glreadpixels

OpenGL ES 2.0 Android - Color Picking

由 六眼飞鱼酱① 提交于 2019-12-13 05:05:18
问题 I'm trying to implement color picking using GLES20.glReadPixels function in android OpenGL ES. The problem is that this function is always returning 0,0,0,0 as color and not the correct color values. Any idea why? My code looks like this: public boolean onTouchEvent(MotionEvent event) { if (event != null) { float x = event.getX(); float y = event.getY(); if (event.getAction() == MotionEvent.ACTION_UP) { int newX = (int)x; int newY = (int)y; ByteBuffer pixel = ByteBuffer.allocate(4); pixel

Get Data from OpenGL glReadPixels(using Pyglet)

由 …衆ロ難τιáo~ 提交于 2019-12-12 05:36:40
问题 I'm using Pyglet(and OpenGL) in Python on an application, I'm trying to use glReadPixels to get the RGBA values for a set of pixels. It's my understanding that OpenGL returns the data as packed integers, since that's how they are stored on the hardware. However for obvious reasons I'd like to get it into a normal format for working with. Based on some reading I've come up with this: http://dpaste.com/99206/ , however it fails with an IndexError. How would I go about doing this? 回答1: You must

Non blocking glReadPixels of depth values with PBO

由 ℡╲_俬逩灬. 提交于 2019-12-11 15:08:19
问题 I am reading a single pixel's depth from the framebuffer to implement picking. Originally my glReadPixels() was taking a very long time (5ms or so) and on nVidia it would even burn 100% CPU during that time. On Intel it was slow as well, but with idle CPU. Since then, I used the PixelBufferObject functionality, PBO , to make the glReadPixels asynchronous and also double buffered using this well known example. This approach works well, and let's me make a glReadPixels() call asynchronous but

How to call glReadPixels on different thread?

由 限于喜欢 提交于 2019-12-11 10:46:07
问题 When I call glReadPixels on another thread, it doesn't return me any data. I read somewhere suggesting that I need to create a new context in the calling thread and copy the memory over. How exactly do I do this? This is the glReadPixels code I use: pixels = new BYTE[ 3 * width * height]; glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels); image = FreeImage_ConvertFromRawBits(pixels, width, height, 3 * width, 24, 0xFF0000, 0x00FF00, 0x0000FF, false); FreeImage_Save(FIF_PNG,

glReadPixels() burns up all CPU cycles of a single core

由 纵饮孤独 提交于 2019-12-11 02:49:54
问题 I have an SDL2 app with an OpenGL window, and it is well behaved: When it runs, the app gets synchronized with my 60Hz display, and I see 12% CPU Usage for the app. So far so good. But when I add 3D picking by reading a single (!) depth value from the depth buffer (after drawing), the following happens: FPS still at 60 CPU usage for the main thread goes to 100% If I don't do the glReadPixels, the CPU use drops back to 12% again. Why does reading a single value from the depth buffer cause the

Problem reading data by glreadpixel() while using depth buffer and anti-aliasing technique

由 心不动则不痛 提交于 2019-12-08 01:26:59
问题 I want to capture the screen of my game using glreadpixel(). it works fine over simulator also on 2g iphone with ios version 3.1.1 . but on ipad with ios version 4.2.1 it doesnt . i came to know the issue regarding this. for ios version 4.0 above on a particular device (ipad) we bind depth buffer and use anti-aliasing technique. And when we use glreadpixel() of opengl that capture data from frame buffer returns all 0 in the destination buffer... if we dont bind the depth buffer to frame

Using OpenGL ES texture caches instead of glReadPixels to get texture data

由 喜欢而已 提交于 2019-12-07 05:34:32
问题 In iOS 5, OpenGL ES Texture caches were introduced to provide a direct way from the camera video data to OpenGL without the need of copying the buffers. There was a brief introduction to texture caches in session 414 - Advances in OpenGL ES for iOS 5 of WWDC 2011. I found an interesting article which abuses this concept further in the end and circumvents a call to glReadPixels by simply locking the texture, and then accessing the buffer directly. glReadPixels is really slow due to the tile

Implementing render-to-vertex-array, glReadPixels fails (invalid operation)

由 跟風遠走 提交于 2019-12-06 08:37:15
问题 I'm trying to copy vertex data from a texture to a vertex buffer, and then draw the vertex buffer. As far as I know the best way to do this is to bind the texture to a fbo, and use glReadPixels to copy it to a vbo. However, I can't seem to get this working: glReadPixels fails with the error "invalid operation". Corrections, examples and alternate methods welcome. :) Here's the relevant code: glEnable(GL_TEXTURE_2D) w, h = 32, 32 vbo = glGenBuffers(1) glBindBuffer(GL_ARRAY_BUFFER, vbo)

Using OpenGL ES texture caches instead of glReadPixels to get texture data

由 最后都变了- 提交于 2019-12-05 12:41:00
In iOS 5, OpenGL ES Texture caches were introduced to provide a direct way from the camera video data to OpenGL without the need of copying the buffers. There was a brief introduction to texture caches in session 414 - Advances in OpenGL ES for iOS 5 of WWDC 2011 . I found an interesting article which abuses this concept further in the end and circumvents a call to glReadPixels by simply locking the texture, and then accessing the buffer directly. glReadPixels is really slow due to the tile-based renderer which is used in iPad 2 (even when you use only 1x1 textures). However, the described

Qt / C++ - Converting raw binary data and display it as an image (i.e. QImage)

由 扶醉桌前 提交于 2019-12-04 14:08:19
问题 I have a C++ Open GL application that renders an animation display, and captures the frame-buffer contents using glReadPixels(), which is then stored as a 1D char array. I can get the buffer contents and save it to a char array, as follow: char * values = (char *) malloc(width * height * 4 * sizeof(char)); glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, values); I then send these raw data over the network using socket, which is not an issue for me. I have a Qt Desktop Client
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