Sculpted prim

A sculpted prim(itive) (or sculpty, sculptie, or just sculpt) is a Second Life 3D parametric object whose 3D shape is determined by a texture. These textures are UV maps that form the rendered 3D sculpted prim. Sculpted prims can be used to create more complex, organic shapes that are not possible with Second Life's primitive system.

A sculpty is a standard RGB texture where the R (red), G (green) and B (blue) channels are mapped onto X, Y, and Z space. Sculpt textures are similar to normal maps, but instead of encoding surface normals they encode surface positions. They are also similar to displacement maps, but instead of a single scalar distance, there are three values — one each for the X, Y, and Z coordinates. Sculpt textures are also very similar to parametric (e.g. NURBS) surfaces. See Sculpted Prims: Under the Hood article for details. Minimum recognized size is 8 x 8. Maximum recognized size is 128 x 128. larger can be uploaded but will be treated as an image and compressed.

The UV map is embedded into the sculpty on creation. When uploaded into the Second Life asset server, and rezzed (rendered), it will form the shape imposed on it. However, the actual texturing must be done in a separate file, the map of which will be based on the conceived shape. For example, a liquor bottle would have its label on its forward face. However, there is only one face on a sculpty as it is either a sphere, torus, cone, or cylinder (cube also exists but the texture covers all the perceived faces so the rule applies). For the liquor label it would be located on a specific section of the lower left quadrant.

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Wikipedia