Instances

How to use Instances

Instances are an excellent way to use hardware-accelerated rendering to draw a huge number of identical meshes (let's imagine a forest or an army).

Instances are built from a mesh with the following code:

import { ImportMeshAsync } from "@babylonjs/core/Loading/sceneLoader";
// In this case we're loading our mesh from an external source.
ImportMeshAsync("https://www.babylonjs.com/assets/Tree/tree.babylon", scene).then(function (result) {
    var mesh = result.meshes[0];
    // Make the "root" mesh not visible. The instanced versions of it that we
    // create below will be visible.
    mesh.isVisible = false;
    for (let index = 0; index < 100; index++) {
        var newInstance = mesh.createInstance("i" + index);
        // Here you could change the properties of your individual instance,
        // for example to form a diagonal line of instances:
        //  newInstance.position.x = index;
        //  newInstance.position.z = index;
        // See below for more details on what can be changed.
    }
});

A mesh can have as many instances as you want.

Each instance has the same material as the root mesh. They can vary in the following properties:

• position
• rotation
• rotationQuaternion
• setPivotMatrix
• scaling

Note: related are thin instances, if you want even more performance but with less control over each instance. See the dedicated page for further information.

Use Instances with Node Material

The Node Material is a powerful tool that allows you to create shaders without having to write GLSL. To use a Node Material on a mesh with instances, you need to add the Instances node to it so that the object is properly instanced:

Expand

The Instances node also gives information on the instance number of the object, which can be useful to, for example, color each instance differently.

Instancing a glTF Object

When you instantiate a glTF object, you need to make sure that the new instance will be under the same parent, or you need to remove the parent from the source object.

This is because every glTF file comes from a right-handed world. To get it into Babylon.js's left-handed world, we add an arbitrary parent with a negative scale on z.

So when instancing a glTF object you have to (either):

• Call source.setParent(null)
• Or call newInstance.setParent(source.parent)

Custom Buffers

You also have the opportunity to specify per-instance values for any attribute. For instance (no pun intended), if you want to have a specific color per instance, you only need to provide a vertex buffer flagged as "instanceable" and fill it with a color for each instance:

import { VertexBuffer } from "@babylonjs/core/Buffers/buffer";
let instanceCount = 1000;
let colorData = new Float32Array(4 * instanceCount);
for (let index = 0; index < instanceCount; index++) {
    colorData[index * 4] = Math.random();
    colorData[index * 4 + 1] = Math.random();
    colorData[index * 4 + 2] = Math.random();
    colorData[index * 4 + 3] = 1.0;
}
var buffer = new VertexBuffer(engine, colorData, VertexBuffer.ColorKind, false, false, 4, true);
box.setVerticesBuffer(buffer);

The last parameter of the VertexBuffer constructor is the one to set to true to flag it as instanceable.

Example: Custom Buffers Example 1

The other way is to register a custom buffer with registerInstancedBuffer:

mesh.registerInstancedBuffer("color", 4); // 4 is the stride size eg. 4 floats here

Using this API, you can specify a new buffer that will be instantiated. This means that each instance will have its own value. You can specify this value on the root mesh and on every single instance:

import { Color4 } from "@babylonjs/core/Maths/math.color";
box.instancedBuffers.color = new Color4(Math.random(), Math.random(), Math.random(), 1);
let instance = box.createInstance("box1");
instance.instancedBuffers.color = new Color4(Math.random(), Math.random(), Math.random(), 1);

The system will take care of updating the internal vertex buffer.

Example: Custom Buffers Example 2

Using Custom Buffers with Node Material

If you want to use custom buffers in conjunction with node materials, you can access the instanced buffers color with the mesh.color block. Make sure you have added the Instances block to your graph and then the mesh.color block will reference the instanced buffers color assigned to the instance.

Expand

Example: Custom Buffers in Node Material

There is a great article from Simon Trushkin, a Senior Technical Artist working at ClickON3D, on using custom buffers with custom blocks in node material. This technique is all about optimization and demonstrating how combining instances, custom buffers, and node material can result in a huge boost to the frame rate of the scene.

Advanced Control

You can decide to control the world matrix instanced buffer the same way you control the custom buffers.

To do so, just run the following code:

mesh.manualUpdateOfWorldMatrixInstancedBuffer = true;

When this mode is activated, you can update the world matrix instanced buffer with this code:

mesh.worldMatrixInstancedBuffer.set(mat, offset); // mat is the matrix you want to store at the given offset
offset += 16; (a matrix is composed of 16 floats

It is recommended to freeze the active meshes when controlling the world matrix instanced buffer to avoid having a discrepancy between the values you store and the number of active instances:

scene.freezeActiveMeshes(true);

You can find a complete example here: Instancing Advanced Control

Support

Instances are supported for collisions, picking, rendering, and shadows. Even if the current hardware does not support hardware-accelerated instances, Babylon.js will still optimize rendering to take instances into account.

Starting from 5.0, instances that have a transparent material applied can be sorted from back to front to remove/limit rendering artifacts. This mode is enabled by setting BABYLON.Mesh.INSTANCEDMESH_SORT_TRANSPARENT = true.

Note that for performance sake the master mesh (the mesh from which instances are created by calling masterMesh.createInstance) is not taken into account in the sorting process. So, to avoid rendering artifacts between this mesh and its instances, this mesh should be disabled (masterMesh.setEnabled(false)).

Using 3D Modeler to Create Instances

Blender

Using Blender, you can create instances of a mesh simply by creating a linked object:

Expand

3ds Max

Using 3ds Max, you can create instances of a mesh simply by creating a clone instance object with a right-click on the object:

Expand

Limitations

• You can use instances with LOD, but one limitation applies in this case: you will have to hide the root objects. Here is an example where LODs reuse instances:

  Instances and LODs

• Instances with a world matrix whose determinant is different from the root mesh's world matrix will be rendered separately (like a regular mesh). This mostly happens when the sign of the scaling vector is different between an instance and the root mesh.

• When using motion blur, the engine needs to store world matrices of the previous frame to compute velocity. Usually, this part is handled internally, but in certain cases you may have to specify these matrices manually. You may in fact see weird blurring artifacts if you update your world matrix buffer manually (using mesh.manualUpdateOfWorldMatrixInstancedBuffer = true;). In that case, to also update previous world matrices, you must enable the corresponding flag:

mesh.manualUpdateOfPreviousWorldMatrixInstancedBuffer = true;

And similarly to world matrices, update the previous world matrices :

mesh.previousWorldMatrixInstancedBuffer.set(previousMat, offset);

Here is an example of manually updating world matrices along with previous world matrices to use motion blur correctly with instances:

Demos

• Trees: Instancing Trees Example
• 10,000 Icospheres: 10,000 Icospheres

Related videos

Further reading

Thin Instances

Learn how to leverage thin instances in your Babylon.js scenes.