py_obj_gravitation

Demonstrates how to implement a classic particle modifier object that applies a simple gravitation effect for each particle.

DETAILS

The ObjectData plugin modifies Cinema 4D basic particles by applying a simple gravitational effect to each particle. To run this example, place the file in the Cinema 4D plugins folder and restart C inema 4D.

Topics:

• Modifying Cinema 4D basic particles
• Applying a gravitational particle force

Files

py_obj_gravitation.pyp

"""Demonstrates how to implement a classic particle modifier object that applies a simple gravitation 
effect for each particle.

The ObjectData plugin modifies Cinema 4D basic particles by applying a simple gravitational effect 
to each particle. To run this example, place the file in the Cinema 4D plugins folder and restart C
inema 4D.

Topics:
    - Modifying Cinema 4D basic particles
    - Applying a gravitational particle force
"""
__copyright__ = "Copyright 2026, MAXON Computer"
__author__ = "Maxime Adam"
__date__ = "25/08/2026"
__license__ = "Apache-2.0 license"
__version__ = "12.0.0"

import os
import c4d

# Be sure to use a unique ID obtained from developers.maxon.net
PLUGIN_ID = 1025246


class Gravitation(c4d.plugins.ObjectData):
    """Gravitation Generator"""

    def ModifyParticles(self, op, pp, ss, pcnt, diff):
        """Called by Cinema 4D to modify C4D particles

        Args:
            op (c4d.BaseObject): the current modifier
            pp (c4d.modules.particles.Particle]): The initial element of the Particle list.
            ss (c4d.modules.particles.BaseParticle]): The BaseParticle List to modify
            pcnt (int): The number of particles in pp and ss list.
            diff (float): The time delta for the particles movement in seconds. Usually the 
                difference in time between two frames, but this can be different for such functions 
                as motion blur.
        """
        # Calculate simple gravitation
        gravitation = 918.0
        amp = diff * gravitation
        img = ~op.GetMg()

        # Iterates all particles
        for s, p in zip(pp, ss):
            # If the particle is not visible, simple go to the next one
            if not (s.bits & c4d.PARTICLEFLAGS_VISIBLE):
                continue

            vv = s.v3

            vv.y -= amp
            p.v += vv
            p.count += 1
        return


if __name__ == "__main__":
    # Retrieves the icon path
    directory, _ = os.path.split(__file__)
    fn = os.path.join(directory, "res", "gravitation.tif")

    # Creates a BaseBitmap
    bmp = c4d.bitmaps.BaseBitmap()
    if bmp is None:
        raise MemoryError("Failed to create a BaseBitmap.")

    # Init the BaseBitmap with the icon
    if bmp.InitWith(fn)[0] != c4d.IMAGERESULT_OK:
        raise MemoryError("Failed to initialize the BaseBitmap.")

    # Registers the object plugin. PLUGINFLAG_HIDEPLUGINMENU hides the natural menu entry of this
    # plugin. Omit this flag or replace it by 0 when you do not have custom menu handling as the SDK
    # (see py_menu).
    c4d.plugins.RegisterObjectPlugin(id=PLUGIN_ID,
                                     str="Py SDK - Gravitation",
                                     g=Gravitation,
                                     description="gravitation",
                                     icon=bmp,
                                     info=c4d.OBJECT_PARTICLEMODIFIER | c4d.PLUGINFLAG_HIDEPLUGINMENU)

Example on GitHub

res/c4d_symbols.h

enum
{
    // End of symbol definition
    _DUMMY_ELEMENT_
};

Example on GitHub

res/description/gravitation.h

#ifndef _GRAVITATION_H_
#define _GRAVITATION_H_

enum
{
};

#endif

Example on GitHub

res/description/gravitation.res

CONTAINER gravitation
{
	NAME gravitation;
	INCLUDE Obase;

	GROUP ID_OBJECTPROPERTIES
	{
	}
}

Example on GitHub

res/strings_us/description/gravitation.str

STRINGTABLE gravitation
{
    gravitation    "Gravitation Generator";
}

Example on GitHub