Keywords: 3D data, geometric primitives, shape analysis, shape abstraction, computational geometry, data fitting. Categories and Subject Descriptors (according. Some of the primitives have multiple representations. A geometric query involving an object might be more effectively formulated with one representation than another. In geometric queries with objects such as polyhedra, the object can be treated as a two-dimensional or a three-dimensional object. Jump to In 3D modelling - In constructive solid geometry, primitives are simple geometric shapes such as a cube, cylinder, sphere, cone, pyramid, torus. In three dimensions, triangles or polygons positioned in three-dimensional space can be used as primitives to model more complex 3D forms.


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3D Modeling Basics

Some of these areas may look a bit complex 3d geometric primitives to an experienced modeler, but remember that there's always more than one way to solve a problem, so if an aspect of the project seems particularly daunting, try to find a creative alternative.

Modeling Approaches Whenever possible, take the simplest path to success when figuring out how a model will be constructed. The KISS Keep It Simple, Stupid principle applies very nicely to 3D work, because complicated models and operations tend to bog down the system and are more likely to cause trouble later on.

Bump and diffusion mapping discussed in Chapter 6, "Texture Mapping" uses bitmapped images and normals manipulation to give the impression that there are additional mesh details on an object. Because of this, mapping can often substitute for lots of detailed mesh, particularly with objects that aren't the focus of attention or are distant in the scene.

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So, think about whether a texture could be used on 3d geometric primitives simpler object even a single flat polygon and still achieve satisfactory results. In addition, think about how the model will be animated in the scene.


If you never see the far side of an object, you may not need to bother modeling 3d geometric primitives. If you're uncertain about whether a given modeling approach will work, do a test run with a quickly defined version of the object to find out.

Semantic Segmentation of Geometric Primitives in Dense 3D Point Clouds

Experimenting in this way will often turn up alternatives that you may not have thought of otherwise. Organizing Your Project Before you start to build a model, take a little time to set up some directories folders to hold the files in an 3d geometric primitives manner.

I recommend creating a "3D Projects" directory and keeping all your original work in that, organized by the name of the individual project or 3d geometric primitives. In this case, you might call the subdirectory "F14 Jet.

This will keep all the files related to the 3d geometric primitives in one easy-to-find directory. Keeping your files organized and grouped together this way also makes the projects easier to back up, because you don't have to hunt all over the hard drive to find the mesh and maps.

NOTE When you start texturing your models, you may find that you'll often use images that came free with your 3D program. I recommend that you make copies of any of these that you use on a given model and 3d geometric primitives them in the Maps directory for that project.

Not only does this enable you to customize the maps for your project, but it also ensures that you'll have all the files you need if you ever try to open the project on a different system 3d geometric primitives that may not have all the stock maps installed.

Now that you have a place for all the files, what about the filenames themselves?

Semantic Segmentation of Geometric Primitives in Dense 3D Point Clouds | ISMAR

Use a clear, descriptive name and add a number with a leading zero to the end so 3d geometric primitives can save off different versions as you work. Properly naming the hundreds of individual objects that may make up a model is also important.


When a model starts to get complex, selecting parts by eye can be difficult. Also, there are situations when you have to choose from an alphabetized list of objects to perform some process on them. You'll find a more in-depth guide to object and file naming conventions in Appendix G, "Planning and Organization.

3d geometric primitives

Geometric primitive

Modeler Concepts Now that you've gotten organized, it's time to move 3d geometric primitives to the software itself. As you 3d geometric primitives, modeling is the process of creating objects with a 3D software program. The term modeler was defined in Chapter 1 as the person who performs this work, but it is also used to describe that portion of the 3D package that deals with object creation, as well.

There are four basic types of modeling systems: Many packages combine these systems because each has its strengths and weaknesses. Polygonal is the most basic, and deals with 3D objects as groups of polygons only.

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