Im trying to draw the vertices of a glb model in my three js scene. The problem is, different models appear to have different vertice orientations.
Im getting the vertices via geometry.attributes.position.array:
scene.traverse(n => {
if (n.isMesh) {
let allVertices = n.geometry.attributes.position.array;
for (let i = 0; i < allVertices.length; i = i + 3) {
modelVertices.push(new THREE.Vector3(allVertices[i], allVertices[i+1], allVertices[i+2]))
}
}
});
Here are 2 examples of 2 different models, one of a bag, and the other being a keyboard.
The keyboard is in the right orientation, but the bag isn’t ( I got the models from different websites ). I figured that if I write the bag coordinates with
modelVertices.push(new THREE.Vector3(allVertices[i], -allVertices[i + 2], allVertices[i + 1])
It would work, but there are more models that this other orientation wouldn’t work either. I want to know how could I know in which direction draw the coordinate of the vertices, according to each model.
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Do you add the object of points to scene?
Try to add it to the object of the bag.
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What do you mean? I’m already adding the points to scene, that’s why I can see them. The problem is not in the visualization (that is already working), but in the vertices that I get from the array.
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I mean, add these points to the object, whose geometry to use for the object of points.
scene.traverse(n => {
if (n.isMesh) {
let points = new THREE.Points(n.geometry, _your_points_material);
n.add(points);
}
});
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scene.traverse(n => {
if (n.isMesh) {
let points = new THREE.Points(n.geometry, new THREE.MeshBasicMaterial({ color: 0xff0000 }));
n.add(points);
}});
Drawing the little red cubes from points.geometry.attributes.position.array, I got the same result. The vertices are sometimes rotated in an axis, deppending on which model I’m using.
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That wouldn’t work on itself, because there are models that the correct orientation sits on another axis, like so:
So the problem isn’t on just one misaligned orientation ( don’t mind the y offset of the drawn vertices, it isn’t relevant ).
I think there is a solution to this because the
GLTF Loader itself loads the object in the correct orientation, but
if I access only its vertices via geometry.attributes.position.array, sometimes they will be misaligned, and sometimes they will be in the correct orientation.
The coordinates in the geometry are the so called “local coordinates”. If you want to find the actual global position of a vertex, you need its “world coordinates”. They are calculated by Object3D.localToWorld.
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