Automating Dynamic Place

markeee

Hi,

I'm trying to write a script to place an object with an irregular shape onto a flat background object (like a floor). Is there a way to reproduce what the Dynamic Place (moving the Y-axis only) until it naturally sits on the floor? I'm writing a script that sets up several image renders at different angles at each frame.

The bounding box can't be used since the shape isn't regular and doesn't shrink wrap properly.

Anyone have a possible direction/solution?

Thanks!

ferdinand

Hello @markeee,

Welcome to the Maxon developers forum and its community, it is great to have you with us!

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About your First Question

I really do not want to demotivate you in your first posting, but what you are trying is not trivial and this is one of the cases where when you have to ask, it is probably not for you. The Place tool is not exposed in the public API and so is not the general Rigid Body Dynamics API. Writing something like the place tool yourself is a very hard task.

What is relatively easy, is just to create an RBD setup, and then animate that for X frames, in the hopes that it until then has settled.

Cheers,
Ferdinand

Result

"""Creates a little RBD setup to place an object on top of another object.

I am using here a plane as the object to settle on, but it could also be a non-planar object. Must
be run as a Script Manager script and will place/create a Platonic, as if it had fallen on the world
grid and settled on the origin of it.

Since this must run a simulation, the script will run a while (and block the UI in the mean time).
One could make this nicer with threading and statusbar spam, but I did not :)
"""

import c4d
import mxutils

doc: c4d.documents.BaseDocument  # The currently active document.
op: c4d.BaseObject | None  # The primary selected object in `doc`. Can be `None`.

def main() -> None:
    """Called by Cinema 4D when the script is being executed.
    """
    # Generate a platonic object and a plane object, scale up the plane, move the platonic 500 units 
    # up on the y-axis, and finally create a little RBD setup.
    platonic: c4d.BaseObject = mxutils.CheckType(c4d.BaseObject(c4d.Oplatonic))
    plane: c4d.BaseObject = mxutils.CheckType(c4d.BaseObject(c4d.Oplane))

    plane[c4d.PRIM_PLANE_WIDTH] = 5000
    plane[c4d.PRIM_PLANE_HEIGHT] = 5000
    platonic.SetMg(c4d.Matrix(off=c4d.Vector(0, 500, 0)))

    mxutils.CheckType(plane.MakeTag(c4d.Tcollider))
    rbd: c4d.BaseTag = mxutils.CheckType(platonic.MakeTag(c4d.Trigidbody))
    rbd[c4d.RIGIDBODY_PBD_CUSTOM_INITIAL_VELOCITY] = True
    rbd[c4d.RIGIDBODY_PBD_CUSTOM_INITIAL_ANGULAR_VELOCITY] = True
    rbd[c4d.RIGIDBODY_PBD_INITIAL_LINEAR_VELOCITY] = c4d.Vector(-.1)

    # Create a dummy document, insert our little rig, and execute the passes for 100 frames, in the
    # hopes that the platonic has settled until then.
    temp: c4d.documents.BaseDocument = mxutils.CheckType(c4d.documents.BaseDocument())
    temp.InsertObject(plane)
    temp.InsertObject(platonic)

    fps: int = temp.GetFps()
    for i in range(100):
        temp.SetTime(c4d.BaseTime(i, fps))
        if not temp.ExecutePasses(None, True, True, True, c4d.BUILDFLAGS_NONE):
            raise RuntimeError(f"Failed to execute pass for {c4d.BaseTime(i, fps)} for {temp}.")

    # Get the matrix from the settled object. We can zero out the x/z pos, so that the objects sits
    # dead-center in the world grid.
    mg: c4d.Matrix = platonic.GetMg()
    mg.off = c4d.Vector(0, mg.off.y, 0)

    # Create a new platonic (with the same settings) and insert into the active document and set our
    # computed matrix.
    result: c4d.BaseObject = mxutils.CheckType(c4d.BaseObject(c4d.Oplatonic))
    result.SetMg(mg)
    doc.InsertObject(result)

    # Cinema 4D will garbage collect #temp and its content on its own, but we can call flush to make
    # it a bit cleaner.
    temp.Flush()

    # Push an update event.
    c4d.EventAdd()


if __name__ == '__main__':
    main()

markeee

Thanks Ferdinand, I totally understand I'm above my head. If I were to hire someone to do this, would it be possible you think? Or even there, it's so pigeon-holed that it's futile.

I will go and read the links you provided.

Markeee