.
Now, I believe I can't apply this kind of system to hexagons since they don't really line up like the squares did.
So how would I go about making a click register within a single hexagon on a grid? I have already drawn out the grid, but I am stuck on what to do to register a click to allow a hexagon to change it's state from un-flipped to flipped. I'm pretty sure I know what to do for the state change itself, but I don't know how to go about this, would it involve something with making a separate Class or something? I would appreciate any help with this.
I'll put a dropbox link here for the progress I made so far, and a pdf manual for graphics.py.
Dropbox: Python files
You can view the python code in your web-browser with dropbox too, I don't really want to fill this page pull of an entire thing of code..
Any help and feedback would be wonderful, thank you c:
so, TL;DR: How do you register a click within a polygon shape in python that allows it to change a value (within a list?) and change its visual appearance.
Just for the general side of your question, you can use a test to check if a point (x, y) is inside a polygon (formed by a list of x, y pairs).
Here's one such solution: http://www.ariel.com.au/a/python-point-int-poly.html
# determine if a point is inside a given polygon or not
# Polygon is a list of (x,y) pairs.
def point_inside_polygon(x,y,poly):
n = len(poly)
inside =False
p1x,p1y = poly[0]
for i in range(n+1):
p2x,p2y = poly[i % n]
if y > min(p1y,p2y):
if y <= max(p1y,p2y):
if x <= max(p1x,p2x):
if p1y != p2y:
xinters = (y-p1y)*(p2x-p1x)/(p2y-p1y)+p1x
if p1x == p2x or x <= xinters:
inside = not inside
p1x,p1y = p2x,p2y
return inside
This can be used in a way that is quite symmetrical to your drawing code, as you also form polygons in the same way for drawing as you would to test to see if the cursor is inside a hex.
You can modify the above implementation also to work with this Point type you are using to draw the polygons.
The rest you should be able to figure out, especially considering that you managed the input handling and drawing for the square grid.
I am starting to work with a CFD fortran program, and want to update the variables that it writes to an output file.
I want to output several columns, I and J coordinates(IL and JL), Water Surface Elevation (SURFEL), Bottom Elevation of coordinate (BELV), Depth of Water (HP) and finally, and this is where I have the question, the Maximum Water Surface Elevation of the coordinate during the simulation (SURFELMAX). L refers to a specific I,J coordinate, LA is the last coordinate in the simulation
So far I have:
DO L=2,LA
SURFEL=BELV(L)+HP(L)
IF (SURFEL.GT.SURFELMAX)THEN
SURFELMAX=SURFEL
ELSE IF (SURFELMAX.GT.SURFEL) THEN
SURFELMAX=SURFELMAX
WRITE(10,200)IL(L),JL(L),SURFEL,SURFELMAX
ENDIF
ENDDO
Everything works ok other than the SURFELMAX, in which the highest recorded surface elevation that occurred in any coordinate in the whole domain is written for each coordinate, i.e. the column is filled with the same value, the highest experienced in the whole domain during the simulation.
Would I need to first allocate an array for SURFELMAX, and have SURFEL checked against it each time to see if it has increased? If so could somebody point me in the right direction for this?
If I understand the requirements correctly, then you want to calculate SURFELMAX before you start writing out. This could simply be:
SURFELMAX = MAXVAL(BELV(2:LA)+HP(2:LA))
WRITE(10,200) (IL(L), JL(L), BELV(L)+HP(L), SURFELMAX, L=2,LA)
(or even as a single line).
It appears I didn't understand correctly; I'll try again - keeping the above as a warning to others.
It seems that you do indeed want SURFELMAX(2:LA) where each element is the highest in a given cell to date.
do L=2, LA
SURFELMAX(L) = MAX(SURFELMAX(L), BELV(L)+HP(L)) ! Store the historical maximum
WRITE (10,200) IL(L), JL(L), BELV(L)+HP(L), SURFELMAX(L)
end do
where, initially, SURFELMAX has been set to a sufficiently small value. You could also explicitly calculate SURFEL if that is needed.
If this is time dependent, then you will have to define a 2-d array SURFELMAX of size (1:LA,1:T) (T = number of time steps, LA = number of active coordinates).
Then increment the time step (say, the iterator is called I_T) outside of the loop through the domain.
Finally assign the maximum value at each coordinate to the SURFELMAX(I_T,L)
I have an array - 2D(100 x 100 in this case) with some states limited within borders as shown on picture:
http://tinypic.com/view.php?pic=mimiw5&s=5#.UkK8WIamiBI
Each cell has its own id(color, for example green is id=1) and flag isBorder(marked as white on pic if true). What I am trying to do is exclude set of cell with one state limited with borders(Grain) so i could work on each grain separately which means i would need to store all indexes for each grain.
Any one got an idea how to solve it?
Now that I've read your question again... The algorithm is essentially the same as filling the contiguous area with color. The most common way to do it is a BFS algorithm.
Simply start within some point you are sure lays inside the current area, then gradually move in every direction, selecting traversed fields and putting them into a vector.
// Edit: A bunch of other insights, made before I understood the question.
I can possibly imagine an algorithm working like this:
vector<2dCoord> result = data.filter(DataType::Green);
for (2dCoord in result) {
// do some operations on data[2dCoord]
}
The implementation of filter in a simple unoptimized way would be to scan the whole array and push_back matching fields to the vector.
If you shall need more complicated queries, lazily-evaluated proxy objects can work miracles:
data.filter(DataType::Green)
.filter_having_neighbours(DataType::Red)
.closest(/*first*/ 100, /*from*/ 2dCoord(x,y))
.apply([](DataField& field) {
// processing here
});