![]() ![]() The ‘natural’ edge or outer bounds of a surface. If trimmed the underlying surface will generally extend past the edge.Īn edge that is not the result of a trim curve on the surface. Surface edges can be either trimmed or untrimmed. The edit points are points on the curve evaluated at these parameter values: The domain is the set of all possible input values to the function that defines the curve or surface.įor example, if the curve degree is three and the knot vector is: These directions are used when mapping texturesĪ circular surface can be like a spider web with one direction converging in the center. You can think of u-, v-, and normal-directions as corresponding to the x, y, and z of the surface. ![]() The normal direction is indicated by the white arrow. The u-direction is indicated by the red arrow, and the v-direction is indicated by the green arrow. The u- and v-directions are like the weave of cloth or screen. You can display the u- and v-directions and the normal direction with the Dir Surfaces have three directions, u, v, and normal. If you arrange its control points in a zig-zag shape, you can get two “bends.”įor curves, the direction is determined originally by the start and end points specified when it was drawn.įor surfaces the normal is a direction that points toward what you can think of as “outside” or “up.” For closed polysurface (cone, cylinder, box, etc.) or single-surface solids (sphere, torus), the normal always points “out.” However, on an open surface or polysurface, the direction of the normal depends on how it was created and can seem arbitrary.Ĭommand displays an object’s normal direction.Įvery surface is roughly rectangular. They have one “bend.”Ī cubic Bézier has degree 3. It has zero “bends.”Ī parabola, hyperbola, arc, and circle (conic section curves) have degree 2. From a NURBS modeling point of view, the (degree –1) is the maximum number of “bends” you can get in each span.Ī line has degree 1. NURBSįunctions are rational polynomials and the degree of the NURBS is the degree of the polynomial. x + 1 is 3 the degree of –x 5 + x 2 is 5, and so on.The “degree” of the polynomial is the largest power of the variable. Sometimes also called control vertex or node.Ĭontrol points are markers or “grips” on objects such as curves, surfaces, lights, and dimensions and cannot be separated from their objects.Ī polynomial is a function like y = 3 This condition is not easy to determine by just looking at where the points are located.Ĭurves and surfaces with G2 continuity are also G1 and therefore G0 continuous.īasis functions. If the radius of curvature is the same at the common end point, curves are curvature continuous (G2). If these all fall on a line then two curves are tangent (G1) at the ends.Ĭurves and surfaces with G1 continuity are also G0 continuous.Ĭurvature continuity between two curves measures position, direction, and radius of curvature at the ends. The direction is determined by the first and second point on each curve. Tangency measures position and curve direction at the ends. If the end points of each curve are in the same location in space, the curves are position continuous (G0) at the ends. In addition, you can save and restore named construction planesĪnd import named construction planes from another Rhino file.Īllow the cursor to move away from the construction plane.Ĭontinuity describes the relationship between curves and surfaces.Įach level of continuity assumes the conditions for the previous level are met. Preset construction planes: World Top, Right, and Front give you quick access to common construction planes. To change the direction and origin of a construction plane, from the menu, use the CPlaneĬommand. The red and green lines meet at the construction plane origin. The dark green line represents the construction plane y-axis. The dark red line represents the construction plane x-axis. The default Perspective viewport, however, uses the world Top construction plane, which is the same construction plane that is used in the Top viewport. The construction plane represents the local coordinate system for the viewport and can be different from the world coordinate systemĬome with construction planes that correspond to the viewport. The construction plane can be set to any orientation, and each viewport’s construction plane is independent of those in other viewports. The construction plane has an origin, x- and y-axes, and a grid. Bumpmaps do not modify the shape of the surface.Ī construction plane is like a tabletop that the cursor normally moves on. A bitmap image that make a surface appear bumpy in a rendered image. ![]()
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