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通过去掉 ComputePositonOffsets() 和 AdjustVertexData() 方法，我可以显示一个三角形，但我添加了一些按钮功能来旋转它以查看屏幕中是否还有更多其他地方，我不知道为什么它生成黑屏。

#include <algorithm>
#include <string>
#include <vector>
#include <stdio.h>
#include <glload/gl_3_2_comp.h>
#include <GL/freeglut.h>

#define ARRAY_COUNT( array ) (sizeof( array ) / (sizeof( array[0] ) * (sizeof( array ) != sizeof(void*) || sizeof( array[0] ) <= sizeof(void*))))
double rotate_y = 0;
double rotate_x = 0;

GLuint CreateShader(GLenum eShaderType, const std::string &strShaderFile) {
    GLuint shader = glCreateShader(eShaderType);
    const char *strFileData = strShaderFile.c_str();
    glShaderSource(shader, 1, &strFileData, NULL);

    glCompileShader(shader);

    GLint status;
    glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
    if (status == GL_FALSE) {
        GLint infoLogLength;
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLogLength);

        GLchar *strInfoLog = new GLchar[infoLogLength + 1];
        glGetShaderInfoLog(shader, infoLogLength, NULL, strInfoLog);

        const char *strShaderType = NULL;
        switch (eShaderType) {
        case GL_VERTEX_SHADER:
            strShaderType = "vertex";
            break;
        case GL_GEOMETRY_SHADER:
            strShaderType = "geometry";
            break;
        case GL_FRAGMENT_SHADER:
            strShaderType = "fragment";
            break;
        }

        fprintf(stderr, "Compile failure in %s shader:\n%s\n", strShaderType,strInfoLog);
        delete[] strInfoLog;
    }

    return shader;
}

GLuint CreateProgram(const std::vector<GLuint> &shaderList) {
    GLuint program = glCreateProgram();

    for (size_t iLoop = 0; iLoop < shaderList.size(); iLoop++)
        glAttachShader(program, shaderList[iLoop]);

    glLinkProgram(program);

    GLint status;
    glGetProgramiv(program, GL_LINK_STATUS, &status);
    if (status == GL_FALSE) {
        GLint infoLogLength;
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLogLength);

        GLchar *strInfoLog = new GLchar[infoLogLength + 1];
        glGetProgramInfoLog(program, infoLogLength, NULL, strInfoLog);
        fprintf(stderr, "Linker failure: %s\n", strInfoLog);
        delete[] strInfoLog;
    }

    for (size_t iLoop = 0; iLoop < shaderList.size(); iLoop++)
        glDetachShader(program, shaderList[iLoop]);

    return program;
}

GLuint theProgram;

const std::string strVertexShader("#version 330\n"
        "layout(location = 0) in vec4 position;\n"
        "void main()\n"
        "{\n"
        "   gl_Position = position;\n"
        "}\n");

const std::string strFragmentShader("#version 330\n"
        "out vec4 outputColor;\n"
        "void main()\n"
        "{\n"
        "   outputColor = vec4(1.0f, 1.0f, 1.0f, 1.0f);\n"
        "}\n");

void InitializeProgram() {
    std::vector<GLuint> shaderList;

    shaderList.push_back(CreateShader(GL_VERTEX_SHADER, strVertexShader));
    shaderList.push_back(CreateShader(GL_FRAGMENT_SHADER, strFragmentShader));

    theProgram = CreateProgram(shaderList);

    std::for_each(shaderList.begin(), shaderList.end(), glDeleteShader);
}

const float vertexPositions2[] = { 0.5, 0.5, 0.5, -0.5, 0.5, 0.5, -0.5, -0.5,
        0.5, 0.5, -0.5, 0.5, 0.5, 0.5, 0.5, 0.5, -0.5, 0.5, 0.5, 0.5, 0.5, 0.5,
        0.5, -0.5, -0.5, 0.5, -0.5, -0.5, 0.5, 0.5, -0.5, 0.5, 0.5, -0.5, 0.5,
        -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, 0.5, -0.5, -0.5, -0.5, 0.5, -0.5,
        -0.5, 0.5, -0.5, 0.5, -0.5, -0.5, 0.5, 0.5, -0.5, -0.5, -0.5, -0.5,
        -0.5, -0.5, 0.5, -0.5, 0.5, 0.5, -0.5 };

GLuint positionBufferObject;
GLuint vao;

void InitializeVertexBuffer() {
    glGenBuffers(1, &positionBufferObject);

    glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions2), vertexPositions2,
            GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

//Called after the window and OpenGL are initialized. Called exactly once, before the main loop.
void init() {
    InitializeProgram();
    InitializeVertexBuffer();

    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);
}

void ComputePositionOffsets(float &fXOffset, float &fYOffset) {
    const float fLoopDuration = 5.0f;
    const float fScale = 3.14159f * 2.0f / fLoopDuration;

    float fElapsedTime = glutGet(GLUT_ELAPSED_TIME) / 1000.0f;

    float fCurrTimeThroughLoop = fmodf(fElapsedTime, fLoopDuration);

    fXOffset = cosf(fCurrTimeThroughLoop * fScale) * 0.5f;
    fYOffset = sinf(fCurrTimeThroughLoop * fScale) * 0.5f;
}

void AdjustVertexData(float fXOffset, float fYOffset) {

    std::vector<float> fNewData(ARRAY_COUNT(vertexPositions2));
    memcpy(&fNewData[0], vertexPositions2, sizeof(vertexPositions2));

    for (int iVertex = 0; iVertex < ARRAY_COUNT(vertexPositions2); iVertex +=
            4) {
        fNewData[iVertex] += fXOffset;
        fNewData[iVertex + 1] += fYOffset;
    }

    glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
    glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertexPositions2), &fNewData[0]);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

}

//Called to update the display.
//You should call glutSwapBuffers after all of your rendering to display what you rendered.
//If you need continuous updates of the screen, call glutPostRedisplay() at the end of  the function.
void display() {
    glUseProgram(theProgram);
    float fXOffset = 0.0f, fYOffset = 0.0f;
    ComputePositionOffsets(fXOffset, fYOffset);
    AdjustVertexData(fXOffset, fYOffset);
    //glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();

    glRotatef(rotate_x, 1.0, 0.0, 0.0);
    glRotatef(rotate_y, 0.0, 1.0, 0.0);

    glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);

    GLubyte indices[] = { 0, 1, 2, 2, 3, 0, 4, 5, 6, 6, 7, 4, 8, 9, 10, 10, 11,
            8, 12, 13, 14, 14, 15, 12, 16, 17, 18, 18, 19, 16, 20, 21, 22, 22,
            23, 20 };    // back

    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_BYTE, indices);

    glDisableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    glFlush();
    glUseProgram(0);
    glutSwapBuffers();
}

//Called whenever the window is resized. The new window size is given, in pixels.
//This is an opportunity to call glViewport or glScissor to keep up with the change in size.
void reshape(int w, int h) {
    glViewport(0, 0, (GLsizei) w, (GLsizei) h);
}

//Called whenever a key on the keyboard was pressed.
//The key is given by the ''key'' parameter, which is in ASCII.
//It's often a good idea to have the escape key (ASCII value 27) call glutLeaveMainLoop() to 
//exit the program.
void keyboard(unsigned char key, int x, int y) {
    switch (key) {
    case 27:
        glutLeaveMainLoop();
        return;
    }

    //  Right arrow - increase rotation by 5 degree
    if (key == GLUT_KEY_RIGHT) rotate_y += 5;
    //  Left arrow - decrease rotation by 5 degree
    else if (key == GLUT_KEY_LEFT) rotate_y -= 5;
    else if (key == GLUT_KEY_UP) rotate_x += 5;
    else if (key == GLUT_KEY_DOWN) rotate_x -= 5;

    //  Request display update
    glutPostRedisplay();
}

unsigned int defaults(unsigned int displayMode, int &width, int &height) {
    return displayMode;
}
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1 回答 1

2 
const float vertexPositions2[] = {0.5,0.5,0.5,-0.5,0.5,0.5,-0.5,-0.5,0.5,0.5,-0.5,0.5,0.5,0.5,0.5,0.5,-0.5,0.5,0.5,0.5,0.5,0.5,0.5,-0.5,-0.5,0.5,-0.5,-0.5,0.5,0.5,-0.5,0.5,0.5,-0.5,0.5,-0.5,-0.5,-0.5,-0.5,-0.5,-0.5,0.5,-0.5,-0.5,-0.5,0.5,-0.5,-0.5,0.5,-0.5,0.5,-0.5,-0.5,0.5,0.5,-0.5,-0.5,-0.5,-0.5,-0.5,-0.5,0.5,-0.5,0.5,0.5,-0.5};

我猜这是组成一个立方体的 3D 向量列表，因为在您的代码下方使用了 24 个（6 个面 * 4 个角）索引，并且所有值都是 0.5 或 -0.5。但是，您告诉 OpenGL 这是一个包含 4 个分量而不是 3 个分量的向量列表：

glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);

将第二个参数设置为 4 是很不寻常的。如果将其设置为 3，OpenGL 会w为您填充组件为 1。试试看。我想如果你这样做，你会看到一个正方形。

最重要的是，我在任何地方都看不到透视投影矩阵。如果您没有，您将获得 2D 投影而不是 3D 投影。事情不会按照你想要的方式出现。在实施旋转和四处移动之前，您需要了解它。

下面的这些行对您的程序没有影响，它们不属于现代图形程序。他们更改了固定函数矩阵堆栈中的矩阵，您不会（我认为不能，因为您使用的是 GLSL 330）在着色器中使用这些矩阵。您必须自己将矩阵定义为统一变量。

glLoadIdentity();

glRotatef(rotate_x, 1.0, 0.0, 0.0);
glRotatef(rotate_y, 0.0, 1.0, 0.0);
于 2012-11-06T21:57:39.223 回答