ba­sics: bridge

In our con­tin­u­ing se­ries of CGI ba­sics, we look at the Bridge func­tion

3D World - - CONTENTS -

Get a thor­ough un­der­stand­ing of the Bridge func­tion

If you’re new to CGI there are far too many tools to choose from in a dizzy­ing ar­ray of soft­ware. This se­ries aims to break ev­ery­thing in CGI down to the very ba­sics, so that every artist can be armed with the knowl­edge of which tool is best. This time we are look­ing at the Bridge func­tion.

Bridge is one of the most help­ful func­tions in a 3D artist’s arse­nal. It is a hugely ver­sa­tile func­tion that can cre­ate the foun­da­tions for a com­plex build, or cre­ate curved and twisted ge­om­e­try all by it­self with a sin­gle click of the mouse.

One of the key things that us­ing Bridge teaches is the con­cept of sur­face nor­mal di­rec­tion on a poly­gon. While poly­gons (or faces) may ap­pear to be a 3D shape, a poly­gon only has one ‘true’ side, and the nor­mal de­notes the per­pen­dic­u­lar di­rec­tion the poly­gon is fac­ing. This mat­ters when us­ing the Bridge tool, as bridg­ing two poly­gons fac­ing the wrong di­rec­tion can cre­ate un­pre­dictable re­sults, and make us­ing the Bridge tool a dis­ap­point­ing ex­pe­ri­ence for new users.

The Bridge tool has the power to rad­i­cally change your ge­om­e­try by re­mov­ing poly­gons at the ends of bridge seg­ments, so make sure you are aware of all the op­tions that the Bridge tool has in each piece of 3D soft­ware.

These op­tions can in­clude fac­tors such as twist­ing, and mak­ing a curved bridge, as op­posed to a lin­ear one.

Some apps can use the Bridge com­mand to cre­ate poly­gons from ver­tices, which is a pow­er­ful way to remesh ge­om­e­try. When work­ing with meshes us­ing Sub-divi­sion meth­ods, like Open Sub­div, mas­ter­ing the Bridge tool is a good way to get to grips with com­plex shapes. For ex­am­ple, cre­at­ing a ba­sic arm be­tween a wrist and shoul­der model.

Cer­tain 3D ap­pli­ca­tions can al­low mul­ti­ple el­e­ments to be bridged with one click, which en­ables com­plex and or­ganic mod­els to be cre­ated eas­ily.

The Bridge tool is a ver­sa­tile com­mand that takes a lot of the pain out of 3D mod­el­ling.

Au­thor Mike Griggs Mike Griggs is a 3D and vis­ual ef­fects artist with vast ex­pe­ri­ence across the in­dus­try, as both a cre­ator and a tech­ni­cal writer. www.cre­ative­

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