opengl-3

问题 I know in 2.0- openGL we can draw a line simply like this. glBegin(GL_LINES); glVertex3f(20.0f,150.0f,0.0f); glVertex3f(220.0f,150.0f,0.0f); glVertex3f(200.0f,160.0f,0.0f); glVertex3f(200.0f,160.0f,0.0f); glEnd(); but how to do similar thing in modern openGL(3.0+) I have read Drawing round points using modern OpenGL but the answer is not about certain point,since I want to draw polygon with points have certain coordinates,it's not quite helpful. I use this code,but it shows nothing except a

问题 I was having extreme trouble getting a vertex shader of mine to run under OpenGL 3.3 core on an ATI driver: #version 150 uniform mat4 graph_matrix, view_matrix, proj_matrix; uniform bool align_origin; attribute vec2 graph_position; attribute vec2 screen_position; attribute vec2 texcoord0; attribute vec4 color; varying vec2 texcoord0_px; varying vec4 color_px; void main() { // Pick the position or the annotation position vec2 pos = graph_position; // Transform the coordinates pos = vec2(graph

问题 I was having extreme trouble getting a vertex shader of mine to run under OpenGL 3.3 core on an ATI driver: #version 150 uniform mat4 graph_matrix, view_matrix, proj_matrix; uniform bool align_origin; attribute vec2 graph_position; attribute vec2 screen_position; attribute vec2 texcoord0; attribute vec4 color; varying vec2 texcoord0_px; varying vec4 color_px; void main() { // Pick the position or the annotation position vec2 pos = graph_position; // Transform the coordinates pos = vec2(graph

问题 I am currently using 3 different shaders (Vertex, Geometry and Fragment), each belonging to a different program, all collected in a single Program Pipeline. The problem is that the Geometry and Fragment have their in varyings zeroed, that is, they do not contain the value previously written by the preceeding shader in the pipeline. for each shader: glCreateShader(...) glShadersource(...) glCompileShader(...) glGetShaderiv(*shd,GL_COMPILE_STATUS,&status) for each program: program[index] =

问题 So, I am trying to implement the picking through id. This means with every drawArray a different unique id will be set as uniform and saved in the red component on a texture. 16 bits are more than enough (65k elements), so I choose to use shorts, I know that uniform variable can be only ui, but I decided to gave it a try anyway I also found another question, here, where the answer contains a small example with shorts However here my code to initialize the framebuffer and two textures, one for

问题 I'm looking forward to implement a LookAt( forward, up ) method where: Vector3 forward = eyePosition - targetPosition; Vector3 up; I've seen some implementations over the web, but analizing the code, I've found potencial misbehaviors... I list them from easiest to hardest: 1) This won't work if UP is a zero vector. 2) This won't work if FORWARD is a zero vector. 3) This won't work if UP and FORWARD are parallels. ... So.. How should this method correctly be implemented? Here is a code example

问题 I have OpenGL rendering code calling glDrawArrays that works flawlessly when the OpenGL context is (automatically / implicitly obtained) 4.2 but fails consistently (GL_INVALID_OPERATION) with an explicitly requested OpenGL core context 3.2. (Shaders are always set to #version 150 in both cases but that's beside the point here I suspect.) According to specs, there are only two instances when glDrawArrays() fails with GL_INVALID_OPERATION: "if a non-zero buffer object name is bound to an

问题 I'm having some trouble using AntTweakBar with modern opengl (dynamic pipeline) and glfw3. I'm using some shaders and i'm pretty sure the problem is something about the camera or the shaders. The keyboard shortcuts are working but I don't have the fancy window I should have :( Here is the source #include <GL/glew.h> #include <GLFW/glfw3.h> #include <iostream> #if __cplusplus <= 199711L #define nullptr NULL #endif #include <cmath> #include <AntTweakBar.h> const GLchar *vxShaderSrc = R"(

问题 I'm having trouble using vertex buffer objects without using a vertex array object. My understanding was that VAOs are just encapsulating the state around VBOs. But shouldn't the VBOs be usable without a VAO? Here's a mini-example. With use_vao=true this works correctly (renders orange rect). With use_vao=false this renders nothing and generates a GL_INVALID_OPERATION error upon glDrawElements . // make sure the modern opengl headers are included before any others #include <OpenGL/gl3.h>

问题 I am using OpenGL3.2 Core Profile on OSX. And I want to do instanced drawing (glDrawArraysInstanced), where I pass a matrix for each instance. My vertex shader builds just fine: #version 150 in mediump vec4 position; in mediump mat4 trf; in lowp vec4 rgb; out lowp vec4 colour; uniform highp mat4 modelcamviewprojmat; void main() { mediump vec4 tpos = trf * position; gl_Position = modelcamviewprojmat * tpos; colour = rgb; } The binding of 'trf' went fine: glBindAttribLocation(program, ATTRIB