OpenGL漫射照明问题

Question

我的漫射照明似乎没有正常工作。

片段着色器：

#version 330 core

out vec4 gl_FragColor;

in vec4 vertexColor;
in vec2 texelCoord;
in vec3 Normal;

struct DirectionalLight
{
    vec3 color;
    float ambientIntensity;
    vec3 direction;
    float diffuseIntensity;
};

uniform sampler2D textureSampler;
uniform DirectionalLight directionalLight;

void main()
{
    vec4 ambientColor = vec4(directionalLight.color, 1.0f) * directionalLight.ambientIntensity;
    
    float diffuseFactor = max(dot(normalize(Normal), normalize(directionalLight.direction)), 0.0f);
    vec4 diffuseColor = vec4(directionalLight.color, 1.0f) * directionalLight.diffuseIntensity * diffuseFactor;
    
    gl_FragColor = texture(textureSampler, texelCoord) * (ambientColor + diffuseColor);
}

顶点着色器：

#version 330 core

layout (location = 0) in vec3 position;
layout (location = 1) in vec2 texCoord;
layout (location = 2) in vec3 normal;

out vec4 vertexColor;
out vec2 texelCoord;
out vec3 Normal;

uniform mat4 transformation;
uniform mat4 projection;
uniform mat4 view;

void main()
{
    gl_Position = projection * view * transformation * vec4( position, 1.0f );
    vertexColor = vec4(clamp(position, 0.0f, 1.0f), 1.0f);
    
    texelCoord = texCoord;
    Normal = mat3(transpose(inverse(transformation))) * normal;
}

我如何创建网格：

void CalcAverageNormals( unsigned int* indices , unsigned int indicesCount , float* vertices , unsigned int verticesCount , unsigned int vertexLength , unsigned int normalOffset )
{
    for ( int i = 0; i < indicesCount; i += 3 )
    {
        unsigned int v1 = indices[i] * vertexLength;
        unsigned int v2 = indices[ i + 1 ] * vertexLength;
        unsigned int v3 = indices[ i + 2 ] * vertexLength;

        glm::vec3 line1( vertices[ v2 ] - vertices[ v1 ] , vertices[ v2 + 1 ] - vertices[ v1 + 1 ] , vertices[ v2 + 2 ] - vertices[ v1 + 2 ] );
        glm::vec3 line2( vertices[ v3 ] - vertices[ v1 ] , vertices[ v3 + 1 ] - vertices[ v1 + 1 ] , vertices[ v3 + 2 ] - vertices[ v1 + 2 ] );
        glm::vec3 normal = glm::normalize( glm::cross( line1 , line2 ) );

        v1 += normalOffset;
        v2 += normalOffset;
        v3 += normalOffset;

        vertices[ v1 ] += normal.x; vertices[ v1 + 1 ] += normal.y; vertices[ v1 + 2 ] += normal.z;
        vertices[ v2 ] += normal.x; vertices[ v2 + 1 ] += normal.y; vertices[ v2 + 2 ] += normal.z;
        vertices[ v3 ] += normal.x; vertices[ v3 + 1 ] += normal.y; vertices[ v3 + 2 ] += normal.z;
    }

    for ( int j = 0; j < verticesCount / vertexLength; j++ )
    {
        unsigned int offset = j * vertexLength + normalOffset;
        glm::vec3 normalVertex( vertices[ offset ] , vertices[ offset + 1 ] , vertices[ offset + 2 ] );
        normalVertex = glm::normalize( normalVertex );

        vertices[ offset ] = normalVertex.x;
        vertices[ offset + 1 ] = normalVertex.y;
        vertices[ offset + 2 ] = normalVertex.z;
    }
}

void CreateTriangle() {

    float vertices[] {
       -0.5f,-0.5f, 0.0f,  0.0f, 0.0f,  0.0f, 0.0f, 0.0f, // Left
        0.5f,-0.5f, 0.0f,  1.0f, 0.0f,  0.0f, 0.0f, 0.0f, // Right
        0.0f, 0.5f, 0.0f,  0.5f, 1.0f,  0.0f, 0.0f, 0.0f, // Top
        0.0f,-0.5f, 0.5f,  0.5f, 0.0f,  0.0f, 0.0f, 0.0f  // Back Z
    };

    unsigned int indices[]{
        0, 1, 2, // Front
        3, 2, 1, // Right
        3, 2, 0, // Left
        3, 0, 1  // Bottom
    };

    CalcAverageNormals( indices , 12 , vertices , 32 , 8 , 5 );

    for ( int i = 0; i < 1; i++ )
    {
        Mesh* obj = new Mesh();

        obj->CreateMesh( vertices , 32 , indices , 12 );
        meshlist.push_back( obj );
    }

}

创建网格()

void Mesh::CreateMesh( float* vertices , unsigned int numVertices , unsigned int* indices , unsigned int numIndices )
    {
        uIndices = numIndices;
    
        glGenVertexArrays( 1 , &vao );
        glBindVertexArray( vao );
    
        /*Create Buffers*/
        glGenBuffers( 1 , &ibo );
        glBindBuffer( GL_ELEMENT_ARRAY_BUFFER , ibo );
        glBufferData( GL_ELEMENT_ARRAY_BUFFER , numIndices * sizeof(unsigned) , indices , GL_STATIC_DRAW );
    
        glGenBuffers( 1 , &vbo );
        glBindBuffer( GL_ARRAY_BUFFER , vbo );
        glBufferData( GL_ARRAY_BUFFER , numVertices * sizeof(float) , vertices , GL_STATIC_DRAW );
    
        glVertexAttribPointer( 0 , 3 , GL_FLOAT , GL_FALSE , sizeof( vertices[ 0 ] ) * 8 , 0 );
        glEnableVertexAttribArray( 0 );
        glVertexAttribPointer( 1 , 2 , GL_FLOAT , GL_FALSE , sizeof( vertices[ 0 ] ) * 8 , ( void* )( sizeof( vertices[ 0 ] ) * 3 ) );
        glEnableVertexAttribArray( 1 );
        glVertexAttribPointer( 2 , 3 , GL_FLOAT , GL_FALSE , sizeof( vertices[ 0 ] ) * 8 , ( void* )( sizeof( vertices[ 0 ] ) * 5 ) );
        glEnableVertexAttribArray( 2 );
    
        /*Unbind Objects*/
        glBindBuffer( GL_ARRAY_BUFFER , 0 );
    
        glBindVertexArray( 0 );
    
        glBindBuffer( GL_ELEMENT_ARRAY_BUFFER , 0 );
    }

如果我旋转网格，我只会得到某种光照：

正常（无照明）：

几天来我一直在努力解决这个问题，但我不确定自己做错了什么。如果你能帮助我，那就太好了。

Answer 1

这个：

Normal = mat3(transpose(inverse(transformation))) * normal;

法线本身应该转换到与光方向矢量所在的坐标系相同的坐标系中，这看起来很可疑。由于法线是矢量，因此 w 应该为零，所以我希望

Normal = view * transformation * vec4( normal, 0.0f );

如果光线方向在相机坐标中或：

Normal = transformation * vec4( normal, 0.0f );

如果光线方向在全局世界坐标中（更有可能是这种情况）...

同时设置着色器输出变量，如 gl_Position 应该是着色器的最后一行，否则您可能会冒 GL 实现在某些实现后优化其余代码的风险。

顺便说一句。 IIRC mat3(transpose(inverse(transformation))) 在 transformation 的情况下与 mat3(transformation) 相同，但正如 Rabbid76 指出的那样，它有其目的...

我能想到的最后一件事是法线方向错误（相反或不一致），在这种情况下我会尝试交换：

max(dot(normalize(Normal), normalize(directionalLight.direction)), 0.0f);

与：

abs(dot(normalize(Normal), normalize(directionalLight.direction));

如果它对您有帮助，您必须检查法线或只是否定点结果...

有关详细信息，请参阅：

...但是我使用 w=1 因为使用的矩阵没有偏移量所以没关系

Answer 2

原来是我的指数顺序出现了三角缠绕问题。由于漫反射因子的计算方式，我通过按逆时针顺序绘制索引来修复此问题。

unsigned int indices[]{
    0, 1, 2, // Front
    3, 1, 2, // Right
    3, 0, 2, // Left
    3, 1, 0  // Bottom
};

转置逆运算是为了修正非均匀尺度矩阵

OpenGL漫射照明问题

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