NormalTag Manual

Table of Contents

• About
• Allocation/Deallocation
• Edit
• Further Reading

About

A NormalTag stores normal vectors for a (polygon) object. For each polygon a set of four vectors is stored (NormalStruct). The class NormalTag is based on VariableTag so the typical workflows on handling tags apply, see BaseTag and VariableTag Manual.

NormalTag objects are an instance of Tnormal.

Allocation/Deallocation

NormalTag instances are created with the usual tools.

• NormalTag::Alloc(): Creates a new NormalTag.
• NormalTag::Free(): Destroys the given NormalTag.

  // This example checks if the given object hosts a Normal tag.
  // If not, a Normal tag is created.
 
  NormalTag* normalTag = static_cast<NormalTag*>(polyObject->GetTag(Tnormal));
  if (normalTag == nullptr)
  {
    const Int32 polyCnt = polyObject->GetPolygonCount();
 
    normalTag = NormalTag::Alloc(polyCnt);
    if (normalTag == nullptr)
      return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
 
    polyObject->InsertTag(normalTag);
  }

Edit

The normal vectors stored in a NormalTag are accessed by obtaining data handles that are used with static functions:

• NormalTag::GetDataAddressR(): Returns a handle to the read-only normal vectors.
• NormalTag::GetDataAddressW(): Returns a handle to the writeable normal vectors.
• NormalTag::Get(): Returns the normal vectors for the given polygon index.
• NormalTag::Set(): Sets the normal vectors for the given polygon index.
• NormalTag::Copy(): Copies the normal vectors from the given handle to the other handle.

  // This example calculates normal vectors, changes them and stores them in the given Normal tag.
 
  // make sure a Phong tag exists
  if (polyObject->GetTag(Tphong) == nullptr)
  {
    BaseTag* phongTag = polyObject->MakeTag(Tphong);
    if (phongTag == nullptr)
      return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
  }
 
  Random random;
 
  NormalHandle handle = normalTag->GetDataAddressW();
 
  for (Int32 i = 0; i < polygonCount; ++i)
  {
    const CPolygon polygon = polygons[i];
 
    // calculate default face normal
    Vector normal = CalcFaceNormal(points, polygon);
 
    NormalStruct normals;
 
    // add random variation
    normal.x += ((random.Get01() * 0.2) - 0.1);
    normal.y += ((random.Get01() * 0.2) - 0.1);
    normal.z += ((random.Get01() * 0.2) - 0.1);
    normal.Normalize();
 
    // define polygon normals
    normals.a = normal;
    normals.b = normal;
    normals.c = normal;
    normals.d = normal;
 
    NormalTag::Set(handle, i, normals);
  }
 
  polyObject->Message(MSG_UPDATE);

Further Reading

• Modeling
• UVWTag Manual
• BaseObject Manual
• BaseTag and VariableTag Manual