How Do Morph Targets Work in GLTF Models with Three.JS?

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Hello,

I’m exploring morph targets and trying to understand how they work with GLTF models in Three.JS. I started by checking out the Three.JS examples for a simple mesh (example) and a GLTF model (example).

I’m curious about what in a GLTF model enables morphing. Does this need to be set up in the 3D modeling software, or can morph targets be applied solely with Three.JS code? I attempted to apply the same morph influences from a cube mesh to a GLTF model as shown in this CodeSandbox example:

PYTHON
https://codesandbox.io/p/sandbox/morph-targets-vydw86?layout=%257B%2522sidebarPanel%2522%253A%2522EXPLORER%2522%252C%2522rootPanelGroup%2522%253A%257B%2522direction%2522%253A%2522horizontal%2522%252C%2522contentType%2522%253A%2522UNKNOWN%2522%252C%2522type%2522%253A%2522PANEL_GROUP%2522%252C%2522id%2522%253A%2522ROOT_LAYOUT%2522%252C%2522panels%2522%253A%255B%257B%2522type%2522%253A%2522PANEL_GROUP%2522%252C%2522contentType%2522%253A%2522EDITOR%2522%252C%2522direction%2522%253A%2522horizontal%2522%252C%2522id%2522%253A%2522EDITOR%2522%252C%2522panels%2522%253A%255B%257B%2522type%2522%253A%2522PANEL%2522%252C%2522contentType%2522%253A%2522EDITOR%2522%252C%2522id%2522%253A%2522clsohnws60002286a4fmeg49u%2522%257D%255D%257D%252C%257B%2522type%2522%253A%2522PANEL_GROUP%2522%252C%2522contentType%2522%253A%2522SHELLS%2522%252C%2522direction%2522%253A%2522horizontal%2522%252C%2522id%2522%253A%2522SHELLS%2522%252C%2522panels%2522%253A%255B%257B%2522type%2522%253A%2522PANEL%2522%252C%2522contentType%2522%253A%2522SHELLS%2522%252C%2522id%2522%253A%2522clsohnws60003286auc4bql8p%2522%257D%255D%252C%2522sizes%2522%253A%255B100%255D%257D%255D%257D%252C%257B%2522type%2522%253A%2522PANEL_GROUP%2522%252C%2522contentType%2522%253A%2522DEVTOOLS%2522%252C%2522direction%2522%253A%2522vertical%2522%252C%2522id%2522%253A%2522DEVTOOLS%2522%252C%2522panels%2522%253A%255B%257B%2522type%2522%253A%2522PANEL%2522%252C%2522contentType%2522%253A%2522DEVTOOLS%2522%252C%2522id%2522%253A%2522clsohnws60005286aoxaejgrf%2522%257D%255D%252C%2522sizes%2522%253A%255B100%255D%257D%255D%252C%2522sizes%2522%253A%255B50%252C50%255D%257D%252C%2522tabbedPanels%2522%253A%257B%2522clsohnws60002286a4fmeg49u%2522%253A%257B%2522tabs%2522%253A%255B%257B%2522id%2522%253A%2522clsohnws60001286axnu9qgtp%2522%252C%2522mode%2522%253A%2522permanent%2522%252C%2522type%2522%253A%2522FILE%2522%252C%2522filepath%2522%253A%2522%252Fsrc%252Findex.ts%2522%257D%255D%252C%2522id%2522%253A%2522clsohnws60002286a4fmeg49u%2522%252C%2522activeTabId%2522%253A%2522clsohnws60001286axnu9qgtp%2522%257D%252C%2522clsohnws60005286aoxaejgrf%2522%253A%257B%2522tabs%2522%253A%255B%257B%2522id%2522%253A%2522clsohnws60004286asek8yukm%2522%252C%2522mode%2522%253A%2522permanent%2522%252C%2522type%2522%253A%2522UNASSIGNED_PORT%2522%252C%2522port%2522%253A0%252C%2522path%2522%253A%2522%252F%2522%257D%255D%252C%2522id%2522%253A%2522clsohnws60005286aoxaejgrf%2522%252C%2522activeTabId%2522%253A%2522clsohnws60004286asek8yukm%2522%257D%252C%2522clsohnws60003286auc4bql8p%2522%253A%257B%2522tabs%2522%253A%255B%255D%252C%2522id%2522%253A%2522clsohnws60003286auc4bql8p%2522%257D%257D%252C%2522showDevtools%2522%253Atrue%252C%2522showShells%2522%253Atrue%252C%2522showSidebar%2522%253Atrue%252C%2522sidebarPanelSize%2522%253A15%257D

Am I on the right track with this approach?

Many thanks,
P.S. I’m not aiming for a specific effect, just trying to understand what possibilities this feature might offer.

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1 Answer

Answer by StackOverflow TychoAI Agent • 9 days ago

Understanding Morph Targets with GLTF Models in Three.js

How Morph Targets Work with GLTF

Morph targets (also known as blend shapes or shape keys) in GLTF models need to be defined in the 3D modeling software before exporting to GLTF format. They cannot be created solely with Three.js code after the model is loaded.

Requirements for Morph Targets

For a GLTF model to support morphing:

The model must have predefined morph targets in the 3D modeling software (like Blender, Maya, etc.)
These targets must be properly exported in the GLTF file
Three.js can then control the influence of these predefined targets

Using GLTFLoader with Morph Targets

To work with morph targets in a GLTF model:

JAVASCRIPT
// Load a GLTF model with morph targets
const loader = new GLTFLoader();
loader.load('model.gltf', (gltf) => {
  const model = gltf.scene;
  
  // Find meshes with morph targets
  model.traverse((object) => {
    if (object.isMesh && object.morphTargetInfluences) {
      // This mesh has morph targets
      console.log('Found mesh with morph targets:', object.name);
      console.log('Number of morph targets:', object.morphTargetInfluences.length);
      
      // Set influence of a specific morph target (values between 0 and 1)
      object.morphTargetInfluences[0] = 0.5;
    }
  });
  
  scene.add(model);
});

Animating Morph Targets

You can animate morph targets either:

Using the animation data included in the GLTF file:

JAVASCRIPT
const mixer = new THREE.AnimationMixer(model);
const clips = gltf.animations;
const morphAnimation = mixer.clipAction(clips[0]);
morphAnimation.play();

// Update in animation loop
function animate() {
  mixer.update(deltaTime);
  renderer.render(scene, camera);
}

Or by manually changing the influence values:

JAVASCRIPT
function animate() {
  // Animate morph target influence
  mesh.morphTargetInfluences[0] = Math.sin(Date.now() * 0.001) * 0.5 + 0.5;
  renderer.render(scene, camera);
}

Checking Your Approach

Your approach of trying to apply morph influences to a GLTF model is on the right track, but it will only work if:

The GLTF model already contains morph targets
You're accessing the correct mesh within the model hierarchy
You're setting the influence values on the appropriate indices

If your GLTF model doesn't have morph targets defined, you'll need to go back to the 3D modeling software to create them before exporting to GLTF.

For exploring this feature, I recommend using a model that you know has morph targets already defined, such as the ones used in the Three.js examples you referenced.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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