# Command Help Помощь по коммандам

Although we won’t be using them for actual modeling in this chapter, let’s take a quick look at how to work with reference images. One option is to create three planes and map each with an orthogonal reference image in the diffuse channel. Another option is to put a different reference image in the background of each viewport. Let’s do the latter. In Chapter 4, we used splines in different compound objects. Patch and NURBS modeling are spline-based systems, so we need to discuss splines in more depth. The term spline originated in ship-building, where a piece of wood would be shaped into a curve by distorting it with two pegs. Mathematicians borrowed the word to describe curves in terms of mathematical functions. In computer graphics, a spline is a curve defined by mathematical functions rather than a straight line segment defined solely by its two vertices. We have a mathematician named Pierre Bézier to thank for the math behind patch surfaces as well as the splines created with the Shape tools in MAX. Bezier splines are also fundamental to vector drawing programs like Illustrator, FreeHand, and CorelDraw, as well as to the Pen tool in Photoshop. You need to understand them if you are going to work with computer graphics. The vertices of an editable spline in MAX have four options for interpolating the tangents of the curve between them: Smooth, Corner, Bezier, and Bezier Corner. Let’s look at what these do to a spline. B-spline is short for basis-spline, a mathematical concept including Bezier splines and NURBS, the two types of splines available in MAX. A rational B-spline is one that is defined mathematically as the ratio of two polynomial functions. A non-uniform B-spline is one in which the influence of a curvature can be varied. A non-uniform rational B-spline is called NURBS for short. Fortunately for those of us who don’t breathe the rarefied air of higher mathematics, we never have to understand any of the math to use NURBS. With NURBS, the curve of a surface is shaped by control vertices (CVs) that do not lie on the NURBS curve. (This is true even of point curves, except in this case, the CVs are not accessible and points on the curve are accessible, in order to provide an alternate interface for modeling. Point curves and surfaces can be converted to their underlying CV form.) Each CV has a weight which determines the extent of its influence over the curve. A Bezier patch is a surface defined by vertices and the tangents of the edges between the vertices. A patch can have either three sides (Tri patches) or four sides (Quad patches). Quad patches tend to be preferred when modeling smooth surfaces, except when a Tri patch is necessary (to fill a hole in a model) or when it is helpful for modeling a particular detail. The vertices of patches can be coplanar (giving you Bezier handles that move together across the vertex) or corner (with independent handles). MAX gives you several ways to model in patches. The traditional way is to start with a patch, subdivide it, add patches, and adjust their curvature. In MAX, primitives, meshes, and loft objects can also be converted to patches and then edited in patch form. Patch modeling has recently enjoyed a rennaisance with MAX users due to the addition of MAX Surface Tools as an additional method of modeling in patches. The old method of working with patches has been called “knitting a house.” The advantage of learning this way of modeling is that it applies to most 3D applications, so you will be able to transfer your skills easily to a job that requires you to model in patches in a different program. The disadvantage is it requires a great deal of patience and practice, but that’s true of most things in 3D. Source. Looking for vector maps of Germany (Deutschland Vektorkarten) for Adobe Illustrator?.”

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