Scratch

Luxturna said he needed some help for his game, so I'm going to give her a guide.
So, he needed help with sensing on his platformer:
   Sensing is difficult, especially since Scratch does not support atomocity. There are many ways to do it efficiently, but the one thing that will glitch so much is: color sensors. The main problem is you go through walls because: the colors on the costume are too thin and it gets through the wall or the whole thing goes into the wall and it get's stuck. So basically, color sensing is off the list.
   However, there are still many other methods, such as the reliable (but tacky and annoying) wall colors. Technically this is still color sensing but more efficient. You also have the most efficient method on Scratch, various versions have been made by me, eRKSToCK, RHY3756547, Rahi-Tak, and Kileymeister. This is what it's all about. Basically when it hits the level sprite, or the basic layout of the sprite, it checks the terrain. It can be: a horizontal wall, a vertical wall, or a 45° slope. So first we will check for a slope (assuming you are using velocities):

change x by (xvel)
if <touching [level v]?>
 change y by (([abs v] of (xvel)) + (1))
end

What this does is it checks for collision, and if it collides with a wall, it reacts to it as if it were a slope. This works because it take the absolute value (abs, always positive) of the x velocity and changes the y position by it, but plus one more to be safe. This way it travels up a 45° slope.
Now we need to check if it's a wall:

change x by (xvel)
if <touching [level v]?>
 change y by (([abs v] of (xvel)) + (1))
 if <touching [level v]?>
  change x by ((xvel) * (-1))
  change [xvel v] by ((xvel) / (-2))
end

Now we have checked for wall collisions and avoided getting stuck. But we still need to enable y collisions. Se first we'll do jumping, add this after the x collision script, but keep it in the same loop:

if <key [up arrow v] pressed?>
 change y by (-3)
 change y by (3)
end

Now your probably asking if I'm drunk. I'm just getting you comfortable with the style. Basically what it's going to do is go down 3 pixels, check for collisions, and move back up. If it hits the floor, that means it can jump, you get it?

if <key [up arrow v] pressed?>
 change y by (-3)
 if <touching [level v]?>
  set [yvel v] to (10)
 end
 change y by (3)
end

Now jumping still won't work, because nothing is commanding it to. Now we'll get to collisions and coming back down.

if <key [up arrow v] pressed?>
 change y by (-3)
 if <touching [level v]?>
  set [yvel v] to (10)
 end
 change y by (3)
end
change y by (-3)
if <not <touching [level v]?>>
 change [yvel v] by (-1)
end
change y by (3)

Now it goes back down, but it still needs to move.

if <key [up arrow v] pressed?>
 change y by (-3)
 if <touching [level v]?>
  set [yvel v] to (10)
 end
 change y by (3)
end
change y by (-3)
if <not <touching [level v]?>>
 change [yvel v] by (-1)
end
change y by (3)
change y by (yvel)

Okay, now collisions.

if <key [up arrow v] pressed?>
 change y by (-3)
 if <touching [level v]?>
  set [yvel v] to (10)
 end
 change y by (3)
end
change y by (-3)
if <not <touching [level v]?>>
 change [yvel v] by (-1)
end
change y by (3)
change y by (yvel)
if <touching [level v]?>
 change y by ((yvel) * (-1))
 change [yvel v] by ((yvel) / (-2))
end

That should work, just make sure you've also implemented a good x moving system. I don't wanna give it all to ya'.

Last edited by chanmanpartyman (2012-07-17 17:52:31)