c++ - opengl 4 中的逐顶点光照问题

Question

我有一个由只有 8 个顶点的立方体组成的模型，我在使用逐顶点定向照明时遇到了问题。不是一次点亮整个模型，而是每个立方体都像 this 一样单独点亮。 .

这是我的顶点着色器:

layout(location = 0)in vec3 vp;
layout(location = 1)in vec3 color;
layout(location = 2)in vec3 normal;

out vec3 fColor;

uniform mat4 model;
uniform mat3 nm;
uniform mat3 partNM;
uniform mat4 modelPart;
uniform mat4 view;
uniform mat4 projection;

void main () {
    gl_Position = modelPart * vec4(vp, 1.0f);
    gl_Position = model * gl_Position;
    gl_Position = view * gl_Position;
    gl_Position = projection * gl_Position;

    mat3 normalMatrix =  partNM*nm;
    vec3 normalDirection = normalize(normalMatrix*normal);
    vec3 lightDirection = normalize(vec3(-1.0, 1.0, -1.0));

    vec3 diffuseReflection = clamp(dot(normalDirection, lightDirection),0.0,1.0);
    fColor = color+diffuseReflection;
}

和我的片段着色器:

in vec3 fColor;
out vec4 frag_colour;

void main () {
    frag_colour = vec4(fColor.xyz,1.0);
}

这是我用来设置法线矩阵的函数:

void Shader::setNormalMatrix(string name,glm::mat4 matrix) {
    glm::mat3 nm = glm::transpose(glm::inverse(glm::mat3(matrix)));
    unsigned int location = glGetUniformLocation(program, name.c_str());
    glUniformMatrix3fv(location, 1, false, &nm[0][0]);
}

以及为我的立方体生成顶点和法线的函数:

std::vector<float> Cube::createCube(float size,float x,float y,float z,float r, float g, float b) {
    VertexType points[8];

    points[0].x = (x*size)+0.0f;
    points[0].y = (y*size)+0.0f;
    points[0].z = (z*size)+size;
    points[0].nx = 0.577350; 
    points[0].ny = 0.577350;
    points[0].nz = -0.577350;
    points[0].r = r;
    points[0].g = g;
    points[0].b = b;

    points[1].x = (x*size)+size;
    points[1].y = (y*size)+0.0f;
    points[1].z = (z*size)+size;
    points[1].nx = -0.577350; 
    points[1].ny = 0.577350;
    points[1].nz = -0.577350;
    points[1].r = r;
    points[1].g = g;
    points[1].b = b;

    points[2].x = (x*size)+size;
    points[2].y = (y*size)+size;
    points[2].z = (z*size)+size;
    points[2].nx = -0.577350;
    points[2].ny = -0.577350;
    points[2].nz = -0.577350;
    points[2].r = r;
    points[2].g = g;
    points[2].b = b;

    points[3].x = (x*size)+0.0f;
    points[3].y = (y*size)+size;
    points[3].z = (z*size)+size;
    points[3].nx = 0.577350; 
    points[3].ny = -0.577350;
    points[3].nz = -0.577350;
    points[3].r = r;
    points[3].g = g;
    points[3].b = b;

    points[4].x = (x*size)+0.0f;
    points[4].y = (y*size)+0.0f;
    points[4].z = (z*size)+0.0f;
    points[4].nx = 0.577350; 
    points[4].ny = 0.577350;
    points[4].nz = 0.577350;
    points[4].r = r;
    points[4].g = g;
    points[4].b = b;

    points[5].x = (x*size)+size;
    points[5].y = (y*size)+0.0f;
    points[5].z = (z*size)+0.0f;
    points[5].nx = -0.577350; 
    points[5].ny = 0.577350;
    points[5].nz = 0.577350;
    points[5].r = r;
    points[5].g = g;
    points[5].b = b;

    points[6].x = (x*size)+size;
    points[6].y = (y*size)+size;
    points[6].z = (z*size)+0.0f;
    points[6].nx = -0.577350; 
    points[6].ny = -0.577350;
    points[6].nz = 0.577350;
    points[6].r = r;
    points[6].g = g;
    points[6].b = b;

    points[7].x = (x*size)+0.0f;
    points[7].y = (y*size)+size;
    points[7].z = (z*size)+0.0f;
    points[7].nx = 0.577350; 
    points[7].ny = -0.577350;
    points[7].nz = 0.577350;
    points[7].r = r;
    points[7].g = g;
    points[7].b = b;
    std::vector<float> rPoint;
    for(VertexType p:points) {
        rPoint.push_back(p.x);
        rPoint.push_back(p.y);
        rPoint.push_back(p.z);
        rPoint.push_back(p.r);
        rPoint.push_back(p.g);
        rPoint.push_back(p.b);
        rPoint.push_back(p.nx);
        rPoint.push_back(p.ny);
        rPoint.push_back(p.nz);
    }
    return rPoint;
}

模型被分成几个部分，这就是为什么我有两个普通矩阵和模型矩阵的原因；一个用于整个模型，一个用于模型的单个部分。是我的代码有问题，还是我需要使用逐片段光照来修复这个错误？

Answer 1

您的问题是网格的拓扑结构。在立方体的角上，3 个面相交。这些面孔中的每一个都有不同的法线。这会在法线拓扑中产生不连续性。或者用更简单的术语来说。每个角必须使用 3 个顶点，每个面一个，面法线指向正确的方向。

当你这样做的时候，你可以移除那些无论如何都不可见的立方体面。