Simplify Process of Reading and Writing Google Draco files Using Java API

How to Get Started with Openize.Drako for Java

Getting started with Openize.Drako is quick and easy. Simply follow these steps:

• Install Openize.Drako: Install the Openize.Drako package via Maven or Gradle.
• Start Converting: Utilize the simple API provided by Openize.Drako to read and write Draco files.

The recommended way to install Openize.Drako for Java is using maven. Please use the following pom dependency snippet for a smooth installation.

<dependency>
  <groupId>org.openize</groupId>
  <artifactId>drako</artifactId>
  <version>1.4.0</version>
</dependency>
 

Read Draco File into DracoMesh in Java

This code snippet efficiently loads a Draco file, and store it in a DracoMesh instance for subsequent operations.

• Open the DRC file named "cube.drc" using Files.readAllBytes.
• Load the 3D mesh from the bytes into a DracoMesh object.

Copy and paste the code snippet below into your main file and execute the program.

 
    byte[] cube = Files.readAllBytes(Paths.get("cube.drc"));
    DracoMesh dm = (DracoMesh)Draco.decode(cube);

Read Draco file and write to Wavefront OBJ in Java

The following code illustrates how to open an existing 3D Draco file, and write to obj format for further processing:

• Open the Draco file file named "input.drc" using Files.readAllBytes.
• Load the Draco mesh from the bytes into a DracoMesh object.
• Find the position attribute using DracoMesh.getNamedAttribute and turn its content to FloatSpan.
• Write control points to output using OBJ's format.
• Read each face corners using DracoMesh.readFace
• Map the face corners to the index of control points using PointAttribute.mappedIndex.
• Write faces to output using OBJ's format.

Copy and paste the code snippet below into your main file and execute the program.

 
  //load draco file
  byte[] bytes = Files.readAllBytes(Paths.get("input.drc"));
  DracoMesh mesh = (DracoMesh)Draco.decode(bytes);
  if (mesh == null)
      throw new IllegalStateException("Input file is not a valid draco file.");
  PointAttribute attrPos = mesh.getNamedAttribute(AttributeType.POSITION);
  FloatSpan points = attrPos.getBuffer().asSpan().asFloatSpan();
  
  try(FileOutputStream fos = new FileOutputStream("output.obj", false)) {
      try (OutputStreamWriter writer = new OutputStreamWriter(fos)) {
          for (int i = 0; i < points.size(); i += 3) {
              writer.write(String.format("v %f %f %f\n", points.get(i), points.get(i + 1), points.get(i + 2)));
          }
          int[] face = new int[3];
          for (int i = 0; i < mesh.getNumFaces(); i++) {
              mesh.readFace(i, face);
              int a = attrPos.mappedIndex(face[0]) + 1;
              int b = attrPos.mappedIndex(face[1]) + 1;
              int c = attrPos.mappedIndex(face[2]) + 1;
              writer.write(String.format("f %d %d %d\n", a, b, c));
          }
      }
  }

Encode control points, triangles to Draco file Programatically in Java

The provided code demonstrates how to programmatically create a Draco file from control points and triangles, and save it as "output.drc" using Java. Here's a breakdown of the steps:

• Create a DracoMesh instance.
• Wrap control points to PointAttribute.
• Add the PointAttribute to DracoMesh.
• Add the triangle indices.
• Create a DracoEncodeOptions object with the specified encoding parameters.
• Encode the mesh to bytes using Draco.encode.

Copy and paste the code snippet below into your main file and execute the program.

 
  Vector3[] controlPoints = new Vector3[]
  {
          new Vector3( -5, 0, 5.0f),
          new Vector3( 5, 0, 5.0f),
          new Vector3( 5, 10, 5.0f),
          new Vector3( -5, 10, 5.0f),
          new Vector3( -5, 0, -5.0f),
          new Vector3( 5, 0, -5.0f),
          new Vector3( 5, 10, -5.0f),
          new Vector3( -5, 10, -5.0f)
  };

  int[] indices = new int[]
  {
          0,1,2, 0, 2, 3, // Front face (Z+)
          1,5,6, 1, 6, 2, // Right side (X+)
          5,4,7, 5, 7, 6, // Back face (Z-)
          4,0,3, 4, 3, 7, // Left side (X-)
          0,4,5, 0, 5, 1, // Bottom face (Y-)
          3,2,6, 3, 6, 7 // Top face (Y+)
  };

  DracoMesh mesh = new DracoMesh();
  PointAttribute attrPos = PointAttribute.wrap(AttributeType.POSITION, controlPoints);
  mesh.addAttribute(attrPos);
  //add triangle indices
  mesh.getIndices().addRange(indices);
  //number of the control points, it's required for the encoder to produce correct result.
  mesh.setNumPoints(8);
  //You can also use following methods to deduplicate the attributes to reduce the file size
  //mesh.deduplicateAttributeValues();
  //mesh.deduplicatePointIds();
  DracoEncodeOptions opt = new DracoEncodeOptions();
  byte[] drcBytes = Draco.encode(mesh, opt);

  Files.write(Paths.get("output.drc"), drcBytes);

Openize.Drako offers an intuitive API, comprehensive format support, and seamless integration with Java applications, empowering developers and users alike to effortlessly manage Draco files. Whether you're converting draco files to other files, or loading draco for rendering, Openize.Drako simplifies the process, ensuring optimal efficiency and quality at every step.

Explore our GitHub repository to contribute, suggest improvements, and enhance this Open Source API: Openize.Drako-for-Java