lesson2.txt

#color 0xffc3e1fe
#coord 305 17
#title The Subframe Lessons
#title 102: Particle Order

#font 7px
#color 0xfffbfbbb
#coord 37 46
#section 2.1 Subframe Order

Here's some bad news:
When you upload a save, Powder Toy messes up the IDs of your particles!

This means that you might have a perfectly working subframe computer,
but when you upload it, it breaks for everyone else.

The good news is, Powder Toy messes up the IDs in a very predictable way.

Particles are assigned IDs in order of their positions in space.
Particles with larger y coords have larger IDs. For particles with
the same y coord, those with larger x coords have larger IDs.

I call this the "subframe order".

#section 2.2 How to Subframe

First, decide on an order of particle updates.

Then, arrange the particles so that their subframe order
matches your desired update order, yet satisfying device constraints.

This isn't always possible; in later lessons we will learn
a variety of tricks to overcome subframe order restrictions.

#section 2.3 Particle Order Reloading

When you test your devices, you always want to ensure that
your particle IDs start out in subframe order.

Thus, before every test, you need to perform a ritual called
"particle order reloading".

#font 5px
#color 0xffbefcc4
#coord 410 48
#section Activity #2.1

For this activity, you need to unpause.

Here are two solid SPRK setups
that are apparently identical.

#space 20

However, one works but not the other.

Explain this.

#answer
Check the ID of the particles.
The CONV and BTRY update in a different order!
#answer

#section Activity #2.2

In the left setup, the CONV and BTRY
are in the correct subframe order
but not the correct ID order.

We can fix the ID order with
particle order reloading.

Here's one way to do it.

1. Ctrl-click this button (local save)

Note that this is __different__ from
creating a stamp.

2. Ctrl-click this button (local load)

Now, the left setup should be
a working solid SPRK.