c++ - OpenGL 纹理映射不起作用

Question

我必须使用 OpenGL API 和着色器对网格进行纹理化。

为此，我执行了以下步骤:

1. 加载图片并创建纹理

   img::ImageLoader imgLoader;
   unsigned char* data = imgLoader.LoadTextureFromFile("../Texturen/brickwork.jpg", &width, &height, true);
   
   glGenTextures(1, &texId);
   glBindTexture(GL_TEXTURE_2D, texId);{
       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   }
   

2. 创建顶点、法线和纹理坐标

   std::vector<float> v, n, t;
   
   // actual calculation is left out to make it more readable
   
   obj = new GLBatch;
       obj->Begin(GL_TRIANGLES, v.size()/3, t.size()/2);{
       obj->CopyVertexData3f(v.data());
       obj->CopyNormalDataf(n.data());
       obj->CopyTexCoordData2f(t.data(), 0);
   }obj->End();
   

3. 加载着色器

   shaders =  gltLoadShaderPairWithAttributes("VertexShader.glsl", "FragmentShader.glsl", 2, 
       GLT_ATTRIBUTE_VERTEX, "vVertex", 
       GLT_ATTRIBUTE_NORMAL, "vNormal",
       GLT_ATTRIBUTE_TEXTURE0, "vTexCoord");
   
   gltCheckErrors(shaders);
   

   (VertexShader.glsl)

   #version 130
   in vec4 vVertex;
   in vec4 vNormal;
   in vec2 vTexCoord;
   
   uniform mat4 mvpMatrix;
   uniform mat4 mvMatrix;
   uniform mat3 normalMatrix;
   /// Light position in Eye-Space
   uniform vec4 light_pos_vs ;
   /// Light diffuse color
   uniform vec4 light_diffuse ;
   uniform vec4 light_ambient ;
   /// Light specular color
   uniform vec4 light_specular ;
   /// Specular power (shininess)
   uniform float spec_power;
   
   /// Material parameters
   uniform vec4 mat_emissive;
   uniform vec4 mat_ambient; 
   uniform vec4 mat_diffuse;   
   uniform vec4 mat_specular;  
   
   /// output
   out vec4 color;
   out vec2 texCoords;
   
   void main()
   {   
       texCoords = vTexCoord;
       // Transform vertex from objekt to clip-space
       gl_Position = mvpMatrix * vVertex ;
   
       // Transform vertex from object to eye-space
       vec4 vertex_vs = mvMatrix * vVertex;
       vec3 ecPos = vertex_vs.xyz / vertex_vs.w;
   
       // Calculate light direction
       vec3 light_dir_vs = normalize(vec3(light_pos_vs.xyz));
   
       // Transform normals from object into eye-space
       vec3 normal_vs = normalize(normalMatrix * (vNormal).xyz) ;
   
       // Viewing vector in eye-space
       vec3 view_dir_vs = normalize(-ecPos );
   
       // Halfway vektor for Phong-Blinn light modell
       vec3 halfway_vs = normalize(view_dir_vs + light_dir_vs ) ;
   
       // Diffuse
       float NdotL = max(dot(normal_vs, light_dir_vs),0.0) ;
       vec4 diffuse_color = NdotL * mat_diffuse * light_diffuse ;
   
       // Specular
       float NdotH = max(dot(normal_vs, halfway_vs),0.0) ;
       vec4 specular_color = pow(NdotH ,spec_power) * mat_specular * light_specular ;
   
       // Color output
       color = mat_emissive + light_ambient*mat_ambient + diffuse_color + specular_color;
   }
   

   (FragmentShader.glsl)

   #version 130
   
   in vec2 texCoords;
   in vec4 color;
   
   uniform sampler2D textureMap;
   
   out vec4 fragColor;
   
   void main()
   {
       fragColor = texture(textureMap, texCoords);
       fragColor *= color;
   }
   

4. 在显示函数中绘制所有内容

   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glEnable(GL_DEPTH_TEST);
   glLineWidth(INDICATOR_WIDTH);
   glBindTexture(GL_TEXTURE_2D, texId);
   
   modelViewMatrix.LoadIdentity();
   modelViewMatrix.Translate(0,0,-5);
   modelViewMatrix.PushMatrix();{
   
       M3DMatrix44f rot;
       m3dQuatToRotationMatrix(rot,rotation);
       modelViewMatrix.MultMatrix(rot);
   
       // set shader
       glUseProgram(shaders);
       // pass matrices
       glUniformMatrix4fv(glGetUniformLocation(shaders, "mvpMatrix"), 1, GL_FALSE, transformPipeline.GetModelViewProjectionMatrix());
       glUniformMatrix4fv(glGetUniformLocation(shaders, "mvMatrix"),  1, GL_FALSE, transformPipeline.GetModelViewMatrix());
       glUniformMatrix3fv(glGetUniformLocation(shaders, "normalMatrix"),  1, GL_FALSE, transformPipeline.GetNormalMatrix(true));
       // pass light properties
       glUniform4fv(glGetUniformLocation(shaders, "light_pos_vs"),1,light_pos);
       glUniform4fv(glGetUniformLocation(shaders, "light_ambient"),1,light_ambient);
       glUniform4fv(glGetUniformLocation(shaders, "light_diffuse"),1,light_diffuse);
       glUniform4fv(glGetUniformLocation(shaders, "light_specular"),1,light_specular);
       glUniform1f(glGetUniformLocation(shaders, "spec_power"),specular_power);
       // pass material properties
       glUniform4fv(glGetUniformLocation(shaders, "mat_emissive"),1,mat_emissive);
       glUniform4fv(glGetUniformLocation(shaders, "mat_ambient"),1,mat_ambient);
       glUniform4fv(glGetUniformLocation(shaders, "mat_diffuse"),1,mat_diffuse);
       glUniform4fv(glGetUniformLocation(shaders, "mat_specular"),1,mat_specular);
   
       drawObject();
   
   }modelViewMatrix.PopMatrix();
   
   gltCheckErrors(shaders);
   glutSwapBuffers();
   glutPostRedisplay();
   

完成所有这些步骤后，结果看起来不错，但没有纹理 :(

这里实际发生的是，每个顶点都映射到我的纹理的相同像素，该像素显然是灰色的。

我尝试了从(0,0) 到(1,1) 和(0,0) 到(width,height) 的纹理坐标 但没有任何改变。

Answer 1

改变

shaders =  gltLoadShaderPairWithAttributes(
    "VertexShader.glsl", 
    "FragmentShader.glsl",
    2, 
    GLT_ATTRIBUTE_VERTEX, "vVertex", 
    GLT_ATTRIBUTE_NORMAL, "vNormal",
    GLT_ATTRIBUTE_TEXTURE0, "vTexCoord");

到

shaders =  gltLoadShaderPairWithAttributes(
    "VertexShader.glsl", 
    "FragmentShader.glsl",
    3, // < -------------------- 
    GLT_ATTRIBUTE_VERTEX, "vVertex", 
    GLT_ATTRIBUTE_NORMAL, "vNormal",
    GLT_ATTRIBUTE_TEXTURE0, "vTexCoord");

因为函数签名中的第三个参数是紧随其后且应链接到着色器的属性数。在这种情况下，有 3 个属性:GLT_ATTRIBUTE_VERTEX、GLT_ATTRIBUTE_NORMAL 和 GLT_ATTRIBUTE_TEXTURE0。 在原始代码中，只有 GLT_ATTRIBUTE_VERTEX、GLT_ATTRIBUTE_NORMAL 链接在一起，因此没有纹理坐标传递给着色器。