Question

我正在尝试使用Qt5和glew在openGL中渲染纹理四边形。特别是我使用的是QopenGLWidget。

我正在使用的代码是从https://open.gl/textures修改的主要变化是使用三角形条而不是元素缓冲区并使用我自己的像素阵列而不是加载图像。

我已经测试过更改，他们使用glfw3工作。

在Qt中我只能看到一个没有颜色的黑色四边形。这只发生在我尝试使用纹理时，如果我删除着色器的纹理部分，它会渲染颜色。

我的着色器编译正常，没有错误（尽管下面的代码中没有错误检查）。

texture(tex, Texcoord)

只是输出零。

所以我的问题是，为什么它只渲染一个黑色四边形？

GLfloat tmpdata[] = {
//pos               //colour            //texCoord
-0.5f, 0.5f,        1.0f, 0.0f, 0.0f,   0.0f, 0.0f, // Top-left
0.5f, 0.5f,         0.0f, 1.0f, 0.0f,   1.0f, 0.0f, // Top-right
-0.5f, -0.5f,       1.0f, 1.0f, 1.0f,   0.0f, 1.0f,  // Bottom-left
0.5f, -0.5f,        0.0f, 0.0f, 1.0f,   1.0f, 1.0f // Bottom-right
};

GLRenderer::GLRenderer(QWidget *parent)
    :
    QOpenGLWidget(parent)
{
// Shader sources
VertSource =
    "#version 150 core\n"
    "in vec2 position;"
    "in vec3 color;"
    "in vec2 texcoord;"
    "out vec3 Color;"
    "out vec2 Texcoord;"
    "void main() {"
    "   Color = color;"
    "   Texcoord = texcoord;"
    "   gl_Position = vec4(position, 0.0, 1.0);"
    "}";
FragSource =
    "#version 150 core\n"
    "in vec3 Color;"
    "in vec2 Texcoord;"
    "out vec4 outColor;"
    "uniform sampler2D tex;"
    "void main() {"
    "   outColor = texture(tex, Texcoord) * vec4(Color, 1.0);"
    // "   outColor = vec4(Color, 1.0);"
    //"   outColor = texture(tex, Texcoord);"
     "}";
}

GLRenderer::~GLRenderer()
{
    glDeleteProgram(shaderProgram);
    glDeleteShader(fragmentShader);
    glDeleteShader(vertexShader);
    glDeleteBuffers(1, &vbo);
    glDeleteVertexArrays(1, &vao);
}

void GLRenderer::initializeGL()
{
glewExperimental = GL_TRUE;
GLenum err = glewInit();
if (err != GLEW_OK)
{
    printf("%s", glewGetErrorString(err));
}

// Create Vertex Array Object
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

// Create a Vertex Buffer Object and copy the vertex data to it
GLuint vbo;
glGenBuffers(1, &vbo);

glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(tmpdata), tmpdata, GL_STATIC_DRAW);

// Create and compile the vertex shader
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &VertSource, NULL);
glCompileShader(vertexShader);

// Create and compile the fragment shader
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &FragSource, NULL);
glCompileShader(fragmentShader);


// Link the vertex and fragment shader into a shader program
GLuint shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glBindFragDataLocation(shaderProgram, 0, "outColor");
glLinkProgram(shaderProgram);
glUseProgram(shaderProgram);

// Specify the layout of the vertex data
GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
glEnableVertexAttribArray(posAttrib);
glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 7 * sizeof(GLfloat), 0);

GLint colAttrib = glGetAttribLocation(shaderProgram, "color");
glEnableVertexAttribArray(colAttrib);
glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(GLfloat), (void*)(2 * sizeof(GLfloat)));

GLint texAttrib = glGetAttribLocation(shaderProgram, "texcoord");
glEnableVertexAttribArray(texAttrib);
glVertexAttribPointer(texAttrib, 2, GL_FLOAT, GL_FALSE, 7 * sizeof(GLfloat), (void*)(5 * sizeof(GLfloat)));

// Load texture
GLuint tex;
glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);

// Black/white checkerboard
float pixels[] = {
    1.0f, 0.0f, 1.0f, 1.0f, 1.0f, 1.0f,
    0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.0f
};
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0, GL_RGB, GL_FLOAT, pixels);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
}

void GLRenderer::paintGL()
{
    // Clear the screen to black
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}

使用Qt5和glew在openGL中渲染纹理

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