Scratch

Here is a method that will give you a velocity type jump but doesn't actually use velocity. It is currently set to do a fairly fast jump. This is a very simple jump that does not work for platforms because it will put the sprite back on the same ground level that it started out jumping from. But it is a great jumping method for something like a side-scrolling player vs. cpu fighting game (Mortal Kombat, Street Fighter, etc)



This is a small script but it does a lot of cool things...
1) the first purple block sets the sprite to it's "bend" costume which looks like it is bending down and getting ready to jump.

2) the WAIT block holds that pose just long enough for it to be seen but not so long as to slow down the entire jump movement

3) SET JUMPING TO YES- I use the variable "jumping" in other parts of the script to make sure that the player cannot hit other keys and do something else while the sprite is still jumping

4) SET JUMP TO 0- The variable "jump" is going to be looped and increased in a range from 0 to 170 in the following REPEAT block loop

5) SWITCH TO COSTUME JUMP- The sprite has already bent down, now it will switch to it's "in the air" leaping-type look

6) REPEAT 17 (and the 2 blocks inside it)- This loop increases the "jump" variable by 10 every time it repeats as well as adjusting the sprite's Y position. The changing Y (the actual jumping action) is figured by getting the Cosine amount of the variable "jump" every loop repetition

7) SWITCH TO COSTUME WALK- Now that the actual jump is over, the sprite is back on the ground so we switch it to it's 'just standing there' look. You could instead make a 'landing' costume or even re-use the "bend" costume if you wanted. But I needed a fast jump and this version looks fine for my purposes

8) SET JUMPING TO NO- And finally, we are resetting that "jumping" variable so that the player can once again hit keys and move however they want to


You can adjust the height of the jump by adjusting the "30" amount in the CHANGE Y BY COS OF JUMP * 30 block. A higher amount will result in a bigger jump, while a smaller amount will decrease the jump height.

You can also adjust the speed of the jump by changing both the number of repeats and the CHANGE JUMP BY 10 amount. For instance..
change the 17 to 35 and the 10 to 5 will give you a slower, smoother jump.

You have to change both numbers a certain way to ensure that the sprite lands at the same ground level that it took off from. See if you can figure out how that works    And if you can't, click the sprite's Y position variable in the Motion blocks so that it stays visible on the screen. Remember what it is, jump, and see what it stops at. Adjust one of the amounts until it lands correctly at the same Y value that it started at.

Happy jumping!

Last edited by Locomule (2010-08-18 01:40:05)