HowTo:FullUnwrap4Clean2

Cleaning Up The Mesh (Part 2)

Watch for pairs of triangles that can be turned into quads and do it; and merge unnecessary vertices. Don't forget to go into line selection mode and menu Select -> Non Manifold, from time to time, watching for lines appearing in the middle of a smooth surface where they shouldn't appear, or missing from sharp edges --where they should always appear. This is the most efficient way to find cracks, internal triangles, blotched smoothing groups and missing facets. I write this because I thought I was done with this mesh, but I'm still finding a lot of areas needing fixes and improvements; --which is why this tutorial is going so slowly.

Also, it's extremely important to minimize the amount of hidden, invisible surface areas. There's many reasons for this; but first of all, what do I mean? I mean, for example, those three square boxes I have at the top, and then again at the bottom of the ship. Originally I put them in as vertical boxes that crossed the whole ship, top to bottom. Later, I cut the boxes so that they barely penetrated the skin. But before finalizing the mesh, one has to cut the skin to elliminate the squares covered by those boxes. Small boxes and things, like the little clamps, though, can just float and cover; but those six boxes are just too big for that. Now, the two main reasons why...

1. The GPU (Graphics Processing Unit; the brains of your videocard) has no way to know that a portion of surface is not visible and disregard it altogether. It does display correctly but by brute force: It checks as it draws each pixel that something isn't drawn in that pixel already that is closer to the camera than what it is currently drawing (AKA "Z-testing). But even if it decides not to *draw* that pixel of the skin (because a pixel of the box was drawn earlier, and is closer to the camera), it still ended up having *read* that pixel --in order to find out; which is a memory access all the same. If in one area of the screen you have 17 polygons, at best, the GPU will write the pixel only once; but it will end up having read it all 17 times. This is called "overdraw", and is one of the prime factors limiting performance in games. Hidden surfaces aren't just wasted; they slow down refresh rate.
2. Hidden surfaces waste texture texels: The larger the hidden surfaces, the more texels are wasted on them. To get the best results and highest detail out of the smallest texture, you need to up the efficiency; so hidden surfaces are out. And, before you ask, no, you cannot place something else over a hidden area, because we'll need an "ambient occlusion baking" that Blender will make for us, but you cannot have overlapping UV islands, or else the occlusion baking will be incorrect. There's really no other solution than to cut off covered/hidden surfaces.

One good way to find hidden surfaces and elliminate them is to take a look at the inside of the ship. In the pic below, we're inside the hull, looking towards the back. You see rectangular depressions at the top and bottom, where those boxes are. You also see horizontal slots to the left and right, near the back. Those are the interiors of the "wings". And inside the slot on the left, you see these bright lines along its "floor" and "ceiling". Those are the edges of the walls of the inner rooms in the dockings, penetrating the wings. I feel they are penetrating too much, and will waste too many pixels...

So, I decide to do something about it:

What I did was push the edges, up and down respectively, until they barely penetrated the surface of the wing.

And sorry if I'm repeating myself, but flipped normals... You need to find them all. I just went into a major hunt for flipped normals and found probably 200 of them. Does it, or does it not look "cleaner" now?

Speaking of normals, you can save yourself major pain by NOT using "Ctrl-N Normals Outside" once you've done your smoothing groups. Blender's algorithm for telling inside from outside is not too smart; and while it works well with closed meshes, it does a disaster once you've split smoothing groups, because, when in doubt, Blender looks at the normals of neighboring polygons; but it won't find neigboring polygons that have been split.

To find blotched normals, one trick I've found is to flip flop the Double-sided button. Turn the ship to get a close view of one area at a time, then press F9 and you'll see the Double Sided button there. It should be off. Turn it on and off repeatedly. Nothing should change in the picture if all the normals are right within that view. If anything changes color, there's a blotched normal there. Make sure you have the Show Normals button, and adjust their length. Faces whose normals are reversed will have just a tiny blue dot in the middle. Highlight them and go W -> Flip Normals.

And then I followed my own advice and did the above systematically, and found another hundred or so blotched normals...

I've also finished a few details inside the front docking area:

And I keep on following my own advice and trying different paint schemes, because I know it will be much more problematic to change my mind later. I'm not even putting half the picture story here; I only make renders when I believe I'm done, which is often after several major changes. Here are my latests "finals" :) ...

And be sure to post a lot of pics of your work in progress. Nothing keeps you more true than putting your work up for others to see. You won't be able to please everyone. Don't even try. But sometimes, a few changes can help a model look "acceptable" to some. Besides, just the anticipation of feedback will encourage you to look for details you may not be totally happy about yourself. Someone was displeased about front-to-back balance of green paint, or the lack thereof, rather. So I added a bit of greenness at the front, and made the wings bare metal. BINGO! Looks much better in my eyes...

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IMPORTANT NOTE:

All polygons in your ship should be smooth-shaded; even those intended to look flat. If you've read the Smooth Groups tutorial you know why, but it won't hurt to reiterate: Flat shaded polygons have all their vertices split as they go into the videocard. Your mesh file may say you have 20,000 vertices, but as they enter the videocard they may multiply to 120,000 vertices. Flat shading is for the lazy. In face selection mode, hit A to highlight all, then W -> Set Smooth. Then flatten whatever needs to look flat by selecting faces in that smooth group (Shift-Ctrl-Alt-F -> 145 helps a lot), and split them with Y. That's what "splitting the smooth groups" is, in case you didn't know.

/IMPORTANT NOTE

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Yes, modelling is a lot of work, indeed; but very rewarding. Okay, time to start placing seams... No, before that a bit of theory about where do we place the seams, and why.

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