PreviewImageProviderInterface Implementation

Table of Contents

• About
• Methods

About

An implementation of maxon::nodes::PreviewImageProviderInterface provides preview images of a node.

Methods

• maxon::nodes::PreviewImageProviderInterface::Initialize(): Called to initialize the provider by safely extracting all data from the given request. See maxon::nodes::PREVIEWIMAGEREQUEST.
• maxon::nodes::PreviewImageProviderInterface::ComputeIteration(): Called asynchronously to indicate the desire to proceed with node preview computation.
• maxon::nodes::PreviewImageProviderInterface::TakeOutput(): Called when performing a successful iteration.

Note

Initialize() should not take long since it blocks the UI. One should create a clone of the given node graph and access that clone in ComputeIteration().

For accessing and searching for nodes in the node graph, see GraphNodes Manual.

Settings provided in Initialize() are:

• maxon::nodes::PREVIEWIMAGEREQUEST::TEXTURESIZE: Defines the requested preview size in pixels.
• maxon::nodes::PREVIEWIMAGEREQUEST::SUBJECT: Points to the node requested for preview.
• maxon::nodes::PREVIEWIMAGEREQUEST::PROGRESSIONTHRESHOLD: Constraints the iterative refinement.
• maxon::nodes::PREVIEWIMAGEREQUEST::URANGE: For 2D previews defines the horizontal range to be sampled.
• maxon::nodes::PREVIEWIMAGEREQUEST::VRANGE: For 2D previews defines the vertical range to be sampled.
• maxon::nodes::PREVIEWIMAGEREQUEST::SCENETYPE: The type of the 3D scene. See also maxon::nodes::NODESPACE::MATERIALPREVIEWIDS.
• maxon::nodes::PREVIEWIMAGEREQUEST::FLIPVERTICALLY: Defines whether a request was made for a flipped version
• maxon::nodes::PREVIEWIMAGEREQUEST::TEXTUREIDS: The set of attributes requested for preview.
• maxon::nodes::PREVIEWIMAGEREQUEST::PROVIDER: Defines the instance of a PreviewImageProviderRef that is used to compute the preview.

  // This example implementation of PreviewImageProviderInterface::Initialize() stores the given texture size,
  // the node path and creates a copy of the given node graph.
 
  MAXON_METHOD maxon::Result<void> Initialize(maxon::DataDictionaryObjectRef request, maxon::Int numThreads)
  {
    iferr_scope;
 
    // store target image size
    _imageSize = request.Get(maxon::nodes::PREVIEWIMAGEREQUEST::TEXTURESIZE, maxon::IntVector2d());
 
    // get node or port for this call
    maxon::GraphNode node = request.Get(maxon::nodes::PREVIEWIMAGEREQUEST::SUBJECT, maxon::GraphNode());
 
    if (node.IsValid() == false)
    {
      return maxon::UnexpectedError(MAXON_SOURCE_LOCATION);
    }
 
    // get graph clone
    maxon::nodes::NodesGraphModelRef graph = maxon::Cast<maxon::nodes::NodesGraphModelRef>(node.GetGraph());
    _graph = graph.GetManager().GetMainView().Clone() iferr_return;
 
    // get node path
    _nodePath = node.GetPath();
 
    // get preview scene if needed
    const maxon::nodes::PREVIEW::SCENETYPE sceneType = request.Get<maxon::nodes::PREVIEW::SCENETYPE>(maxon::nodes::PREVIEWIMAGEREQUEST::SCENETYPE, maxon::nodes::PREVIEW::SCENETYPE::MatPreviewDefault);
    UseVariable(sceneType);
 
    return maxon::OK;
  }

  // These are example implementations of ComputeIteration() and TakeOutput().
  // ComputeIteration() is called asynchronously so it must operate on the previously stored copy of the graph.
 
  MAXON_METHOD maxon::Result<void> ComputeIteration(const maxon::JobRef parentThread)
  {
    iferr_scope;
 
    // the path either references a port/node or is nullptr (render the material node)
 
    // get node the node from the graph copy
    const maxon::GraphNode node = _graph.GetNode(_nodePath);
 
    // depending on the node, fill the image
 
    // prepare image
    _currentResult = NewObj(maxon::nodes::SamplesFloat32) iferr_return;
    maxon::nodes::SamplesFloat32& result = *_currentResult;
 
    result.Resize(_imageSize.x * _imageSize.y) iferr_return;
 
    // fill image
    for (maxon::Int y = 0; y < _imageSize.y; ++y)
    {
      for (maxon::Int x = 0; x < _imageSize.x; ++x)
      {
        maxon::nodes::SampleFloat32& sample = result[x + y * _imageSize.x];
        sample = maxon::nodes::SampleFloat32(maxon::Vector32(1.0, 1.0, 1.0));
      }
    }
 
    _final = true;
 
    return maxon::OK;
  }
 
  MAXON_METHOD maxon::Result<maxon::nodes::PreviewImageProviderOutput> TakeOutput()
  {
    iferr_scope;
 
    maxon::nodes::PreviewImageProviderOutput output;
    // provide information on the rendering process if the preview image is rendered iteratively.
    output._iterationCount = 2;
    output._currentIterationIndex = 1;
 
    maxon::nodes::PreviewImageProviderOutputImage image;
    // store image data
    image._imageSize = _imageSize;
    image._samplesFloat32Linear = _currentResult;
    image._isFinal = _final;
 
    output.SetResult(image) iferr_return;
 
    return output;
  }
 
private:
  maxon::IntVector2d               _imageSize;
  maxon::nodes::SamplesFloat32Ref  _currentResult;
  maxon::Bool                      _final;
  maxon::NodePath                  _nodePath;
  maxon::nodes::NodesGraphModelRef _graph;