Sculpted Prims: 3d Modeling Glossary
From Second Life Wiki
(This is work in progress)
- Sculpted prims
- A new prim type in Second Life. A sculpted prim is a prim whose shape is determined by a texture — its “sculpt texture”. Sculpted prims will allow for custom and more complex shapes to be brought into SL and used in building.
- Sculpt Texture or “Sculpt Map”
- Sculpt Textures are image files that contain the data for the shape of a sculpted prim. A sculpt texture is a standard RGB texture where the R, G and B channels are mapped onto X, Y, and Z space. A sculpt texture is very similar to a “normal map”, but instead of encoding surface normals it encodes surface positions. See this wiki page for a detailed explanation.
- Stitching type
- Remember, a sculptie map is really a flat (i.e. 2 dimensional) square which is applied to and deforms a Second Life prim. As a square, it has edges. If you want to shape it into something that doesn't have edges (i.e. is 3 dimensional), you need to "stitch" those edges together.
- Sphere: when you select spherical stitching, the left and right sides of the square are stitched to each other, and the top and bottom edges are stitched to a single point.
- Cylinder: when you select cylindrical stitching, the left and right sides of the square are stitched to each other, but the top and bottom are left unstitched.
- Torus: when you select torus stitching, the left and right sides of the square are stitched to each other, and the top and bottom are also stitched to each other.
- Planar: when you select planar stitching, all the sides are left unstitched. (This is the same as selecting "none".)
- Ambient Occlusion
- A methood of calculating light and shadow on a 3d model with simulated ambient (non-directional) light. Some programs refer to this as "sky light". This is a fairly easy way to bake pre-rendered shadows onto a model.
- An edge is any line drawn between two verticies and are one of the three sub-components of a polygon model that can be manipulated.
- Faces, also called polygons, are one of the three editable sub-components of a polygon model.
- Level of Detail (LOD)
- Objects in 3D graphics are usually represented by a web or mesh of polygons, each with various properties such as colour and texture. When the camera is very close to an object, you need a lot of polygons to represent the detail. When the camera is far away, you only need a few larger polygons. This improves SL efficiency (i.e., reduces lag). Why bother to compute all the details of objects when they are too far away to be visible anyway?
- NURBS Modelling
- NURBS is short for “Non Uniform Rational Bézier Spline”. This modelling method uses a series of curves and control points to define the model’s shape. If you have already worked with the Pen tool in Photoshop, Illustrator and similar programs, you’ve worked with Bezier curves in 2D. NURBS take the same concept into 3D. According to Qarl Linden, NURBS are the best thing to use for sculpt prims; it makes some sense since he worked most recently in movie special effects where NURBS are commonly used.
- Polygon Mesh
- The Polygon Meshis the most common modelling method used in 3D computer graphics (including Second Life). The process involves the direct manipulation of polygons (triangles and quadrilaterals), faces, vertices and edges to produce the desired shape.
- Subdivision Surface
- Also known as 'subsurf': a method of modelling which takes some of the best features of both NURBS and polygon meshes in which you manipulate a series of control points on a model. The number of control points can be increased (subdivided) or decreased at will, offering great flexibility between fine and coarse control.
- Texture Maps
- In SL, textures are usually used to store pictures of something.
A Texture Map is 3D graphics lingo for an image that uses the colours to represent some data. In the case of sculpties, it is the <x,y,z> coordinate of the surface of the object. The textures most SLers know and love are also known as “diffuse maps” or “colour maps” within most programs; some people may also be familiar with “opacity maps”, “bump maps” and “normal maps”.
- Unwrapping is the process of manually taking a 3d model, defining its seams, and creating a flat template that defines how textures appear on that object. Clothing and skin designers are familiar with the SL avatar templates provided by Linden Lab and other residents; those are the end-result of an unwrapping process.
- UVW Mapping
- The data in a model that defines the positioning of its textures, either automatically, via an unwrapping process or using a preset projection such as planar mapping, face mapping, box mapping, spherical mapping, etc.
- In a polygon mesh a vertex is a single point in 3d space and the smallest editable component of a model. The plural is vertices (the correct Latin plural) or vertexes (a less-used alternative with an Anglicised ending).
Two verticies joined create an edge, three or more create a face. Faces are sometimes called polygons or polys.