without getting into the code itself, here is a good way to handle jumping:

check if the jump key is pressed. if so, check if your character is immediately on top of a platform and if vertical velocity is not negative (meaning the character is not rising). if this is all true, set the character's velocity to some negative value, depending on how high you want to make him jump.

each frame, acceleration should be a positive constant, causing the velocity to change constantly and the end result to be a clean arc, assuming no things get in the way. while the velocity is negative, check above your character's head, from the topmost pixel's starting position to the position it would be in at the end of the frame. if there is a platform in the way, set the character's vertical position so that that topmost pixel is immediately below the obstruction and set vertical velocity to 0 (or maybe a positive amount, if you want him to bounce off). similarly, when velocity is positive, check beneath the character in the range between the bottommost pixel's starting position and ending position during a frame.

EDIT: if you want to allow jumping higher by holding down the key, set a "timer" variable to some positive value. decrement it by one every frame until it is zero, and, while the value is non-zero and the jump key is held down, maintain a constant vertical velocity rather than adjusting it due to gravity.

EDIT 2: also, if your platforms are tilemap-based (i.e. have constant-ly sized blocks making up platforms), that collision detection gets lots easier, as you can just check if the projected position is inside of the space taken up by a tile.

Thanks guys.

Taking from what you said shmibs, I actually did find a way to make jumping better. I simply took out the code "If Y<55, Y+1->Y", because the code I implemented was better.

If getKey(54) and (pxl-Test(X,Y+8))
15->J
End
If J>0
Y-1->Y
J-1->J
End
If (pxl-Test(X,Y+8)=0) and (J=0)
Y+1->Y
End

It was similar to the code that I saw earlier in the Axe forums, except that I needed to adjust within my code, which promptly made me remove the "Y<55" thing.


Hayleia, I sort of don't know much about inflation, so I don't really know if I can do the operation about making the positions different than 256 (unless I already did do it, but I didn't notice). I think I do understand what you're saying, however, about my character skipping a lot of pixels. When I made a 8x8 square on the screen, my character couldn't even stay on half of the square without falling through. I hope that that was what you meant. I guess I could just search through the forums again.


One question though: How could I change the code so that my character doesn't have to be on a line in order to jump? One part of my game deals with this (kinda).

Unfortunately,  the program won't run on my calculator (TI-83+).  ???There were some minor errors on there when I compiled the code with the parser, but I fixed them. I assume that just had to do with the un-optimized code you noted. Either way, I always have to reset RAM whenever I run the compiled program, which pretty much freezes the calc instantly. Did I have to involve it in my original code?

Anyways, I did sort of get your reasoning with the 10 vs 256 pixel realistic jumping. Without running the program, it already seems to make sense. The VY and Y vars are a bit complex to understand. Though to get the full idea, I guess I have to run the program, which, well...

I'm sorry if I'm not picking up things quickly,  it's just that I'm not that experienced in Axe as I should be. I know what each of the commands in my jumping program do, it's just that learning new commands or routines can be frustrating for me.

Thanks for the help you're you (and shmibs) are giving me. Like I said, I pick up concepts a bit slowly sometimes.

The program works now. I just didn't know that you had to space the section of your While command.   
I also learned more optimization tricks, like DispGraphClrDraw (even though you said the code was unoptimized; I think I know what you mean by that)


Now I really understand the difference. I guess this would be of some use to my game, because it does look more smooth than the 10 pixel jump (I'm talking about the 256 pixel inflation).


Thanks for the help. Now one last thing before I consider the topic solved: How do you make your character jump if there is no "platform" (Line) beneath him? Taking from my code a couple replies back, I don't know if I should just change the entire routine or not.

...inflation by 256 makes the jump a lot slower but by changing some constants you can get a pretty fast jump "even" with inflation by 256.

Cool... I'll have to look more into that later. In the program, the jump was rather slow, but if there is a way to make it go faster, its definitely something I'll look into. Thanks for showing me that.


Taking out the pxlText(X,Y+8) won't help. My character just falls through the screen if I place him on no platform. If I do place him on a platform, however, my character jumps infinitely as long as I hold the "2nd" button. I tried altering more of the code that had to do with jumping, but no luck. I think I'm getting somewhere though, so it shouldn't take too long before I can find a solution. But if it involves a completely new command, then I'll be stuck again.


Is it possible to render a line invisible but still in the game? If so, I could just make an invisible line, and make the code treat it as a platform that my character can jump on, but in-game the player won't see it.