Scratch

thats a lot to complicated

BirdByte wrote:

ZombieHappines wrote:

thats a lot to complicated

The script you are thinking of IS complicated. Lots of trigonometry is involved in the basics.

yes but there has to be one a little shorter

i want a regular square that does that stuff without the side changing and the side length
sorry i meant square

Last edited by ZombieHappines (2012-08-25 23:02:29)

Hey, I made a simpler script that hopefully does what you need. It's still not easy though - what you're trying to do is kind of complicated.

Start with creating a 50px by 50px square    Since it's a bit of a hassle, I made one and uploaded it on Scratch Resources here 

First of all, you want to be able to nicely control the *rotation* of the square with the arrow keys. For that we'll use something similar to the common velocity or speed method for scrollers. Instead of controlling the sprite's vertical/horizontal movement, we'll use it for rotation:

when  clicked
set 
turn speed ▼
 to 
0
forever
if 
key 
left arrow ▼
 pressed?
change 
turn speed ▼
 by 
-1
if 
key 
right arrow ▼
 pressed?
change 
turn speed ▼
 by 
1
set 
turn speed ▼
 to 
turn speed
 * 
0.9

Now, you'll want to make a script that turns the sprite using this (turn speed) variable.
We also have to set the y position so that it looks like the square is rolling over its corner. For that, we'll need some math.

when  clicked
forever
set 
angle ▼
 to 
direction
 + 
45
 mod 
90
 - 
45

This is the angle of the square, compared to it being flat on the ground (a number ranging from -45 to 0 to 45). It's also the amount of degrees we still have to turn before it's lying down on it's side.

Now for the turning/positioning:

when  clicked
forever
turn  
turn speed
 degrees
set y to 
-100
 + 
sqrt ▼
 of 
2
 - 
1
 * 
25
 * 
abs ▼
 of 
angle
 / 
45

The turning is kind of obvious.

The second block is a little harder. If you'd be interested in understanding it, (sqrt(2) - 1) * 25 is the difference between 1) the distance from the center to the side and 2) the distance from the center to a corner. If the square is standing on a corner, you want to add that to the y position (so it's a little higher). If it's on its side, you add nothing. If it's somewhere in between, you add something that is somewhere in between 0 and the full difference between those 2 distances.

-100 is a fixed position, so you can change this to move your sprite up/down.

Note that this is actually just approximate and not physically correct - but it sure looks like it 

You can experiment with your project at this point, you'll notice that the square rotates nicely, and moves as if it's rolling over its corners.

What we haven't done yet, is making it "fall" onto its side realistically. That's also kinda hard. That's what this script does:

when  clicked
forever
if 
not 
key 
left arrow ▼
 pressed?
 and 
not 
key 
right arrow ▼
 pressed?
if 
abs ▼
 of 
angle
 > 
3
"accelerate" to fall on its side
if 
angle
 > 
0
change 
turn speed ▼
 by 
45
 - 
abs ▼
 of 
angle
 * 
-0.03
else
change 
turn speed ▼
 by 
45
 - 
abs ▼
 of 
angle
 * 
0.03
else
almost on its side, realign it
set 
turn speed ▼
 to 
0
stop turning
point in direction 
round
direction
/
90
*
90

I'm still cleaning up my project I made to go with this tutorial before I share it, but you should really try to make your project from this tutorial - you'll hopefully understand how everything works    If you can't get it to work, I'll a working version of this project later.

Enjoy!

Last edited by JSO (2012-08-26 15:07:38)

ZombieHappines wrote:

thanks so much

Let me know how it works out 

PS: I fixed the first script in the tutorial. I forgot to add

set 
turn speed ▼
 to 
turn speed
 * 
0.9

Last edited by JSO (2012-08-26 15:09:17)