光源设置不正确

Posted 2023-02-22

【中文标题】光源设置不正确

【英文标题】：light source is not set correctly

【发布时间】：2021-04-06 17:35:01

【问题描述】：

我有这段代码，但灯光似乎无法正常工作，当我渲染对象时它是黑暗的，然后当我旋转它时，光源似乎也旋转了。我无法弄清楚问题出在哪里。我尝试修改灯光的模型，但仍然无法正常工作

这是程序：

while (!glfwWindowShouldClose(window))
    

        /* Render here */
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
        glm::mat4 view = glm::mat4(1.0f); 
        glm::mat4 projection = glm::mat4(1.0f);
        projection = glm::perspective(glm::radians(45.0f), (float)width / (float)heigh, 0.1f, 100.0f);

        view = glm::translate(view, glm::vec3(0.0f, 0.0f, transZ)); //this is for scroll mouse
        view = glm::translate(view, glm::vec3(0.0f, 0.0f, -2.0f));
        view = glm::translate(view, glm::vec3(0.0f, 0.0f, -5.0f));
                
        glUseProgram(programT);
        int lightColorLoc = glGetUniformLocation(programT, "lightColor");
        glUniformMatrix4fv(lightColorLoc, 1, GL_FALSE, glm::value_ptr(glm::vec3(1.0f, 0.0f, 0.0f)));

        int objectColorLoc = glGetUniformLocation(programT, "objectColor");
        glUniformMatrix4fv(objectColorLoc, 1, GL_FALSE, glm::value_ptr(glm::vec3(1.0f, 0.5f, 0.31f)));

        glm::vec3 lightPos(2.0f, 4.0f, 5.0f);
        int lightPosLoc = glGetUniformLocation(programT, "lightPos");
        glUniformMatrix4fv(lightPosLoc, 1, GL_FALSE, glm::value_ptr(lightPos));

        int projectionLocLight = glGetUniformLocation(programT, "projection");
            glUniformMatrix4fv(projectionLocLight, 1, GL_FALSE, glm::value_ptr(projection));
        glm::mat4 modelLight = glm::mat4(1.0f);
        int modelLocLight = glGetUniformLocation(programT, "model");
        glUniformMatrix4fv(modelLocLight, 1, GL_FALSE, glm::value_ptr(modelLight));

        glm::mat4 viewLight = glm::mat4(1.0f); 
        int viewLocLight = glGetUniformLocation(programT, "view");
        glUniformMatrix4fv(viewLocLight, 1, GL_FALSE, glm::value_ptr(viewLight));

        int viewLoc = glGetUniformLocation(programT, "view");
        glUniformMatrix4fv(viewLoc, 1, GL_FALSE, glm::value_ptr(view));

        int projectionLoc = glGetUniformLocation(programT, "projection");
        glUniformMatrix4fv(projectionLoc, 1, GL_FALSE, glm::value_ptr(projection));

        model = glm::rotate(model, glm::radians(rotX), glm::vec3(1.0f, 0.0f, 0.0f));
        model = glm::rotate(model, glm::radians(rotY), glm::vec3(.0f, 1.0f, .0f));
        model = glm::rotate(model, glm::radians(rotZ), glm::vec3(.0f, 0.0f, 1.0f));
        int modelLoc = glGetUniformLocation(programT, "model");
        glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));

                 

        glGenerateMipmap(GL_TEXTURE_2D);
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, textureArray[0]);
        glUniform1i(glGetUniformLocation(programT, "ourTexture"), 0);
            


            glBindVertexArray(VAOArray[0]);
        glDrawArrays(GL_TRIANGLES, 0, myMeshes.at(0).Indices.size());
    

        
        /* Swap front and back buffers */
        glfwSwapBuffers(window);

        /* Poll for and process events */
        glfwPollEvents();
        glfwSetKeyCallback(window, key_callback);
        glfwSetScrollCallback(window, scroll_callback);
        glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
        
    

以下是我的顶点着色器：

#version 330 core


layout (location = 0) in vec3 RealPos;
layout (location = 1) in vec3 vertex_color;
layout (location = 2) in vec2 vertex_textcoord;
layout (location = 3) in vec3 RealNor;


out vec3 vs_pos;
out vec3 vs_color;
out vec2 vs_text;
out vec3 normal;
out vec3 FragPos;

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


void main()

    vs_pos = RealPos;
    vs_color = vertex_color;
    vs_text=vertex_textcoord;
    
    normal=RealNor;
    FragPos = vec3(model * vec4(vs_pos, 1.0));
    
    gl_Position = projection * view * model * vec4(vs_pos, 1.0);

以下是片段着色器：

#version 330 core

in vec2 vs_text;
in vec3 normal;
in vec3 FragPos;

uniform vec3 lightPos;
out vec4 gl_FragColor;



uniform vec3 objectColor;
uniform vec3 lightColor;


uniform sampler2D ourTexture;



void main()

    vec3 norm = normalize(normal);
    vec3 lightDir = normalize(lightPos - FragPos);
    float ambientStrength = 0.1;
        vec3 ambient = ambientStrength * lightColor;
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = diff * lightColor;
    vec3 result = (ambient + diffuse) * objectColor;
    gl_FragColor =  texture(ourTexture, vs_text) * vec4(result,1.0);

我该如何解决这个问题？

【参考方案1】：

片段着色器中的光照计算是在世界空间中完成的。因此，您必须将法线向量与法线矩阵从对象空间转换到世界空间：

mat3 normalMatrix = transpose(inverse(mat3(model)));

normal = normalMatrix * RealNor;
FragPos = vec3(model * vec4(vs_pos, 1.0));

见Why is the transposed inverse of the model view matrix used to transform the normal vectors? 和Why transforming normals with the transpose of the inverse of the modelview matrix?

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想象一下桌子上的旋转器和阅读灯。你的眼睛就是照相机。 model 矩阵模拟旋转。这会导致旋转器的不同侧面在旋转时被照亮。但是，灯的位置不会相对于您的位置发生变化。 当您改变您的位置（眼睛的位置）时，灯的相对位置会发生变化。这可以通过更改view 矩阵来建模。