Opengl 光照适用于模型的顶部、底部、正面、背面，但不适用于模型的侧面

Question

我有一个由五个立方体组成的模型，整个模型都有纹理，我添加了灯光，它对立方体的顶部、底部、字体和背面都有效，但对侧面无效，还有一个阴影问题，因为在应该遮蔽的地方有光。为此，我正在使用基于 Tao 框架的 Matlab .NET opengl 包装器，我承认这是不寻常的。

如果需要，我可以提供完整的代码，但现在，这是我的照明代码

%% Lighting 

% Enable Light
Gl.glEnable(Gl.GL_LIGHTING);
% Vector for light position (directional light - try a positional one)

% Get Projection matrix in array of length 16
projmatrix = NET.createArray('System.Single', 16);
Gl.glGetFloatv(Gl.GL_PROJECTION_MATRIX,projmatrix);
% Reshape to 4x4 matrix
projmatrix=reshape(double(projmatrix),[4 4]);
% Use the inverse projection matrix to get the light fixed with the camera
LightPosCam=(projmatrix)\[0.3 0.5 -0.6 0]';

LightPos= NET.convertArray(LightPosCam, 'System.Single', 4);
Ambient =  NET.convertArray([0.000001 0.000001 0.000001 .1], 
'System.Single', 4); 
Diffuse=  NET.convertArray([0.7 0.7 0.7 1], 'System.Single', 4); 
Specular=  NET.convertArray([0.6 0.6 0.6 1], 'System.Single', 4); 

% Turn on Lighting
Gl.glEnable(Gl.GL_LIGHTING);
Gl.glEnable(Gl.GL_LIGHT0);

Gl.glLightfv(Gl.GL_LIGHT0,Gl.GL_POSITION,LightPos);
Gl.glLightfv(Gl.GL_LIGHT0,Gl.GL_AMBIENT,Ambient);
Gl.glLightfv(Gl.GL_LIGHT0,Gl.GL_DIFFUSE,Diffuse);
Gl.glLightfv(Gl.GL_LIGHT0,Gl.GL_SPECULAR,Specular);

% Constant attenuation (for distance, etc.)
% Only works for fixed light locations!  Otherwise disabled
Gl.glLightf(Gl.GL_LIGHT0, Gl.GL_CONSTANT_ATTENUATION, 1.0);
Gl.glLightf(Gl.GL_LIGHT0, Gl.GL_LINEAR_ATTENUATION, 0.0);
Gl.glLightf(Gl.GL_LIGHT0, Gl.GL_QUADRATIC_ATTENUATION, 0.0);
Gl.glLightModeli(Gl.GL_LIGHT_MODEL_LOCAL_VIEWER, Gl.GL_TRUE);

% Normalize vectors
Gl.glEnable(Gl.GL_NORMALIZE);

% Enable ColorMaterial
% Gl.glEnable (Gl.GL_COLOR_MATERIAL ) ;
% Set the Material Properties
floor_ambient = NET.convertArray([0, 0, 0, 0 ], 'System.Single', 4); 
floor_diffuse = NET.convertArray([0.8, 0.8, 0.8, 1.0 ], 'System.Single', 4); 

floor_specular= NET.convertArray([0.7,0.7,0.7, 1 ], 'System.Single', 4);
floor_emission= NET.convertArray([0.2,0.0,0.0, 1 ], 'System.Single', 4);
floor_shininess = 120;
Gl.glMaterialfv(Gl.GL_FRONT, Gl.GL_AMBIENT, floor_ambient);
Gl.glMaterialfv(Gl.GL_FRONT, Gl.GL_DIFFUSE, floor_diffuse);
Gl.glMaterialfv(Gl.GL_FRONT, Gl.GL_SPECULAR, floor_specular);
Gl.glMaterialfv(Gl.GL_FRONT, Gl.GL_SHININESS, floor_shininess);
Gl.glMaterialfv(Gl.GL_FRONT, Gl.GL_EMISSION, floor_emission);

% Gourang shanding
Gl.glShadeModel(Gl.GL_SMOOTH);

% Specular color enable

Gl.glLightModeli(Gl.GL_LIGHT_MODEL_COLOR_CONTROL,
Gl.GL_SEPARATE_SPECULAR_COLOR);
%  Gl.glTexEnvf(Gl.GL_TEXTURE_ENV, Gl.GL_TEXTURE_ENV_MODE, 
Gl.GL_MODULATE);
% Gl.glEnable(Gl.GL_BLEND);

这里是我的代码，只有一个立方体

     %% Draw Sats
        % Select our texture

        Gl.glEnable(Gl.GL_NORMALIZE)

        %     Bottom Face  
        Gl.glEnable(Gl.GL_TEXTURE_2D);
        Gl.glBindTexture(Gl.GL_TEXTURE_2D, data.TextureID8);  %%Metalic Texture
        Gl.glBegin(Gl.GL_QUADS);
            Gl.glNormal3f(0,0,-1);
            Gl.glTexCoord2f(0,0);
            Gl.glVertex3f(cornersx(1), cornersy(1), cornersz(1));  
            Gl.glNormal3f(0,0,-1);
            Gl.glTexCoord2f(1,0);
            Gl.glVertex3f(cornersx(2), cornersy(2), cornersz(2));   
            Gl.glNormal3f(0,0,-1);
            Gl.glTexCoord2f(1,1);
            Gl.glVertex3f(cornersx(4), cornersy(4), cornersz(4));   
            Gl.glNormal3f(0,0,-1);
            Gl.glTexCoord2f(0,1);
            Gl.glVertex3f(cornersx(3), cornersy(3), cornersz(3));   

        %     Top Face
           Gl.glEnd()

        Gl.glBindTexture(Gl.GL_TEXTURE_2D, data.TextureID3);  %%Glyph1 Texture
        Gl.glBegin(Gl.GL_QUADS);
            Gl.glNormal3f(0,0,1);
            Gl.glTexCoord2f(0,0);
            Gl.glVertex3f(cornersx(7), cornersy(7), cornersz(7));               

        Gl.glNormal3f(0,0,1);
        Gl.glTexCoord2f(1,0);
        Gl.glVertex3f(cornersx(8), cornersy(8), cornersz(8));               

        Gl.glNormal3f(0,0,1);
         Gl.glTexCoord2f(1,1);
         Gl.glVertex3f(cornersx(6), cornersy(6), cornersz(6));              

        Gl.glNormal3f(0,0,1);
        Gl.glTexCoord2f(0,1);
        Gl.glVertex3f(cornersx(5), cornersy(5), cornersz(5));
        Gl.glEnd()

        % Front Face
        Gl.glBindTexture(Gl.GL_TEXTURE_2D, data.TextureID);  
        Gl.glEnable(Gl.GL_TEXTURE_2D);  
        Gl.glBegin(Gl.GL_QUADS);
        Gl.glNormal3f(0,-1,0);
        Gl.glTexCoord2f(0,0);
        Gl.glVertex3f(cornersx(1), cornersy(1), cornersz(1));               

         Gl.glNormal3f(0,-1,0);
         Gl.glTexCoord2f(1,0);
         Gl.glVertex3f(cornersx(5), cornersy(5), cornersz(5));              

        Gl.glNormal3f(0,-1,0);
        Gl.glTexCoord2f(1,1);
        Gl.glVertex3f(cornersx(6), cornersy(6), cornersz(6));               

        Gl.glNormal3f(0,-1,0);
        Gl.glTexCoord2f(0,1);   
        Gl.glVertex3f(cornersx(2), cornersy(2), cornersz(2));

        %     Back Face

        Gl.glNormal3f(0,1,0);
        Gl.glTexCoord2f(0,0);
        Gl.glVertex3f(cornersx(3), cornersy(3), cornersz(3));               

        Gl.glNormal3f(0,1,0);
        Gl.glTexCoord2f(1,0);
        Gl.glVertex3f(cornersx(4), cornersy(4), cornersz(4));               

        Gl.glNormal3f(0,1,0);
        Gl.glTexCoord2f(1,1);
        Gl.glVertex3f(cornersx(8), cornersy(8), cornersz(8));               

        Gl.glNormal3f(0,1,0);
        Gl.glTexCoord2f(0,1);
        Gl.glVertex3f(cornersx(7), cornersy(7), cornersz(7));

        %     Right Face

         Gl.glNormal3f(-1,0,0);
         Gl.glTexCoord2f(0,0);
         Gl.glVertex3f(cornersx(4), cornersy(4), cornersz(4));              

         Gl.glNormal3f(-1,0,0);
         Gl.glTexCoord2f(1,0);
         Gl.glVertex3f(cornersx(2), cornersy(2), cornersz(2));              

         Gl.glNormal3f(-1,0,0);
         Gl.glTexCoord2f(1,1);
         Gl.glVertex3f(cornersx(6), cornersy(6), cornersz(6));              

        Gl.glNormal3f(-1,0,0);
        Gl.glTexCoord2f(0,1);
        Gl.glVertex3f(cornersx(8), cornersy(8), cornersz(8));

        %     Left Face

         Gl.glNormal3f(1,0,0);
         Gl.glTexCoord2f(0,0);
         Gl.glVertex3f(cornersx(3), cornersy(3), cornersz(3));              
         Gl.glNormal3f(1,0,0);
         Gl.glTexCoord2f(1,0);
         Gl.glVertex3f(cornersx(1), cornersy(1), cornersz(1));                  
         Gl.glNormal3f(1,0,0);
         Gl.glTexCoord2f(1,1);
         Gl.glVertex3f(cornersx(5), cornersy(5), cornersz(5));                  
         Gl.glNormal3f(1,0,0);
         Gl.glTexCoord2f(0,1);
         Gl.glVertex3f(cornersx(7), cornersy(7), cornersz(7));
        Gl.glEnd()

Finally a gif of my model and the issue in action.

Answer 1

我发现有两个潜在问题：

如果您只是左右脸有问题，可能只是您不小心翻转了它们的表面法线。我会试试这个：
```
Gl.glNormal3f(1,0,0);   % For all of the right face vertices
Gl.glNormal3f(-1,0,0);  % For all of the left face vertices
```
当表面法线指向错误的方向时（即进入你的立方体），这意味着多边形的背面朝外。当您调用 Gl.glMaterialfv 时，您指定 Gl.GL_FRONT 而不是 Gl.GL_FRONT_AND_BACK，这意味着背面没有被点亮。我猜这就是为什么您看不到侧面应用照明的原因。
我不知道你的顶点顺序是否重要，这样当从立方体的外面看时，它们应该始终以围绕面的顺时针或逆时针顺序指定.由于我不知道您的 cornersx、cornersy 或 cornersz 数据是什么样的，因此我无法判断您将它们定义为顺时针还是逆时针。但是，我可以告诉你，你的一张脸的顺时针顺序与其余的不同：左脸，顶点顺序为3 -> 1 -> 5 -> 7。我对您的照明框架了解不多，无法说明这是否会成为问题，但为了保持一致性，您可能希望改为按 1 -> 3 -> 7 -> 5 的顺序定义左脸的顶点。

Opengl 光照适用于模型的顶部、底部、正面、背面，但不适用于模型的侧面

Opengl lighting works top,bottom,front, back but not on the sides of the model

opengl

matlab

lighting

tao-framework

shading