I am trying to understand this and I do but I need to understand it better from a mathematical point, is there any article or video about this subject I could not find anything concrete.
Thank you!
@Tibi any chance you can formulate your question as to what you’re trying to understand?
Yes of course.
I don’t understand completely how the bounding box works, I understand the concept but I need to know more, for example, I don’t understand completely the x,y, and also min and max.
In a project that I am making to position an object under another object that was scaled, I am using this approach to get the first object size and adding y/2 to the object that I want under the first object but I thought the y-axis starts from the center so why I have to divide it by 2 makes no sense to me, it is really unclear to me how it works…
Heres a 1 minute MS Paint job. The box gets wrapped around to the smallest values of the model local coordinate. So for example in this picture, the minimum in x is one very ear tip and maximum of x is the end of the other ear tip. So if you want the length of the model in the x, its x=xmax-xmin. Same for the rest of the axis. The axis is set to three js standards. Im having a hard time trying to understand about your project tho.
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I understand now… so the origin is in the center… thank you is clear 
I have this piece of code to position a shadow under a model…
// Calculate the size of the group’s bounding box
const groupBoundingBox = new THREE.Box3();
groupBoundingBox.setFromObject(this.group, true);
const groupSize = new THREE.Vector3();
groupBoundingBox.getSize(groupSize);
// Determine the position of this.group.
const groupPosition = this.group.position.clone();
// Calculate the yOffset to align this.shadowGroup under this.group
const shadowPositionY = groupPosition.y - groupSize.y / 2 + this.shadowPlanePositionOffsetY;
// Set the position of this.shadowGroup to align it under this.group on the y-axis
this.shadowGroup.position.set(0, shadowPositionY, 0);
// Update this.shadowPositionY if needed
this.shadowPositionY = shadowPositionY;
What I don’t understand is why I need to divide the y of the group size to position the shadow exactly under the model since y is in the center… dose getSize returns the actual size on all axis?
while it might be, most of the times it’s not. that is why there is a need in separate min and max values
Ok I will do it the right way, thank you for clarifying this!
just a question relative to this example, if the monkey face inside the orange box is off by 5 degree z axis (face rotate to the left a littlebit), how can i detect the angle of obj relative to the orange box?
If you set the objects rotation to 0,0,0, and it’s still not aligned, then there is No Trivial Way to determine its orientation… (except for svd which is hard af good luck: Singular value decomposition - Wikipedia)