Mech Modelling - And Confusion....

David Wakelin

Hi guys,

I've been given the task to make a Mech at uni - following someone else's rough design. I've approached it (with some advice from polycounters) by splitting it into several parts;



In this case; Toe/Foot/Leg/Port/Guns.

My problem is that, whilst I understand how mechs function with hundreds of different mechanical parts; springs, coils, wires, etc; and as I place this stuff around my mesh - How does this eventually become 1 object?

I know I'd have to retop obviously; but surely a mech is different to a organic humanoid which for example would have clothes attached to the body?

I don't understand because surely a mech consisting of hundreds of different pieces wouldn't be able to be retopped due to some parts being too complex; and then contain many UV islands; or even then if it wasn't 1 single object - be animated & rigged?

Any help would be GREATLY appreciated. I'm getting lost here.

ZacD

1: You model everything as separate parts. It's easier to work with pieces when you need to fix parts of a model, and you get better performance when working with smaller chunks.

2: You create the low poly. For a mech and even characters, a lot of the parts are separated, but you merge a lot of the objects, example https://dl.dropbox.com/u/1177306/spree_pcount/normal.png Obviously your mech wont have that many pieces, but its the same idea. I would break off any part that would need to move separately into its own piece of geometry. For a normal character you would still do this with belts, hats, big bracelets, earrings, buckles, etc.

3: You bake out a normal, AO, and cavity map.


Just look at these threads
http://www.polycount.com/forum/showthread.php?t=106041
http://www.polycount.com/forum/showthread.php?t=105793

David Wakelin

Now when you say merge; do you mean literally merge vertex's or literally just combine them to make them one object?

From the first link (dropbox link) I see the low poly is literally a bunch of items all placed ontop of each other; nothing really joined by topolgy? is that correct?

tigerija

No mesh should consists of elements. Shin, Thigh, Pelvis, Torso...

David Wakelin

tigerija wrote: »

No mesh should consists of elements. Shin, Thigh, Pelvis, Torso...

Tiger...

Don't have a clue what you meant there...

I'm not fussed about the way I break it up - I can understand the approach, as thats like any character... welll any model at all; its literally more about Mechs and the way their retopped...

ZacD

David Wakelin wrote: »

Now when you say merge; do you mean literally merge vertex's or literally just combine them to make them one object?

From the first link (dropbox link) I see the low poly is literally a bunch of items all placed ontop of each other; nothing really joined by topolgy? is that correct?

Just combined, no need to merge the vertexes on anything if it looks fine separate.

You don't need joined topology for most things. That starts to become an issue once you start animating things that will deform, like people (rigid mechs don't really have to worry about this).

David Wakelin

So in theory; I wouldn't need anything to connect until the final baked - retopped version? As this is what will be animating? I mean obviously I will need connections on the legs for my mech; (as this is what would be animated) but for rigid parts; its unncessary?

ZacD

There's really 2 things to keep in mind when doing the low poly for this. The first thing is what parts need to be able to move, mechs are made up of pivots and joints, if the foot is going to move separately from the leg, it should be a separate piece on the low poly. The second thing you have to worry about is how well the geometry is going to support the normal map. Normal maps do a great job with surface detail, so if the detail is close to shape of a larger part of the mech, it should be able to bake onto it fine (bolts, wires that follow closely to a larger object, vents, any small detail that doesn't really affect the shape or silhouette). If part of the mesh looks like a separate cylinder, its a good idea to keep it as a separate piece of geometry. Stuff like wires, shocks, bars, should be separate. Also if it would take a lot of work to merge/retopo the wireframes of 2 objects together, think about having them separate.

David Wakelin

ah ok thats great cheers Zac,

So in terms of movement for a mech; is this the correct sort of rig?

(crude as it may be)

McGreed

Yeah, that would be the bones (missing the back toe though). You don't have to merge each seperate part into one mesh UNLESS the engine requires it, or its more organic with bending. Since its mechanic, its much easier to just keep all parts as seperate models with pivot point where their base rotation is.

Overall you wouldn't need to merge anything together into one mesh unless its better for the engine or you want to have less objects to fiddle with.

I made one spider mech in Uni, and I also had that piston part, which needs to be in two parts. You can take a look at this youtube video for that: [ame="http://www.youtube.com/watch?v=T0zhIOU3fDg"]3D Studio Max - Rig an Hydraulic Piston - YouTube[/ame] or just google for "3d rigging hydraulics piston".

Found a quick image of part of my spider leg, you can see I had a lot of parts, which was all seperate (please note though that I only did highpoly model and animated it, was newbing back then):
EDIT: Hmm, for some reason the image refuse to appear. Anyway, url is: http://mcgreed.dk/portfolio/bloodmech/blood_mech_wire_leg_v01.jpg

EDIT: Oh and something very important I found when trying to make moving parts, block everything out first, and rig it, to see if it can actually work. I ended up having to redo the mechanics of the legs because two sections could only bend like 5 degrees, and would make it tiptoe around the place.