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Update:
This thread is now for tile-modding...

1. (1 more new setting added) Settings for 2-sided/doubly-sided tiles: post 9
HystericalParoxysm has offered an easier-to-understand instruction here
2. Settings for animated tiles: post 26
3. Settings for pool-tiles and pool-wallpapers: post34
4. Settings for pool-surface-tiles: post39

Additional info:
1. bumpping settings for tiles and wallpapers are basically the same, may read here
2. How to edit the" directory of compressed files"
http://www.modthesims2.com/showthread.php?t=132612
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I'm not considering a step-by-step tutorial so far, but people are welcome to break the production barrier by making step-by-step tutorials about them without permission, but it's nice to inform me of your nice tutorial(s).

Also, for those HCP product beginning modders,
reading the following threads will help you advance in HCP-product modding.

1. RGiles's Tutorial: Transparency in Floor Tiles (Updated 16 Apr)
http://www.modthesims2.com/showthread.php?t=37846
2. Numenor's Recolouring Objects with Object Workshop (NEW tutorial)
http://www.modthesims2.com/showthread.php?t=102356
3. Frillen's Tutorial: Transparent Floor tiles
http://www.modthesims2.com/showthread.php?t=71559
4. JWoods' Modding InfoCenter - Creating an Animation Cell Re-Color
http://www.modthesims2.com/showthread.php?t=82395
5. Jwoods' Modding InfoCenter - Understanding The TXTR File and Formats
http://www.modthesims2.com/showthread.php?t=86151
6. Animation via texture-rotation
http://www.modthesims2.com/showthread.php?t=71672
7. Tech Discussion: The Material Definition ("TXMT", a.k.a. "MATD")
http://www.modthesims2.com/showthread.php?t=35769
8. How to interconvert txtr and LIFO files, may read here
9. Wiki: TXMT/Parameters/CategorisedList/TexturalAnimation
http://www.sims2wiki.info/TXMT/Para...xturalAnimation
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sete stdMatCullMode cullClockwise (none cullClockwise cullCounterClockwise)
#attrdescription Culling (usually back-face) of primitive rendering

For floor tiles, as long as in their txmt's properties,
"stdMatCullMode" is set to "none", the floor tile can have their bottom wrapped with the same floor tile texture.

But, Since I did alter other properties and txmt type of the floor tiles, I'll have to test more on what are necessary.

The second pic shows the wireframe (basically the graphical presentation of the mesh of the floor tile)

So, from now on, bottomful floor tiles can be done by this setting.
For a temporary guideline, may jump to post 9, but may read advices and experiences from other posts to enhance the insight.