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Author Topic: [Help plz] Sprite allong a line.  (Read 10174 times)

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Offline Happybobjr

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[Help plz] Sprite allong a line.
« on: January 12, 2011, 06:12:30 pm »
I know this is a dumb question but, how can i make a sprite move along a line?
I feel like the answer is obvious but i just can''t figure it out.
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Offline yunhua98

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Re: [Help plz] Sprite allong a line.
« Reply #1 on: January 12, 2011, 06:13:38 pm »
YOU COULD DISPLAY IT AND THEN USE hORIZONTAL/vERTICAL, OR increment the x/y coordinate...  by a constant value

stupid caps lock...

Read it this way, lol:  you could display it and then use horizontal/vertical, or increment the x/y coordinate by a constant value.
« Last Edit: January 13, 2011, 04:27:00 pm by yunhua98 »
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Offline Happybobjr

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Re: [Help plz] Sprite allong a line.
« Reply #2 on: January 12, 2011, 06:15:15 pm »
If I understand what you are saying, I don't think that would be the appropriate way to solve my problem for my needs.
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Offline Michael_Lee

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Re: [Help plz] Sprite allong a line.
« Reply #3 on: January 12, 2011, 06:17:51 pm »
This might not be the most efficient method, but try this:

Code: [Select]
[Sprite data]->Pic1
Sprite X-coordinate ->X
Sprite Y-coordinate ->Y
Sprite X-momentum ->S
Sprite Y-momentum ->T

.Main loop
While 1
    Stuff
    More stuff
    ClrDraw
    X+S->X
    Y+T->Y
    Pt-On(X,Y,Pic1)
End

You could make it move in a sort of diagonal pattern if you set both the X and Y values to differing numbers, though it'll skip a little...
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Re: [Help plz] Sprite allong a line.
« Reply #4 on: January 12, 2011, 06:22:03 pm »
Do you mean a user-defined line?
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Offline Happybobjr

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Re: [Help plz] Sprite allong a line.
« Reply #5 on: January 12, 2011, 06:24:57 pm »
Quote from: SirCmpwn on January 12, 2011, 06:22:03 pm
Do you mean a user-defined line?
umm... i think.
I want it to be like axe's line algorithm except only draw one pixel at a time. and instead of it being a pixel, i want it to be a sprite.
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Offline AngelFish

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Re: [Help plz] Sprite allong a line.
« Reply #6 on: January 12, 2011, 06:25:33 pm »
Quote from: happybobjr on January 12, 2011, 06:15:15 pm
If I understand what you are saying, I don't think that would be the appropriate way to solve my problem for my needs.

What are your needs?

Also, sorry about the downrating. I accidentally clicked it.

EDIT: Ninja'd.

You can just use a For( loop and increment the X and/or Y position.
« Last Edit: January 12, 2011, 06:26:39 pm by Qwerty.55 »
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Offline Happybobjr

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Re: [Help plz] Sprite allong a line.
« Reply #7 on: January 12, 2011, 06:28:11 pm »
Quote from: Qwerty.55 on January 12, 2011, 06:25:33 pm
Quote from: happybobjr on January 12, 2011, 06:15:15 pm
If I understand what you are saying, I don't think that would be the appropriate way to solve my problem for my needs.

What are your needs?

Also, sorry about the downrating. I accidentally clicked it.

EDIT: Ninja'd.

You can just use a For( loop and increment the X and/or Y position.

Umm, it says it was rated up ???

a bullet that can pretty much go any direction that is determined by the tanks barrel (I think that's the right word.)
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Offline Michael_Lee

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Re: [Help plz] Sprite allong a line.
« Reply #8 on: January 12, 2011, 06:29:29 pm »
Quote from: happybobjr on January 12, 2011, 06:24:57 pm
Quote from: SirCmpwn on January 12, 2011, 06:22:03 pm
Do you mean a user-defined line?
umm... i think.
I want it to be like axe's line algorithm except only draw one pixel at a time. and instead of it being a pixel, i want it to be a sprite.

Try modifying this:
http://ourl.ca/4129/138496
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Offline AngelFish

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Re: [Help plz] Sprite allong a line.
« Reply #9 on: January 12, 2011, 06:32:59 pm »
Well, you'd have to rotate the sprite, but that's simple.

Take this example code:
Code: [Select]
While 1
   Pt-On(X,Y,<pointer>
   Dispgraph
   Pt-change(X,Y,<pointer>
   If <collision detected>
      Goto <Collision handling>
   Else
      X+A->X
      Y+B->Y
   End
End
To change the direction, just change A and B.

PS: I accidentally downrated your post, so I uprated in response.
« Last Edit: January 12, 2011, 06:34:14 pm by Qwerty.55 »
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Offline Happybobjr

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Re: [Help plz] Sprite allong a line.
« Reply #10 on: January 12, 2011, 06:34:20 pm »
Crud, more complex stuff :/

Thank you.  I'll take a look
Quote from: Michael_Lee on January 12, 2011, 06:29:29 pm
Quote from: happybobjr on January 12, 2011, 06:24:57 pm
Quote from: SirCmpwn on January 12, 2011, 06:22:03 pm
Do you mean a user-defined line?
umm... i think.
I want it to be like axe's line algorithm except only draw one pixel at a time. and instead of it being a pixel, i want it to be a sprite.

Try modifying this:
http://ourl.ca/4129/138496

Qwerty@  The problem is that i don't know what a and b are. I only know the start point and endpoint.
« Last Edit: January 12, 2011, 06:35:20 pm by happybobjr »
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Offline Michael_Lee

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Re: [Help plz] Sprite allong a line.
« Reply #11 on: January 12, 2011, 06:37:53 pm »
Quote from: happybobjr on January 12, 2011, 06:34:20 pm
Crud, more complex stuff :/

Thank you.  I'll take a look
Quote from: Michael_Lee on January 12, 2011, 06:29:29 pm
Quote from: happybobjr on January 12, 2011, 06:24:57 pm
Quote from: SirCmpwn on January 12, 2011, 06:22:03 pm
Do you mean a user-defined line?
umm... i think.
I want it to be like axe's line algorithm except only draw one pixel at a time. and instead of it being a pixel, i want it to be a sprite.

Try modifying this:
http://ourl.ca/4129/138496
* Michael_Lee shrugs
Yeah.  It's fairly easy to make things go in straight lines, or 45 degree angle lines, but getting things to move at other angles and slopes without skipping a bunch of pixels isn't something I've managed to figure out in Axe.
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Offline AngelFish

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Re: [Help plz] Sprite allong a line.
« Reply #12 on: January 12, 2011, 06:38:41 pm »
Quote from: happybobjr on January 12, 2011, 06:24:57 pm

Qwerty@  The problem is that i don't know what a and b are. I only know the start point and endpoint.

You don't know what direction the tank is shooting in? Um, I'm not sure any line drawing algorithm is useful if you don't have the information to figure that out. It can be pretty easily derived from the start and endpoints though.
« Last Edit: January 12, 2011, 06:40:09 pm by Qwerty.55 »
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Offline Michael_Lee

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Re: [Help plz] Sprite allong a line.
« Reply #13 on: January 12, 2011, 06:42:13 pm »
It's easy to derive the slope, true, but if you have a steep vertical slope, your object will end up skipping a bunch of pixels, possibly throwing off collision detection and
making the speed look irregular.

If the tank isn't allowed to fire too high or too low, then you could probably just use an easier method and derive the slope of the line, increment the X value each loop, crunch the new Y value, then display the bullet.
« Last Edit: January 12, 2011, 06:42:24 pm by Michael_Lee »
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Offline Happybobjr

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Re: [Help plz] Sprite allong a line.
« Reply #14 on: January 12, 2011, 06:45:23 pm »
So no one knows how to follow along Bresenham's line algorithm?
Edit: Qwerty will you rate that one back down? (to 0 not -1 :P)
« Last Edit: January 12, 2011, 06:46:29 pm by happybobjr »
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