complete understanding of blender uv mapping

 Blender UV maps are inevitable for Blender beginners to start modeling. It's not that difficult to operate, so anyone can do it with a little commentary.

On the other hand, the UV map looks simple, but if you create a suitable blender UV map, it tends to be troublesome later. In this article, we will explain in detail the points to note when creating a UV map as well as creating it.

What is a UV map?

I will explain the UV map again so that even beginners can understand it. A blender UV map is a map that specifies the texture coordinates of the 3d model.

In 3DCG using polygons, textures are attached to a 3d model like a sticker. At this time, the correct model cannot be displayed unless you know "where to attach the texture to which part of the model". ..

U and V in the UV map correspond to the axes X and Y.

Since we are already using the xyz axis in the 3D space of the object, U and V are used to distinguish them.

Expand the model to a UV map

UV map expansion in Blender is done in Edit mode. From Edit mode, select all the meshes faces you want to expand (A key) and press the U key. From the pop-up that appears, select Unwrap to expand the UV map.

Insert seams

Since it expands from a solid to a plane, it cannot be expanded unless there is a cut somewhere. This break is called a seam in Blender.

To insert a seam, select the edge you want to insert a seam from Edit mode and right-click. If you select Mark Seam from the popup, a red line will appear on the edge. The seam is now set on that edge.

Don't put it on a flat surface (important !!)

It doesn't mean that you can put the seams anywhere. The part that should not be seamed is the flat part. The reason is that seam breaks can be noticeable when the models are at a distance. This is a problem that is hard to notice in Blender, but it is often noticeable when you bring it to a game engine.

Once the seams are noticeable after the model is complete, it is very difficult to edit the UV map from there. Be careful not to put the seams on a flat surface, as you may get disappointing results like the one below.

Check for UV crushed areas

It's a mistake you often notice after you start painting a texture in blender. Since the solid is forced into the flat surface, the UV may be crushed due to insufficient seam insertion.

If this happens, the texture resolution will be insufficient for that part, and it will become jaggies when painted. Check for crushed areas when unfolding UVs.

Hide Crease and Sharp

Beginners may not have used it, but setting creases or sharps on the mesh will overwrite the seam display. If you don't know where you put the seams, hide the creases and sharps from Overlays> Mesh Edit mode.

Deploy without seams

Actually, there is a way to develop UV without inserting seams. These can be selected from the U key, but some of them are difficult to handle, so I will explain them.

Smart UV Project

UV unfolds the mesh automatically. 

The Smart UV Project develops UVs relative to the angle of the edges. Therefore, the number of divisions is often tremendous or distorted. It is used when you want to quickly preview the temporarily set material.

It is never used for UV maps of finished products.

Lightmap Pack

Lightmap is a map that often appears in game engines, you can make all the polygons rectangular and spread them as square as possible.

Since the mesh connections are ignored, the polygon correspondence becomes very confusing.

Follow active Quads

You can unify the shape to the UV of the selected polygon.

The caveat is that the shape on the UV map is the reference, not the shape of the 3D view. You can make other polygons have the same shape by running Follow active quads with the UVs close to a rectangle, as shown in the figure below.

Projection system

The development of the projection system is as follows :

  • Cube projection
  • Cylinder projection
  • Sphere projection
  • Project From View
  • Project From View(Bounds)

Cube projection

Project the model onto the cube and split the mesh for each polygon that appears in the cube. I can't think of anything to use. I don't need it.

Cylinder projection/ Sphere projection

Project it onto the cylinder and unfold it. It is developed like a world map drawn in the Mercator projection. Cylinder projection and spherical projection give similar results. use? Is it a globe?

Project From View/ Project From View(Bounds)

Project From View allows you to transfer the mesh you see in the 3D view to a UV map in its original size. This is fairly usable, so it's worth remembering. Project From View (Bounds) expands the projection expansion to the limit.

Lay out the UV map

If you can develop the UV well, you can place the UV. From here, I will explain the layout of UV.

Margin with a margin

Margin is the distance between polygons.

For models that are successfully seamed, I think 10 to 20 polygons will be expanded on the UV map. In the UV layout, these should be placed so that they do not interfere with each other.

If the polygons overlap, when you paint one polygon, the other polygon will also be affected.

Group by material

It's best not to line up randomly and cluttered.

It's common to notice texture mistakes once the model is complete, and collecting UVs for each material can sometimes be recovered by lightly modifying the texture in photoshop. Compared to the trouble of repainting from scratch, it is much easier, so it is recommended to lay out UVs for each material as much as possible.

Hit the pin

Once you have decided on the UV position, don't forget to hit the pin. You can fix the UV by hitting a pin.

  • P key to hitting the pin
  • Alt + P to unlock

From experience, it's good to hit the pin with any UV. It is quite possible that the UVs are moving without you noticing it. Especially from Blender 2.8, a new function called Live Unwrap has been added, which makes UV movement easier.

Beware of Live Unwrap

Live Unwrap is disabled by default, but because it's directly under Unwrap, it can be unknowingly enabled. The function of Live Unwrap is a function that automatically re-executes Unwrap when a seam is added.

Do you already know what happens if you don't hit the pin?

If you solidify your UV layout and then make some minor tweaks to your seams, that's a blow away. Let's hit the pin! !!


I split the article because the number of characters was quite large just by blender UV mapping

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