View source for Jumping

There are many ways to make a sprite appear to '''jump''', depending on how you want a [[sprite]] to and how realistic it looks.  This article contains a number of them, categorized from least-realistic to most realistic. The {{key press|up}} key is usually used for jumping in games, but sometimes {{key press|Space}}, {{key press|Z}},{{key press|X}},{{key press|W}}, or even the mouse is used for jumping.

==Simple jumping==
The following is commonly used in animations and results in a sprite effectively teleporting upwards, and then downwards again.
<scratchblocks>
when green flag clicked
forever
  if <key [up arrow v] pressed?> then //typical jumping key
    change y by (50)
    wait (0.5) secs
    change y by (-50)
  end
</scratchblocks>

The below script results in the sprite moving up if the up arrow is pressed.

<scratchblocks>
when green flag clicked
forever
  if <key [up arrow v] pressed?> then //typical jumping key
    change y by (5)
  end
</scratchblocks>
It was used in the Scrolling Demo [[project]] by [[Sample Projects|SampleProjectsTeam]].

Another jumping method which works very effectively and realistic is this.
<scratchblocks>
when green flag clicked
forever
  if <key [up arrow v] pressed?> then //typical jumping key
    repeat (10)
      change y by (20)
  end
    repeat (10)
      change y by (-20)
  end
</scratchblocks>
This is very fast but you can adjust the speed by adding a "wait block" before the "change y" block.

==Falling==
The following script "teleports" the sprite upwards, and then has it fall back down at a constant rate, until it lands on a platform.

<scratchblocks>
when green flag clicked
forever
  if <key [up arrow v] pressed?> then //typical jumping key
    change y by (50)
    repeat until <touching color [#000000]?> //color of the ground
      change y by (-5)
    end
  end
end
</scratchblocks>

The next script makes the sprite rise up at a constant rate and fall back down at a constant rate.

<scratchblocks>
when gf clicked
forever
if <key [up arrow v] pressed?> then //typical jumping key
repeat (10)
change y by (5)
end
repeat until <touching color [#000000]?> //color of the ground
change y by (-5)
end
end
</scratchblocks>

==Limited Jumps==
In most video games, you cannot jump more than a certain number of times, and you cannot jump in midair. This can be implemented in Scratch.

The pink blocks labeled "jump" represent a compatible jump script.

To allow you to only jump on the ground, use the following script.

<scratchblocks>
when gf clicked
forever
if <<key [up arrow v] pressed?> and <touching color [#000000]>> then // typical jumping key, color of the ground
change y by (5)
jump::custom
end
</scratchblocks>

Double jumping is a common element in video games. Although not possible in real life, these scripts can make you jump up to two times.

<scratchblocks>
when gf clicked
forever
if <touching color [#000000]?> then // color of the ground
set [jumps v] to [0]
end

when gf clicked
forever
if <<key [up arrow v] pressed?> and <touching color [#000000]>> then // typical jumping key
change y by (5) // this will keep the first script for resetting the jump count
change [jumps v] by (1)
jump::custom
else
if <<key [up arrow v] pressed?> and <(jumps) < [2]>> then // This will keep you from jumping more than twice
change [jumps v] by (1)
jump::custom
end
end
</scratchblocks>

To make the sprite jump up to ''n'' times, change the ''2'' to an ''n''.

==Realistic Jumping==
To make a simple jumping game (not to be confused with [[platformer]]), follow this script:

<scratchblocks>
when green flag clicked
go to x: [*input*] y: [*input*]
set [y speed v] to [0] //This is just for setting everything up
</scratchblocks>

Then enter this snippet of code:

<scratchblocks>
when [space v] key pressed
set [y speed v] to [*input*]
repeat (((y speed) * (2)) + (1))
change y by (y speed)
change [y speed v] by [-1]
end
</scratchblocks>

If one of the scripts do not work, it can be changed.

==Physically Accurate Jumping==
===With Ground Detection===
A more realistic effect for jumping commonly used in games is the following, using a [[variable]] to control the vertical speed of a sprite (simulating gravity) is this:

<scratchblocks>
when green flag clicked
set [y speed v] to [0] //How fast the sprite is moving upwards.
forever
  change y by (y speed)

when green flag clicked
forever
  ...//Check if the player is on the ground.
  if <touching color [#000000]?> then // The color of the platforms.
    set [y speed v] to (0)
    ...//Check if the player wants to jump.
    if <key [up arrow v] pressed?> then
      ...//Jump!
      set [y speed v] to (9.9)
    end
  end
  change [y speed v] by (-0.5) // Gravity
</scratchblocks>

===Without Ground Detection===
If one does not need to sense the ground and simply want a realistic, gravitational jump, that will end at the starting point, the following script can replicate the jump:
<scratchblocks>
when gf clicked
forever
if <key [up arrow v] pressed?> then
set [y vel v] to (10)
repeat (21)
change y by (y vel)
change [y vel v] by (-1) //simulates gravity
end
end
</scratchblocks>

==See Also==

* [[Simulating Gravity]]
* [[Velocity]]
* [[Physics Engine]]

[[Category:Scripting Tutorials]]
[[Category:Physics Tutorials]]
[[ja:ジャンプする]]