SketchyPhysics - New Grip System for Cars ! !

MrDailyBlah

Ever built a sketchyphysics car? And theres no grip on the ground? Well never fear, 'cos MrDailyBlah is here....(!) (!)

I recently fiddled around with the raytest function, and i thought i could incorporate it in to the sim...

A floor in sketchyphysics is perfectly smooth...it doesnt create friction like a normal surface would. To create more grip, the most obvious solution is to apply negative thrust to the car's body or suspension, but this collapsed the wheel hinges.

I tried to use magnetism as a solution, and i found that if i could use the raytest function, i could find a point under each wheel on the floor, to each of which i can teleport a magnetic object, attracting the wheels to the floor and creating grip without collapsing the car...

That was it in a nutshell... here's the code i used -


# paste the following into the floor
onstart{
# a way to simplify Sketchup.active_model.raytest
def newRay(p,d)
ray=Sketchup.active_model.raytest(p,d)
return ray
end
}
# then i copied the following script 2 each wheel
ontick{
t=[0,0,-1]
ray1=newRay(position,t)
ray2=newRay(ray1[0],t)
s=@simulation.findBody("sphere...") # the magnetic object; theres a unique one 4 each wheel
s.teleport ray2[0] if (ray2!=nil) and (s!=nil)
}

heres a demo of the script

P.S. make sure u know how it works befor u copy it... ( )

iichiversii

This is great, nice feature, thanks

mptak

What a nice Holiday present. Can't wait to try it...(once I understand it (:)).

Don East

Where did you put this script?
Don

MrDailyBlah

@don east said:

Where did you put this script?
Don

u need to put it in the "scripted" section of the Sketchyphysics UI (neither the "ontick" or "ontouch" section would work...)

hobbnob

Hehe not a bad idea, but you could just have put push([0,0,-1]) in the ontick field of the wheel, does exactly the same thing

(little extra note, if you want to have the vehicle turn on it's side/upside down and still have it work, then encase your steering block around the drive joint (either hinge or motor dependign on your preference) and they won't collapse)

MrDailyBlah

@hobbnob said:

Hehe not a bad idea, but you could just have put push([0,0,-1]) in the ontick field of the wheel, does exactly the same thing

(little extra note, if you want to have the vehicle turn on it's side/upside down and still have it work, then encase your steering block around the drive joint (either hinge or motor dependign on your preference) and they won't collapse)

uh..well.. push([0,0,-1]) creates a violent vibration in the wheels.. so its not that simple..

p.s. i looked in ControllerCommands.rb and found the push()method is the same as $sketchyPhysicsToolInstance.pushBody(), which creates the vibration i talked about...

hobbnob

I haven't had that problem in the 4 years I've been using sketchyphysics, you sure you've got your wheels geom and ontick interval set up correctly?

MrDailyBlah

@hobbnob said:

I haven't had that problem in the 4 years I've been using sketchyphysics, you sure you've got your wheels geom and ontick interval set up correctly?

sure as pants man..

ashscott

Yeah I have the same issue with Hobbnobbs micro script - I am building a walking machine - the fluctuation which is somehow included in hobbnobs micro script causes my machine do hover and float around slowly.

When I implement MrDailyBlah's I get the kind of traction for my machine's feet that I was looking for. Can increase traction by changing the value'-1' in the part of the script that goes in the wheel to '-2'. Nice work

I've got no idea where the vibration is coming from - funnily enough, the other two variables marked '0' in hobbnobs script control push in a certain direction. You can make your machine/vehicles hover in certain directions using these variables.

ashscott

I've added a little complexity that is causing this script to crash SP when I try to run it.

As far as I can tell it has something to do with the raytest function - potentailly related to the issue described on this thread: http://forums.sketchucation.com/viewtopic.php?f=180&t=30558

I have tested it in SU7 as well but am getting the same issue - basically the model explodes, the POV zooms way out and all I can find left in the model is a bunch of endpoints (like on the end of a tapemeasure guide......can anyone shed some light?

Ash

MrDailyBlah

@ashscott said:

I've added a little complexity that is causing this script to crash SP when I try to run it.

As far as I can tell it has something to do with the raytest function - potentailly related to the issue described on this thread: http://forums.sketchucation.com/viewtopic.php?f=180&t=30558

I have tested it in SU7 as well but am getting the same issue - basically the model explodes, the POV zooms way out and all I can find left in the model is a bunch of endpoints (like on the end of a tapemeasure guide......can anyone shed some light?

Ash

that's right sir...
i used raytest to find the point where the wheels touch the floor, then i teleport magnets to them to attract the wheels...

ashscott

But Raytest has a tendency to cause SU to flip out - know of a workaround or why I am having the symptoms described?

MrDailyBlah

@ashscott said:

But Raytest has a tendency to cause SU to flip out - know of a workaround or why I am having the symptoms described?

uh... nooo...
u'd better consult pros like Wacov..

ashscott

So you're not getting the issues I described two posts ago.....?

I seem to get it no matter how I run it (apparently the raytest issue was clashing with SU8 but I can't even get it working right in SU7)

MrDailyBlah

@ashscott said:

So you're not getting the issues I described two posts ago.....?

I seem to get it no matter how I run it (apparently the raytest issue was clashing with SU8 but I can't even get it working right in SU7)

try reinstalling sketchup or SP or sumthing ...