Create 3D Mesh and Scene

Create a 3D Cube Mesh

A Mesh is defined by a set of control points and the many n-sided polygons as needed. This article explains how to define a Mesh.

In order to create a Mesh surface, we need to define control points and polygons as follows:

• Define the Control Points
• Create Polygons with PolygonBuilder Class
• Create Polygons

Here’s an example to attach a Phong material to the cube node:

Define the Control Points

A mesh is composed by a set of control points in space, and polygons to describe the mesh surface, to create a mesh, we need to define the control points:

The control points of all geometries in Aspose.3D use homogeneous coordinate, so it’s Vector4 instead of Vector3 in the example code.

Example:

// Initialize control points
Vector4List controlPoints = new Vector4List(8);
controlPoints.add(new Vector4( -5.0, 0.0, 5.0, 1.0));
controlPoints.add(new Vector4( 5.0, 0.0, 5.0, 1.0));
controlPoints.add(new Vector4( 5.0, 10.0, 5.0, 1.0));
controlPoints.add(new Vector4( -5.0, 10.0, 5.0, 1.0));
controlPoints.add(new Vector4( -5.0, 0.0, -5.0, 1.0));
controlPoints.add(new Vector4( 5.0, 0.0, -5.0, 1.0));
controlPoints.add(new Vector4( 5.0, 10.0, -5.0, 1.0));
controlPoints.add(new Vector4( -5.0, 10.0, -5.0, 1.0));

Create Polygons

The control points are not renderable, to make the cube visible, we need to define polygons in each side:

List<Vector4> controlPoints = defineControlPoints();
// Initialize mesh object
Mesh mesh = new Mesh();
// Add control points to the mesh
mesh.getControlPoints().addAll(controlPoints);
// Create polygons to mesh
// Front face (Z+)
mesh.createPolygon(new int[] { 0, 1, 2, 3 });
// Right side (X+)
mesh.createPolygon(new int[] { 1, 5, 6, 2 });
// Back face (Z-)
mesh.createPolygon(new int[] { 5, 4, 7, 6 });
// Left side (X-)
mesh.createPolygon(new int[] { 4, 0, 3, 7 });
// Bottom face (Y-)
mesh.createPolygon(new int[] { 0, 4, 5, 1 });
// Top face (Y+)
mesh.createPolygon(new int[] { 3, 2, 6, 7 });

Create Polygons with PolygonBuilder Class

We can also define polygon by vertices with PolygonBuilder class:

List<Vector4> controlPoints = defineControlPoints();
// Initialize mesh object
Mesh mesh = new Mesh();
// Add control points to the mesh
mesh.getControlPoints().addAll(controlPoints);
// Indices of the vertices per each polygon
int[] indices = new int[]
{
    0,1,2,3, // Front face (Z+)
    1,5,6,2, // Right side (X+)
    5,4,7,6, // Back face (Z-)
    4,0,3,7, // Left side (X-)
    0,4,5,1, // Bottom face (Y-)
    3,2,6,7 // Top face (Y+)
};
int vertexId = 0;
PolygonBuilder builder = new PolygonBuilder(mesh);
for (int face = 0; face < 6; face++)
{
    // Start defining a new polygon
    builder.begin();
    for (int v = 0; v < 4; v++)
        // The indice of vertice per each polygon
        builder.addVertex(indices[vertexId++]);
    // Finished one polygon
    builder.end();
}

Now it’s finished, to make the mesh visible, we need to prepare a node for it.

How to Triangulate a Mesh

Triangulate mesh is useful for game industry because the triangular is the only supported primitive that GPU hardware supports (non-triangular data are triangulated in driver-level, which is inefficient in real-time rendering)

In this version we only triangulated the polygons since it’s required by 3ds file exporting, normals/uvs and other vertex elements are lost during this procedure, we can implement this in the future.

In this example, we triangulate a Mesh by importing FBX file and saved it in FBX format.

// The path to the documents directory.
String MyDir = RunExamples.getDataDir();
// Initialize scene object
Scene scene = new Scene();
scene.open(MyDir + "document.fbx");
scene.getRootNode().accept(new NodeVisitor() {
    @Override
    public boolean call(Node node) {
        Mesh mesh = (Mesh)node.getEntity();
        if (mesh != null)
        {
            // Triangulate the mesh
            Mesh newMesh = PolygonModifier.triangulate(mesh);
            // Replace the old mesh
            node.setEntity(newMesh);
        }
        return true;
    }
});
MyDir = MyDir + RunExamples.getOutputFilePath("document.fbx");
scene.save(MyDir, FileFormat.FBX7400ASCII);

Create a 3D Cube Scene

This topic demonstrates how to add Mesh geometry to the 3D scene. The example code places a cube and save 3D scene in the supported file formats.

Create a Cube Node

A node is invisible, but the geometry attached to the node can be rendered.

The Mesh class object is being used in the code. We can create a Mesh class object as narrated there.

Example:

// Initialize scene object
Scene scene = new Scene();
// Initialize Node class object
Node cubeNode = new Node("cube");
// Call Common class create mesh using polygon builder method to set mesh instance
Mesh mesh = Common.createMeshUsingPolygonBuilder();
// Point node to the Mesh geometry
cubeNode.setEntity(mesh);
// Add Node to a scene
scene.getRootNode().getChildNodes().add(cubeNode);
// The path to the documents directory.
String MyDir = RunExamples.getDataDir();
MyDir = MyDir + RunExamples.getOutputFilePath("CubeScene.fbx");
// Save 3D scene in the supported file formats
scene.save(MyDir, FileFormat.FBX7400ASCII);

NOTE: The entities attached to the root node are usually ignored in CAD/CAM softwares, so we need to create a new node to render the geometry.