2D texture mapping is when “2D images [are] wrapped around an object’s surface, much like a sheet of rubber that’s wrapped around an object. To use an image texture, you start with any type of picture file (PIC, GIF, TIFF, PSD, DDS, etc.) such as a photo or a file made with a paint program” (Softimage User Guide). One uses a UV map to make sure that the image is ‘wrapped’ correctly around the object. Furthermore it is possible to alter the UVs as to make sure the texture is projected onto the object without distortion etc.
(Softimage Users Guide)
Where as 3D textures “are generated mathematically, each according to a particular algorithm.Typically, they are used for gradients, repeating patterns such as checkerboards, and fractals that mimic natural patterns such as wood, clouds, or marble…3D textures are projected “into” objects rather than onto them. This means they can be used to represent substances having internal structure, like the rings and knots of wood” (Softimage Users Guide).
There is one draw back to 3D texture mapping because “they [do] take longer to render than projected 2D textures. [However] procedural textures do give a better rendered result close up because pixels can be recomputed (rather than interpolated) at close proximity” (Softimage Users Guide).
But 3D textures have multiple benefits one of the most important is that “because 3D procedurals exist throughout 3D space, you often get good results on objects that would otherwise be hard to map. Instead of trying to wrap a 2D texture around a complicated sculpture, you can apply a 3D procedural and it appears to be perfectly mapped” (maya-doc.com).
(Softimage Users Guide)
One can apply 3D textures through “Softimage’s shader library, [which] contains both 2D and 3D procedural textures” (Softimage Users Guide).
Projecting Textures
“Each texture must be associated to a texture projection. The projection controls how the texture is applied across the surface of an object” (Softimage Users Guide).
Planar texture mapping “projects a texture along an axis onto the specific plane” (Softimage User guide). There are three options for how you would like your texture projected, either along the xy axis, the xz axis or along the yz axis.
Cylindrical projection allows one to “project a texture from a virtual cylinder around an object towards the central axis of the cylinder” (Softimage User guide).
Spherical Projection “maps a texture onto an object similar to a beach ball, with some distortion at the +Y and – Y poles” (Softimage Users Guide). In other words it will pull the texture from the +Y pole to the –Y pole of an object.
UV projections, unlike the previous two mentioned, can only be applied to NURB surfaces. “UV projections follow the UV parameterization of NURBS surface objects (no relation to texture UV coordinates). A UV projection behaves like a rubber skin stretched over the object’s surface. The points of the object correspond exactly to a particular coordinate in the texture, allowing you to accurately map a texture to the object’s geometry” (Softimage User Guide).
Camera Projections: “A camera projection projects a texture from the camera onto the object’s surface, much like a slide projector does. This is useful for projecting live action backgrounds into your scene so you can model and animate your 3D elements against them. Changing the camera’s position changes the projection’s position. Once you have positioned the texture on the surface to your liking, you can freeze the projection” (Softimage Users Guide).
A Cubic Projection is “when you apply a cubic projection to an object, the object’s faces are assigned to a specific face of a cubic texture support, based either on the orientation of their polygon normals or their proximity to a face. The texture is then projected from each face of the support using a planar or spherical projection method.
Unique UVs Projection can only be applied to polygons and there are two possible ways of doing it:
1. Individual Polygon packing, which “assigns each polygon’s UV coordinates to its own distinct piece of the texture so that no one polygon’s coordinates overlap another’s.
This is useful for render mapping polygon meshes. Typically, you apply textures to an object using a projection type appropriate to its geometry. Then you can rendermap the object using a new Unique UVs projection to output a texture image that you can reapply to the object. The texture is applied to texture each polygon properly without you worrying about “unfolding” it to fit properly” (Softimage Users Guide).
However as usefull as this form of mapping my sound it has one draw back. “A polygon-packing style Unique UVs projection only produces good results if you use a texture created specifically for the projection, for example, an image created using Render Map” (Softimage Users Guide).
2. Angle Grouping is applied after you have decided on a projection direction, you can then group “together neighboring polygons whose normal directions fall within a specified angle tolerance. This process is repeated until all of the object’s polygons are in a group. The groups — or islands — are then assigned to distinct pieces of the texture so that no two islands’ coordinates overlap each other” (Softimage Users Guide).
Contour Stretch Uvs Projects, is another method of U mapping which can only be applied to polygons. This method allows “you to project a texture image onto a selection of an object’s polygons. Rather than projecting according to a specific form, a contour stretch projection analyzes a four-cornered selection [of nodes] to determine how best to stretch the polygons’ UV coordinates over the image.
Contour stretch projections do not have the same alignment and positioning options as other projections. Instead, you select a stretching method that is appropriate to the selection’s topology and complexity… [They are] useful for a number of different texturing tasks, particularly for applying textures to tracks and roads on irregular, terrain-like meshes” (Softimage Users Guide).
Unfold Projection “creates a UV texture projection by ‘unwrapping’ a polygon mesh object using the edges you specify as cut lines or seams. When unfolding, the cut lines are treated as if they are disconnected to create borders or separate islands in the texture projection. The result is like peeling an orange or a banana and laying the skin out flat” (Softimage Users Guide).
(Softimage Users Guide)
Works Cited
Maya-doc.com. Texture Mapping. No place of publication. No date. Web. 12 March 2011
Softimage. Softimage Users Guide. Autodesk, 2011. Software.
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