Three.js place one box upon another - three.js

Question

To display rack structure, placing one box upon another. But y Position calculation fails.Currently creates gap between boxes. Please inform how could it be fixed, whether camera or light effect creates a problem. As per rack size, altering y position. Data contain size and starting place.
```
var data = [{"id": 10075,"size": 3,"slotNumber": 1},{"id": 10174,"size": 7,"slotNumber": 4}];
var rackListGroup;
init();
function init() {
scene = new THREE.Scene();
scene.background = new THREE.Color( 0x999999 );
var light = new THREE.AmbientLight( 0xffffff );
light.position.set( 0.5, 1.0, 0.5 ).normalize();
scene.add( light );
camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 0.1, 1000 );
camera.position.fromArray([0, 0, 140]);
scene.add( camera );
rackListGroup = new THREE.Mesh();
rackListGroup.name = "Rack List"
var i;
for (i = 0; i < 1; i++) {
rackListGroup.add(drawRack(10, i))
}
scene.add(rackListGroup);
render();
}
function drawRack(size, rackNo){
var rackGroup = new THREE.Group();
rackGroup.name = "rack "+rackNo;
var yPosition = -42;
var xPosition = -20 + parseInt(rackNo)*40;
var slot = 1, counter = 0;
var slotWidth = 5;
while(slot <= parseInt(size)){
var slotSize = data[counter].size;
slot = slot + slotSize;
yPosition = yPosition + slotSize* slotWidth;
var geometry = new THREE.BoxGeometry( 30, slotWidth*slotSize, 5 );
var material = new THREE.MeshBasicMaterial( { color: 0xff0000 } );
var shape = new THREE.Mesh( geometry, material );
shape.name = data[counter].name;
shape.position.set(xPosition, yPosition, 0);
rackGroup.add(shape);
var boxGeometry = new THREE.BoxBufferGeometry( 30, slotWidth*slotSize, 5, 1, 1, 1 );
var boxMaterial = new THREE.MeshBasicMaterial( { wireframe:true } );
var box = new THREE.Mesh( boxGeometry, boxMaterial );
box.name = data[counter].name;
box.position.set(xPosition, yPosition, 0);
rackGroup.add(box);
if(counter+1 < data.length){
counter++;
}
}
return rackGroup;
}
```

Answer 1

I've tried your code and I see a misunderstanding between the objects position and the objects height to be able to stack them on top of each other.
You use one variable for yPosition and you need 2 variables, the reason is that geometries are positioned based on its axes center, so it means a 15 units height mesh positioned at y=0 it will place indeed at -7.5 units below the y=0 position and the upper side of the geometry will be at 7.5. So next slot to stack will be needed to place (conceptually) at y = 7.5 + (topSlotHeight / 2).
That's why your calculation of the next slot to stack y position is wrong. I have created this fiddle with the solution, and I have added a gridHelper at y=0 for your reference and the OrbitControls to be able to check it better. Now it works perfectly doing like this, storing the accumulated base position of the previous slot in yBaseHeight and the yPosition for the slot on top:
var slotHeight = (slotSize * slotWidth);
yPosition = yBaseHeight + (slotHeight / 2);
yBaseHeight = yBaseHeight + slotHeight;
PD.- I saw you start placing objects at y=-42, I started from y=0 to show better the effect.