In Softimage, a texture is more than just an image or a shader. Applying a texture to an object creates a variety of elements that define the texture in the scene and control the way it appears on the object to which it is applied.
Every time you select a picture to use as a texture, an image source file and an instance of the image—called an image clip—are created. For more information on image source and image clip files, see Clips & Sources.
Several image clips can be created from a source file. An instance or clip of the image source file is created every time it is used. You can then edit each one slightly, according to your needs.
For example, if you are using the same picture file (source) for both your surface texture and your bump map, you can apply a slight blur onto the picture file without affecting the picture being used as a surface texture because they are using different image clips. For more information on editing image clips, see Editing Textures.
Texture Projections and Supports
Texture projections and texture supports are created every time you apply a texture. The following is a brief description, but you can find extensive information about both projections and supports in Projections and Supports.
Regardless of the number or types of textures you wish to apply, each texture must have a texture projection defined in order to be applied to your selection. Every texture shader allows you to create a texture projection “on the fly” using the Texture Projection controls in the shader’s property editor. For more information on the different types of texture projections, see Types of Texture Projection.
As you apply texture projections, a graphical representation of the projection is added to the object(s) in the 3D views. This object is called the texture-support object and is displayed as a dark green wireframe.
Projections and supports allow you to precisely control the 2D texturing pipeline. The texture support controls how a 2D texture is applied to a 3D object, while the projection records where the texture appears on the object. A single support can hold multiple projections.
Texture Projections vs. Texture Maps
Texture maps are properties that combine texture images and texture projections. They are used in particle and hair simulations where you apply them to mappable parameters. For example, you could use a texture map to control particle emission, hair color, and so on, instead of using a single value.
As a general rule texture maps are not used for actual texturing. This is because the texture and projection information are not included in a shader that you can attach to an object’s material. However, you can use map lookup shaders to bring texture maps into the render tree, where you can connect them to materials and other shaders.
For more information about texture projections, see Projections and Supports.
For more information about texture maps, see Parameter Maps [Scene Elements].
To use a texture map in the render tree
1. Select the object to which the map is applied (or its material) and press 7 to open a render tree.
2. From the render tree menu bar, choose Nodes > Map Lookups > Color.
The Color Map Lookup shader will output the texture map as a color value. You can use other types of map lookup shaders to output is as other types of values (scalar, vector, and so on).
3. Connect the Map_lookup_color shader to one or more ports on the material node or another shader.
This establishes a connection between the shader and the object, allowing the shader to look up the object’s maps.
4. Double click the Map_lookup_color shader to open its property editor.
5. From the Map list, choose the map that you wish to use.
Applying a texture projection to an object creates a set of texture coordinates — often called UV coordinates or simply UVs — that control where the texture corresponds to the surface of the object.
• On a polygon object, each vertex can hold multiple UV coordinates — one for each polygon corner that shares the vertex. The portion of the texture enclosed by a polygon’s UVs is mapped to the polygon.
• On NURBS objects, UV coordinates are not stored at the vertices; instead, they are generated based on a regular sampling of the object‘s surface. However, as with polygon objects, the portion of the texture enclosed by, say, four UVs is mapped to the corresponding portion of the object
You can view and adjust UV coordinates using the texture editor, where they are represented by sample points. When you select sample points, you are actually selecting the UV coordinates held at the corresponding position on the object.
For example, as you can see in the images below, the center point of a 2x2 polygon grid holds four UV coordinates. When you select the corresponding sample point in the texture editor, you are selecting all four coordinates (although it is possible to select a single polygon-corner’s UV coordinate). For more information about working with UVs in the texture editor, see Working with UVs in the Texture Editor.
When you create a texture projection on an object, a texture operator is created. The texture operator controls where the projection “reads” in the object’s operator stack, which determines how the texture appears on the object’s surface — particularly when the object is deformed.
In the explorer, the texture operator does not appear in the object’s operator stack. Instead it appears under the object’s Texture Projection node.
To see where a texture operator is reading in the main operator stack, hold the mouse pointer over the TextureOp node, and read the tooltip.
You can reposition the texture operator in the operator stack to change how the texture responds when the object is deformed. This is described in Texture Projections and the Operator Stack.
Autodesk Softimage v.7.5