Check for and correct the following problems. Tools mentioned are from Maya; I haven't yet poked around in Blender to find the equivalents.
In Maya, find problems easily by going into the "Mesh" dropdown -> CleanUp. CHECK THE BOX. DO NOT LET MAYA CLEANUP AUTOMATICALLY!
Once in the cleanup tool, check the following boxes:
- Faces with more than 4 sides
- Faces with holes
- Lamina faces (faces sharing all edges)
- Nonmanifold geometry
- Edges with zero length (default slider setting)
Also check "Select matching polygons" instead of cleanup. DO NOT LET MAYA CLEANUP AUTOMATICALLY!
Clicking either "Apply" or "Cleanup" (Cleanup will close the window) will now highlight any problem geometry found in your selected model(s). It won't tell you what the problems are, necessarily, so use this checklist and fix each of them:
1. N-gons
N-gons are faces with more than 4 sides; the computer (typically) only understands and properly saves 3- and 4-sided faces. One common way these show up is when the modeler incorrectly deletes edges without also merging or removing the extra vertices. They usually can be corrected by adding new edges between existing vertexes.
2. Faces with Holes
These are faces with a hole inside that is unsupported by any other geometry. Often they are also n-gons, as the edges around the hole are considered additional sides by the computer. They break horribly, so badly even your modelling program won't know what to do with them. Just adding new edges won’t fix these. Delete the affected face and re-do it.
3. Bent/Warped Faces
These aren’t always a problem for the computer, but it is generally best practice to correct ones that are severely warped by adding another edge along the crease(s).
4. Convex and Concave Faces.
These are faces were one corner “cuts into” the shape, creating a V (if 4-sided), or when one vertex is all the way out in the boonies. Though not always a problem, these can cause strange deformations when animating, and are best corrected by splitting the faces up with a new edge.
5 Lamina Faces
These are faces that are occupying the exact same place in space, sharing vertexes and sides. They corrected by deleting one of the extra faces.
6. Non-Manifold Geometry
There are a few different types of these that cause problems for the computer.
Type 1: Edge shared by more than two faces. Fixed by deleting the extra face(s) or remodeling so that those faces connect elsewhere.
Type 2: Edge shared by faces with normals facing opposite ways. (Normals are the orientation of the face, aka, which side is see-through and which is textured when viewed ingame.) To correct, select the backwards face and flip its normal. In Maya this can be done through the Mesh Display dropdown -> Reverse (selected face) or Mesh Display dropdown -> Conform (all selected faces will flip to whatever conformation is most common).
Type 3: Face connected with only one vertex to other faces. To correct, delete the offending face, or add a new one connecting the two.
7. Check UVs
To minimize stretching, smearing, and poor resolution, all UVs should be laid as flat as possible and have the same texel density across a model. Seams should either be hidden in an area the player won't see or prevented through the use of a repeating texture. (Sometimes this isn't always possible; when in doubt, put seams on a sharp edge or in a place the camera won't point at in normal gameplay.)
No UVs should overlap on the texture map. No UVs should be going outside the 0.0-1.0 bounds on the texture map. UVs should make good use of the entire texture map for efficiency.
To test all this stuff in Maya, click on the checkered test texture while in the UV Editter. Ensure all squares are of the same size throughout the entire model and are not misshapen. Note this won’t always be possible; do the best you can. Do not worry if they meet at odd angles along the seams or aren't lined up straight with your edges; these squares are a visual guide for your resolution, not for how well your texture repeats.
The above isn't great coverage of the texture map, but as you can see, the squares are mostly uniform and the UVs do not overlap. They also stay within 0.0-1.0 bounds.
8. History Deleted
The more history you have, the more likely something is going to get corrupted and break in future saves. It's good practice to delete your history on all objects every other save, and also when you turn your model in to go to the next stage of production.
9. Transformations Frozen and Model Aligned with Grid
This sets your objects to be at 0,0,0 rotation and transformation, making them easier to manipulate when imported to another program. It is also good practice to line your objects up along the grid, so they are easier to manipulate inside a modeling program as well.
10. Pivot Point?
I need to experiment with this one...
2016-01-19 19:35
1 month 3 days ago
Much better picture of proper UVs:
2016-01-19 19:35
1 month 3 days ago
Update, September 13th, 2022. Note some of this information may be WRONG; I am still learning.
Check for and correct the following problems. Tools mentioned are from Maya; I haven't yet poked around in Blender to find the equivalents.
In Maya, find problems easily by going into the "Mesh" dropdown -> CleanUp. CHECK THE BOX. DO NOT LET MAYA CLEANUP AUTOMATICALLY!
Once in the cleanup tool, check the following boxes:
Faces with more than 4 sides
Faces with holes
Lamina faces (faces sharing all edges)
Nonmanifold geometry
Edges with zero length
Also check "Select matching polygons" instead of cleanup. DO NOT LET MAYA CLEANUP AUTOMATICALLY!
Clicking either "Apply" or "Cleanup" (Cleanup will close the window) will now highlight any problem geometry found in your selected model(s). It won't tell you what the problems are, necessarily, so use this checklist and fix each of them:
1. N-gons
N-gons are faces with more than 4 sides; the computer (typically) only understands and properly saves 3- and 4-sided faces. One common way these show up is when the modeler incorrectly deletes edges without also merging or removing the extra vertices. These are usually corrected by adding new edges between existing vertexes or deleting any extra vertices that are not vital to holding the object’s shape.
2. Faces with Holes
These are faces... with holes. There’s a hole inside the face that is unconnected to the outside edges and the computer’s brain has no idea what to do with them. Often they are also n-gons, as the edges around the hole are considered additional sides by the computer. Unfortunately, just adding new edges won’t usually fix these. Delete the affected face and re-do it.
3. Bent/Warped Faces
The computer struggles with these as it doesn’t always remember which way the face is supposed to bend. The easiest way to correct these is by adding another edge along the crease.
4. Convex and Concave Faces.
These are faces where one corner “cuts into” the shape, creating a V (if 4-sided), or when one vertex is all the way out in the boonies. Though not always a problem, these can cause strange deformations when animating, and are best corrected by splitting the faces up with a new edge.
5. Lamina Faces
These are faces that are occupying the exact same place in space, sharing vertexes and sides. They corrected by deleting one of the extra faces. Finding them can be tricky.
6. Non-Manifold Geometry
There are a few different types of these that cause problems for the computer.
Type 1: Edge shared by more than two faces. Fixed by deleting the extra face(s) or remodeling so that those faces connect elsewhere.
Type 2: Edge shared by faces with normals facing opposite ways. (Normals are the orientation of the face, aka, which side is transparent and which is textured when viewed ingame.) To correct, select the backwards face and flip its normal. In Maya this can be done through the Mesh dropdown -> Reverse (selected face) or Mesh dropdown -> Conform (all selected faces will flip to whatever conformation is most common).
Type 3: Face connected with only one vertex to other faces. To correct, delete or detach the offending face, or add a new one connecting the two.
7. Check UVs
UVs should be laid as flat as possible and sized/proportioned correctly so that stretching, smearing, and poor resolution is minimized. No UVs should overlap on the texture map; an exception can be made for shells that are expected to be exactly the same in the finished project, like identical leaves, nails, or buttons. No UVs should be going outside the 0.0-1.0 bounds on the texture map axes; other programs you import the model into will fail to read these properly. UVs should make good use of the entire texture map for efficiency. Seams should either be hidden in an area the player won't see or put along a sharp edge.
To test in Maya, click on the square testing texture while in the UV Editter. Ensure all squares are of the same size throughout the entire model and are not misshapen. Note this won’t always be possible; do the best you can.
(TEST: what kind of texture maps does Morrowind use, specifically if bump maps are needed.)
(TEST: Does Morrowind know what to do with UV sheets or use the +1.0 spaces.)
8. History Deleted
The more history you have, the more likely something is going to get corrupted and break in future saves. It's good practice to delete your history on all objects every other save, and also when you turn your model in to go to the next stage of production.
9. Transformations Frozen and Model Aligned with Grid
This sets your objects to be at 0,0,0 rotation and transformation, making it easier to manipulate.
10. Pivot Point
Your pivot point will be imported into the construction kit when you import your model. Therefore it’s best if you center it for easy manipulation. (TEST: does the object “fall” to the ground properly if the pivot is truly centered or does it need to be on the bottom?)
11. Texel Density
All UV shells on the same object should have the same texel density. An exception can be made for small pieces like trimming or eyes where you want to add more detail. You can ensure this by using (Get/Set). Once the texel density is set for all the shells, you must resize all of them at once to maintain the density. Never stretch or squash the shells because this will deform your texels.
12. All UV shells should be facing the same way. In Maya, you can see this by (menu): red shells are backwards and must be flipped by (button). Purple shells are overlapping and also backward.
Best Practices:
1. Deleting Unnecessary Geometry
All geometry should help to define the shape; extra edges should be removed or merged down. One good way to test if an edge is necessary is to do the silhouette test: if the edge or vertex does not make a noticeable difference to the object’s shape when viewed as a silhouette, it is probably unnecessary. (Note that some geometry may instead be needed to prevent bad geometry like n-gons or non-manifold geometry).
2. Bevels
A bevel is a softening of a hard edge. In most games, especially one with Morrowind’s resolution, these don’t typically matter, but they can help to prevent anti-aliasing and other bad rendering along a sharp edge. They are best applied to any edge that bends by 90 degrees or more (whether convex or concave). Maya can automatically add bevels by (menu), but be sure to check for n-gons after using this tool. 1 division is enough for game modelling.
3. Edge Rings and Edge Loops, Modelling with 4-sided faces
These don’t contribute to the final product but are highly helpful for models that might need tweaking or work done by multiple modellers. An edge ring is a collection of edges that can be selected all at once by double-clicking; they are most useful when they encircle objects such going around the circumference of a character’s arm or a vase’s lip. An edge loop is a series of four-sided faces (they MUST be four-sided to be properly detected by Maya’s algorithm) that connect in a ring and can also be selected all at once. They are useful for going around the edges of things like signs, shields, and other flat objects, where they aid in tweaking a silhouette without you having to mess with any interior geometry. Modelling in 4 sides is key to making edge rings and edge loops appear, as well as make your model easier to tweak. (TEST: Does Morrowind only do triangles?)
4. Unnecessary Back Sides
To save on processing, not all objects have to be 3-D. For things like leaves on ground clutter or walls where the player will never see a back side, these can simply be 2-D planes. (Ensure that the normal, or textured side, is facing the correct direction.)
5. Model in Parts
Each piece of a project should be a separate object in your modelling program. When rendering, this can add realistic shadowing to your creation, as well as make it easier to manipulate on the backend and while texturing. When in doubt, look at how the object was made in real life: a cabinet will have several pieces of a wood, a handle, and nails: all of these would be modelled separately and moved to be touching each other (never overlapping). A character might have a different object for their hair and different parts of their clothing. A plant may have different parts for their leaves vs. their trunk or stem vs. their root system. A rock with a crystal jutting out might have a separate object for each crystal plus the base rock. Anywhere you might see a shadow or division between an object is a good place to make separate objects; otherwise someone would have to texture the division in and this rarely looks as good. (TEST: Does Morrowind’s engine import these as one object or multiple? Does Morrowind do automatic shadowing?)
6. Don’t model what is never seen.
Similar to #4, don’t model what is never seen. An example might be nails vs nail heads: if an object is never going to be animated to be taken apart, the full shaft of the nails in it will never be seen and thus not modeled. A simple cylinder will do for the nail head. Another example might be a drawer: if the drawer is never opened, all you have to model is the outward face. Be sure to communicate with your animators and designers on more complicated projects on what parts are expected to be visible.
7. Modelling with Animation in mind
The inverse to #6: model parts that might appear when the object is posed differently, such as making the teeth and tongue for a monster that can open its mouth or the inside of a chest that is supposed to open. (Note that in Morrowind, almost no statics are animated, so this is of more importance for creatures and characters).
When modelling creatures, be mindful of geometry around areas that will see a lot of bending: add enough edges it can do so without stretching the texturing or adding odd angles. Put ball joints in most limbs; even if this is not true to life, this is easiest for an animator to work with. (TEST: This might not be true. More when I get to rigging.)