Animating a Car on a Path in 3ds Max - Part 03 - Turning the Wheels
In this tutorial, you establish the relationship between the car’s front wheels and the steering wheel, so that the front wheel’s turn when the steering wheel rotates.
- Recorded in: 3ds Max 2015
- This tutorial is intended for use with 3ds Max version 2015 or higher.
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Now that you have the car wheels spinning properly based on car travel, the next step is to control the turning of the front wheels.
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What I call Turning in this case is a rotation you apply to the front wheels as the car steers left or right.
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Here you will establish a link between the turning of the front wheels and the rotation of the steering wheel.
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This way, you'll be able to keyframe the rotation of the steering wheel and the front wheels will react to that change.
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Continue working on your file. You can also use the file named Car-Rig_wheel-turn.max if you need to catch up.
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Select the steering wheel and set your rotation mode to Local.
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As the steering wheel rotates on its local Z-axis, you want the front wheel helpers to also pivot on their local Z-axis.
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Make sure the steering wheel is selected and right-click to access the Quad menu.
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Choose Wire Parameters > Transform > Rotation > Zero Euler XYZ > Z Rotation.
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With the rubber band appearing, the next step is to select the Front Left wheel helper.
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As mentioned in the last movie, it's easy to make a mistake and pick the wrong object instead.
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Rather than risk that, use the H key or the Scene Explorer to select the Car_hlp_FL helper object.
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Wire the steering wheel to the helper's Transform > Rotation > Zero Euler XYZ > Z Rotation
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In the Wiring dialog, set the direction so that the steering wheel controls the helper,
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and click Connect.
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Do not dismiss the dialog just yet. Make sure the steering wheel is selected and test out the results by rotating it locally on its Z-axis.
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Not bad but the rotation is inverted.
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Place a - (minus) sign in front of the formula and update it.
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Try it again…
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Much better but you still need to fine-tune it.
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Usually, a steering wheel lock-to-lock range as it is called is far superior to that of a turning wheel.
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The front wheels on an average car may turn to about 45 degrees left or right giving them a range of about 90 degrees.
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A steering wheel however typically has about 3.5 revolutions, from left lock to right lock.
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In fact, the ratio between steering wheel and front wheel rotations is often about 14:1 on a regular car.
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Sports car may have a smaller ratio, maybe 9:1 or 10:1.
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It's even smaller on race cars. A Formula 1 car for example is probably closer to a 3:1 ratio.
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On your average every-day car, especially one built in the sixties, the ratio is around 14:1
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Therefore, divide the formula by 14 and update it again.
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Test the results; they should be quite a bit more natural this time around.
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Copy the formula using Ctrl+C,
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and repeat the procedure for the right wheel helper.
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Dismiss all wiring dialogs when done.
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With the car animated to travel along the path, you will now animate the steering wheel based on the path curves.
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Select the steering wheel and make sure you are in Local Rotate mode.
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Also, switch back your Time Display to Frames only, to ensure keyframes do not fall into the subdivisions.
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Enable Auto Key and take a global look at the animation.
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For the first 10 frames or so, the car is practically moving in a straight line.
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Go to Frame 10,
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and right-click the Time Slider bar.
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In the Create Key dialog, make sure only Rotation is enabled and click OK.
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This creates a rotation key at frame 10 ensuring no rotational changes happen before that frame.
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Now scrub the animation until the car is in the middle of the first turn.
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Frame 52 looks about right.
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Zoom in for a better view and rotate the steering wheel on its local Z-Axis until the front wheels are aligned with the turn.
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Zoom back again and scrub the animation until the car is in the middle of the second turn.
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Frame 112 looks good.
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Zoom in again and rotate the steering wheel the other way,
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until the front wheels look properly aligned.
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Finally go to the frame where you feel the wheel should be straight again,
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frame 140 seems like a good fit.
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Here you need to bring back the steering wheel to its original position.
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Although we didn't take note of the rotation values we established a second ago, there is an easy way to reverse them.
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One way is to copy the keyframe at frame 10 which represents the steering wheel at the original 0 angle.
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This can be done by holding the Shift key and moving the keyframe from 10 to 140.
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Another easier way comes courtesy of freezing the transforms earlier in the tutorial.
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Because of that, you can use Alt with a right-click and then choose Rotation to Zero.
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This realigns the steering wheel to its original state and creates a keyframe since Auto Key is enabled.
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Exit Auto Key when done.
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Adjust your view,
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and scrub the animation to test the results.
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At this point, you may want to reset the Time Display to Frames and Ticks to smooth the viewport playback.
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The animation is getting better but you can improve on it still.
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A heavy car from the sixties tends to have a lot of body roll when taking a turn.
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You need to establish a link between the body rotation and the steering wheel.
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This way, every time the car makes a turn, the body will lean a bit towards the outside of the turn.
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This is what you do in the next movie.