Texture projections generated from the toolbar (Get > Property > Texture Projection > projection type) are explicit texture projections.
The difference between implicit and explicit texture projection is subtle, but it can make a big difference when it comes to rendering.
When using an explicit texture projection, the texture shader uses the projection that has already been made available on the object’s defined coordinates, whether they be UV, Cylindrical, Spherical, and so on. Texture projections are explicit by default.
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Texture projections generated from the toolbar (Get > Property > Texture Projection > projection type) are explicit texture projections. |
An implicit texture projection rebuilds the texture coordinates for every pixel. Implicit texture projection is slightly slower to render because it performs its own projection computation (based on a predefined projection model; that is, spherical, planar, and so on) at each pixel, as opposed to using predefined interpolated UV data like explicit projections.
You would make a texture projection implicit to obtain a better overall result for spherical and cylindrical projections over a model with few polygons. For example, when mapping a texture onto a sphere (using either spherical or cylindrical projection), implicit texturing produces more accurate results at the spheres’ poles than does explicit projection.
To make a texture projection implicit
1. Select the texture projection you want to make implicit by using one of the following methods:
- Select the object and click the Clusters button in the Select panel.
or
- Select the object and choose Explore > Texture Projections from the Select panel.
2. From the explorer that appears, expand the Texture Coordinates icon to expose the texture projections assigned to the selected object. Click on the projection’s icon to open its property editor.
3. In the Texture Projection property editor, define the projection’s UV Generation as Implicit. The texture projection will use the coordinates you defined in step 2 to calculate its own implicit projection.
4. Set the projection coordinates, triangle intersection, and space transformation, as well as the projection method and plane.
For more information on the options in the Texture Projection property editor, refer to Texture Projection Property Editor and Texture Projection Definition Property Editor.
Transforming Implicit Projections
Implicit projections can take longer to transform than explicit projections depending on the transformations that you want to make. You can perform basic transformations using the texture support object. This allows you to control the scaling, rotation, and translation of the projection. Transforming texture supports is described in Scaling, Rotating, and Translating the Texture Support Object.
Adjusting texture coordinates is more difficult because the Modify Projection tool (j key) is not available for implicit projections. Instead, you can perform UVW transformations on the texture coordinates from the Texture Projection property editor, as described in Transforming Texture Projections.
Applying a Purely Implicit Projection
Creating a purely implicit projection is not like creating a regular implicit projection. Rather than creating an explicit projection and making it implicit, you create a purely implicit texture right from the start.
The purely implicit projection has no texture support. It is completely defined by you from the texture projection property editor. Although more mathematically accurate, a purely implicit projection has only a Scale, Rotate, Translate (SRT) box in the texture projection property editor, which makes it a little trickier to manipulate than using a manipulator icon. Transforming a texture projection from its property editor is described in Transforming Texture Projections.
To apply a purely implicit texture projection
1. Select the object, objects, group or hierarchy to which you will apply an implicit texture.
2. From a toolbar, choose Get > Property > Texture Projection > Create New Projection.
3. In the Create Texture Projection dialog box, select Purely Implicit from the Projection Type menu.
4. Name the projection and support in the Projection Name and Support name text boxes, respectively, and click OK. The implicit texture projection is applied to the selected object.
5. To change the implicit projection’s attributes, use one of the following methods:
- Select the object and click the Clusters button in the Select panel.
or
- Select the object and choose Explore > Texture Projections from the Select panel.
6. From the explorer that appears, expand the Texture Projection icon to expose the texture projections assigned to the selected object.
7. Click the Implicit projection’s icon to open its property editor.
8. In the Implicit Projection property editor, you can define the projection’s coordinates, triangle intersection, and space transformation, as well as projection method and plane.
For more information about the implicit texturing options, click the 
icon in the Texture Projection property editor.
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