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Creating a game sprite: Texture mapping Part 2: Creating a UV Map

6. September 2013

 

As I mentioned in the prior tutorial section creating a UVMap is basically like wielding a pair of virtual scissors to cut your 3D object up so it can be smushed flat.  As we saw earlier, the default unwrap map is pretty, subpar:

 

Default unwrap:

default

 

Let’s start cutting things up.  First we will default the wings.  In 3D view, make sure you are in Edit mode and Edge selection, then select the edges at the base of the wing, like so:

image

 

Now we want to mark the selected as a seam.  Press CTRL + E to bring up the Edge menu, and select Mark Seam.

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Or you could use the button in the Tools panel of 3D View:

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Both options do exactly the same thing.  Once the seem is marked it will appear as red:

image

 

Now you can see the result of marking a seam.  In 3D view, select all edges ( A ) and take a look at the UV window:

image

 

We now have a completely separate collection of UVs ( called a UV island ).  I still wouldn’t want to paint over these UVs yet, so we have a bit more work to do.  In order to be able to flatten the wing even more, lets mark another set of seams, like below:

image

 

Now look what happened to the UVs

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That is certainly much easier to paint over!  Of course, you could have split the wing top and bottom easy enough but each additional seam makes painting a bit trickier.

 

Remember the textured view of our jet from the previous tutorial:

badUVs

Instead of a checkerboard texture on the wing, you just got a white blotch.  Now that we marked the wing seams, look at the result:

image

 

MUCH better!  Ultimately our goal is to make the entire jet have a checkered texture like that.  The process is exactly the same, just keep marking seems in the model until the UV layout makes sense.  Let’s repeat the same process on the back wing and then the tail.  If you make a mistake, you can simply Clear Seam on the selected seam.  To completely undo your changes, select all edges and do CTRL+E –> Clear Seam and you are back to default.

 

I marked the following seams on the back tail and wing:

image

 

 

Resulting in this UV layout:

image

 

And in our rendered view:

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Next lets cut the jet in half vertically.  Select the continuous loop all the way around the jet, it will meet up with the wing cut:

Front:

image

 

Back:

image

 

Highlighted:

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You want a continous edge around the entire jet that will cut it between top and bottom.  Once selected, mark the seam.

image

 

Now mark the area surrounding the air intake:

image

 

This however results in an unwanted seam, shown below marked in green:

image

 

Select those edges and then select Clear Seam.

 

Now we have:

image

 

And the following UV layout:

image

 

Keep in mind, Blender automatically sets the positions, so yours might be a bit different layout wise.

 

Finally, lets seperate the cockpit away from the fusalage:

image

 

The cockpit:

image

 

And finally, the tail:

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And now our fully UV mapped model:

image

As you can see, the texture pattern flows pretty well over our image.  There are portions where we might get into a bit of trouble but they aren't areas where we are going to need details, so we should be good to go!

 

 

Well, that sucked, there has to be an easier way!

 

Yeah, actually, there is.  Blender has something called a Smart UV Project.  To use it, in 3D View, in edit mode, select all, then press U.  In the resulting menu select Smart UV Project:

 

image

 

Then a dialog will appear:

image

 

As I understand it, Smart UV looks at your model and separates UVs based on the angle between shapes.  So for example, since the wing essentially meets the fusalage at 90 degrees, it will easily be split into it’s own UV group.  Play around with the angle limit until you get a grouping you like.  Here is the result at 66 degrees.

 

image

 

Not ideal, but certainly a hell of a lot easier!

 

 

We only touched on a very small bit of what you can do with UVmaps.  Just keep in mind, if you add another seam ( and thus generate another Unwrap ), the positions will be reset.  Otherwise you can scale, turn, relocated, etc… UV coordinates to your hearts content.  If you don't want them to be scaled again, you can Pin (p) a UV in place.

 

Selection Options

 

You may find that you want to select Polygons from the UV layout screen.  By default it’s setup that what you select in the 3D view will be selected in the UV view, but it’s possible to do the opposite.

You need to click the “Keep UV and edit mode mesh selection in sync” button.

image

 

Now making a selection ( such as using the B)ox select mode ) in the UV window:

image

 

Will select the corresponding polygons in the 3D view:

image


Click here for the Next Part

 

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