Object Moves When Game Starts

Game Engine Game Engine Support and Discussion
1

I’ve been working on a system to use mesh vertices to place a grid of blocks (Similar to a rain system I have done that shuffled objects around). I have a script that makes the child empty run through its parent’s vertices adding cubes if a near sensor is False. This works and keeps the framerate stable, but recently my mesh has been teleporting to [0,0,0] when the game starts. This causes the blocks to be put where I don’t want them and the near sensor on the empty is off (meaning it keeps making blocks). Before this happened I tried resetting the parent object’s position, but had to delete it and start again. All new meshes I make seem to have this problem. Is there a fix?

2

you can skip the first frame either by using states or combining the sensors with an inverted delay sensor.

3

Thanks, but I’m unsure that would work since it appears that either the object or the mesh is moving when the game starts. I used print(own.position) ant it looks like just the mesh is moving independent of the object center. Shouldn’t the mesh stay with the object center?

4

Post a file that we might be able to debug. From the initial observation, it doesn’t sound a familiar problem.

5

BrokenTestPlace.blend (461 KB)

This should show the problem.

6

A few things:

  • The near sensor won’t update until the next frame, after all blocks have been added.
  • The check “if x == False” is better done with “if not x”
  • You’re spawning on vertex coordinates, in object space. You need to convert them into world space.
  • Don’t use .position. it’s deprecated because it’s ambiguous.
  • Don’t use script mode, it’s pretty clunky :wink: 

from bge import logic


# place blocks where the empty is.
def place_block(obj, vertex_position):
    x = round(vertex_position.x)
    y = round(vertex_position.y)
    z = round(vertex_position.z)        
    
    block = obj.scene.addObject("Cube", obj)
    block.worldPosition = [x, y, z]


def place(cont):
    own = cont.owner
    scene = own.scene
    near = cont.sensors["Near"]


    if near.positive:
        return


    parent = own.parent
    parent_mesh = parent.meshes[0]            


    # run through the vertices of the parent mesh and place blocks.       
    transform = parent.worldTransform
    for i in range(parent_mesh.getVertexArrayLength(0)):
        vertex = parent_mesh.getVertex(0,i)
        spawn_position = transform * vertex.XYZ
        place_block(own, spawn_position)
7

Thanks, but don’t you mean “Don’t use script mode”, because your script is written for module mode.

8

Oops! Thanks!