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:
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:
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 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.
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); |