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我正在尝试使用 OpenGL 渲染纹理。我用作测试的纹理是一堆白色背景上的黑色矩形，如下所示：

白色背景上的一些黑色矩形

但是，在渲染时，纹理似乎在其自身之上多次复制和叠加：

具有扭曲版本纹理的渲染帧

我使用以下方法设置场景：

std::string vertexSource = ShaderLoader::load("vertexSource.vert");
const char* vsource = vertexSource.c_str();
std::string fragmentSource = ShaderLoader::load("fragmentSource.frag");
const char* fsource = fragmentSource.c_str();

int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vsource, NULL);
glCompileShader(vertexShader);
int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fsource, NULL);
glCompileShader(fragmentShader);
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);

float vertices[] = {
            0.5f,  0.5f, 0.0f,
            0.5f, -0.5f, 0.0f,
            -0.5f, -0.5f, 0.0f,
            -0.5f,  0.5f, 0.0f,
            1.0f, 1.0f,
            1.0f, 0.0f,
            0.0f, 0.0f,
            0.0f, 1.0f,
};
unsigned int indices[] = {
            0, 1, 3,
            1, 2, 3
};

glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glGenBuffers(1, &EBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1,2,GL_FLOAT, GL_FALSE, 2* sizeof(float), (void*)(sizeof(float)*12));
glEnableVertexAttribArray(1);

glBindBuffer(GL_ARRAY_BUFFER, 0);

glBindVertexArray(0);

unsigned char* data = stbi_load("image.png", &width, &height,&nrOfChannels, 0);
glGenTextures(1, &textureId);
glBindTexture(GL_TEXTURE_2D, textureId);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
glGenerateMipmap(GL_TEXTURE_2D);
stbi_image_free((void *) data);

我的渲染代码是：

glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glBindTexture(GL_TEXTURE_2D, textureId);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

我的顶点着色器是：

#version 330 core
layout (location = 0) in vec3 inVertex;
layout (location = 1) in vec2 inTexture;

out vec2 TextureCoordinate;

void main()
{
    gl_Position = vec4( inVertex, 1 );
    TextureCoordinate = inTexture;
}

我的片段着色器是：

#version 330 core
out vec4 FragColor;

in vec2 TextureCoordinate;

uniform sampler2D Texture;

void main() {
    FragColor = texture(Texture,TextureCoordinate);
}
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1 回答 1

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当一个具有 3 个通道 ( GL_RGB) 的图像加载到纹理对象时，GL_UNPACK_ALIGNMENT需要设置为 1。默认GL_UNPACK_ALIGNMENT为 4，因此假设图像的每一行对齐为 4 个字节。缓冲区中的像素大小为 3 个字节并且被紧密打包，这会导致错位。

glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
glPixelStorei(GL_UNPACK_ALIGNMENT, 4); // default

由于图像格式为 PNG，因此图像很可能有 4 个通道（GL_RGBA）。nrOfChannels在指定纹理图像之前进行评估：

unsigned char* data = stbi_load("image.png", &width, &height, &nrOfChannels, 0);
// [...]

unsigned int format = nrOfChannels == 4 ? GL_RGBA : GL_RGB; 
glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);

也可以stbi_load通过显式将 4 传递给最后一个参数来强制生成具有 4 个通道的图像：

int reqChannels= 4; 
unsigned char* data = stbi_load("image.png", &width, &height, &nrOfChannels, reqChannels);
// [...]

glTexImage2D(GL_TEXTURE_2D, GL_RGBA, format, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
于 2021-01-17T09:43:57.623 回答