"They've put themselves in a box. I don't know how they're going to get out of it."

[Icemage]

Originally Posted by Descendency

Would you like to tell the creators of Madden 07 that the Wii isn't a capable machine since it had more features than the 360 or the PS3? I didn't say you could port the same code to the Wii. I said you could achieve the same objectives by taking respectable shortcuts. You will get a cut down product, but the fact is the gamer won't know the difference outside of the graphics unless they own both.

Is that the same way PS3 owners of Madden '08 are annoyed over getting 30FPS instead of 60FPS on the other consoles? I'll have to remember that.

[Power666]

Originally Posted by Icemage

Yes, that's the same trailer in SD. The seesaw is one example of what I'm talking about - they can't possibly be using a bounding box or composite object intersection on that seesaw - in fact, even with 10 years of programming under my belt, I have no clue how they managed to pull off a physics engine that would correctly interpret that object combination as a fulcrum + balance beam.

If every object in the game were a circle, square, or triangle, then I'd agree with you, but from what I can see, those are just the basic building blocks because they wanted to keep the interface relatively simple - and has little or nothing to do with the way the physics engine handles the geometry of the objects.

The catch here is that the complex objects are generated from those very basic shapes. That's where a lot of the optimizations can come from. Calculating things like the center of mass for a systems is simply the average of the center of mass of the smaller shapes (assuming the same materials of course). Properties like this do not need to be calculated for every frame but rather only once after the object has been modified.

Bounding boxes are useful as the raw number of object-object interactions can quickly be reduced. It is an optimization hidden away from the user but it obviously isn't the only source of collision detection. A bounding box would be the detector to use the more complex equations.

Originally Posted by Icemage

Look at things like the baskets of peppers - those aren't even vaguely geometric in shape, and yet they all fall and collide realistically. I don't see how you could break those down into circle/square/triangle interactions and still get the results we're seeing.

That can actually be made with 12 basic shapes. One large solid circle, a smaller circle to cut from the bigger ones to create an 'O' shape and then one square to cut the 'O' in half. This would have to be for each layer which I think the game has four. (The number of shapes required to make the final cut maybe one if there is a box that effects all layers simultaneously. That'd bring the number of simple shapes down 9.) There may need to be another shape or two that acts as a pin that links them all together but I'm not sure of this.

Then again, I don't think that the basket full of peppers was user generated content. Pre-defined objects like this that come with the game can easily have pre-calculated properties for attributes like mass, center of mass etc.

[Icemage]

Originally Posted by Power666

The catch here is that the complex objects are generated from those very basic shapes. That's where a lot of the optimizations can come from. Calculating things like the center of mass for a systems is simply the average of the center of mass of the smaller shapes (assuming the same materials of course). Properties like this do not need to be calculated for every frame but rather only once after the object has been modified.

You could certainly calculate the center of mass ahead of time, but there's the caveat of how to handle objects that are interacting with your object. In the case of the seesaw, the engine is calculating momentum transferral from the players and transmitting it to the other end of the seesaw - no small feat, as I'm sure you'll agree.

Bounding boxes are useful as the raw number of object-object interactions can quickly be reduced. It is an optimization hidden away from the user but it obviously isn't the only source of collision detection. A bounding box would be the detector to use the more complex equations.

I'm sure some sort of modified collision box is used - possibly just a polygonal one, since we agree that the interactions on each plane are two-dimensional.

That can actually be made with 12 basic shapes. One large solid circle, a smaller circle to cut from the bigger ones to create an 'O' shape and then one square to cut the 'O' in half. This would have to be for each layer which I think the game has four. (The number of shapes required to make the final cut maybe one if there is a box that effects all layers simultaneously. That'd bring the number of simple shapes down 9.) There may need to be another shape or two that acts as a pin that links them all together but I'm not sure of this.

Then again, I don't think that the basket full of peppers was user generated content. Pre-defined objects like this that come with the game can easily have pre-calculated properties for attributes like mass, center of mass etc.

I disagree with your opinion that the peppers are formed of basic shapes. They're irregular, and the final falling position for each one suggests that however the collision method is calculated, it's using the true contours of the shape we're seeing on-screen, not some sort of mock approximation using regular polyhedra or polygons, Tycho Brahe-style.

[Descendency]

Originally Posted by Icemage

Is that the same way PS3 owners of Madden '08 are annoyed over getting 30FPS instead of 60FPS on the other consoles? I'll have to remember that.

The same publishers that produce more AA games per year than any other company?

[polymer]

The fact that the debate of whether 2D physics is complicated or not is pretty confident on both sides, makes your whole "I'll laugh at you!" comment much less threatening...

[Icemage]

Originally Posted by polymer

The fact that the debate of whether 2D physics is complicated or not is pretty confident on both sides, makes your whole "I'll laugh at you!" comment much less threatening...

If you don't have the math and physics background to follow the conversation, that's not my problem.

[Fyrus]

Power usually knows what he's talking about. At least about computers.

[Power666]

Originally Posted by Icemage

You could certainly calculate the center of mass ahead of time, but there's the caveat of how to handle objects that are interacting with your object. In the case of the seesaw, the engine is calculating momentum transferral from the players and transmitting it to the other end of the seesaw - no small feat, as I'm sure you'll agree.

Actually that's pretty much what you'd cover in a basic dynamics course for engineering (I never took one myself, I stopped at statics and 'mechanics and materials').

Originally Posted by Icemage

I disagree with your opinion that the peppers are formed of basic shapes. They're irregular, and the final falling position for each one suggests that however the collision method is calculated, it's using the true contours of the shape we're seeing on-screen, not some sort of mock approximation using regular polyhedra or polygons, Tycho Brahe-style.

To repeat myself:
Then again, I don't think that the basket full of peppers was user generated content. Pre-defined objects like this that come with the game can easily have pre-calculated properties for attributes like mass, center of mass etc.

I presented my solution for a user defined basket because it quickly came to mind on how to emulate one. I know there are a few objects that users can't create. I saw a flopping fish in the trailer for example.

[Power666]

Originally Posted by Fyrus

Power usually knows what he's talking about. At least about computers.

Durrrrrrrrrrrrrrrrrr..... I like monkeys.

[Icemage]

Originally Posted by Power666

Actually that's pretty much what you'd cover in a basic dynamics course for engineering (I never took one myself, I stopped at statics and 'mechanics and materials').

I never took dynamics in college either, but I think we can agree that the math and concepts involved in that discipline are fairly complex - even by "our" standards, when applied to non-static 3D environments.

In the last several posts, you've attempted to isolate and present these white-room simplifications of what's happening inside the game engine to defend the concept of how "simple" the physics engine in LBP is. Yes, I am sure there are many shortcuts taken inside the engine itself, but I do not believe they've done anything quite so case-specific as you've been suggesting.

To repeat myself:
Then again, I don't think that the basket full of peppers was user generated content. Pre-defined objects like this that come with the game can easily have pre-calculated properties for attributes like mass, center of mass etc.

I presented my solution for a user defined basket because it quickly came to mind on how to emulate one. I know there are a few objects that users can't create. I saw a flopping fish in the trailer for example.

See above comment.

Building an engine full of single-use exception code is just asking for trouble when you're going to allow users to build and generate their own content with the tools we see on display. Unless you're seriously suggesting that Media Molecule have added special code for every non-standard object they've added into the engine, I don't see where this line of disputation is going.