多个过剩窗口，但显示功能相同

Question

我试图在两个窗口中渲染模型。但它只在一个窗口中呈现。是否可以在具有不同回调函数的两个窗口中呈现？

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <GL/glew.h>
#include <GL/freeglut.h>
#define WINDOW_TITLE_PREFIX "Chapter 2"

int CurrentWidth = 800,
    CurrentHeight = 600,
    WindowHandle = 0;

unsigned FrameCount = 0;

GLuint
    VertexShaderId,
    FragmentShaderId,
    ProgramId,
    VaoId,
    VboId,
    ColorBufferId;

const GLchar* VertexShader =
{
    "#version 400\n"\

    "layout(location=0) in vec4 in_Position;\n"\
    "layout(location=1) in vec4 in_Color;\n"\
    "out vec4 ex_Color;\n"\

    "void main(void)\n"\
    "{\n"\
    "   gl_Position = in_Position;\n"\
    "   ex_Color = in_Color;\n"\
    "}\n"
};

const GLchar* FragmentShader =
{
    "#version 400\n"\

    "in vec4 ex_Color;\n"\
    "out vec4 out_Color;\n"\

    "void main(void)\n"\
    "{\n"\
    "   out_Color = ex_Color;\n"\
    "}\n"
};

void Initialize(int, char*[]);
void InitWindow(int, char*[]);
void ResizeFunction(int, int);
void ResizeFunction1(int, int);
void RenderFunction(void);
void RenderFunction1(void);
void TimerFunction(int);
void TimerFunction1(int);
void IdleFunction(void);
void IdleFunction1(void);
void Cleanup(void);
void CreateVBO(void);
void DestroyVBO(void);
void CreateShaders(void);
void DestroyShaders(void);

int Wh1;

int main(int argc, char* argv[])
{
    Initialize(argc, argv);

    glutMainLoop();

    exit(EXIT_SUCCESS);
}

void Initialize(int argc, char* argv[])
{
    GLenum GlewInitResult;

    InitWindow(argc, argv);

    glewExperimental = GL_TRUE;
    GlewInitResult = glewInit();

    if (GLEW_OK != GlewInitResult) {
        fprintf(
            stderr,
            "ERROR: %s\n",
            glewGetErrorString(GlewInitResult)
        );
        exit(EXIT_FAILURE);
    }

    fprintf(
        stdout,
        "INFO: OpenGL Version: %s\n",
        glGetString(GL_VERSION)
    );

    CreateShaders();
    CreateVBO();

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
}

void InitWindow(int argc, char* argv[])
{
    glutInit(&argc, argv);

    glutInitContextVersion(4, 0);
    glutInitContextFlags(GLUT_FORWARD_COMPATIBLE);
    glutInitContextProfile(GLUT_CORE_PROFILE);

    glutSetOption(
        GLUT_ACTION_ON_WINDOW_CLOSE,
        GLUT_ACTION_GLUTMAINLOOP_RETURNS
    );

    glutInitWindowSize(CurrentWidth, CurrentHeight);

    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);

    WindowHandle = glutCreateWindow(WINDOW_TITLE_PREFIX);
    std::cout<<WindowHandle<<std::endl;
    if(WindowHandle < 1) {
        fprintf(
            stderr,
            "ERROR: Could not create a new rendering window.\n"
        );
        exit(EXIT_FAILURE);
    }
    glutSetWindow(WindowHandle);
    glutReshapeFunc(ResizeFunction);
    glutDisplayFunc(RenderFunction);
    glutTimerFunc(0, TimerFunction, 0);
    glutCloseFunc(Cleanup);
#if 1
    Wh1 = glutCreateWindow("sasd"); 
//  std::cout<<i<<"s"<<std::endl;
    glutReshapeFunc(ResizeFunction1);
    glutDisplayFunc(RenderFunction1);
    glutTimerFunc(0, TimerFunction1, 0);
    glutCloseFunc(Cleanup);
    glutSetWindow(Wh1);
#endif

}

void ResizeFunction(int Width, int Height)
{
    CurrentWidth = Width;
    CurrentHeight = Height;
    glViewport(0, 0, CurrentWidth, CurrentHeight);
}


void ResizeFunction1(int Width, int Height)
{
    CurrentWidth = Width;
    CurrentHeight = Height;
    glViewport(0, 0, CurrentWidth, CurrentHeight);
}

void RenderFunction(void)
{
    ++FrameCount;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glDrawArrays(GL_TRIANGLES, 0, 3);

    glutSwapBuffers();
    glutSetWindow(WindowHandle);
    glutPostRedisplay();
    glutSetWindow(Wh1);
    glutPostRedisplay();
}

void RenderFunction1(void)
{
    ++FrameCount;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glDrawArrays(GL_TRIANGLES, 0, 3);

    glutSwapBuffers();

    glutSetWindow(WindowHandle);
    glutPostRedisplay();
    glutSetWindow(Wh1);
    glutPostRedisplay();
}

void IdleFunction(void)
{
    glutSetWindow(WindowHandle);
    glutPostRedisplay();
    glutSetWindow(Wh1);
    glutPostRedisplay();
}

void IdleFunction1(void)
{
    glutSetWindow(WindowHandle);
    glutPostRedisplay();
    glutSetWindow(Wh1);
    glutPostRedisplay();
}
void TimerFunction(int Value)
{
    if (0 != Value) {
        char* TempString = (char*)
            malloc(512 + strlen(WINDOW_TITLE_PREFIX));

        sprintf(
            TempString,
            "%s: %d Frames Per Second @ %d x %d",
            WINDOW_TITLE_PREFIX,
            FrameCount * 4,
            CurrentWidth,
            CurrentHeight
        );

        //glutSetWindowTitle(TempString);
        free(TempString);
    }

    FrameCount = 0;
    glutTimerFunc(250, TimerFunction, 1);
}
void TimerFunction1(int Value)
{
    if (0 != Value) {
        char* TempString = (char*)
            malloc(512 + strlen(WINDOW_TITLE_PREFIX));

        sprintf(
            TempString,
            "%s: %d Frames Per Second @ %d x %d",
            WINDOW_TITLE_PREFIX,
            FrameCount * 4,
            CurrentWidth,
            CurrentHeight
        );

        //glutSetWindowTitle(TempString);
        free(TempString);
    }

    FrameCount = 0;
    glutTimerFunc(250, TimerFunction, 1);
}

void Cleanup(void)
{
    DestroyShaders();
    DestroyVBO();
}

void CreateVBO(void)
{
    GLfloat Vertices[] = {
        -0.8f, -0.8f, 0.0f, 1.0f,
         0.0f,  0.8f, 0.0f, 1.0f,
         0.8f, -0.8f, 0.0f, 1.0f
    };

    GLfloat Colors[] = {
        1.0f, 0.0f, 0.0f, 1.0f,
        0.0f, 1.0f, 0.0f, 1.0f,
        0.0f, 0.0f, 1.0f, 1.0f
    };

    GLenum ErrorCheckValue = glGetError();

    glGenVertexArrays(1, &VaoId);
    glBindVertexArray(VaoId);

    glGenBuffers(1, &VboId);
    glBindBuffer(GL_ARRAY_BUFFER, VboId);
    glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
    glEnableVertexAttribArray(0);

    glGenBuffers(1, &ColorBufferId);
    glBindBuffer(GL_ARRAY_BUFFER, ColorBufferId);
    glBufferData(GL_ARRAY_BUFFER, sizeof(Colors), Colors, GL_STATIC_DRAW);
    glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, 0);
    glEnableVertexAttribArray(1);

    ErrorCheckValue = glGetError();
    if (ErrorCheckValue != GL_NO_ERROR)
    {
        fprintf(
            stderr,
            "ERROR: Could not create a VBO: %s \n",
            gluErrorString(ErrorCheckValue)
        );

        exit(-1);
    }
}

void DestroyVBO(void)
{
    GLenum ErrorCheckValue = glGetError();

    glDisableVertexAttribArray(1);
    glDisableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);

    glDeleteBuffers(1, &ColorBufferId);
    glDeleteBuffers(1, &VboId);

    glBindVertexArray(0);
    glDeleteVertexArrays(1, &VaoId);

    ErrorCheckValue = glGetError();
    if (ErrorCheckValue != GL_NO_ERROR)
    {
        fprintf(
            stderr,
            "ERROR: Could not destroy the VBO: %s \n",
            gluErrorString(ErrorCheckValue)
        );

        exit(-1);
    }
}

void CreateShaders(void)
{
    GLenum ErrorCheckValue = glGetError();

    VertexShaderId = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(VertexShaderId, 1, &VertexShader, NULL);
    glCompileShader(VertexShaderId);

    FragmentShaderId = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(FragmentShaderId, 1, &FragmentShader, NULL);
    glCompileShader(FragmentShaderId);

    ProgramId = glCreateProgram();
        glAttachShader(ProgramId, VertexShaderId);
        glAttachShader(ProgramId, FragmentShaderId);
    glLinkProgram(ProgramId);
    glUseProgram(ProgramId);

    ErrorCheckValue = glGetError();
    if (ErrorCheckValue != GL_NO_ERROR)
    {
        fprintf(
            stderr,
            "ERROR: Could not create the shaders: %s \n",
            gluErrorString(ErrorCheckValue)
        );

        exit(-1);
    }
}

void DestroyShaders(void)
{
    GLenum ErrorCheckValue = glGetError();

    glUseProgram(0);

    glDetachShader(ProgramId, VertexShaderId);
    glDetachShader(ProgramId, FragmentShaderId);

    glDeleteShader(FragmentShaderId);
    glDeleteShader(VertexShaderId);

    glDeleteProgram(ProgramId);

    ErrorCheckValue = glGetError();
    if (ErrorCheckValue != GL_NO_ERROR)
    {
        fprintf(
            stderr,
            "ERROR: Could not destroy the shaders: %s \n",
            gluErrorString(ErrorCheckValue)
        );

        exit(-1);
    }
}

Answer 1

glutDisplayFunc以及所有其他回调，在调用函数时为任何窗口设置回调。因此，如果您要为特定窗口设置显示回调，请在致电glutDisplayFunc后致电glutSetWindow。

  

我找出了gldrawArrays创建新vbo重绘所需的问题。我不知道为什么。

这是因为每个窗口代表一个单独的 OpenGL上下文。除非您明确地共享对象（通过特定于平台的调用），否则每个上下文都将拥有自己的独立对象。您不能使用彼此创建的缓冲区，而无需显式共享（在新上下文中创建对象之前这样做）。

Answer 2

Opengl函数不是线程安全的。因此，多个窗口中的gldrawArrays可能在两个线程中运行。所以他们的行为是不明确的。