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AppGameKit Classic Chat / SetViewOffset() and looping world

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nz0
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Posted: 8th Mar 2013 00:02
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Just trying to decide if using setviewoffset() will work OK if I have a world (e.g. 8 screens wide) and I want to loop around to the start again when I've traversed 8 screens.

Is there an effective way to clamp up the end/beginning loop of your world when using setviewoffset() ?

I could do this myself by tracking *everything* but setviewoffset() makes things easier, what with FixSpritetoScreen() etc.

If I was looping graphics like this, I'd have an extra screen's worth (e.g. screen 9) which was a duplicate of screen 1 and flip over at the edge of screen 8.

Doesn't work so well if you've got enemies, bullets etc. going over the screen threshold...

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baxslash
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Posted: 8th Mar 2013 10:29
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This is definitely possible but you will have to check the possition of objects and duplicate them near the edge of the loop.


this.mess = abs(sin(times#))
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Digital Awakening
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Posted: 8th Mar 2013 12:31
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You could also move the world location of the rooms and simply keep everything else where they are.


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Marl
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Posted: 8th Mar 2013 19:31
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You might be able to scissor it - that would save moving everything but the offset.
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nz0
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Posted: 8th Mar 2013 20:16
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The problem is the wrap. I'd have to duplicate sprites where they cross over screen 8, as Baxslash said. Quite a bit of management.

Scissoring would still be required at the right of screen 8 and left of screen 1, but this would leave an (overlapping) sprite on the screen which was made up of 2 sprites potentially. Also some jiggery-pokery on handling the wrap with the offset.

The only other option (as I see it) is to track every object in the game and reposition them accordingly. This would make sense as I could deal with the "offscreen" ones in the same iteration. Still, plenty of challenges then

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Digital Awakening
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Posted: 8th Mar 2013 21:03
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Why not move room 1 to the end of room 8, and then room 2 to the end of room 1 etc. Wouldn't that work?


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nz0
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Posted: 8th Mar 2013 21:09
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It's not rooms per-se. Think Defender, where you scroll about the exterior of an asteroid or planet.

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Digital Awakening
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Posted: 8th Mar 2013 21:46
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Ah, I see. Then the easiest solution might be to not use SetViewOffset at all. Keep the player in the center of the screen and move everything else. But if you are using the built in collisions then this might not work or be efficient.


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baxslash
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Posted: 10th Mar 2013 16:42
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Marl has the best solution by far, check if your view offset is over the edge of the world and use set scissor to draw the first side of the screen, then use set scissor again to draw the other half. You still have to draw some objects twice when they overlap or by cleverly using drawSprite after rendering the background for all ships etc but it would be the fastest solution can imagine.


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nz0
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Posted: 10th Mar 2013 17:15
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I ditched the setviewoffset. It got much more messy considering I would need to loop around the other way.

In the end, it's easier to track everything and apply the world offset to the x co-ordinate. The trick is to have a buffer "screen" at each extreme of the "world". I really didn't like the idea of duplicate drawing (potentially a sprite could be made up of 2 halfs of 2 different sprites!)

I have a world 8 screens wide (plus 1 overlap screen at each end)

To wrap it I have to do the following:

if you are >screen 6, reposition items that are on screen 1 to screen 8. When you hit screen 8, reset pointer to screen 1

Similar behaviour for going the other way.

@Digital: Why your concern over built in collisions?

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Digital Awakening
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Posted: 10th Mar 2013 19:25
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Quote: "@Digital: Why your concern over built in collisions?"


I'm not too familiar with the collision system so I could be wrong here. But I recall posts about slowdowns or problems when moving around static objects or something. If you use SetViewOffset then you can make the level out of static objects that doesn't move around and I believe that should be faster. Of course, if you don't use static objects at all it wouldn't matter.


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nz0
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Posted: 13th Mar 2013 00:22
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Well, I ditched SetviewOffset() so I guess no worries then?

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Digital Awakening
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Posted: 13th Mar 2013 08:26
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That's the opposite of what I meant.


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nz0
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Posted: 13th Mar 2013 09:44
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Not using SetviewOffset() means I don't need to use fixed sprites either.

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