切線空間，切線/ Binormal計算

Question

我有以下代碼來計算切線，bitangents。我可以使用普通映射成功渲染一些網格示例。

我有一個特定的網格問題，它計算與正常的切線共陰點。

任何幫助將不勝感激，以確定原因。

的例子是這樣的一個：

V0：（-9.860292,6.589309，-8.947665） V1：（-9.860292,0.000000，-8.947665） V2（-8.068345,0.000000，-8.947665）

UV0：（-0.073677，-0.141450） UV1：（-0.074518，-0.140732） UV2（-0.074243，-0.140732）

deltaPos1：（0.000000，-6.589309,0.000000） deltaPos2：（ 1.791947，-6.589309,0.000000）

deltaUV1：（-0.000841,0.000718） deltaUV2：（-0.000566,0.000718）

正常：（1.000000,0.000000,0.000000） Tanget：（6516.150391，-0.000000，-0.000000）， 二重（7632.445312，-9177.340820，-0.000000）

void MeshRenderer::computeTangentBasis(
              // inputs 
              std::vector<unsigned int>& indices, 
              std::vector<glm::vec3> & vertices, 
              std::vector<glm::vec2> & uvs, 
              std::vector<glm::vec3> & normals, 
              // outputs 
              std::vector<glm::vec3> & tangents, 
              std::vector<glm::vec3> & bitangents 
              ){ 

    tangents.clear(); 
    bitangents.clear(); 

    GLMHelper glmHelper; 
    for (unsigned int i=0; i<indices.size(); i+=3){ 


     // Shortcuts for vertices 
     int index0 = indices[i]; 
     int index1 = indices[i+1]; 
     int index2 = indices[i+2]; 

     glm::vec3 & v0 = vertices[index0]; 
     glm::vec3 & v1 = vertices[index1]; 
     glm::vec3 & v2 = vertices[index2]; 

     std::cout << " v0: " << glmHelper.convertVec3(v0) << " v1: " << glmHelper.convertVec3(v1) << 
     ", v2 " << glmHelper.convertVec3(v2) << std::endl; 

     // Shortcuts for UVs 
     glm::vec2 & uv0 = uvs[index0]; 
     glm::vec2 & uv1 = uvs[index1]; 
     glm::vec2 & uv2 = uvs[index2]; 

     std::cout << " uv0: " << glmHelper.convertVec2(uv0) << " uv1: " << glmHelper.convertVec2(uv1) << 
     ", uv2 " << glmHelper.convertVec2(uv2) << std::endl; 

     // Edges of the triangle : postion delta 
     glm::vec3 deltaPos1 = v1-v0; 
     glm::vec3 deltaPos2 = v2-v0; 

     std::cout << " deltaPos1: " << glmHelper.convertVec3(deltaPos1) << " deltaPos2: " << glmHelper.convertVec3(deltaPos2) << std::endl; 

     // UV delta 
     glm::vec2 deltaUV1 = uv1-uv0; 
     glm::vec2 deltaUV2 = uv2-uv0; 

     std::cout << " deltaUV1: " << glmHelper.convertVec2(deltaUV1) << " deltaUV2: " << glmHelper.convertVec2(deltaUV2) << std::endl; 

     float r = 1.0f/(deltaUV1.x * deltaUV2.y - deltaUV1.y * deltaUV2.x); 
     glm::vec3 tangent = (deltaPos1 * deltaUV2.y - deltaPos2 * deltaUV1.y)*r; 
     glm::vec3 bitangent = (deltaPos2 * deltaUV1.x - deltaPos1 * deltaUV2.x)*r; 

     // Set the same tangent for all three vertices of the triangle. 
     // They will be merged later, in vboindexer.cpp 
     tangents.push_back(tangent); 
     tangents.push_back(tangent); 
     tangents.push_back(tangent); 

     // Same thing for bitangents 
     bitangents.push_back(bitangent); 
     bitangents.push_back(bitangent); 
     bitangents.push_back(bitangent); 



     std::cout << "i:" << i << " Normal: " << glmHelper.convertVec3(normals[i]) << " Tanget: " << glmHelper.convertVec3(tangent) << 
     ", bitangent " << glmHelper.convertVec3(bitangent) << std::endl; 

    } 

    // See "Going Further" 
    for (unsigned int i=0; i<vertices.size(); i+=1) 
    { 
     glm::vec3 & n = normals[i]; 
     glm::vec3 & t = tangents[i]; 
     glm::vec3 & b = bitangents[i]; 

     // Gram-Schmidt orthogonalize 
     t = glm::normalize(t - n * glm::dot(n, t)); 

     // Calculate handedness 
     if (glm::dot(glm::cross(n, t), b) < 0.0f){ 
      t = t * -1.0f; 
     } 

    } 


} 

Answer 1

的問題是，下面的代碼是錯誤的：

// Set the same tangent for all three vertices of the triangle. 
    // They will be merged later, in vboindexer.cpp 
    tangents.push_back(tangent); 
    tangents.push_back(tangent); 
    tangents.push_back(tangent); 

    // Same thing for bitangents 
    bitangents.push_back(bitangent); 
    bitangents.push_back(bitangent); 
    bitangents.push_back(bitangent); 

它應該是：

 // Set the same tangent for all three vertices of the triangle. 
     tangents[index0] = tangent; 
     tangents[index1] = tangent; 
     tangents[index2] = tangent; 

     // Same thing for bitangents 
     bitangents[index0] = bitangent; 
     bitangents[index1] = bitangent; 
     bitangents[index2] = bitangent;