OpenGL/C++：将多个纹理传递给一个着色器时出现问题

Question

我按照 https://learnopengl.com/Lighting/Lighting-maps 上的教程进行操作，但在使用多个纹理（一个用于镜面反射，一个用于漫反射照明）时遇到了一些奇怪的错误。当只使用一个纹理时一切正常，但在使用两个纹理后，立方体要么只渲染黑色，要么只应用镜面反射纹理。

我在 Whosebug 上搜索了所有类似的问题并通读了 OpenGL 文档，但仍然无法弄清楚为什么第二个纹理不起作用。

这是我的 main.cpp 的渲染循环部分，它创建了应该用两个纹理渲染的立方体。着色器和纹理都可以正常加载和编译。

// Load textures
    Texture groundTexture = Texture("GROUND", TEXTURE_DIR+"png/container2.png");
    Texture groundSpecular = Texture("SPECULAR", TEXTURE_DIR+"png/container2_specular.png");

    // Load shaders
    Shader textureShader = Shader("SIMPLE_TEXTURE", SHADER_DIR+"vertex/texture_lighted.vs", SHADER_DIR+"fragment/texture_lighted.fs");
    Shader lampShader = Shader("WHITE", SHADER_DIR+"vertex/basic.vs", SHADER_DIR+"fragment/white.fs");

    // projection matrix
    glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);

    // shader configuration
    // --------------------
    textureShader.use();
    // Get the uniform variables location.
    GLuint diffLocation = glGetUniformLocation(textureShader.ID, "material.diffuse");
    GLuint specLocation  = glGetUniformLocation(textureShader.ID, "material.specular");

另一个奇怪的事情是，如果我将 0 和 1 更改为 groundTexture.ID 和 groundSpecular.ID，至少镜面反射部分会渲染，即使 glUniform1i 期望这里的单位编号而不是纹理- ID。

    // Then bind the uniform samplers to texture units:
    glUseProgram(textureShader.ID);
    glUniform1i(diffLocation, 0);
    glUniform1i(specLocation, 1);


    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        // Calc time
        float currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;

        // input
        // -----
        processInput(window);

        // render
        // ------
        glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // be sure to activate shader when setting uniforms/drawing objects
        textureShader.use();
        textureShader.setVec3("light.position", lightPos);
        textureShader.setVec3("viewPos", camera.Position);
        // light properties
        textureShader.setVec3("light.ambient", 0.2f, 0.2f, 0.2f);
        textureShader.setVec3("light.diffuse", 0.5f, 0.5f, 0.5f);
        textureShader.setVec3("light.specular", 1.0f, 1.0f, 1.0f);
        // material properties
        textureShader.setFloat("material.shininess", 64.0f);

        // view/projection transformations
        glm::mat4 view = camera.getViewMatrix();
        textureShader.setMat4("projection", projection);
        textureShader.setMat4("view", view);

        // world transformation
        glm::mat4 model = glm::mat4(1.0f);
        textureShader.setMat4("model", model);

        // bind texture-maps
        glActiveTexture(GL_TEXTURE0 + 0); // Texture unit 0
        glBindTexture(GL_TEXTURE_2D, groundTexture.ID);
        glActiveTexture(GL_TEXTURE0 + 1); // Texture unit 1
        glBindTexture(GL_TEXTURE_2D, groundSpecular.ID);
        glActiveTexture(GL_TEXTURE0 + 0); // Texture unit 0

        // render the cube
        glBindVertexArray(VAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);

为了完整起见，这也是我的着色器-class 和纹理-class:

#include "shader.h"
#include <stdlib.h>
#include <string.h>
#include <glad/glad.h>
#include <iostream>
#include <glm/ext.hpp>
#include <fstream>
#include <sstream>

/*
 * Creates a new Shader.
 * name = name of the shader
 * vShader = vertex shader
 * fShader = fragment shader
 */
Shader::Shader(std::string name, std::string vShaderPath, std::string fShaderPath) {
    this->name = name;
    this->vShaderPath = vShaderPath;
    this->fShaderPath = fShaderPath;
    compileAndLink();
}

Shader::Shader(const Shader& s) {
    this->name = s.name;
    this->vShaderPath = s.vShaderPath;
    this->fShaderPath = s.fShaderPath;
    compileAndLink();
}

void Shader::compileAndLink() {

    std::string vShader, fShader;
    std::ifstream v_inFile, f_inFile;
    std::stringstream v_strStream, f_strStream;

    // Read File for vertexShader
    v_inFile.open(vShaderPath);
    if (!v_inFile.is_open()) {
        std::cout << "ERROR LOADING VERTEX SHADER FILE: " << vShaderPath << std::endl;
    } else {
        v_strStream << v_inFile.rdbuf();
        vShader = v_strStream.str();
    }

    // Read File for fragmentShader
    f_inFile.open(fShaderPath);
    if (!f_inFile.is_open()) {
        std::cout << "ERROR LOADING FRAGMENT SHADER FILE: " << fShaderPath << std::endl;
    } else {
        f_strStream << f_inFile.rdbuf();
        fShader = f_strStream.str();
    }

    // Compile and link
    const char* vertex_shader = vShader.c_str();
    const char* fragment_shader = fShader.c_str();

    // vertex shader
    int vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertex_shader, NULL);
    glCompileShader(vertexShader);
    // check for shader compile errors
    int success;
    char infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    // fragment shader
    int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragment_shader, NULL);
    glCompileShader(fragmentShader);
    // check for shader compile errors
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    // store reference in ID
    ID = glCreateProgram();

    // link shaders
    glAttachShader(ID, vertexShader);
    glAttachShader(ID, fragmentShader);
    glLinkProgram(ID);

    // check for linking errors
    glGetProgramiv(ID, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(ID, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }

    // clean up
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

}

/*
 * Tell OpenGL to use this shader-program.
 */
void Shader::use() {
    glUseProgram(ID);
}

和

#include <glad/glad.h>
#include <iostream>
#define STB_IMAGE_IMPLEMENTATION
#include "../image-loader/stb_image.h"
#include "texture.h"

Texture::Texture(std::string name, std::string path) {
    this->name = name;
    this->path = path;
    createTexture();
}

Texture::Texture(const Texture& t) {
    this->name = t.name;
    this->path = t.path;
    createTexture();
}

void Texture::createTexture() {
    unsigned int texture;
    glGenTextures(1, &texture); // generate one texture

    // Load file
    int width, height, nrChannels;
    unsigned char *data = stbi_load(this->path.c_str(), &width, &height, &nrChannels, 0);

    if (data) {
        GLenum format;
        if (nrChannels == 1)
            format = GL_RED;
        else if (nrChannels == 3)
            format = GL_RGB;
        else if (nrChannels == 4)
            format = GL_RGBA;

        glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);

        // Set Texture Parameters
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); // x
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); // y
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        stbi_image_free(data); // clean up

    } else {
        std::cout << "Failed to load texture" << std::endl;
    }

    this->ID = texture;
}

void Texture::use() {
    glBindTexture(GL_TEXTURE_2D, this->ID);
}

我正在使用 OpenGL 4.4，初始化如下，很高兴加载 OpenGL 函数指针。

glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 4);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

提前致谢。

编辑：这是两个着色器（显然很重要）： texture_lighted.vs（顶点着色器）

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;

out vec3 FragPos;
out vec3 Normal;
out vec2 TexCoords;

void main()
{
    gl_Position = projection * view * model * vec4(aPos, 1.0);
    FragPos = vec3(model * vec4(aPos, 1.0));
    TexCoords = aTexCoords;
    // transpose normal vectors with normal matrix of model matrix
    Normal = mat3(transpose(inverse(model))) * aNormal;
}

和texture_lighted.fs（片段着色器）

#version 330 core
out vec4 FragColor;

struct Material {
    sampler2D diffuse;
    sampler2D specular;
    float shininess;
};

struct Light {
    vec3 position;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};

in vec3 FragPos;
in vec3 Normal;
in vec2 TexCoords;

uniform vec3 viewPos;
uniform Material material;
uniform Light light;

void main()
{
    // ambient
    vec3 ambient = light.ambient * texture(material.diffuse, TexCoords).rgb;

    // diffuse
    vec3 norm = normalize(Normal);
    vec3 lightDir = normalize(light.position - FragPos);
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = light.diffuse * diff * texture(material.diffuse, TexCoords).rgb;

    // specular
    vec3 viewDir = normalize(viewPos - FragPos);
    vec3 reflectDir = reflect(-lightDir, norm);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);
    vec3 specular = light.specular * spec * texture(material.specular, TexCoords).rgb;

    vec3 result = ambient + diffuse + specular;
    FragColor = vec4(result, 1.0);
}

Answer 1

贴图的名称（值）由glGenTexture, the named texture has to be bound to a texturing target by glBindTexture, before the texture image is specified by glTexImage2D生成后。
glTexImage2D为当前绑定到指定目标的纹理定义纹理图像：

glGenTextures(1, &texture); 

// [...]

glBindTexture(GL_TEXTURE_2D, texture); 
glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);

OpenGL/C++：将多个纹理传递给一个着色器时出现问题

OpenGL/C++: Problem passing multiple textures to one shader

opengl

shader

glsl

glfw

glad