Wednesday, August 18, 2010

Discovering Blender : Applying UV Mapping

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In this tutorial I will show you how to apply UV mapping, mark seams, export UV layout that will help you in creating your texture.
Open blender, if you don’t have a cube create one (spacebar Add-mesh-Cube)
Start Cube
Toggle to edit mode (Tab) then in edge mode (ctrl + tab + 2)
Edit Edges
We are going to mark seam in order to be able to unfold the mesh without too much distortions, to do that we are going to mark the edge that will represent the cuts. Select the highlighted seven highlighted edges as shown in the image below.(shift + Rightclick) and hit Ctrl + E to bring the Edge Specials Menu and choose mark seam. Once done the selected edge are now orange. If you want to remove a seam choose clear seam from previous menu.
Mark Seams
Now split your screen (see this tutorial) and open an Image editor window.
Image Editor Selection
Then select all the faces by hitting A once (or twice!) (face mode in editmode Ctrl +tab +3) and press U which brings the UV Calculation menu, select Unwrap.
UV Calculation
You should then see something like this in the image editor, if not check if all seams have been marked.
Unwrap result
Now we can rescale and move the vertices. You can use shortcuts in the editor like S (scale), G (Move/Grab), R (Rotate), B (Box selection), falloff selection (O) will work too.
Reloc UV
Now we can export the layout that will serve as a base for our texture. Go to UVs->Scripts->Save UV Face Layout. Define the export resolution and press OK.
Layout Resolution
You should then end with something like this.
Layout Export Result
This will serve you as a template to paint your texture. Once we’ve created our texture in our favorite painting application (Photoshop, Gimp or Paint..) we can apply it to the object. For this tutorial I used an image made by Moony, that you can get HERE which was really well suited for this example. Once rotated scaled and cleaned of useless parts I obtained this:
Color Texture
Now back to Blender Add a material to the object in the material tab (F5) if it doesn’t have one already and add a texture if it doesn’t have one too.
Then go in the Map Input tab and press UV button
Color Texture
In the texture panel (F6) select image type : image and load the newly created texture.
Now toggle the model into edit mode and go back in the Image/UV editor here we will set the previously loaded texture as the active texture for the object.
Set Active Texture
Which should show you something like this
Adjusting UVs
You can tweak the uv here a little more precisely to match every lines. In the 3D port you can switch display mode to display the active texture.
Display Texture Mode
This is one way to apply a texture to an object, there are several others which all have their advantages and limitations. This one is very flexible, you can have variations on every faces of the cube and you can bake ambient occlusion and shadows with this kind of coordinate, the downside is that it waste some texture space and would need a high resolution texture to show details without becoming to blurry, the seams will also need special attention to make them the least visible possible.
The following picture was rendered with baked AO in 1sec 77
Baked  raytrace AO
The next one with raytraced AO in 1 min 9 sec
Raytrace AO
Another method would have been to mark every edge as a seam, unwrap and stack all the faces in the same space (You can rotate them by 90° increment). This would make a much better use of the texture space and solve the seams junction problem. But this kind of UV is not suited for baking shadow or ambient occlusion since all the faces of the mesh refers to the same part of the image.
You can apply several UV Coordinate sets to one object in Blender by clicking the new button next to UV Texture Label.
New UV
And you can use this to achieve several things, like displacement (Displacement Modifier).
Displacement Modifier
the displacement map
Displacement Map
With subdivision and displacement
Displacement render
Next time we will see how to generate a normal map from a high resolution mesh.

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