Blender 3D：零基础到专业级-单元2：基本建模和着色
Why Use Curves?
::为什么要使用曲线?
You’ve learned how versatile mesh objects can be, and how they can easily produce flat surfaces with sharp edges and even give a convincing representation of curved surfaces with rounder edges. So why do we need a separate kind of curve object at all?
::网状物体有多么多功能, 它们可以很容易地产生带有尖的平面, 甚至可以很好地呈现带有圆边的曲面.
There are important reasons.
::有重要的原因.
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The various kinds of curves and surfaces/patches (Bézier, NURBS etc) were used in computer graphics before meshes were developed. In the days when memory was more expensive, they offered a more compact way to represent complex shapes. Even now, they are still common in CAD and other technically-oriented graphics applications, where they make it easy to precisely specify the shape of a curve. Thus, if you are importing data from such applications, you will need the ability to represent such curves—even if you end up converting them to meshes before applying materials and textures for rendering.
::在网格开发之前,计算机图形中使用了各种类型的曲线和表面/补丁 (贝齐尔,NURBS等).在内存更昂贵的时候,它们提供了更紧的方式来表示复杂的形状.即使现在,它们仍然在CAD和其他技术导向的图形应用中很常见,在那里它们可以很容易地精确地指定曲线的形状.因此,如果您从这些应用程序中导入数据,您需要能够表示这些曲线,即使您最终在应用材料和纹理进行染之前将它们转换为网格. -
You can use curves as guides for shaping meshes. This makes it easier to construct certain kinds of complicated curved shapes. Particularly since it is simpler to make changes to the curve (with fewer control points), than after it has been converted to a mesh. To this end, Blender defines
scaling radius
and
tilt angle
settings for curve control points, which make no difference to the appearance of the curve itself, but have an effect when it is used to deform another shape.
::您可以使用曲线作为图形网格的指导.这使得构建某些类型的复杂曲线形状变得更容易.特别是因为对曲线进行更改 (控制点较少),比将其转换为网格后更简单.为此,Blender定义了曲线控制点的缩放半径和倾斜角度设置,这对曲线本身的外观没有任何影响,但当它被用于变形另一种形状时,它会产生影响.
Bézier Versus NURBS
::贝齐尔与NURBS
In the following pages, you will come across two kinds of curves/patches.
::在下面的页面上,你会看到两种曲线/补丁.
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If we consider that a
surface
needs to always be two-dimensional or more. A
curve
, that in one dimension is simply a line, needs at least be two dimensional when represented in a surface for the curvature to be expressed. What Blender calls a two dimensional “surface” is elsewhere in computer graphics commonly referred to as a
patch
.
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Bézier
objects only occur in Blender as curves, while
NURBS
(“
N
on-
U
niform
R
ational
B
-
S
pline) objects can be curves or surfaces. If you’ve used 2D drawing programs like Inkscape or Adobe Illustrator, you would have come across Bézier curves before. NURBS curves are a mathematical generalization of these, which are heavily used in CAD applications. Unlike Bézier curves, NURBS curves allow the specification of a variable
weight
for each control point, which governs how closely the curve passes to that point.
::贝济尔对象在Blender中只以曲线形式出现,而NURBS (非统一的理性B-Spline) 对象可以是曲线或表面.如果您使用了像Inkscape或Adobe Illustrator这样的2D绘图程序,您将会遇到贝济尔曲线.NURBS曲线是它们的数学概括,在CAD应用中大量使用.与贝济尔曲线不同,NURBS曲线允许为每个控制点指定可变重量,这决定了曲线到该点的距离.
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That‘s right, “NURBS” is singular, not plural. You will often hear people say “one NURB, many NURBs”, but really it should be “one NURBS, many NURBSes”. Or alternatively, you can finesse the issue by only using “NURBS” as an adjective: “one NURBS curve/surface/object, many NURBS curves/surfaces/objects”.
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