Texture positioning - Overview
Contents
Overview
When using textures, you need to define how the 2D texture is positioned onto the 3D object. This is often referred to as Texture mapping or Texture projection, depending on the method that is used. It is one of the most important aspects of texturing. When you don't take care of proper positioning of your textures, the result will be disappointing at least.
Texture positioning is either done per shader (material) or per object.
- Per shader (material)
- Fast, but less suitable for complex shapes and it is less precise.
- Per Object
- Effective for more complex shapes; it may be more laborious but it can be very precise.
When texture placement is determined by the shader, the shader contains a texture projection node, which determines scale, direction and projection method. Any UV-map that is specified in the object will be ignored.
When texture placement is determined by the object, a UV-map is constructed. This maps the 2D coordinates (u and v) of a texture onto the 3d coordinates of an object. Maya offers various tools and methods to create such an UV-map:
- Texture positioning - UV Normal mapping
- Texture positioning - UV mapping
- Texture positioning - UV Texture Editor
Which method to use?
| Projection Mapping | UV Normal Mapping | UV Mapping | UV Texture Editor | |
|---|---|---|---|---|
| per object or shader | shader | object | object | object |
| Ease of Use | + | ++ | + | - |
| Control | + | -- | + | ++ |
| Links | Texture positioning - Projection mapping | Texture positioning - Normal mapping | Texture positioning - UV mapping | Texture positioning - UV Texture Editor |
Projection mapping
Projection mapping is an effective methode for texturing basic shapes or multiple objects at the same time. This is beceause projection mapping is independant of the object, it only depends on the material. When you make a projection mapping an extra projection node is created in the 3d viewport of maya. This node is important as it determines the way the projection is mapped (scale, place, ect).
Note!: Unfortunately it is not possible to see a correct view of a file texture with projection-mapping in the view-port, if you want to work with projection mapping you will have to test your placement via small renders.
Texture positioning - Projection mapping
UV Normal mapping
Normal mapping is the fastest texture method. The downside is that you have little control over the placement.
When texturing using normal mapping, the texture is projected in the normal direction of each polygon face of your object. If necessary the texture may be stretched by Maya automatically to fit it for placement.
You can adjust the placement using UV-mapping. This supersedes the normal mapping: When no UV-map has been specified for the object, Maya defaults to normal mapping. UV-mapping is covered in the next section.
Texture positioning - Normal mapping
UV mapping
UV mapping, requires like UV-texturing some prior knowledge about UV's and the "UV Texture Editor". The UV texture editor displays the UV space of the object. As each polygon object has its CV points in 3D space, defining the objects' shape, each CV also has a UV coordinate defining its position in a 2D space. This is necessary for texturing, because an image is a 2D object. So in order to place a 2D object in 3D, UV coordinates are used. An objects surface can be completely unfolded in 2D space. The image to the side shows an example of how you can imagine a cube to be unfolded in 2D space. The UV texture editor is then used to reshape the 2D unfold of the object or make a snapshot of the layout and form a custom texture for it in photoshop (more on this later on). To access the UV texture editor go to Window > UV Texture Editor.
With UV Mapping you manually choose a projection type of the texture on your object. It is kind of a combination of normal mapping and projection mapping. You use projections to determine how the texture will be placed on your object, but in contrast to projection mapping this methode is more a per object mapping.
The computer doesn't automatically know where a texture has to be projected on an object and how large the texture has to be projected on the object. Texture mapping is comparable with the projection of an image by a beamer on a wall. The image is the texture, the wall is the object and the beamer is in this case the projector. The projector defines the location and size of the texture on an object and the computer will automatically tile the texture to completely cover the surface.
When an object gets assigned a shader that has one or more textures attached to it, the size and location of the projection has to be defined. The size of the projection depends on the size which the texture represents.
Texture positioning - UV mapping
UV Texturing
UV texturing, requires like UV-mapping some prior knowledge about UV's and the "UV Texture Editor". The UV texture editor displays the UV space of the object. As each polygon object has its CV points in 3D space, defining the objects' shape, each CV also has a UV coordinate defining its position in a 2D space. This is necessary for texturing, because an image is a 2D object. So in order to place a 2D object in 3D, UV coordinates are used. An objects surface can be completely unfolded in 2D space. The image to the side shows an example of how you can imagine a cube to be unfolded in 2D space. The UV texture editor is then used to reshape the 2D unfold of the object or make a snapshot of the layout and form a custom texture for it in photoshop (more on this later on). To access the UV texture editor go to Window > UV Texture Editor.
In Architecture, UV Texturing is often used to quickly generate a facade of a building by placing an image of the facade on the 3D object. This makes it especially useful in the early stages of design, for example to add more detail to a mass model. Because the facade is defined by an image it can be quickly changed by altering the image of the facade (eg: in Photoshop). The UV Texture Editor generates an image of the geometry exploded into panes. This makes it possible to edit the content of the panes. Some knowledge of Photoshop might be beneficial to be able to edit the image. With UV texturing you completely manually determine the UV layout and texturing of your object, in contrast to the UV mapping methode, in which you use predetermined mapping shapes to unfold the UV's of your object and place your texture. This method gives you a lot of freedom in unfolding UV's and it is often used in texturing game or animation movie characters.
Note!: In the UV texture editor the UV's are unfolded in the 0-1 (zero to one) space. It is of the utmost importance that with texturing the UV's stay in the 0-1 space. Placing UV's outside the 0-1 space can cause difficulties with texture placement in the UV Mapping and UV texturing methode.
