Update positions of geometry

Questions
1

I am trying to update the positions of the vertices, after I constructed the geometry but I am unable to do so . I have read the “how to update things” page on threejs docs but still no success.

Here is the simple fiddle with a single geometry : Three.js base - JSFiddle - Code Playground

Can somebody point me where I am going wrong…

2

Try this. It is not exactly what your code intends to do (the function below just randomly moves vertices), but it shows one possible way to update vertices’ coordinates:

function updateGeometry() {
    if (mesh != null) {
        let g = mesh.geometry;
        let p = g.getAttribute('position');

        for (let i = 0; i<p.count; i++) { 
            let x = p.getX(i) + 0.01*(Math.random()-0.5);
            let y = p.getY(i) + 0.01*(Math.random()-0.5);
            let z = p.getZ(i) + 0.01*(Math.random()-0.5);
            p.setXYZ(i, x, y, z);
        }
        
        p.needsUpdate = true;
    }
}

image

1 Like
3

thanks @PavelBoytchev !

I guess I needed was

p.needsUpdate = true;

I thought that was already going to get updated when I called geometry.needsUpdate = true;

Now my function is :

function updateGeometry() {
    if (mesh != null) {
                
        let gPA = mesh.geometry.attributes.position;
        let geomPosAttr = gPA.array;
        let l = geomPosAttr.length;

        for (let i = l - 4; i > -1; i -= 1) 
            geomPosAttr[i] = positionArray[i] + positionArray[i] * Math.random()*100;
    
        gPA.needsUpdate = true;
    }
}
1 Like