FieldData Manual

Table of Contents

• About
• FieldData
• Example
• Further Reading

About

FieldData is the base class for custom field objects (see FieldObject Manual).

A new FieldData based class is registered with RegisterFieldPlugin().

FieldData

In a FieldData based class the following functions can be implemented:

• FieldData::GetFieldFlags(): Returns the flags defining the behaviour of the field object (FIELDOBJECT_FLAG).
• FieldData::InitSampling(): Initializes the sampling process.
• FieldData::Sample(): Samples the object.
• FieldData::FreeSampling(): Clears internal data.

For related data types see FieldObject Manual.

Example

// This example shows the implementation of a custom field object.
 
// ------------------------------------------------------------------------------
// This example field defines the field value based on the global space position.
// ------------------------------------------------------------------------------
class ExampleField : public FieldData
{
  INSTANCEOF(ExampleField, FieldData)
 
public:
  // ------------------------------------------------------------------------------
  // Allocation of a new instance
  // @return    New ExampleField instance or nullptr.
  // ------------------------------------------------------------------------------
  static NodeData* Alloc()
  {
    iferr (NodeData * const result = NewObj(ExampleField))
    {
      DebugStop();
      return nullptr;
    }
    return result;
  }
 
  virtual maxon::Result<maxon::GenericData> InitSampling(const FieldObject& op, const FieldInfo& info) const
  {
    // calculation done before sampling
    return {};
  }
 
  virtual void FreeSampling(const FieldObject& op, const FieldInfo& info, maxon::GenericData& extraData) const
  {
    // freeing internal data after sampling
  }
 
  virtual maxon::Result<void> Sample(const FieldObject& op, const FieldInput& inputs, FieldOutputBlock& outputs, const FieldInfo& info, const maxon::GenericData& extraData) const
  {
    // handle each input position
    for (Int i = inputs._blockCount - 1; i >= 0; --i)
    {
      // get position
      const Vector pos = inputs._position[i];
 
      // calculate value
      const Float distance = pos.GetLength();
      const Float value = distance / 1000.0;
 
      // set value
      outputs._value[i] = value;
    }
 
    return maxon::OK;
  }
 
  virtual FIELDOBJECT_FLAG GetFieldFlags(const FieldObject& op, const BaseDocument* doc) const 
  { 
    return FIELDOBJECT_FLAG::NONE; 
  }
};

  // This example registeres the given FieldData plugin.
 
  const Bool registerFieldSuccess = RegisterFieldPlugin(fieldPluginID, "Example Field"_s, "Global Falloff"_s, 0, ExampleField::Alloc, "fexample"_s, nullptr, 0);
 
  if (registerFieldSuccess == false)
    return maxon::UnknownError(MAXON_SOURCE_LOCATION);

Further Reading

• MoGraph Overview
• FieldObject Manual
• Common Plugin Concepts