[SP2]Basic Tutorial Posted (Moved & Improved) 5/11/08
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Chris
It's amazing what the hand of the master can do. Thanks.
Last night I looked at a few working models (mainly the steam engine) and came to realize that jointed objects should touch for stability. I deliberately kept them apart, to preclude interference. I learned that when my ball joint at the apex of the drag strut jammed against the bogie early on, and when I was swinging the gear doors through the outer skin. I opened the joint separation clearances, and the interference problems went away. I guess that gapping now has to be done more judiciously.I was about to change my LG model to tighten the hinge and servo joints, and your edits show I'm on the right track. Based on that revelation, I'm going to experiment with large disks at the joints (to be hidden) just to act as stabilizers. Yet that confuses me as Curbs demo has very widely separated joints, and his is very stable.
Adding mass is a surprise. I noticed you placed capsules on some parts. Any reason why those and not just a simple cube (to be hidden)? What governed the size?
I noticed the servo joint is visually gone, but its physics remain. I know we can delete a joint group drawing, and it still works, but with the joint gone, there seems no way to delete it if needed, or see it for reference. Did you remove it for any reason?
Anxiously awaiting the new SP version. Any idea on its release date?
Curbs.
Thank you as well for the demo.As far as overthinking the problem, I am very prone to that. The old planner in me. I'll spend an hour planning how to do a 10 minute job.
However, my process as stated was the result of about a dozen trial-and-error exercises, mainly on the failed LG door hinging. I have the paper trail to prove it. It is very conceivable I led myself up the proverbial garden path, but I tried all combos of grouping and attaching to get to there, all starting from scratch (deleting the joints). Having little experience in SP, I may not know the better way, and discovery may or may not show me that way. I used your tut as a starting point, and it worked in some cases, but not all. That is how I found that servos and hinges attach a bit differently.
My next planned trial was to do as you suggested, draw everything, attach the joints all at the same time, then group them in a logical order, also, I surmised from the free end back to the base, but I ran out of time yesterday. It seems we think alike in many ways; it just takes my old bones longer to get there.
And so far, I have only played with servos, hinges and used a ball joint and "U"joint a very few times. I've had zero success with sliders for what I want to do with them.
I also came to the conclusion, that I had to tighten my joints (see above to CP).
Yet your right hand demo shows a wide joint separation, but it is stable, with no bounce or dislocations at extreme ends. Why are mine so loosey-goosey?Have a good trip; it's time for me to play.
jgb
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@jgb said:
Chris
Adding mass is a surprise. I noticed you placed capsules on some parts. Any reason why those and not just a simple cube (to be hidden)? What governed the size?No reason for those shapes or sizes. I just wanted to make sure they didnt touch any other parts. Size was just "bigger". I did the whole thing in about 5 minutes.
@jgb said:
Chris
I noticed the servo joint is visually gone, but its physics remain. I know we can delete a joint group drawing, and it still works, but with the joint gone, there seems no way to delete it if needed, or see it for reference. Did you remove it for any reason?Anxiously awaiting the new SP version. Any idea on its release date?
The servo is still there. Its just inside the geometry a bit. Use xray. Did you know that there is a layer for joints? You can show hide them easily that way.
No release date for the next version yet. I am still trying to finalize what features it will have.
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Your 5 minutes is my 5 hours, if I succeed.
Yes I knew about the Joint layer, just didn't occur to me.
Thanks
jgb
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Sorry to be a baby but could you or someone else please give me clear install instructions i get the following error message "Error Loading File SketchyPhysics.rb
No such file to load -- SketchyPhysics\sketchyphysicstool.rb" and nothing appears in the open SU document, thanx for the fantastic tut i hope to get to use it soon, regards -
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.
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Absolutely top notch addition to the tutorial.
The new sections were full of "I didn't know that!!!" and now I gotta play with this.
One minor note, a very common spelling error, in section 6, 1/2 way down, the sentence "NOTE: These blocks are SEPERATE groups" is spelled SEPARATE. I do it all the time.
Also I have not lost interest in this "project". I have been sidetracked back to an unrelated (to SU or SP) project, a patent application which is now in final review before the USPTO application, and there is a lot to do in that. The application is about 75 pages, and part is in a language (legalese) I don't work well in. To quote Arnie, "I'll be back" in about a week or 2.
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Just started using SP and so far your tutorial is the best I have located. i have a question on the UI. When I edit the properties of a joint as you have explained I do not get the same window. My window does not have the UI as you describe with the posibility of the movement slide. My motor setting works as do other atributes but the UI form only has the Controls, Solids, Joints Tools
I can't seem to attach a JPG.
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@moving2time said:
Just started using SP and so far your tutorial is the best I have located. i have a question on the UI. When I edit the properties of a joint as you have explained I do not get the same window. My window does not have the UI as you describe with the posibility of the movement slide. My motor setting works as do other atributes but the UI form only has the Controls, Solids, Joints Tools
I can't seem to attach a JPG.
Make sure you have the right version:
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Why does a pin that is built such that it is located through an opening in a block pass through the block walls when the model is operated as if the block had no mass? I was expecting a colision. Picture a 3D leter "D" with a pin that passes through the opening. I thought that when you ran the animation the pin would sit inside the "D" and you could lift the "D" with the pin but the pin just passes through the walls of the "D". I tried the same thing by opening the "D" up so that it was more like a "G" so that the hole was more like an exterior wall folded inside and it still passes through the wall. Once it passes through it will collide with the exterior walls of the object. I atttached the pin to an arm on a slide to hold and control the pin.
I'm just trying out ideas. This idea could have some usefull applications in curving geometry where an object must slide and rotate such as an inside cam. I may need to build a joint with a slide and hinge to simulate the motion but i was hoping the colision of the two objects would accomplish the cation.
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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.
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Actually, I was going to mention the Arch Example because I tried creating the hole with blocks joined together like the arch just because of the comlications shown in the Arch Example. The pin is a cylinder so that shouldn't be an issue. I'm wondering if it would have anything to do with the way an "L" shaped group would look. The "L" is surrounded by a completly encompasing rectangle similar to your arch example when it is grouped. Actually, I'm still not sure why the arch doesn't fill in even though it's created from a bunch of smaller groups. Maybe I am joining my groups wrong?
Thanks for your time!
Joe
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Hey I was wondering whether it's possible to actually make any keys on my computer actual control keys for my car model for example is it possible to make the up arrow the acceleration or the down button reverse the car or the space bar handbrake and so on.
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Would that be the beginning of sketchup games?
Great tutorial here... -
great tutorial i have and will be relying on this tutorial for a while as today i have just begun to use sketchy physics and was instantly hooked.
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Thanks a lot !
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Thanks for the nice tutorial. I think I discovered (the hard way) the difference between making a component of a shape and making a group before adding a hinge or other joint. i.e. groups work with hinges and components do not.
If I have it right, you might add that hint to the tutorial.
Thanks again, it got me going....On another topic, has anyone designed logic gates in sketchyphysics? I am thinking of a mechanical digital computer....with balls for bits and some levers for the AND or XOR gates....did a quick google but nothing popped up right away...
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very nice tutorial
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