I know you are right, and I do make my models that way, but, in the 3D warehouse, you are not going to find many that follows that rule! They all use an electron thin wall, and don't even know about front/back faces! Let alone paper thin glass (no thickness)!! That's why I try to get some 3ds files, then use AccuTrans3D to convert it to KMZ so that I can load it in SKP.

However, you're obj importer is by far the best of all! Thank you, and it's free!

Your renderer looks fantastic too. Great job, and thanks for taking the time to answer my post.

Great! Thank you. I will use your other tool. What about a face with 2 materials where front and back are visible, say, the back is visible from a mirror when rendered?

FYI I found a simple model that does not convert properly. All faces are oriented correctly and it export fine with SKP obj export...
http://sketchup.google.com/3dwarehouse/details?mid=b4b51fe2bdeeeedf56c58b78d29fd8a9&prevstart=24

Thanks again TIG

Thanks for this great plugin. Way better than Sketchup OBj Export.

I have one request, is it possible to also export back faces that have a color or material, and not those that don't? Say, instead of creating a new face for the back like SKP export do, can yours assing a new OBJ command? For example...

usemtl White
bf 9/9/9 10/10/10 11/11/11

bf for backface!

That way, we can load the obj and detect any back faces as oppose to treat them as a new face and have duplicate triangles!

I don't know if I make any sense?

Thanks

Count me in as well.

I see what you mean. But since "material to material" can take a very long time to set up, perhaps we can use my suggestion to at least setup the default settings for "material to material"? It'll be better than all being zero!

I voted "Disagree" because for anyone running the software for the first time will get lost because and just because of the lack of help. I had a hard time, but now, it's all easy for me. I didn't even know how to make a thruster go along the X instead of the Y until =Physicsguy=, Wacov and CPhillips replied to my post. But I had to ask, and be persistent about it. Not every new users will come here and many long time users don't even know this board exist!

Sketchup and SketchyPhysics are the most and easiest 3D software you can get. Unfortunately, they are not advertised properly, and the help file is poor. Thanks to the online vids or I'd still be wondering how this thing works.

I think the original request was to have a multi directional spring, so that if the object was moved away from its anchor, it would come back, no natter which XYZ it moved to. Now that I think of it, you already have a spring, why not make one multi directional as well?

Here's your flying car Wacov

Well, I suppose we could have only one setting instead of "material to material". What about...

Friction: range from 0% to 100%
The higher the number, the more friction.

Say...

Glass will slide very easily on a smooth wood table.
Glass will slide a bit on sand paper.
Glass will not slide at all on Scotch tape.
Sand paper will slide a bit on Scotch tape.

So we can say...

Glass.Friction == 1; // because it slides easy on smooth surfaces.

WoodTop.Friction == 3; // About like glass but not as much.

SandPaper.Friction == 30; // because it does slides on smooth surfaces, such as when sanding wood.

ScotchTape.Friction == 100; // because it doesn't slide at all on just about any surfaces.

Now we can calculate how to affect the velocity of an object when it slides on another...

if F1 == F2 then V == F1 else V == Abs(F1-F2);

where...
F1 = friction of the first object.
F2 = friction of the second object.
V the resulting percentage the objects speed should decrease on every frame...

Glass --> Glass = 1%
Glass --> WoodTop = 2%
WoodTop --> Glass = 2%
Glass --> SandPaper = 29%
Glass --> ScotchTape = 99%
SandPaper --> ScotchTape = 80%
SandPaper --> WoodTop = 27%
ScotchTape --> WoodTop = 97%

I think the material interaction should not be done using the "material to material" approach. We should use the laws of physics. In real life, what make rubber stick to glass? Well, there is how porous the object is, its flexibility, how smooth it is. That's 3 things I can think of right now. Having settings such as these for each material would simplify the task, and then we would not need to do material to material.

I guess if the object is obstructed by another, it will push it out of the way, or slide along it to try to return back home. Using a spring will not work. At least, that's what I think he's trying to accomplish.

@cphillips said:

Yes that is more or less how it works. If it was just a matter of setting mass it would be easy, but it also has all the other properties of a material like friction.

Part of the problem is that you need to setup material to material values. So if you have wood and ice you have a wood/wood table and a ice/ice table and a wood/ice table. Then if you add say steel then you need all those plus steel/steel and steel/wood and steel/ice. As you can see it adds up to a lot of tables to fill in. The UI is going to be tricky.

Why the need for material to material values? If one material has more friction than another one, it shouldn't make any difference what material it comes into contact with, because both material will then be evaluated to simulate the proper friction, say, rock(friction=10) on glass(friction=1) will slide more than rock(friction=10) on rock(friction=10)

@wacov said:

Oh, don't forget setVar("var") and getVar("var"). This creates and retrieves global variables that carry between frames.

This will be very handy, thank you.

@wacov said:

Sure beats my explanation... in the future, it simplifies things if you post your answer in the FAQ thread, Chris will delete it when he's copied it to the main post.

oh, I thought it was the other way around, post it here, and then he'll delete it and add it to the FAQ!

@wacov said:

That's how it SHOULD be IF it's implemented. That's (I think) how it works in the newton physics playground, so the same kind of thing could be done with SP.

Makes perfect sense to me.

To use SketchyPhysics, you first need to install the latest Google SketchUp 3D designer. SketchyPhysics is not a "stand alone" program, it is a plugin for SketchUp, therefore, requiring SketchUp to run. You can download the free or the Pro version of SketchUp. Use the following URL to view the current available version...
http://sketchup.google.com/
Select the version for your OS, run it, and follow the on screen prompts.

Now that you have installed SketchUp, use the following link to view the latest SketchyPhysics downloads...
http://code.google.com/p/sketchyphysics/downloads/list
Again, run it, and follow the on screen prompts. It will install itself in the SketchUp Plugins folder.

After you have installed both SketchUp and SketchyPhysics, run SketchUp and go to the "View/Toolbars" menu. You will see some new menu items "Sketchy...". If there are no checkmark next to them, click them to add one. This will make the on-screen toolbar visible for easy access. Move the toolbars as you see fit. SketchyPhysics will also be listed in the "Plugins" menu, and in the right click context menu of objects.

To run a SketchyPhysics model, use the following link to search the Google 3D warehouse for SketchyPhysics models...
http://sketchup.google.com/3dwarehouse/search?q=SketchyPhysics&styp=m&scoring=d

Once the model is loaded in your SketchUp, click on the "Play" simulation button. Some model may require you to use your keyboard/mouse/joystick to manipulate the simulation, as in a car game for example. Note that when running a simulation, you can not perform any modifications to the model. Anything that you move while the simulation is running will react as in real life. Click the "Play" button again to Pause the simulation, or the "Reset" button to stop it all together and then you can edit the 3D model and make changes.

@wacov said:

The physics material would be entirely separate from the SketchUp material; so you'd be able to set a box to behave like wood, but it could be painted as steel. These materials would be like templates, with settings you can modify, like density and friction. Maybe a material manager could be implemented? The UI's kinda crowded.

If it's going to work that way, then it'll be perfect, as long as we can make our own material of course. Do you know for sure that's how it'll be, or you're just guessing?

@cphillips said:

I wish I could just say I weigh 180 and have it be so.

In short the physics engine doesn't support absolute weighting of stuff.

In physics as in real life the weight (mass) of something is determined by how much stuff in it and how dense it is. Steel is denser then wood so it weighs more. Thats why the physics engine uses materials.

I understand what you are saying CPhillips, but without density, mass, weight or whatever we call it, some simulations can not be done properly. If you collide a ball of steel with a ball of wood, both of the same size (not mass), the simulation is very incorrect, they both propel in equal force, and that's way wrong. It doesn't matter for gravity as object of different weight will fall at the same speed, but when they collide, it's a new ball game. Material should not be used for this purpose, an object should have a "Mass,Density or whatever" attribute that we can set, regardless of what material we use. Material is for the look.

Take a look at your demo of the car you just did. When the whole car hit the wheel of another, it breaks off, at the same rate as if a wheel hit that wheel. Not very realistic don't you think? Not just for your car demo, but for other simulations. Say, a pool table where the 9 ball is made of gold, then what? it act just as the rest of the balls, that's just not right! We should be able to drop a rock on a piece of wood and have it react realistically. I piece of wood can't just hit a rock and make it fly off the ground!

He said "Some groups may collide even if they seem to be separate" and from his screen shot, it looks like his cylinders are set as a box, and the corners will collide but to the eyes, it shouldn't. Set the cylinders as "Cylinder" and the collision should work normally, if not, set them as "Convexhull".

Perfect Thank you guys

@cphillips said:

No weight because objects dont have materials yet. Thats planned for SPIV.

I'm confused CPhillips. What do materials have to do with the weight of an object? If we make a box and assign 12lb to it, then it doesn't matter if it's solid or hollow, or what material it is, isn't it??