opengl

问题 I am trying to write a lookat function that uses glm::quat to represent rotations, based of off this answer. I am running into trouble getting a correct angle however. This is my lookat function: void Camera::LookAt(float x, float y, float z) { glm::vec3 lookVector = glm::vec3(x, y, z); assert(lookVector != position); glm::vec3 direction = glm::normalize(lookVector-position); float dot = glm::dot(glm::vec3(0, 0, -1), direction); if (fabs(dot - (-1.0f)) < 0.000001f) rotation = glm::quat

问题 When do I use the STD140 for uniform blocks in OpenGL? Although I am not a 100% sure, I believe there is an alternative to it which can achieve the same thing, called "Shared". Is it just preference for the coder? Or are there reasons to use one over the other? 回答1: Uniform buffer objects are described in http://www.opengl.org/registry/specs/ARB/uniform_buffer_object.txt The data storage for a uniform block can be declared to use one of three layouts in memory: packed , shared , or std140 .

问题 When do I use the STD140 for uniform blocks in OpenGL? Although I am not a 100% sure, I believe there is an alternative to it which can achieve the same thing, called "Shared". Is it just preference for the coder? Or are there reasons to use one over the other? 回答1: Uniform buffer objects are described in http://www.opengl.org/registry/specs/ARB/uniform_buffer_object.txt The data storage for a uniform block can be declared to use one of three layouts in memory: packed , shared , or std140 .

问题 Would someone care to explain the difference to be between a VertexBuffer , a VertexArray , a VertexBufferObject , and a VertexArrayObject ? I'm not even sure if these are all terms for different things, but I've seen all of them appear in the OpenGL spec. I know that a VertexBuffer simply contains vertices and nothing else, once bound, and once I've set the vertex pointers, I can use DrawArrays to draw it. I've done it this way many times. I am using what I think is a VertexArray, which

问题 I am trying to use lighting on a cube but I don't understand where am going wrong. I can be able to view the light source but the rest of the screen appears black so I don't understand why the cube is disappearing. Here is the code: /*Header Inclusions*/ #include <iostream> #include <GL/Glew.h> #include <GL/freeglut.h> // GLM Math inclusions #include <glm/glm.hpp> #include <glm/gtc/matrix_transform.hpp> #include<glm/gtc/type_ptr.hpp> using namespace std; // Uses the standard namespace #define

问题 I am trying to use lighting on a cube but I don't understand where am going wrong. I can be able to view the light source but the rest of the screen appears black so I don't understand why the cube is disappearing. Here is the code: /*Header Inclusions*/ #include <iostream> #include <GL/Glew.h> #include <GL/freeglut.h> // GLM Math inclusions #include <glm/glm.hpp> #include <glm/gtc/matrix_transform.hpp> #include<glm/gtc/type_ptr.hpp> using namespace std; // Uses the standard namespace #define

问题 I'm using G++ to link my project to glew32, glfw, opengl32, glu32, etc, everything compiles fine - however at the link stage everything but glViewport links and I get this error: undefined reference to '_glViewport'. I find this... odd since everything else was fine and I'm kinda at a loss for what to do. I look forward to any advice on what to try and or do. 回答1: As per my comment, you need to link with the OpenGL libraries, when you compile do (Linux/cygwin) g++ -o target source.c -lGL To

问题 So basically I am using the windows api to create an emty window and then I use OpenGL to draw to that window from different threads. I managed to do this just with one thread , but getting and dispatching system messages so that the window is usable was slowing down the frame rate I was able to get, so I'm trying to get another thread to do that in parallel while I draw in the main thread. To do this I have a second thread which creates an empty window and enters an infinite loop to handle

问题 The following code shows a straight cylinder/pipe in OpenGL C language. #include <stdio.h> #include <stdlib.h> #include <GL/glut.h> #include <math.h> #define PI 3.1415927 void draw_cylinder(GLfloat radius, GLfloat height, GLubyte R, GLubyte G, GLubyte B) { GLfloat x = 0.0; GLfloat y = 0.0; GLfloat angle = 0.0; GLfloat angle_stepsize = 0.1; // Draw the tube glColor3ub(R-40,G-40,B-40); glBegin(GL_QUAD_STRIP); angle = 0.0; while( angle < 2*PI ) { x = radius * cos(angle); y = radius * sin(angle);

问题 The following code shows a straight cylinder/pipe in OpenGL C language. #include <stdio.h> #include <stdlib.h> #include <GL/glut.h> #include <math.h> #define PI 3.1415927 void draw_cylinder(GLfloat radius, GLfloat height, GLubyte R, GLubyte G, GLubyte B) { GLfloat x = 0.0; GLfloat y = 0.0; GLfloat angle = 0.0; GLfloat angle_stepsize = 0.1; // Draw the tube glColor3ub(R-40,G-40,B-40); glBegin(GL_QUAD_STRIP); angle = 0.0; while( angle < 2*PI ) { x = radius * cos(angle); y = radius * sin(angle);