How do you go about having a vehicle make a "natural" looking left or right turn,eg. coming to and or from a stop at a street intersection? When I use the "Y" rotate the vehicle seems like it slides.

I haven't ever tried this but the centre of rotation will be somewhere along the rear axle.  Most modern vehicles have differential gearing which allow one set of wheels to rotate faster than the other, depending on the direction of the turn.  

Oddly enough, there's a new US built "muscle" car with a fixed rear axle, which, IMO, is stone age engineering.  But I digress

I would guess that on a left turn, the centre of rotation will be near to, or at, the left rear wheel, and near to, or at the right rear wheel on right turns.

If the turn would describe an arc--not likely--the center of rotation would need to be at the center of that arc.  In other words, at the center of the circle that arc would be a part of.  I don't animate in Poser, but I doubt that you can change the center point during an animation.

The solution might be a lot of keyframes, more or less, depending the mode of animation, linear, interpolated, etc.  Both X and Z translations would need to be used along with the Y rotation.  Sounds messy ;)  Good luck!

John

Quote - If the turn would describe an arc--not likely--the center of rotation would need to be at the center of that arc.  In other words, at the center of the circle that arc would be a part of.  I don't animate in Poser, but I doubt that you can change the center point during an animation.

The solution might be a lot of keyframes, more or less, depending the mode of animation, linear, interpolated, etc.  Both X and Z translations would need to be used along with the Y rotation.  Sounds messy ;)  Good luck!

John

I will try this

I got to thinking about this, and if you're talking about turning a corner, like an intersection, a center somewhat outboard of the inner rear wheel would probably work best.  If you want to make just one turn like that, then changing the center point might pay off.  A subsequent turn in the other direction would rely on being able to animate the change.

If you want to try changing the center point, select the body, or the equivalent of the hip, chassis maybe.  Go to top view and open the joint editor (under Windows menu).  A green cross will appear.  As you hover your cursor over it, it will change to a bull's eye.  Then you can grab it and reposition it.

John

Quote - I got to thinking about this, and if you're talking about turning a corner, like an intersection, a center somewhat outboard of the inner rear wheel would probably work best.  If you want to make just one turn like that, then changing the center point might pay off.  A subsequent turn in the other direction would rely on being able to animate the change.

If you want to try changing the center point, select the body, or the equivalent of the hip, chassis maybe.  Go to top view and open the joint editor (under Windows menu).  A green cross will appear.  As you hover your cursor over it, it will change to a bull's eye.  Then you can grab it and reposition it.

John

Hey man thanks, I never would have thought of doing things this way, I have to play with the "X" and "Z" as well it takes some getting used to. If you have any more suggestions keep 'em coming!!

No problem.  Thanks for firing up my brain ;)

Another trick that could be useful for animation, that I know will work in Poser because I have used it to make props make world rotations whether they want to or not, is to parent an object to an invisible primitive such as a ball.  A figure can be parented under the Figures menu.

This would probably be more elegant than moving the center point, as you would still have the original when you needed it.  Translating the car while rotating the ball might be easier.  Don't know.  This would still be a one-shot deal, as trying to move the ball to the other side would just move the car, and you can't change parent during an animation.  Useful for a lot of things, though.

John

Quote - No problem.  Thanks for firing up my brain ;)

Another trick that could be useful for animation, that I know will work in Poser because I have used it to make props make world rotations whether they want to or not, is to parent an object to an invisible primitive such as a ball.  A figure can be parented under the Figures menu.

This would probably be more elegant than moving the center point, as you would still have the original when you needed it.  Translating the car while rotating the ball might be easier.  Don't know.  This would still be a one-shot deal, as trying to move the ball to the other side would just move the car, and you can't change parent during an animation.  Useful for a lot of things, though.

John

Ok, I'm going to work on this one too..

Further thinking.  Moving the ball would control the car, but moving the car would leave the ball behind.  A child can move independently.

So you would want to use the ball to translate the car as well.

John

Attached Link: http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=1499769

Thanks for the link, nruddock!  I'm on a dialup, so it will take a while to load.  VK's a great source.  That's who I learned ERC from.  The Cobra that he gave away in this forum a couple of years ago is an amazing machine!

John

I'm going to read this one through too!!

Quote - How do you go about having a vehicle make a "natural" looking left or right turn,eg. coming to and or from a stop at a street intersection? When I use the "Y" rotate the vehicle seems like it slides.

Ok, I go try to explain this.
See it this way, draw a circle, thats the turn your car makes.
Now the "Y" rotate you mention is the center of the circel, in other words outside the car.
Its NOT at the inner back wheel. Take a look at a car when it makes a turn, the inner back wheel is not standing still. This would happen if the turning point is there.

With regards to diferentiated axes of a car.
Look at that circle again and place a car on it, you see that the inner wheels make a smaller circel than the outher wheels. This means that the outher wheels have to rotate faster than the inner, this is where a diferential is used. A "fixed" rear or drive axel is only used on terain cars, and normaly can be turned off and on.
Using a fixed axel on a hard road will couse damage to the drive work and tires since one wheel will be forced to to rotate the same speed as the other wheel in a turn.
In soft terain this is not a problem since the soft material like sand compensates for this.
This "fixed" axle takes away the disadvantage of a diferential in terain, like if one wheel gets stuck it stops turning and the diferential only drives the other wheel.

I hope this all made a bit sence

Quote -
Ok, I go try to explain this.
See it this way, draw a circle, thats the turn your car makes.
Now the "Y" rotate you mention is the center of the circel, in other words outside the car.
Its NOT at the inner back wheel. Take a look at a car when it makes a turn, the inner back wheel is not standing still. This would happen if the turning point is there.

Yup, you're right there.  However, the centre of rotation must change, since a car does not execute a turn all at once.  The front wheels eventually go to their "turn" position, then straighten out again.  I confess I have absolutely no idea how to represent this, though.

Quote -
*With regards to diferentiated axes of a car.
Look at that circle again and place a car on it, you see that the inner wheels make a smaller circel than the outher wheels. This means that the outher wheels have to rotate faster than the inner, this is where a diferential is used. A "fixed" rear or drive axel is only used on terain cars, and normaly can be turned off and on.
Using a fixed axel on a hard road will couse damage to the drive work and tires since one wheel will be forced to to rotate the same speed as the other wheel in a turn.
In soft terain this is not a problem since the soft material like sand compensates for this.
This "fixed" axle takes away the disadvantage of a diferential in terain, like if one wheel gets stuck it stops turning and the diferential only drives the other wheel.

I hope this all made a bit sence :smile*:

Well, yes.  And that's my point.  The vehicle I mentioned (I honestly cannot remember who makes it) has only the fixed option, which seems silly to me.  It would make more sense to have the option of a diff lock, rather than be stuck (pun intended) with a fixed axle.

You can move the pivot point of the car using joint editor in Poser.

Quote - Yup, you're right there.  However, the centre of rotation must change, since a car does not execute a turn all at once.  The front wheels eventually go to their "turn" position, then straighten out again.  I confess I have absolutely no idea how to represent this, though.

Good point, pfhew this was a long time ago for me.
Best way to solve this might be the next:
Draw a spoke from the center to the circle and place the back wheels on that spoke.
In a turn the front wheels wil follow the circle but leave the circle first when they steer.
The back wheels alway's follow the front wheels and stay on the circle until they are forced off by steering of the front wheels who wil go follow another traject. If this is another turn, you have to redraw the circle again.
A steering car is more complicated than you might think

Quote - Well, yes.  And that's my point.  The vehicle I mentioned (I honestly cannot remember who makes it) has only the fixed option, which seems silly to me.  It would make more sense to have the option of a diff lock, rather than be stuck (pun intended) with a fixed axle.

Very true.
The only thing I can think of is that the wheels turn freely on ballbearings on the axel.
Diff lock was the word I was loking for, in general you find those on terain cars.
The only fixed axle I can think of might be on a dragracer, since those only drive straight and they can rule out any losses in the drive train by removing the differential.
I also think that some tracktor pullers use this, but I am not sure about both.

Quote - Good point, pfhew this was a long time ago for me.
Best way to solve this might be the next:
Draw a spoke from the center to the circle and place the back wheels on that spoke.
In a turn the front wheels wil follow the circle but leave the circle first when they steer.
The back wheels alway's follow the front wheels and stay on the circle until they are forced off by steering of the front wheels who wil go follow another traject. If this is another turn, you have to redraw the circle again.
A steering car is more complicated than you might think

Ok, I did some more thinking on this matter.
The above is not complete corect and only work on a wide turn.
Place the front wheels on that circle
The center of the axe is on the crosing point of the spoke and the circle.
Since the front wheels steer, they wil follow a circle.

Now the rear wheels wil take a "short cut" becouse they dont steer and therefor wont follow a circle but more a eclips. However they follow the front wheels.
The shorter the turn, the more they cut off.
Remember when you steer tight around a corner, you feel the rear wheels go over the curb.

There is actualy much more to it, like the Ackerman principle. But I think it gets to complicated for a poser animation