# LittleBigPlanets object modelling question

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hi all, i'm trying to figure out how the guys form Mm has implemented the level constructor form LitteBigPlanet in particular the object modeling (take a look ^^ http://www.gametrailers.com/player/21598.html ). my hypothesis: - some kind of strong boolean algorithm - merged contours and tessellation - metaballs like shapes (Cube, Cylinders, etc...) with negative for boolean like difference - Constructive solid geometry anyone has oder ideas to share ?? thanks in advance for your help. Vinn P.S. I'm basing my ideas only from the tons of video on-line concerning this game, if some one has played the game maybe can make a better hypothesis. P.P.S. forgive me for my bad English ^^

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In LBP, all the shapes the player can create are essentially 2-dimensional (even though you do have 3 discrete extrusion depths available). It is relatively easy to implement edge following (polys from bitmap) and boolean operations on 2d shapes. The base material texture is linearly mapped and tile-repeated in xy plane, regardless of material shape or size, so it is trivial to do.

That said, despite its simplicity as compared to "real" game development, I still find LBP's level construction quite fun.

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it was simpler than I thought....

anyway do you know a fast edge following algorithm ?

^__^

thanks again,
Vinn

[Edited by - ivanvinn on November 17, 2008 5:46:28 AM]

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I haven't had the need to write one myself, but the basic algorithm is as follows:

1. Find a point where the absolute derivative (rate of change) of the bitmap is within your desired value treshold.
2. Seek neighbouring pixels for the same treshold.
3. Draw a line segment as far as the derivative follows a straight path. Upon encountering a deviation in the values, start a new line segment.
4. Set the current seek point to the start of the new line segment.
5. Repeat from step 2 until you have a closed polyline.

In a 1-bit bitmap, the absolute derivative is always either 0 or 1 so the treshold is extremely simply defined.

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thanks again for your help ^^

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