Vrm Mtoon Outline

Critical Properties

material.outlineWidthMode    // 'none' | 'worldCoordinates' | 'screenCoordinates'
material.outlineWidthFactor  // Number - the actual width value
material.isMToonMaterial     // Boolean - true for MToon materials
material.needsUpdate         // Set to true after modifying properties

Solution: Switch to Screen Coordinates

To make outlines stay consistent regardless of zoom/scale:

function adjustOutlineThickness(vrm, screenFactor = 0.005) {
    vrm.scene.traverse((object) => {
        if (object.isMesh || object.isSkinnedMesh) {
            const materials = Array.isArray(object.material) ? object.material : [object.material];
            
            materials.forEach(material => {
                if (!material || !material.isMToonMaterial) return;
                
                // Check if this material has outlines enabled
                const hasOutline = material.outlineWidthFactor > 0 && 
                                   material.outlineWidthMode !== 'none';
                
                if (hasOutline) {
                    // Switch to screen coordinates mode
                    material.outlineWidthMode = 'screenCoordinates';
                    material.outlineWidthFactor = screenFactor;
                    material.needsUpdate = true;
                }
            });
        }
    });
}

Factor Value Guidelines

For screenCoordinates mode:

Detection Pattern

To diagnose outline issues, log all materials:

function debugOutlineMaterials(vrm) {
    let count = 0;
    vrm.scene.traverse((object) => {
        if (!object.isMesh && !object.isSkinnedMesh) return;
        
        const materials = Array.isArray(object.material) ? object.material : [object.material];
        materials.forEach(material => {
            if (material?.isMToonMaterial || 'outlineWidthFactor' in material) {
                count++;
                console.log({
                    name: material.name || '未命名',
                    type: material.type,
                    isMToonMaterial: material.isMToonMaterial,
                    outlineWidthMode: material.outlineWidthMode,
                    outlineWidthFactor: material.outlineWidthFactor
                });
            }
        });
    });
    console.log(`Found ${count} MToon/Outline materials`);
}

Important Notes

[!IMPORTANT] Call timing matters! The function must be called AFTER currentModel is set. In vrm-core.js, the loadModel() function sets manager.currentModel near line 923. Any function that accesses currentModel must be called after this point.

[!NOTE] Materials named "XXX (Outline)" are outline pass materials automatically created by three-vrm. They share properties with the main material but render the outline effect.

API Reference (three-vrm MToon)

The enum values for outlineWidthMode:

// From three-vrm.module.min.js
{
    None: "none",
    WorldCoordinates: "worldCoordinates", 
    ScreenCoordinates: "screenCoordinates"
}