[quote:7u7r5om6]What I still don't understand is the ability to have these things (katamaris) grow. I'm not entirely sure myself of how it would work conceptually, not just on Construct. I tried adding the size value of the pickup to the size value of the ball when it picks it up but it didn't work out so well.[/quote:7u7r5om6]
make the physics sprite visible, and set the opacity to 20 percent
make sure it is on top of everything else
so you can see the physics circle, but you can see the trash and katamari through it
now watch what happens when it gets bigger
your bigger sprite probably isn't repositioning itself to be circling around the katamari and the trash, it's just making a big invisible circle around the original katamari.
you have to figure out the math to make the new size be circling the katamari plus the junk.
it should stretch to an oval, and set itself to an angle thats the best fit for the trash
math is power
and the math section of the system expressions wiki
will come in handy
for this to work, you may have to destroy the original physics sprite and create a new one in it's place in order to align the physics circle with the trash it's supposed to be circling. the physics behavior doesn't allow you to move objects without using the physics itself to do it. you can copy over the velocity and angular velocity to the new object so it will continue to move the way the original one did
may also use a second invisible sprite to choose which objects should be picked up
because if you think about it, if you pick up a pencil and it's poking far out from the karamari, causing it to roll differently, you don't want guys sticking to the tip of the pencil. it's a growing circle around the katamari itself, even if the trash is changing the overall shape with one or two odd items, it never loses it's roundness for too long, so the collision mask should grow, but not in the same way the physics object does.
EDIT: For dropbox, make sure you put the file you want to share in the public folder of dropbox, and then rightclick and copy public link