Strange issue. No clue. Do we need to keep vertices in mesh.verts in any particular order?

Archive Cycles Development
1

Hi,

I am generating a mesh with two different methods…

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The mesh generated with 1st method is displayed properly but the other one is displayed messy. (Textures are not displayed properly)

I have implemented a test code to compare these two meshes. It says they are same.
The below is my test code.

I could not understand why the 2nd mesh is not working. Any clue?

Do we need to keep vertices in mesh.verts in any particular order?

Thanks in advance.

bool feq(const float3 &a, const float3 &b)
{
  if (a.x != b.x) {
    return false;
  }
  if (a.y != b.y) {
    return false;
  }
  if (a.z != b.z) {
    return false;
  }
  return true;
}
    void compare(ccl::Mesh &m1, ccl::Mesh &m2)
    {
      if (m1.triangles.size() != m2.triangles.size()) {
        std::cout << "Not same number of triangles\n";
        return;
      }
      std::vector<int> attribute_element_sizes;
      attribute_element_sizes.resize(0);

      std::vector<const char *> m1_attribute_buffers;
      m1_attribute_buffers.resize(0);

      std::vector<const char *> m2_attribute_buffers;
      m2_attribute_buffers.resize(0);
      std::vector<ustring> attribute_names;
      attribute_names.resize(0);

      ccl::AttributeSet &m1_attribute_set = m1.attributes;
      for (auto it = m1_attribute_set.attributes.begin(); it != m1_attribute_set.attributes.end(); it++) {
        const ccl::Attribute &attribute = *it;

        int element_size = attribute.data_sizeof();
        const char *buffer = attribute.buffer.data();
        attribute_element_sizes.push_back(element_size);
        m1_attribute_buffers.push_back(buffer);

        attribute_names.push_back(attribute.name);
      }
      int i = 0;
      ccl::AttributeSet &m2_attribute_set = m2.attributes;
      for (auto it = m2_attribute_set.attributes.begin(); it != m2_attribute_set.attributes.end(); it++) {
        const ccl::Attribute &attribute = *it;
        if (attribute_names[i] != attribute.name) {
          std::cout << "Attribute names not same\n";
          return;
        }

        int element_size = attribute.data_sizeof();
        const char *buffer = attribute.buffer.data();
        if (attribute_element_sizes[i] != element_size) {
          std::cout << "Element sizes not same\n";
          return;
        }
        m2_attribute_buffers.push_back(buffer);
        i++;
      }

      for (i = 0; i < m1.triangles.size(); i++) {
        int m1_vertex_index = m1.triangles[i];
        int m2_vertex_index = m2.triangles[i];

        if (!feq(m1.verts[m1_vertex_index], m2.verts[m2_vertex_index])) {
          std::cout << "Vertex is not same\n";
          return;
        }

        for (int j = 0; j < attribute_element_sizes.size(); j++) {
          int element_size = attribute_element_sizes[j];
          for (int k = 0; k < element_size; k++) {
            if (m1_attribute_buffers[j][(m1_vertex_index * element_size) + k] !=
                m2_attribute_buffers[j][(m2_vertex_index * element_size) + k]) {
              std::cout << "Data not same: " << attribute_names[j] << "\t" << m1.name << "\t" << std::endl;
              return;
            }
          }
        }
      }

      int triangles_count = m1.triangles.size() / 3;
      for (i = 0; i < triangles_count; i++) {
        if (m1.shader[i] != m2.shader[i]) {
          std::cout << "Shader not same\n";
          return;
        }
        if (m1.smooth[i] != m2.smooth[i]) {
          std::cout << "Smooth not same\n";
          return;
        }
      }

       std::cout << "______________________________SAME_________________________________________" << std::endl;
    }
2

BTW, I am re-using the vertex only if,

  • 3d coordinates is same
  • Normal is same.
  • UV for all UV channels is same
  • Vertex Color is same
3

Got it. We need to specify attribute element values at triangle level. I mean, if there are n triangles, there will be n*3 elements in an attribute.

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