Lesson5 - 3D Modeling

Modeling

involves creating or recreating the shape of an object

primitives

In computer graphics, a set of objects known as ____________ are used to approximate simple geometric shapes

polygonal modeling

the 3D scene objects are generated by putting together many flat surfaces, known as polygons or faces.

3D objects

are modeled using polygon meshes to recreate the surface that is being approximated, which is typically four -sided quadrilaterals (quads) or three - sided triangles (tris)

n-gons

polygons with more than four sides, namely ___________, are also used for polygonal modeling

polygonal models

are relatively more convenient to create and to render, especially when it comes to organic modeling, polygonal meshes can be quite useful and efficient.

avoid faceted appearance

shortcoming of polygonal modeling is that it requires many flat surfaces to _________________ of the final models created.

Extrusion

refers to selecting a face from a polygonal mesh or an edge and pulling it out. _____ a face or a polygon results in more polygons being created.

Bevel

this refers to the creation of inclined surfaces, and can be referred to inward bevel or outward bevel

Bridge

an operation where the edges of the polygons can be bridged together to create objects by combining two 3D objects

Constructive Solid Geometry (CSG)

refers to the use of Boolean Operations (AND, OR, NOT) to create complex designs and intricate shapes

Box modeling

is a common technique for 3D modeling compound scene models that are composed of multiple parts.

can be used to create both organic models and hard -surface models

Part modeling

very much works like the usual modeling we have discussed, wherein we use storyboards before starting the actual digital modeling .

has its application in the industry where compound parts and assemblies are involved, and where dimensional accuracy is important.

Computer -Aided Design (CAD)

applications in manufacturing, design, and many other engineering applications can use part modeling.

This allows intricately and accurately designing components that serve as parts of large assemblies .

Grouping

refers to the process when all objects constituting a larger object are together to act as one single unit (or object).

Root

Topmost object in the hierarchical structure. The parent object that is above all other parent objects in the scene.

Node

All elements in hierarchy referred to as _______. Any object, either a parent or a child, is a node.

Branch

The hierarchical link or path that represents the association between parent object and its child object.

Parent

A scene object in the scene that is depend on (controlled by) a parent

Sibling

Children of the same parent node.

descendants

all children of a parent object (including all the parent(s) of the child's parent object)

ancestors

all parents of a child object in a 3D model (including all the parents(s) f the child's parent object).

leaf

The objects (nodes) that do not have children. They represent the lowest level within the hierarchy.

deformation operations

A set of processes known as __________________ can be used to create complicated designs quickly even from simple primitives.

Deformations

are interlinked to the concept of transformation in the sense that you can apply a specific __________along a specific axis and you can also constrain the values of allowable __________.

Bend

Curvatures or turns in an object by an angle (up to 360°) about x, y, or z axis.

Skew

Affects the object's geometry by offsetting and controlling the magnitude of ______ applied. This can be applied about a specific axis and also to the object in its entirety or just to specific elements within the geometry.

Slice

Generates new polygons, lines, and vertices by applying a plane that cuts into the object.

Stretch

This is a variant of the scale procedure to make the object skinny or thin around the center areas.

Displace

Pushes and redesigns an object's geometric form to achieve alternative configurations.

Lattice

Converts edges of objects into beam or girder or other similar shaped elements at the vertices.

Noise

Controls and confines the vertex positions of objects. Capable of generating different effects such as terrain and texture, and this should be applied along a plane (as a combination of axes, e.g., xy plane encompassing x- and y-axes).

Ripple

Generates a ripple effect on the selected object in a coaxial manner. This can be manipulated by regulating the number of ripples and the center of the ripple propagation.

Taper

Yields an elongated or narrowing effect on an object by scaling the ends in a contrasting manner; by scaling up one end or side of the object and scaling down the other end or side.

Twist

Curves an object about a selected axis; this can be controlled using the pivot point of application and using constraints on the axis.

Fillet

Molding or trimming applied at the point where two edges meet. Applying a smooth connection between surfaces.

Bevel

Removing hard edge between surfaces by substituting with a slanting edge or plane.

Round

A modified version of beveling, which rounds/smoothens the straight or hard edges using an adjustable number of facets. The number of facets/segments can be adjusted based on the degree of smoothing required.

Blend

Merging two surfaces using a new surface that is generated and controlled using control points.

Purge

Removing redundant vertices in the models generated using curved patches to reduce file size and the rendering time.

Fitting

Dragging noncontiguous model surfaces to fit and match their edges to eliminate minor gaps among surfaces.

External and Internal Navigation

This refers to the user navigating inside or outside a structure, and is closely related to the poly-count and file-size considerations

texture

Besides the polygons, another thing a modeler needs to be mindful of is ____________, as models combine high polycount and textures to create a photorealistic 3D model.

Raster images used as textures

also contribute to the overall file size, and displaying texture images with large file sizes also influences the rendering time.

ImgFS(kb) = ((ResolutionDPI) 2 x Winch x Hinch x bitDepth) / BitsInKB

Raster image file formats (or bitmaps) can be very large in size. It is calculated using this formula:

Raster images

such as JPGs, are often used for photographs and are utilized to create "photorealistic" representations

24 -bit

The standard bit depth for digital images nowadays is ______, which is known as True Color, and supports 16,777,217 colors

True Color

The standard bit depth for digital images nowadays is 24 -bit, which is known as _________, and supports 16,777,217 colors

Curves

are almost ubiquitous; they are found everywhere.

control points

A curve's shape is controlled by points known as "___________", and when connected, they form a control polygon

Explicit Representation

In common language, the word explicit refers to something that has no uncertainty or vagueness and is straightforward or clear

explicit function

is one which is expressed in terms of the independent variable.

If the value of the independent variable changes, the value of the dependent variable changes accordingly.

explicit refers to something that has no uncertainty or vagueness

Implicit Representation

the implicit function is defined in terms of both the dependent and independent variables

This means that we cannot find the solution to an equation with only x and y, but rather, another number.

Parametric Representation

The basic meaning of parametric is a parameter is used to define an ordered pair of x and y.

Also known as parametric curve, this representation expresses x and y values in terms of another variable, usually time.

open curves

curves that have two distinct end points are known as _________, while curves that are closed do not have end points.

closed curves

the starting point and the end point are the same (circle, ellipse)

encompass an area within them (U or C -shaped lines)

simple curve

according to the definition of a curve, does change its direction, but it does not intersect itself while doing so.

upward curve

A curve that points towards the upward direction is called an _______. An upward curve is also known as a concave curve

downward curve

A curve that points towards the downward direction is called a _________. A downward curve is also known as a convex curve

control points or anchor points

The points we made in the Cartesian plane are used as guides to create the curve.

They can be known as __________ or _________, depending on how they are used.

control points

They are ______________ if the curve passes through them, and they are also known as interpolating curves

anchor points

They are _____________ if they influence the curve, also known as approximating curves

Splines

are mathematical functions that smoothly interpolate between a set of control points.

They ensure continuity (smoothness) between adjacent segments.

cubic spline

The most common type is the __________, which uses cubic polynomials.

Bézier Curves

were popularized by French engineer Pierre Bézier who applied these curves to design and manufacturing applications, especially for automobiles.

are a specific type of spline that relies on control points and anchor points to shape the curve .

Pierre Bézier

Bézier curves were popularized by French engineer _______________

approximate a polygonal shape

The idea pf Bezier curves is to _____________ formed by a set of vertices using a polynomial curve

Isaac Jacob Schoenberg

invented the term B -spline that is short for Basis Splines in 1988

B -splines

can help overcome the limitations imposed by the Bézier curve wherein a change to any one control point affects the curve globally

tackle this problem by restricting the changes to the particular segment of the entire curve containing the control point being changed

Nonuniform Rational B-Splines (NURBS)

extend B-splines by introducing weights for control points, which allow for varying influence and precise representation of complex shapes

are an excellent tool for creating smooth surface and representing organic objects

extruding and lathing

Sweeping techniques such as ____________ are extremely time -saving modeling techniques that are widely used to create intricate 3D objects efficiently

Lathe

In machine tool operation, a ________ is a mechanical device that clamps or holds in position the material and spins it around an axis so that tools can be used on it to create the final product

surface of revolution

A 3D surface generated by lathing is known as a ___________

Lofting

involves creating an intricate 3D object using two two -dimensional objects like splines

cross section or the shape spline

Typically with lofting, two splines are needed: One of these two splines serves as the _______________, and the other one serves as the path spline serving as the path along which the shape can extruded.

Subdivision

refers to dividing further or a subordinate division.

Edges

can be added or subtracted, which automatically causes a corresponding change in the number of vertices or polygons connected to those edges

Organic modeling

is a valuable tool to model organic (natural, life-like) character models

organic

The term ______________ in the modeling context refers to something similar to living organisms and attributes of living organisms, especially from the external appearance and behavior

free -form modeling

can be used, as it can involve or be used in tandem with other modeling techniques

You can analogize ______________ to the building or molding of objects using modeling clay

free -form deformation (FFD)

r free -form modeling as the digital counterpart of such procedures in which you will be deforming (or manipulating) your 3D object in multifarious ways, which is the reason that free -form modeling is also referred to as ____________