[Bf-committers] Drop to ground mod idea

michaelw@cowtoolsmedia.co.uk michaelw at cowtoolsmedia.co.uk
Fri Dec 16 07:55:42 CET 2011

I did a car rig using the shrinkwrap modifier with bones representing the contact point for each wheel...

You can then drive a root for the body by constraining It's position to all 4 contact points by weighting the position constraint for each point as follows:


This gives the average position of all 4.

I also had a bone targeting from front left wheel to front right and another for the back.

I just averaged the orientation of these on my body root bone.

A similar thing would 'just work' for the ocean sim case...

The rig had some nice stuff on top of this that allowed easy animation of drift, body roll, suspension and steering, but that gets more complicated.

I'd probably use bullet for more complicated cases.

Just trying to point out that the functionality exists for many of these use cases already if you read the manual and have a modicum of rigging knowledge.

I don't disagree that a quick drop to ground with option to orient as well would be a usefull script.

-- Sent from my HTC Desire on 3 --

----- Reply message -----
From: "Erwin Coumans" <erwin.coumans at gmail.com>
Date: Thu, Dec 15, 2011 22:18
Subject: [Bf-committers] Drop to ground mod idea
To: "bf-blender developers" <bf-committers at blender.org>

A good starting point seems to use Bullet for that.
Is there still a plan to integrate/merge Bullet in Blender (outside of BGE)?


On 15 December 2011 23:09, Campbell Barton <ideasman42 at gmail.com> wrote:

> On Tue, Dec 13, 2011 at 7:24 PM, Knapp <magick.crow at gmail.com> wrote:
> > I keep finding cases were I need a stack modifier that drops something
> > to the ground.
> > Examples of this are:
> >
> > A big group of trees that are in the dirt but the dirt is done with a
> > cloud texture into a displacement mod. Getting each tree to the right
> > place is a real pain. Then you adjust the cloud text and have to do it
> > all over again.
> >
> > A boat on dynamic or ocean sim water. How do you get it to float with
> > the waves in an animation? With ocean sim you don't even have an
> > animated mesh to parent to. Being able to drop a vert to the water
> > surface would be great. In the case of a big ship you might even want
> > to drop 4 points on the ship to the water surface and not just a point
> > of the surface but an average of the surface in an area under the
> > boat.
> >
> > A car driving over rough ground in a film. Also a real pain to do but
> > a drop to mesh surface would be great! Perhaps for each wheel.
> >
> > Mod options:
> > to surface or plane or coordinate like +100 X.
> > Surface as defined by a vert, surface point or an averaged area
> > Direction (a vector?) to fall.
> > Depth of penetration into surface.
> > What is doing the touching, IE a point from the object or an offset
> > from origin or the lowest surface etc.
> > Perhaps some way to make the 4 points of a car that touch change the
> > rotation of the object with possible locking of axis (plural form?).
> >
> > Possible problems is that it is heading into the direction of physics
> > and might need more data, for example over time, than is easy to
> > implement. Even with these limits I would find it useful even as a
> > simple drop to point along an axis but much better as drop to surface.
> >
> > I am sure something like this must exist for the BGE but I want it for
> > film and still picture making.
> >
> > I found this script.
> >
> http://wiki.blender.org/index.php/Extensions:2.5/Py/Scripts/Object/Drop_to_ground
> >
> > Is there anything else that I might have missed or another way to do
> this?
> >
> > --
> > Douglas E Knapp
> Hi, firstly I think we should have at least 1 tool for simple drop to
> group functionality (with some options for offset and orient to the
> grounds shape).
> Further this gets a bit tricky because there is not one right way to
> solve the problem, with how the tool functions (do you try to
> intersect the base of the object with the grounds surface for
> example), implementation too - could use objects/duplis/particles etc.
> As for animation, for this I think a separate tool is needed since for
> animation you get too many variables/issues
> * how to follow surface without jittering, to follow surface over one
> point or 4+ points on each corner of the object,
> * some option to smooth out motion or dampen it
> * a useful way to change speed
> * how to manage multiple objects (possibly even have them not run into
> eachother)
> * you may want other objects to match this speed - like wheels of a
> vehicle turning.
> If a developer doesn't have an immediate use case its a bit arbitrary
> as to which issues you try to solve and how much detail you go into.
> --
> - Campbell
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