What does UV Mapping do exactly?

[Jacki Silverfall]

Is it just to give an object individual faces to texture?

Does it matter which way the faces are facing on the UV map, like say your trying texture a woodgrain. Do you have to have the faces facing the way you want the woodgrain to go? Or can you turn the texture once inworld?

What is the hot keys for hiding/unhiding a part of an object? I can hide it but don't know how to make it reappear. :(

I have a million dumb questions....

Jacki

 

[Chip Midnight]

UV mapping controls the way the texture wraps onto the surface of the model.

Here's a video that explains the basics:

[Rolig Loon]

Take a look at these two video tutorials :

http://blog.machinimatrix.org/coffee-cup-tutorials-iv-uv-mapping/

http://cgcookie.com/blender/2011/01/21/intro_uvmapping/

A UV map is like a dress pattern.  It's a 2D map of your 3D model.  Once you have created it, you use it almost exactly the way you would lay out a dress if you were going to cut out fabric pieces.  Each "pattern" area in your UV map corresponds to a specific shape and location on your 3D model.  If you are creating a texture in Photoshop or GIMP, you use the UV map as an overlay or guide so you know where the textures you are drawing will show up on the model eventually. The orientation and scale of the texture does make a difference, just as it would if you were using a dress pattern to cut out fabric. 

The areas on your UV map do not correspond to faces on your 3D model, unless you have deliberately made them do that. 

[Pix Jigsaw]

If you are using Blender,  Hide is the H key.   Unhide is Alt H.  You can also find the command at the top of the Mesh menu.

[Peggy Paperdoll]

@ Rolig:

I know what a UV map is but I've never been able to discribe so concisely as you just did..........the dress pattern comparison is so simple yet discribes it near perfectly.  Geeze, I wish I could say things so simply.  Thank you.

@ Chip:

My god it's been years since I've seen a post by you..........please, come back more often. 

 

And to Jacki:

I think you got your answer by two of the best.........good luck with your texturing. 

[Jacki Silverfall]

Thank you all for your replies. I know they might sound like dumb questions but until this all clicks in my head it seems a bit scattered and overwhelming.

/me waits for my AH HA moment

Jacki

[Chip Midnight]

Thanks, Peggy It seems incredibly strange having a post count of only 50! haha. I'm back around and creating content again so I should be sticking my head in the forums more often.

[Drongle McMahon]

To be horribly technical, and probably not as helpful as Rolig, the UV map is just the collection of positions in the 2D texture image space* that correspond to each vertex in 3D space. When the texture is applied. it is done one triangle at a time. The texture from the triangle defined by the UV coordinates of the three vertices making the triangle is stretched to fit the triangle in 3D space that is made with the same three vertices.

One consequence of this is that the textuire continues across any two triangles sharing an edge in the 2D UV map. Thus the texture covered by a UV "island" consisting of many triangles appears stretched over the corresponsing 3D triangles. The representation of the UV map in the authoring software is simply a drawing of the vertices and polygons in the 2D texture space. Superimposing this on the texture shows which areas of the texture will be allocated to which polygons of the mesh surface. This leads to the useful and accurate dress pattern analogy.

Texture stretching may be different in direction and amount for different triangles, leading to distortion of the texture in the 3D surface. The task of the modeller is to ensure that any such distortions (such as the direction of woodgrain) is consistent with the desired appearance of the textured mesh.

Sometimes, the pattern does not flow across adges. These edges are the UV seams, separating the UV islands. In these cases, the UV coordinates for a single 3D vertex are different depending on which triangle is being textured. In the SL data format, this requires the whole data for that vertex to be duplicated. This is why seams and fragmented UV maps (many islands) increase download weight and usually increase land impact. However, fewer seams generally leads to greater texture distortion on the 3D mesh. So a compromise has to be arrived at.

*Generally the texture space is treated as periodic, so positions that fall outside the defined texture area are treated as being on a plane which has the texture infinitely repeated in all directions.