I have it working now, at least sort of. I had to move the steering column off the model and use a box pulling the truck like you did in your example. I can hide those groups so they won't show in the final animation, but I would expect there to be a better way. So far it's been the only way I could get the front wheels to turn properly.

Another question is why the box sinks and drags the front wheels down with it. I have it set to no collision to avoid the box bumping across the ground. Is there a way to keep the wheels from sinking with the box?

Also, is there a way to increase the speed of the truck following the curve? It would be great if the speed could actually vary (slower as it comes around the corner and then increasing to approximately 30mph).

[edit] I found this explanation at google codes:

setVelocity takes a vector that is the direction the object will

#be moving and the length of the vector is how fast. It is different
#from push because it actually sets the objects velocity rather than
#just try to push it.
onstart{
setVector([0,0,10]) #set object to moving straight up at speed 10
}
The sample code you had written has setVelocity(dir.to_a). I'm a little confused why this code starts setVector, but setVelocity([0,0,10]) works as described. I assumed dir.to_a would replace the distance and direction in this code. Adding the third variable doesn't seem to do anything.

AnimationTest5.skp

I agree, it's very close. I think the front wheels should turn right or left at the same time. Right now they swivel around the hinge independently so one wheel turns left while the other turns right. Maybe it's only the steering column that I'm missing? The rear wheels on the truck and trailer are fine as they are.

I've made a lot of progress understanding how the various elements fit and work together. Your example has been very helpful. In the attached model I can't figure out how to make the front axle and the hinge between the truck and trailer all turn at the same time. As they are now, the two parts are connected with the ball joint, and the hinge joints work to turn the truck properly. The front wheels also turn, but are completely independent of one another. If I regroup things in a different manner, the front hinge joints turn the wheels together, but it's as if the rear hinges aren't there and the truck and trailer unit act as one. Where have I gone wrong in the various joint connections and groups I've made?

Once I have that figured out I intend to add the cab of the truck (hopefully that won't cause problems when I group additional geometry to the base that's there now. Then I think I can use the script you provided previously to move the truck along the path and pull the trailer along behind. I feel like I'm getting close.

[edit] As I've thought about this more, I believe the front axle needs to be grouped to get the wheels to turn together. When I try grouping them and leaving the joints connected as they are in the model, the wheels don't turn at all. I must not have the hinges joined to the right part of the model.

AnimationTest5.skp

Do the faces "bleed together" in your flat plan view or only after you have attempted to drape/intersect with the terrain below? If the faces are not formed correctly in plan, you should check out several discussions on this forum (including one from this week) on importing AutoCAD files into Sketchup. There are several plugins available here or at smustard.com (some free or $) that can be used to clean up autocad files and possibly fix the problem you've described. If the faces are not forming correctly after your merge the lines with the terrain, you could redraw the missing edges with Fredo's Tools on Surface.

It's also possible that the size of the model is affecting this. On large models, Drape will sometimes grind my machine to a halt. Maybe you could try breaking the city geometry into parts and draping those smaller pieces onto the terrain below. With less geometry to process, it's possible you will get a better result.

Wow, this looks great. I've started playing with Shaderlight for some of my projects as well. Would you mind posting an image of the raw SU with textures on for comparison?

Wow, thank you so much! I'm excited to dig into this and figure out how it works.

I get an error when pressing run:
Error starting simulation: : undefined method 'parent' for nil:NilClass C:Program...Plugins/SketchyPhysics3/ClassExtensions.rb:59:in 'definition'

I've gotten this error numerous times when downloading for the tuts I've worked through. Usually I have to redo all the joints to get the animation to run. There must be an easier way though.

[Edit] I reconnected two joints, then turned the camera scripting on, and voila, it works! Not sure how any of the things I did actually changed anything. Thanks again, I think this will be very helpful.

Mr. K, thanks for all your help. I've been able to figure out so much more by following those links you gave me. Is there a tutorial/guide for working with curves? I've downloaded CurveTest3 and CurveControllers1 and tried to dissect them. I can replicate what I see in CurveTest3, but I'm not sure what is happening in the controllers file.

Is there a way to define how an SP object interacts with the curve? The attached file has a simple cube, a curve, and a tutorial car. For now I just want to figure out how to move the cube along the path keeping the bottom edge of the cube centered on the curve. As you will see, the cube moves backwards from what I want and hops up and down along the curve. Eventually I would like something more complex (like the car with joints) to move along a similar path. Can you offer any suggestions?

Test_Curve.skp

Mr. K, this information is exactly the place I needed to start. Thanks for the link; not sure why I couldn't find that page on my own before. I'll post a model after I get a better understanding of things. I thought I read 3.2 was still beta so I currently have 3.1 installed. I'll get the upgrade.

If you don't have the Make Faces plugin, you definitely need it. It's free at Smustard: http://www.smustard.com/script/MakeFaces

Everything appears coplanar. The problem is that you have short overlapping lines. There are several scripts to select/label/delete them. Stray Lines is one example. I used Select Curve and zoomed into the areas where the selection stopped, deleted the unnecessary line, selected the curve again, and repeated.

Ok, I'm so confused, and need some more direction on what I'm doing wrong or where to start. This is what I think I need to do: Make a truck and trailer with a hinge joint connecting them. Create a curve path, assign the truck and trailer to that path, and animate the sequence. At the same time that animation is running, I need to move the camera on a path (preferably with SU animate), and export the entire sequence to AVI.

I've read the 3.1 FAQ, watched tutorials on YouTube, and downloaded example models. Only one of the videos I've found actually has sound or explanations, and I've found it very difficult to follow the steps people are doing. In particular, I've had very little success recreating anything with joints that I've seen in the videos. A lot of the videos I've seen show a dialog with sliders, but I've found nothing that looks like that or anything that explains what they do or how to go about creating those options. Most of the models I've downloaded from 3DW do nothing, explode, or cause a bugsplat. CurveTest3 worked for me, but the other curve tutorials give me an error about not being able to find a parent file and/or cause a bugsplat.

I have a good understanding of SU, a rudimentary understanding of ruby, and am confident I can model what I need to model if I could find any kind of resource to teach me the basics of SP. Can someone point me towards better "starter" videos/tutorials/guides or provide some feedback on viability of the process I've described above?

There's a script called Dashed Lines at Smustard. I thought I purchased it, and was going to post an example but I don't see the plugin anywhere. Anyway, you might look into it and see if it would work for your situation.

[edit] I knew I had dashedlines.rb! Here's an example of what it does.

Chris, one other thing about your system that I appreciate is your conformance to Rick Wilson's Organizer.rb. It is so nice to be able to move scripts into subfolders rather than trying to sort through a huge list in the plugins menu.

Or try Tools on Surface.

Mr. K and Kris, thanks for the suggestions and links. I really only need it to "look realistic." We'll be doing the actual turning movement calculations in AutoCAD, but a close approximation of the turning truck with the hinged trailer will work fine for presentation purposes. I'll have to check out the simulator at home since my work's internet filter says that site is a gaming site and has blocked it.

I have a need to animate a semi-truck turning onto a street I've designed in SketchUp. Large trucks like the one I've modeled don't necessarily turn a true 90-degree corner, and the trailer follows a slightly different path than the cab of the truck itself. (I have the exact path defined in AutoCAD, if that's helpful). I have SU Animate and had planned to animate the truck that way, but I need for the truck/trailer to follow two slightly different animation paths, but still be joined at the hitch so the truck appears to turn as a single unit. I'm familiar with the general concept of SketchyPhysics and have watched various demos, but never tried it out for myself. Would physics be the best method to create this, or is there another way that would be better?

You could use Extrude Edges by Edges and Tools on Surface. First group all the vertical lines and weld the path into a single curve. The highest desired elevation appears to be at the start of the path; copy that vertical line to the end point. Group these lines. Extrude edges by edges using this group and the flat animation path you've drawn. Now use Line on Surface to connect the vertical points you've drawn. When the degree of curvature between the two points nears or is greater than 18 0degrees, you'll need to calculate the midpoint elevation and draw to that intermediate point before continuing on. The process isn't automated, but I think it will be easier than manually figuring all of the centerpoint elevations. Hopefully this makes sense; I can post something if it doesn't.

TIG, the fixtreed.rb is fantastic! The script eliminates several steps from a fairly lengthy process I developed to use Tree[d] models. Thank you!

The images and layout look great. Nice work! There is a typo on the Howard Street office building page.

Some of the bamboo drives from Basecamp were loaded with the wrong template. A couple people who loaded 8 while they were there had the same issue. I would bet that if you update to the new point-version you will get the correct templates.