问题
I am writing a openGL program(C++) which draws a ground with two 3D objects above it. The programming tool I use is Xcode version 8.0(8A218a)(OSX 10.11.6).
my code(main.cpp):
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <iostream>
#include <fstream>
using namespace std;
using glm::vec3;
using glm::mat4;
GLint programID;
//initialize all OpenGL objects
GLuint groundVAO, groundVBO, groundEBO; //ground
bool checkStatus( //OK
GLuint objectID,
PFNGLGETSHADERIVPROC objectPropertyGetterFunc,
PFNGLGETSHADERINFOLOGPROC getInfoLogFunc,
GLenum statusType)
{
GLint status;
objectPropertyGetterFunc(objectID, statusType, &status);
if (status != GL_TRUE)
{
GLint infoLogLength;
objectPropertyGetterFunc(objectID, GL_INFO_LOG_LENGTH, &infoLogLength);
GLchar* buffer = new GLchar[infoLogLength];
GLsizei bufferSize;
getInfoLogFunc(objectID, infoLogLength, &bufferSize, buffer);
cout << buffer << endl;
delete[] buffer;
return false;
}
return true;
}
bool checkShaderStatus(GLuint shaderID) //OK
{
return checkStatus(shaderID, glGetShaderiv, glGetShaderInfoLog, GL_COMPILE_STATUS);
}
bool checkProgramStatus(GLuint programID) //OK
{
return checkStatus(programID, glGetProgramiv, glGetProgramInfoLog, GL_LINK_STATUS);
}
string readShaderCode(const char* fileName) //OK
{
ifstream meInput(fileName);
if (!meInput.good())
{
cout << "File failed to load..." << fileName;
exit(1);
}
return std::string(
std::istreambuf_iterator<char>(meInput),
std::istreambuf_iterator<char>()
);
}
void installShaders() //OK
{
GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
const GLchar* adapter[1];
//adapter[0] = vertexShaderCode;
string temp = readShaderCode("VertexShaderCode.glsl");
adapter[0] = temp.c_str();
glShaderSource(vertexShaderID, 1, adapter, 0);
//adapter[0] = fragmentShaderCode;
temp = readShaderCode("FragmentShaderCode.glsl");
adapter[0] = temp.c_str();
glShaderSource(fragmentShaderID, 1, adapter, 0);
glCompileShader(vertexShaderID);
glCompileShader(fragmentShaderID);
if (!checkShaderStatus(vertexShaderID) ||
!checkShaderStatus(fragmentShaderID))
return;
programID = glCreateProgram();
glAttachShader(programID, vertexShaderID);
glAttachShader(programID, fragmentShaderID);
glLinkProgram(programID);
if (!checkProgramStatus(programID))
return;
glDeleteShader(vertexShaderID);
glDeleteShader(fragmentShaderID);
glUseProgram(programID);
}
void keyboard(unsigned char key, int x, int y)
{
//TODO:
}
void sendDataToOpenGL()
{
//TODO:
//create solid objects here and bind to VAO & VBO
//Ground, vertices info
const GLfloat Ground[]
{
-5.0f, +0.0f, -5.0f, //0
+0.498f, +0.898, +0.0f, //grass color
+5.0f, +0.0f, -5.0f, //1
+0.498f, +0.898, +0.0f,
+5.0f, +0.0f, +5.0f, //2
+0.498f, +0.898, +0.0f,
-5.0f, +0.0f, +5.0f
};
GLushort groundIndex[] = {1,2,3, 1,0,3};
//Pass ground to vertexShader
//VAO
glGenVertexArrays(1, &groundVAO);
glBindVertexArray(groundVAO);
//VBO
glGenBuffers(1, &groundVBO);
glBindBuffer(GL_ARRAY_BUFFER, groundVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(Ground), Ground, GL_STATIC_DRAW);
//EBO
glGenBuffers(1, &groundEBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, groundEBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(groundIndex), groundIndex, GL_STATIC_DRAW);
//connectToVertexShader
glEnableVertexAttribArray(0); //position
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 6, 0);
glEnableVertexAttribArray(1); //color
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 6, (char*)(sizeof(float)*3));
}
void paintGL(void)
{
//TODO:
//render your objects and control the transformation here
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//translate model
glm::mat4 modelTransformMatrix = glm::translate(glm::mat4(), vec3(+0.0f, +0.0f, -3.0f));
//perspective view
glm::mat4 projectionMatrix = glm::perspective(+40.0f, +1.0f, +1.0f, +60.0f);
//ultimate matrix
glm::mat4 ultimateMatrix;
//register location on the graphics cards
GLint ultimateMatrixUniformLocation = glGetUniformLocation(programID, "ultimateMatrix");
/*GLint modelTransformMatrixUniformLocation = glGetUniformLocation(programID, "modelTransformMatrix");
GLint projectionMatrixUniformLocation = glGetUniformLocation(programID, "projectionMatrix");*/
//drawing the ground
/*glUniformMatrix4fv(modelTransformMatrixUniformLocation, 1, GL_FALSE, &modelTransformMatrix[0][0]);
glUniformMatrix4fv(projectionMatrixUniformLocation, 1, GL_FALSE, &projectionMatrix[0][0]);*/
glBindVertexArray(groundVAO);
ultimateMatrix = projectionMatrix * modelTransformMatrix;
glUniformMatrix4fv(ultimateMatrixUniformLocation, 1, GL_FALSE, &ultimateMatrix[0][0]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0);
glFlush();
glutPostRedisplay();
}
void initializedGL(void) //run only once
{
glewInit();
glEnable(GL_DEPTH_TEST);
sendDataToOpenGL();
installShaders();
}
int main(int argc, char *argv[])
{
/*Initialization*/
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutCreateWindow("Try");
glutInitWindowSize(700, 700);
//const GLubyte* glversion = glGetString(GL_VERSION);
/*Register different CALLBACK function for GLUT to response
with different events, e.g. window sizing, mouse click or
keyboard stroke */
initializedGL();
//glewExperimental = GL_TRUE;
glutDisplayFunc(paintGL);
glutKeyboardFunc(keyboard);
/*Enter the GLUT event processing loop which never returns.
it will call different registered CALLBACK according
to different events. */
//printf("OpenGL ver: %s\n", glversion);
glutMainLoop();
return 0;
}
VertexShaderCode.glsl:
#version 430 // GLSL version your computer supports
in layout(location=0) vec3 position;
in layout(location=1) vec3 vertexColor;
uniform mat4 ultimateMatrix;
out vec3 theColor;
void main()
{
vec4 v = vec4(position, 1.0);
gl_Position = ultimateMatrix * v;
theColor = vertexColor;
}
FragmentShaderCode.glsl:
#version 430 //GLSL version your computer supports
out vec4 theColor2;
in vec3 theColor;
void main()
{
theColor2 = vec4(theColor, 1.0);
}
Functions: checkStatus, checkShaderStatus, checkProgramStatus, readShaderCode, installShaders should be all fine.
void keyboard() can be ignored since I havent implemented it yet(just for keyboard control).
I implemented the object "Ground" in sendDataToOpenGL(). But when I compiled and ran the program, "thread 1: exc_bad_access (code =1, address=0x0)" occured in the line of VAO:
And the pop-out window is just a white screen instead of a green grass(3d).
I have tried a method which was provided in other stackoverflow post: using glewExperimental = GL_TRUE;. I didnt see any errors by using that, but the popout screen vanished immediately just after it appeared. It seems that it couldnt help the problem.
Can someone give me a help? Thank you!
回答1:
glGenVertexArrays is available in since OpenGL version 3.0. If vertex array objects are supported can be checked by glewGetExtension("GL_ARB_vertex_array_object").
Glew can enable additional extensions by glewExperimental = GL_TRUE;. See the GLEW documantation which says:
GLEW obtains information on the supported extensions from the graphics driver. Experimental or pre-release drivers, however, might not report every available extension through the standard mechanism, in which case GLEW will report it unsupported. To circumvent this situation, the
glewExperimentalglobal switch can be turned on by setting it toGL_TRUEbefore callingglewInit(), which ensures that all extensions with valid entry points will be exposed.
Add this to your code:
glewExperimental = GL_TRUE;
glewInit();
来源：https://stackoverflow.com/questions/46376020/opengl-glgenvertexarrays-thread-1-exc-bad-access-code-1-address-0x0