How do I calculate viewportbottom at zElevation(n)

I'm creating object outside layout bottom of layout ViewportBottom(0) + 200 So we cannot se it being created. then I set its z elevation to int(random(-150,0))

but in runtime we can clearly see objects are being created. How can I fix it?

Set it invisible till you finish positioning it if you do it over multiple frames?

Or depending on the size of the object you’d need to create it further off screen so it’s not seen.

So you want the projected bounding box of the object at different z elevations.

You may be able to get somewhere with the expressions to convert from a position to a layer.

Mathematically you should be able to calculate it with the object’s position and the fov of the camera. Basically a 3d projection to the screen if you want to find more info about that online.

A third way is to just do some trial and error.

Like set y to y to self.y-k*self.zelevation

Fiddle around with the value of k till everything is just offscreen.

Thanks I'll try this.

To expound on the math idea here’s how to calculate the y to place the object just off the bottom of the screen. Untested but the math should be correct.

Var s=0

Start of layout
— create sprite at 320,240
— sprite: set zelevation to random(-150,0)
— set s to 3dcamera.DefaultCameraZ/(sprite.zelevation-3dcamera.DefaultCameraZ)
— sprite: set y to viewportHeight(0)/2/s+self.height/2+scrolly