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Questions tagged [ray-picking]

56 questions
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Unprojecting Screen coords to world in OpenGL es 2.0

Long time listener, first time caller. So I have been playing around with the Android NDK and I'm at a point where I want to Unproject a tap to world coordinates but I can't make it work. The problem is the x and y values for both the near and far…
BlondesDoingMath
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Detecting objects near cursor to snap to - any alternatives to picking ray?

In the problem of detecting objects near the mouse cursor to snap to (in a 3d view), we are using the picking ray method (which basically forms a 3d region of the cursor's immediate neighborhood and then detects objects present in the region). I…
Alex Bausk
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opengl glkit color-picking glreadpixels always returns zero colored pixels (0,0,0)

The following code can be a complete template for color-picking with glkit. I just need to understand why all the pixels in the offscreen buffer are colored (0,0,0) as printed below to the nslog. Note: the vertices array is defined in an header file…
user2492853
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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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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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Ray picking mess

I am using ray picking to find the boundaries for a character. It's not optimal, but it's the best I can do and will have to do; I need to have (close to) pixelperfect collisions and also I have lots and lots of objects. I do not however get the…
RobotRock
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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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In Three.js Picking Ray, How Objects moves only X,Z? not Y

now Objects move every direction. but I want to Objects move only X or Z, not Y. I try this. but result is not good. on MouseMove // OBJECT SELECTED if ( SELECTED ) { var intersects = ray.intersectObject( PICKING_PLANE…
user1658740
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how to get colors by glreadpixels?

I am trying to get a color of touch point on the screen in Android. but it shows me only RGB = (0, 0, 0) value. I have searched other sites. it said that i should add some codes below but it didn`t change…
Mungunbat Enkhbayar
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Getting a ray for raypicking in openGL ES

OK, so I used this code for a ray for opengl ES but I'm getting an error with the this.P0 = farCoOrds; this.P1 = nearCoOrds; at the very end of the code. It says, Cannot Resolve Symbol Here is the code: public class Ray { public static…
Dakota Miller
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Trackball issue with Raypicking

I'm trying to develop a 3D raypicking in my OpenGL scene. I have a working OBJ loader with a trackball. char* model_file = NULL; /* name of the obect file */ GLuint model_list = 0; /* display list for object */ GLMmodel* model;…
Gorgo
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