As long as we're making a Christmas list here, I'll add my requests.

1. I think this has been asked before, but can we have a start setting for servos and pistons? They always jump to their halfway point when an animation starts, and sometimes I don't want them to move until I move them.

2. Any chance of a non-static mesh? It sure would save time trying to make swiss-cheese style objects!

3. Also, what is this mysterious "magnet" joint I have seen some models using in the warehouse? Is this planned on being a part of the next SP? If it is, can you turn it on and off, reverse polarity, or set the strength like an electromag?

Even if none of these things happen, I'm still stoked with SP the way it is now! Great work!

I've been failing miserably at trying to make a hopper that will drop it's contents in a predictable way.

I've tried different size spheres, different size holes, and even put the entire hopper assembly on a motor to spin with no success. About half of the contents make it through and then the rest "bind" up and don't drop.

The only thing I can think of is adding some kind of "mixer" to the hopper to keep things moving inside.

My goal is to have one (or two) spheres at a time to fall out of the bottom until it's empty. Dimensions are not important right now, just a working model would be great. If anyone has any solutions, let me know!!!

hopper1.skp

Without a picture or the skp file, it's hard to see what's going on, but there are two possible reasons for what is happening.

First of all, check the bottom of the shape page of the tutorial. It explains that a "hole" in an object won't behave like a hole unless the object is set to static mesh. But if you want to make the object moveable, the only other way to make a hole is to make the object a "group of groups." (DEBUG your geometry and see what's going on.) Take a look at the pic below, and you'll see the arch is actually seen as a half-circle when debugged.

The other reason is that if the "pin" is not a true 3-D shape, it probably won't interact with the model. If it's just a line, it won't work, instead make it a small cylinder.

Hope that helps, and DEBUG DEBUG DEBUG.

Check out the model below. The "D" objects have their collision geometry turned on so you can see what's happening.

d_rings.skp

Just changed the address of the tut:

http://sketchyphysicstutorial.googlepages.com/home

I also added two new pages covering the basics of using the UI, setting multiple joints to move at the same time, and some other stuff I've learned.

Hey guys, I had some time to kill on a plane recently, and thought I'd share this creation. (Thanks again to C. Phillips, you made an international flight go by in what seemed like just minutes because of my SP addiction!!!) Well....that and a half-dozen Bloody-Mary's ....anyway...

This started as a ragdoll, and then I became ambitious with the idea of making a walker... and well, it ended up some where in-between. He doesn't really "walk", he more or less "hops" around stupidly, but I still find it quite entertaining.

If you do play with it, I suggest right clicking the body and select "Camera Follow" after you press the run button. From there just move the single joint slider back and forth at different speeds to see how much of an idiot you can make him be.

I've learned alot from this one, and I might get the time this week to update the tut with some tips on using the UI and making multiple joints move in sync.

(If anyone can tweak this one and actually make him "walk", I'd love to see it!)

(And yes, it is not a TRUE walker because I cheated and hid two gyro's in the calves.)

dancebot.skp

WOW! Those renderings are phenomenal! Great work guys.

JGB: Try the joint tut again, I just did it step by step from a blank SU file, and it worked fine.

I think you may be overthinking the whole joint-grouping thing, and it's probably my fault for posting the tut before Chris' insight.

I am confused as to why you would joint-connect a part and a joint, and then group them together. The grouping will negate the joint-connecting you just did. Usually it is one or the other (joint-connect or group.) I find it helpful to group the joint and object right away, so I can think of them as one piece. Then I just have to find another object to joint-connect them to to make it work.

I don't want to confuse you if you have a method that works, as there are multiple ways to do it, but I think you'll have more success with:
(1 joint/1 object grouped)---joint connected to----(parent object)

(Thanks Chris for the simplicity of helping me understand that.)

I also haven't set the shape of the resulting groups, but haven't had a problem yet.

I agree if you edit a shape and it changes it's geometry, the joint may make it work differently, but as long as the original axis is maintained, you should't have a problem. And yes, there is no shame in deleting a joint and putting a new one in if you're thoroughly confused.

As far as a hinge, servo, and motor, I've found they all attach the same way, but this "way" may change from model to model. If you can make a hinge work right in a certain model, then a motor or a servo should be able to be substituted the exact same way in that model.

I think a lot of the problem stems from breaking joint-connections when new groups are made. As soon as you re-group an object with something else, any joint connections made to it previously will be lost.

As far as burying joints where you can't see them, don't be afraid to place a joint off of the part itself, as long as the axis will work for you. I haven't looked at your model yet, but I made a simple 3 arm, 2 servo, 1 hinge model (inspired by your original model) that can show how easy it is to start a "chain" of joint-connected groups.

This first shot shows that there are 2 servos and 1 hinge, each on moving parts:

The second shot shows an exploded view with the joint-part grouping, and even though none of the parts touch, the axis' are all still the same, and it moves exactly like the unexploded model:

Take a look at the model, delete the joints if you want and try to put them back in using the 1,2,3 method:

1. Add a joint for a moveable part.
2. Group the joint and the part.
3. Joint connect the joint to a "parent" to "ride on."

The pics don't show the connecting, but if you start at the ball arm and work your way back to the block, each joint-connected parent is the piece behind it. (Which is another group including a joint.)

The only thing to watch out for is the breaking of joints when you make new groups. I first added all my joints and did the grouping, then I started the joint-connecting process so I knew there wouldn't be any broken connections.

(Also disregard the gyros, they just keep the ball-arms from going crazy when you move them.) And don't apply any of this discussion to the gyros, they seem to be a whole different beast!

Anyway, I'll be traveling out of country for a few days and I don't know what my internet acces will be, but if I get a chance to look at your model, I will, It was already looking great before.

joint grouping2.skp

Thanks for the tip, I've wondered the same thing.

You're right about using it to set up a scene. I would hate to try and make that bowl full of fruit in Sketchup WITHOUT SP! That would be a LOT of move copying, and the placement probably would never look right.

After seeing Remus' model, it sparked my imagination:

How else could you model a jar full of gumballs without SP?

I've attached the model. It's a whole lotta fun to press PLAY and watch it fill up! (Sorry if you don't like white gumballs, I didn't feel like coloring tonight!)

Gumball Machine1.skp

Excellent model!

I have updated the tutorial based on "the better way" of jointing and grouping.

The basic process boils down to:

1. Add a joint for the part you want to make move.
2. Make the moveable part and the joint a group.
3. Joint-connect the joint to a “parent” object in the model.

Thanks for the suggestions guys, hopefully people will a better understanding with the new tut, I know I do!

New jointing page here: http://curbs77.googlepages.com/sketchyphysicsjoints22

Ahh. Thanks for the different perspective Chris.

In the car example, my thought process was this:

I would Joint-connect the wheel to the thing that makes it spin. (The hinge.) And then group the hinge with the body I wanted it to “stick” to.

But now I see why you might want to do it in reverse. Like you said, it’s easier to move a wheel when it’s grouped with its joint. And if the model becomes more complex, there would be less tracing of groups and broken connections if each object is only grouped to its one joint.

But intuitively, it still just seems backwards to me, so I guess I’ll make the redneck quote of the day and say,

“It just don’t make sense ‘till you think about it.”

I might have to add a full page to the tut about choosing how to group joints and when you would want to do it one way or the other.

Lildood is spot on about the gear hanging up on the fuselage. Try making the gear work in a blank model with nothing else in it. I bet you'd get your servo and hinge to work.

When you add the problem of the fuselage getting in the way, it makes it look like your joints aren't working right and leads you in the wrong troubleshooting direction.

I fixed your joints by adding the hinge you were talking about. (It is grouped to the bogie and jointed to the crank.) It then looked like it wasn't moving, but it was "trying" so I knew the problem was somewhere else in the model. I set everything else in the model to "ignore" and got the gear to work by itself. I also added two gyros to simulate the missing drag struts. (You can delete them to see how floppy the gear is with no struts or gyros.)

Then it was just a matter of finding the piece that it was hanging up on. When I changed the fuselage state to "ignore" it worked fine.

As far as I know, there is no good way to make a shape with a hole in it work in SP besides static mesh.

If the fuselage isn't going to be static in the final model, you would have to make a group of groups to simulate the hole like Lildood said. (See pic below.)

I guess the troubleshooting for this one would be:

1. Make a back-up copy of the original model.

2. Delete everything not directly related to the parts you're trying to make move. (Or set them to "ignore")

3. Solve jointing issues and make just the part work correctly.

4. Add back the rest of the model a piece at a time to see where it's hanging up.

When in doubt, delete everything else so you're only dealing with one problem at a time.

Attached is your model with the mods. It is 99% complete, but still has a problem: The wheels don't fit through the door, so the fuselage is still set to ignore. From this point, Debug your wheels (I think they're square.) And move your fuselage to where the wheels will fall through it. (You'll have to change its state from ignore so you see where the wheels are hitting.)

Have fun, I think you were closer than you thought.

BMF-LG-demo_Modified.skp

Dude, this was a GREAT problem, and I may have to change my beginners Tut to reflect what I learned from this model. I also think your model was excellent with the text explaining exactly what each part was. It was easy to see what you wanted to do, and why it wasn't doing it. (Waaaay better than just a box of random parts and someone saying, "Fix it!")

Looking back at the rest of this thread, I see Lildood pretty much nailed it: The ball joints weren't grouped to anything and were static. (Wish I would've read his post before I started this, but it was fun learning anyway.) But i don't think you need a double link to make it work, it should be fine with one simple servo and three joints.

So here's what I came up with:

Simple solution: The ball joints couldn't move. So I grouped the ball joints to make them moveable and fixed the problems that this caused.

And here's the entire troubleshooting process:

Problem: Something is preventing the servo from turning. (Most likely another joint is static.)

NOTE: Ball joints suspect.

Troubleshooting Procedure:

1. Checked ball joint connections: OK.

2. Checked ball joint grouping: No grouping. This makes them STATIC...and therefore their slave groups are STATIC.

NOTE: Problem found.

RESOLUTION:

1. Grouped each ball joint to its respective door so it will move with the door.

Tested results:

Solution caused new problem: Doors fall off original hinge and servo.

Suspected Cause: Grouping of ball joints and doors created a "NEW" group...thus breaking the original hinge/door & servo/door connections.
RESOLUTION:

(Using Joint connector) Re-connected servo to "newly" grouped door & Re-connected hinge to "newly" grouped door.

Tested: Success.

Other Problems noted: When door is swung completely closed (to the right) servo binds and becomes separated slightly from static wall.

Solution not explored because in a "real-world-environment" the door would never be forced past the "closed" position. Therefore the model works perfectly in its "normal operating ranges."

Suggestions for new model:

1. Replace Ball joints with hinges, they will serve a similar, but simpler solution.

2. Move servo and hinge down to mid-points of doors to make a better "hinge motion" instead of a "corners-connection".

Here's the fixed model:

http://curbs77.googlepages.com/NeedHelp01_Resolved.skp

-Curbs

JGB: I just saw your post about making a beginners tut. My apologies...I didn't mean to step on toes if you already had a work-in-progress. I just saw the same void as you... an incredible program that there was NO information for!

But I'd definitely like to work with other beginners (like myself) and the Vets with the answers and maybe get a community Wiki-style guide put together that we each could add to.

I really like your idea of sharing "what went wrong" and "how you solved it." Troubleshooting is KEY! I also want to add a few pages, one dedicated to each joint and how to use it. (I'm having a LOT of fun with adding a servo to a rag-doll model right now.)

FYI: I solved your door-hinge problem and am going to post it on your thread. (That was a GREAT problem that made me think!)

-Curbs

Thanks for the kind words everyone.

I updated the first page with a link back to these forums and a credit to Chris for being the genius behind the whole thing. I also expanded on the 2nd jointing page explaining a little more about grouping joints. (Or at least as much as I understand it.)

Feel free to link to it anywhere you want, but it is just a free Google page, so it might crash if there's too much traffic. But I'll cross that bridge if it ever happens... I just want to see more people using SP and posting videos!

-Curbs

Edited by CPhillips Apr 1, 2009.
I am making this tutorial Sticky again. Even though its for 2.0 it all still applies.

Hi everyone, I discovered Sketchyphysics just a few weeks ago, and my already unhealthy addiction to SU increased exponentially!

However, as a new user I couldn't find any information on how to use the program. So after a lot of frustration, I finally got a (basic) grasp on it, and I'd like to share a starters guide with anyone who's interested.

This is just to share a few basic concepts with a new user, and it is in no way a "Dummies Guide" or true help page...just a diving board for those who are TOTALLY lost.

Any comments are appreciated, (good or bad) as it's a work in progress.

Edit: NEW address:

http://sketchyphysicstutorial.googlepages.com/