Problem with Quads- basic modeling

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  cookepuss polycounter lvl 11

  Sep 2012

  I made pretty much the same sort of katana in C4D too - back when I did my Hit-Girl model.
  
  
  
  Here are my suggestions:
  
  
  
  In case you can't read my chicken scratch...
  
  My suggestions for the first problem are pretty basic
  
  1. Check the normals on you faces. Reversed normals might not draw if you've got backfaces or 2-sided off in wherever you're exporting it to, UDK in this case.
  
  Fixing reversed normals is pretty easy. The quickest way is to select all faces. When you do that, they should all appear to be the same color - usually orange. If you see a few blue colored faces in the mix, those are reversed. Usually, aligning your normals will get them to all point in the same direction. If that doesn't work, you may have to manually select each wrong face and use the reverse normals command.
  
  2. It could be an issue of export. C4D's export can be wonky sometimes, especially OBJ. Your best OBJ export option will almost always be Keith Young's Riptide plugin. There's a free version at skinprops.com that should do the trick.
  
  For your second problem.... EASY solution. I drew the fix on the image. Check it out in the image above. Really easy. Just use your modeling tools to connect those vertices and create new edges. Thankfully, with the way you modeled it, they should turn out to be all quads and be nice & pretty.
  
  

  Some of the faces appear from a certain angle but dissapear at another angle.
  Could it be something with the normals ?

  Could be. Could also be if a quad has vertices that aren't exactly co-planar, which is easy enough to happen. That's why game models internally become triangles before rasterization. Triangles are always co-planar.
  

  Do I need to "check" or do something with them when I add faces just
  like that ?

  There's an old and free C4D plugin called Geomcheck. It'll tell you if you've got all sorts of geometry problems. HERE: http://www.lotsofpixels.com/c4dplugins/geomCheck/
  

  Edit: I fixed both of them in UDK by realigning the normals with some kind of options.

  Realign them in C4D next time. No real reason. Just good practice, getting your geo all straightened out before export.
  

  Do I always want to use quads in game modeling ?

  That depends.
  
  IF you're going to detail your model in ZBrush then yes. Or at least mostly quads. ZBrush or any program that uses Catmull-Clark subdivision surfaces (like C4D HyperNURBS) tends to perform better with quads. Triangles in subdivision surfaces tend to create weird surface defects like warps and dimples. They're pretty nasty when trying to sculpt in detail. Use triangles sparingly when exporting to ZBrush and such.
  
  For game modeling in general, it's okay to use triangles. Internally, by the hardware, quads are usually converted anyway since triangles render faster. For game modeling, you really don't necessarily have to avoid triangles. Personally, I don't like working with them since they just make my models look messy. I tend to hide what few triangles I do use in oddball places where they won't usually be seen.

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  Shrike interpolator

  Sep 2012

  Well thanks a lot
  
  Yes, i meant that I realigned them in Cinema, that was fine. The broken edge was fine after that in UDK aswell, but I can fix the 10tagon ( lol..) like you said however.
  
  That with the quads and triagles makes a lot more clear for me.
  
  But what about degenerates ? What are they ? And all above quads is wrong ?

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  cookepuss polycounter lvl 11

  Sep 2012

  But what about degenerates ? What are they ?

  Degenerates are not really a single problem, but a class of problems.
  
  A polygon can degenerate when it distorts or twists on itself. For example, imagine a quad twisting so much that it looks like a bow tie. You'll simultaneously have the front face and back face visible, which is wrong. That could be considered a degenerate polygon.
  
  Another example would be if the points of a polygon collapse in such a way that they form a line or a single point. That's not really a polygon then. There's no physical surface area. It won't render out. A good example of this would be.... Imagine a 12 point n-gon. Imagine collapsing every other vertex to the polygon's centroid. This would give you a star-like shape of lines radiating from the center. Collapsing these vertices screwed the pooch since there's no longer really anything to render. You've got a data structure for a polygon, but no actual surface. The polygon degenerated.
  

  And all above quads is wrong ?

  Wrong schmong. Whatever gets the job done.
  
  I personally prefer, when at all possible, to model using all quads. For starters, when it comes to sculpting and detailing your model in ZBrush or Mudbox, quads are the path of least resistance. On top of that, by sticking to quads, I can see my edge & poly loop flow much better. This is particularly important if I intend on animating a character since topology can directly inform and influence deformation. Maintaining a particular edge flow with triangle can be tougher, imo, since you might have to do a fair bit of edge spinning just to get things flowing in the right direction.
  
  Trying to maintain an all (or mostly) quad workflow isn't so hard. You develop some tricks and habits. For example, take this character I just started. My first step is to lay down a single polygon. To get my loops, I extruded edges along certain paths. To add in looped detail, I cut a trail along the edge rings in-between the loops. To add in the ears, to replace the placeholders, I'll just make sure that the number of points on the perimeter of the ear's connecting edges match the hole I'll create. Believe it or not, with practice, it all actually tends to work itself out as all quads. When it doesn't.... hide the triangle. In the case of the ear here, I'd hide it behind the ear or inside the canal.
  
  You don't have to stick with an all quad methodology though. For game modeling and stuff that won't necessarily be subdivided, you can mix and match quads with triangles. That's perfectly fine. The one thing you don't want to do is use ngons - polys with more than 4 vertices. That's just going to create a nightmare situation if you're not careful. The can make life easier, but they don't really promote good or stable topology.
  
  Ngons have their place. Archvis people tend to use them since they make for a clean & client friendly wireframe. However, I personally wouldn't use them. Making holes in ngons isn't pretty. Without adding edges, the renderer could interpret the hole as an overlapping poly. Watching ngons fall apart when you bend or twist them isn't a nice thing to see either. Your model can turn into a messy mush of twisting geo. I'd just avoid ngons altogether.

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