Alpha Mapping
from eltyio
Alpha Mapping Tutorial, for low polygon modelTyio - d’Ettorre Olivier-ThomasTYiO Infographie
http://tyio.3dvf.net
 
Alpha Mapping permit low polygons count for good anti aliasing purpose. On this exemple, i take a wheel of a Porsche Car, low poly one with 890 tripatchs for the wheel (tire/rim/caliper/disk). I use alpha mapping for the rims only, on this exemple.First at all, we have to modelling to get the lower poly count as possible, but no polygon aliasing visible . For this, make a cylinder with (for me, the optimal for polycount/smooth) 24 sides.

Then normal it, delete caps and make inner extrusion with the border tool (for max ^^). You’ll have the rim outer part. TIPS: detach all part, then, you won’t have trouble select all polys with the same smooth group, you’ll be able to use the global part selection .

Secondly, you’ll model the inner part of the rim. For this rim’s type, 7 inner part, so, 25.7° between each part (so, 25,7 / 2 between two part ) . Note you’ll have to becarefull about the poly count, because you’ll array this part, and so, get a lot of polys.

Now, you’ll have to put a uvwmapping on this part, and then, adjust it in the unwrap panel TIPS: as you ca see, the both part look to have similar mapping coordinate, cool, it’ll be usefull for me to pain the map , conserving the same mapping for all array part ^^.

Then, you can array the part, separating them first, and you have the inner part ^^

The next part consist to make the flask of the rim. Look the way i use to minimize the number of poly ;) (252 tri for the flask+center part, center part is only 132 tri)

you can now, assemble the three part you done previously, TIPS: note you can have the inner part (the array part ^^), going through the flask, you’ll see the tips later ;)

Now, the mapping of the flask part, as you can see here , a simply planar coordinate :^^

You can separate the center screw of the flask center. As i quote previously, i add the center part with the flask mapping, to get more easy the texture ^^ For the first exporting –with texport as usual ^^-, make an instance, with the inner part of the rim, you’ll be able to do the texture more easily. The texture now, it’s a simplar diffuse texture, and a black and white partTIPS: you can use inner glow white, on the black shape, do to smoother again

So, here the mesh with texture applied on it, on the left, the difuse, on the right, the opacity

And the part assembled together :

And the same with the rim + caliper + disk

For the finishing of the tutorial, i show you the render, textured and without texture.