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Questions tagged [picking]

147 questions
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Three.js particles vs particle system and picking

I have an app that uses a Three.js ParticleSystem to render on the order of 50,000 points. I have spent a lot of time searching for efficient ways to do picking (ray-casting) so as to be able to interact with individual points but have not found a…
MikeCantor
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OpenGL Picking selects on wrong places

I'm trying to recognize a drawn object on a mousPressEvent in OpenGL in Qt with picking. I did some research but wasn't able to find the problem. Clearly it recognizes something (because the return value of glRenderMode(GL_RENDER) is often an…
stanthecomputerman
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Why might a program null pointer in Eclipse when it works in another IDE?

I'm having trouble getting some code working in Eclipse. It is Java code with elements from Processing and it works in the Processing IDE but gives an immediate null pointer exception in Eclipse. It also involves another library called Picking. I…
user3308885
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Picking implementation

Apologize in advance for what may be dumb questions. I'm trying to understand the picking implementation in three.js. Last I looked at the code, it appeared to be doing mathematical intersections in JavaScript. Is that true? If so, couldn't an off…
Paul Jacobs
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Understanding implementation of glu.PickMatrix()

I am working on an OpenGL project which requires object selection feature. I use OpenTK framework to do this; however OpenTK doesn't support glu.PickMatrix() method to define the picking region. I ended up googling its implementation and here is…
stoney78us
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How to pick up a sprite?

A simple question: how could I pick up a sprite in libgdx? By this, I mean that when I click / touch the screen, it checks which (if any) sprite is clicked.
manabreak
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opengl iOS glkit color picking

Its about picking a 3d object using color-picking. I draw my mesh (update: Which resides in a static header file and is displayed fine to the screen in the same project) to a new offscreen framebuffer and then I use glReadPixels to identify if the…
user2492853
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I would like to compile this file in qt creator (4.7)

Im new using Qt and OpenGl and I would like to compile this file, but I can't. I really would like to try this example because I want to understand how "picking function" works. What should I do? This is the code: (You can find it…
Irene Lopez
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Android Open Gl Object Selection

In open GL there is a term called picking. Which is used to determine which object on the screen was selected. Can someone explain to me what the difference between using picking and putting a touch based listener in each and every instance of a…
Rafiq Flucas
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ask about D3DXIntersect function:(

// get the current transform matrices D3DXMATRIX matProjection, matView, matWorld, matInverse; ENGINE.GetDevice()->GetDevice()->GetTransform(D3DTS_PROJECTION, &matProjection); …
user1658740
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Color Picking on Android in OpenGL ES 2.0

I have implemented a color picking method and it also works; sometimes. The problem is when I call my method in the onSurfaceChanged method, it does read back the correct pixels. But when I call my method in the onTouchevent of the GLSurfaceView, it…
user2468462
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Picking Ray is inaccurate

I'm trying to implement a picking ray via instructions from this website. Right now I basically only want to be able to click on the ground to order my little figure to walk towards this point. Since my ground plane is flat , non-rotated and…
s3rius
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Assign a given id in an object in opengl

I am working on a multi-agent application. During a simulation I display the agents present at any timestep. This agent have their own specific id. I want to identify and interact with those object by using picking. My picking method is working but…
arno69
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Picking a framework element with Kinect (Like Ellipse or Rectangle)

I (literally) want to catch a framework element using NUI of Kinect. Assuming that I have an ellipse on my Grid (or Canvas), I should be able to pick an ellipse using my program. In order to do this, I thought that I have to determine the exact…
BedirYilmaz
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Three.js picking is not working correctly with custom geometry

I have a problem with picking implementation. I found a number of different examples doing what I want, but I really cannot make it work as it should. I mainly followed this example Basically, I have some meshes in my scene and, double clicking any…
aleGrazioli
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