Merging Models from ModelBuilder in LibGDX

问题

I'm a new to LibGDX 3D facilities and I'm wondering how I can merge two cylinders created using the ModelBuilder#createCylinder class.I have two ModelInstances :

The first one is a white cylinder,
The second a red cylinder with the same properties

How can get only one cylinder to render (instance / model / object / whatever can be rendered) composed of the red above the white one (or vice versa).

Pixmap pixmap1 = new Pixmap(1, 1, Format.RGBA8888);
pixmap1.setColor(Color.WHITE);
pixmap1.fill();
Texture white = new Texture(pixmap1);
//...
Texture red = new Texture(pixmap2);

model1 = modelBuilder.createCylinder(4f, 6f, 4f, 16, 
        new Material(
                TextureAttribute.createDiffuse(white), 
                ColorAttribute.createSpecular(1,1,1,1), 
                FloatAttribute.createShininess(8f))
        , Usage.Position | Usage.Normal | Usage.TextureCoordinates);
model1I_white = new ModelInstance(model1, 0, 0, 0);
//...
model2I_red = new ModelInstance(model2, 0, 0, -2f);

Then I render ModelInstance with ModelBatch#render.

回答1:

Instead of using createCylinder(), you can create 2 cylinders with the MeshBuilder class, and compose your final cylinder with part().

meshBuilder.begin();
meshBuilder.cylinder(4f, 6f, 4f, 16);
Mesh cylinder1 = meshBuilder.end();

meshBuilder.begin();
meshBuilder.cylinder(4f, 6f, 4f, 16);
Mesh cylinder2 = meshBuilder.end();


modelBuilder.begin();

modelBuilder.part("cylinder1", 
    cylinder1,
    Usage.Position | Usage.Normal | Usage.TextureCoordinates,
    new Material(
        TextureAttribute.createDiffuse(white), 
        ColorAttribute.createSpecular(1,1,1,1), 
        FloatAttribute.createShininess(8f)));

modelBuilder.part("cylinder2",
    cylinder2,
    Usage.Position | Usage.Normal | Usage.TextureCoordinates,
    new Material(
        TextureAttribute.createDiffuse(red), 
        ColorAttribute.createSpecular(1,1,1,1), 
        FloatAttribute.createShininess(8f)))
    .mesh.transform(new Matrix4().translate(0, 0, -2f));

Model finalCylinder = modelBuilder.end();

回答2:

Thanks a lot to Aurel for sharing the code.

Probably libGdx's Api changed slightly so I'll post the complete code wich worked for me

    MeshBuilder meshBuilder = new MeshBuilder();
    meshBuilder.begin(VertexAttributes.Usage.Position | VertexAttributes.Usage.Normal);
    meshBuilder.part("id1", GL20.GL_TRIANGLES);
    meshBuilder.box(1f, 1f, 1f);
    Mesh mesh1 = meshBuilder.end();

    meshBuilder.begin(VertexAttributes.Usage.Position | VertexAttributes.Usage.Normal);
    meshBuilder.part("id2", GL20.GL_TRIANGLES);
    meshBuilder.cylinder(1f, 1f, 1f, 16);
    Mesh mesh2 = meshBuilder.end();


    ModelBuilder modelBuilder = new ModelBuilder();
    modelBuilder.begin();

    modelBuilder.part("part1",
            mesh1,
            GL20.GL_TRIANGLES,
            new Material(ColorAttribute.createDiffuse(Color.RED)));

    modelBuilder.part("part2",
            mesh2,
            GL20.GL_TRIANGLES,
            new Material(ColorAttribute.createDiffuse(Color.RED)))
            .mesh.transform(new Matrix4().translate(1, 0, 0f));

To preserve a color for every mesh add VertxtAttributes.Usage.ColorPacked as meshBuilder.begin()

        meshBuilder.begin(VertexAttributes.Usage.Position | VertexAttributes.Usage.Normal | VertexAttributes.Usage.ColorPacked);

来源：https://stackoverflow.com/questions/21670740/merging-models-from-modelbuilder-in-libgdx

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libgdx