Generating and Storing Tangents and Binormals

In Softimage, tangents and binormals can be generated whenever they are needed for a particular effect. Once generated, tangent and binormal data can be stored in a color at vertices (CAV) property or baked directly into separate image map files. The method used for generating and storing tangents and binormals is dependent on the tool you are working with (different tools provide different options and modify the data differently).

The object for which you are generating tangents and binormals needs to have a texture projection. If it does not, one will be automatically applied for you. The tangent and binormal data is computed based on the object's vertex normals and its texture coordinates provided by the texture projection.

Creating a standalone set of tangents or binormals from the Get > Property menu is a convenient and flexible way of pre-processing tangent and binormal data for use in games development. When using the Get > Property > Tangent and Binormal menu commands, the data is written to unclamped floating-point color values by default. This means that true tangent and binormal values are encoded in the color at vertices (CAV) property. For more information about how to modify the data type being written to the CAV, see Setting the Data Type for Tangents and Binormals.

• Get Property Tangent (from any toolbar) generates a set of tangents for a selected polygon mesh object and stores them in a color at vertices (CAV) property named Tangents by default.

• Get Property Binormal (from any toolbar) generates a set of binormals for a selected polygon mesh object and stores them in a color at vertices (CAV) property named Binormals by default.

  See Applying Tangent and Binormal Properties.

In addition, RenderMap, RenderVertex, and Ultimapper are tools that allow you to generate and store tangent and binormal data in normal and U/V basis maps or CAVs. When using these tools, the data in normal and U/V basis maps or CAVs is stored in a biased form (and represented in the 0 to 1 range).

• Get Property Render Map samples each point on the object's surface to burn U basis (tangent) and V basis (binormal) maps into separate image files. See Basis Vector Maps.

  RenderMap can also generate a normal map as a separate image file. If you set the Space option to Relative to UV Basis the normal map is encoded with the needed tangents and binormals. See Generating the Normal Maps.

• RenderVertex samples the object's polynodes to burn U basis (tangent) and V basis (binormal) maps into new or existing color at vertices (CAV) properties. See Basis Vector Maps.

  RenderVertex can also burn a normal map into a color at vertices (CAV) property. If you set the Space option to Relative to UV Basis the normal map will be encoded with the needed tangents and binormals. See Generating the Normal Maps.

• Get Property Ultimapper can be used to bake the normals generated from a high resolution source into a map that can be applied to a low-resolution destination object. If you select Normal in Tangent Space, the normal map is encoded with the needed tangents and binormals. See Transferring Attributes.