glreadpixels

问题 Ok I'm going to keep this as simple as possible. I want to pass data between shader programs. I'm using readPixels currently to do that but I feel it may be slowing operations down and I'm exploring faster options. what my program does: program1 does my rendering to the canvas. program2 does some wonderful operations in it's shaders that I want to pass to program1. MY QUESTIONS: is it possible to use the vbo from program2 and pass that to program1 for rendering? From what it sounds like in

问题 In my program I am trying to select an object on right mouse click event using glReadPixels method. Window for rendering is created using wxWidgets (by extending wxFrame and wxGLCanvas). However, I am getting wrong values. He is tutorial that I used I was suggested to use this approach as it seems faster and easier than ray casting. My code: #include "MyGLCanvas.h" #include <glm/glm.hpp> #include <glm/gtc/matrix_transform.hpp> #include <glm/gtc/type_ptr.hpp> BEGIN_EVENT_TABLE(MyGLCanvas,

问题 How to take a screenshot of an OpenGL window in C++ and save it to file. I found the glReadPixels() function, but I don't know what to do next. Where I can set path to a file, for example? If not difficult, write code, please. 回答1: This piece of code captures the OpenGL window and export to a BMP file. You must have FreeImage library to run it. // Make the BYTE array, factor of 3 because it's RBG. BYTE* pixels = new BYTE[3 * width * height]; glReadPixels(0, 0, width, height, GL_RGB, GL

问题 How to take a screenshot of an OpenGL window in C++ and save it to file. I found the glReadPixels() function, but I don't know what to do next. Where I can set path to a file, for example? If not difficult, write code, please. 回答1: This piece of code captures the OpenGL window and export to a BMP file. You must have FreeImage library to run it. // Make the BYTE array, factor of 3 because it's RBG. BYTE* pixels = new BYTE[3 * width * height]; glReadPixels(0, 0, width, height, GL_RGB, GL

问题 How to take a screenshot of an OpenGL window in C++ and save it to file. I found the glReadPixels() function, but I don't know what to do next. Where I can set path to a file, for example? If not difficult, write code, please. 回答1: This piece of code captures the OpenGL window and export to a BMP file. You must have FreeImage library to run it. // Make the BYTE array, factor of 3 because it's RBG. BYTE* pixels = new BYTE[3 * width * height]; glReadPixels(0, 0, width, height, GL_RGB, GL

问题 I have rendered a 3D scene in OpenGL viewed from the gluOrtho perspective. In my application I am looking at the front face of a cube of volume 100x70x60mm (which I have as 1000x700x600 pixels). Inside this cube I have rendered a simple blue sphere which sits exactly in the middle and 'fills' the cube (radius 300 pixels). I now want to read the color value of pixels (in 3D) at specific points within the cube; i.e. I wish to know if say point (100,100,-200) is blue or blank (black).

问题 I'm writing a game using android ndk. I'm using picking to select objects in opengl. For that i have an offscreen framebuffer object where i render into and i use glReadPixels() to get the color from the FBO. The color then encodes the id of the clicked object. The problem is glReadPixels() does not work. It just does not read any color values. Is there anything I have to do, to make it work? GLubyte pixel[4] = {0,0,0,0}; glReadPixels(x, y , 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, (void *)pixel);

问题 So basically I was messing about with LWJGL for a while now, and I came to a sudden stop with with annoyances surrounding glReadPixels() . And why it will only read from left-bottom -> top-right. So I am here to answer my own question since I figured all this stuff out, And I am hoping my discoveries might be of some use to someone else. As a side-note I am using: glOrtho(0, WIDTH, 0 , HEIGHT, 1, -1); 回答1: So here it is my screen-capture code which can be implemented in any LWJGL application

问题 I am writing an OpenGL ES 2.0 app for the iPhone (iOS 4.1). At the end of the computations, which are done in the shaders, i need to write back some data to the CPU. As far as I know this can be done by glReadPixels(). In order to keep precision, i want to use half_float or float textures between the shaders, which seem to be supported by extensions. Question: Is it possible to read float or half_float textures with glReadPixels() ? Thanks, Lars 回答1: I have faced up to this problem either.

问题 I'm using glReadPixels to read data into a CVPixelBufferRef . I use the CVPixelBufferRef as the input into an AVAssetWriter . Unfortunately the pixel formats seem to be mismatched. I think glReadPixels is returning pixel data in RGBA format while AVAssetWriter wants pixel data in ARGB format. What's the best way to convert RGBA to ARGB ? Here's what I've tried so far: bit manipulation along the lines of argb = (rgba >> 8) | (rgba << 24) using a CGImageRef as an intermediate step The bit