Basic 3D Programming - Learning LibGDX Game Development - page 391

Model and ModelInstances
A model represents a 3D asset. It stores a hierarchy of nodes. A node has a transform
and optionally a graphical part in the form of a MeshPart and Material . A model
can be rendered by creating ModelInstance from it. This instance has an additional
transform to position the model in the world, and allows the modification of
materials and nodes without destroying the original model. The original model is the
owner of any meshes and textures; all instances created from the model share these
resources. Disposing of the model will automatically make all instances invalid.
We create a sphere model using LibGDX's ModelBuilder . It can create basic shapes
such as box, sphere, cone, capsule, cylinder, and so on, as follows:
public Model model;
public ModelInstance instance;
ModelBuilder modelBuilder = new ModelBuilder();
model = modelBuilder.createSphere(2, 2, 2, 20, 20,
new Material(ColorAttribute.createDiffuse(Color.YELLOW)),
Usage.Position | Usage.Normal);
instance = new ModelInstance(model);
In the preceding code, a sphere is created with the width, height, and depth set to
2 units and the horizontal and vertical divisions are set to 20 . You have to provide
materials and attributes to create any model. Finally, ModelInstance is created from
that model. After using the model, we dispose of it by calling model.dispose() .
The ModelBatch class
The ModelBatch class is used to render the model instance as follows:
modelBatch.begin(cam);
modelBatch.render(instance, environment);
modelBatch.end();
In the render method, we clear the screen, call modelBatch.begin() , render our
ModelInstance , and then call modelBatch.end() to finish rendering. While
rendering the model using modelBatch.render() , we provide the environment
along with the rendering ModelInstance . The model batch is disposed of by calling
modelBatch.dispose() .