Image and Procedural Texture Mapping Techniques

No matter how well a surface is modeled, even if its form is an exact copy of the original subject, it will not appear naturalistic and have a bland appearance. By applying textures, objects will have more visual complexity and appear more believable or aesthetically appealing to a viewer. There are two kinds of approaches to texture mapping that are called image and procedural texture mapping. The following discusses these techniques in texturing through XSI.

Image textures
These textures are any image in a picture file that one wishes to use to wrap around the surface of a form. These are particularly useful for forms that require specific images on particular parts or sides of them.

Procedural textures
These textures are generated mathematically and are calculated to simulate natural materials. There are two types of procedural textures that are 2d and 3d. 2d procedural textures only simulate an objects surface appearance while 3d procedural textures are used to simulate a forms internal structure. The software calculates how the surface of the form would appear depending on how it would it be structured internally. For example, the appearance of grain on wood is determined by how the layers of wood would be structured inside it.

Materials and Texture projections
When working with textures one should select the texture view mode from the top corner of the view screen so one can see the textures that one has assigned to their surface. Before a texture can be applied on a surface one has to prepare it. First a material has to be assigned to it. To do this the surface must be selected and a material selected from the materials tab such as a Phong, Lambert or Blinn. A menu will pop up that allows one to determine the aspects of the surface such as its colour, reflection, ambient light, ect.

Another step one has to take before being able to add a texture to a surface is to assign how the texture would be projected over a surface. Depending what shape the object is determines what type of texture projection one is required to use to project the texture on the objects surface. For example if one has a sphere as an object, one should use a spherical texture projection. If wants to place an object onto a flat surface one should select one of the uv, xy, yz, and xz texture projections depending on what axis the surface is positioned. To assign one of these texture projections to a surface one must select the object, click on the property tab, texture projections and then select the texture projection that is suitable for the object. The scaling, sizing and positioning of the texture projection object will determine how an image is projected onto a surface.

Image texture mapping
Finally one can apply an image to the surface of the object. To view the materials and edit them one can open the 'material manger'. In this menu one can view different textures and materials in the 'render tree' as 'nodes' and edit, add or delete them. To add an image texture to a material one has to select the material from the material manager and press enter. This will reveal options to edit the material. To add an image as a texture one can select the plug tab next to the diffuse bars and select 'image'. This will give one the option to load an image from outside of XSI. The image will be wrapped around a forms surface depending on the texture projection. To edit how the texture is projected with more control one can select the Texture editor with Alt+7. This allows one to move vertices that determine how the image is displayed over a surface.

Procedural texture mapping
2d procedural textures can be applied on an objects surface in a similar way as one does with an image texture. By clicking on the plug button, in the material's option window, one can select one of many texture presets. The program will mathematically calculate how the texture will cover the object depending on a certain algorithm. To edit the texture one can access its options by selecting its node from the render tree and pressing enter.

3d procedural textures can be applied by to an object to clicking on the nodes tab above the render tree, selecting texture generators and choosing a texture. This will create a convoluted surface on the surface of a form instead of just being an image on a surface that gives the illusion of textures.


References.

Digital tutors DVD
XSI tutorials