General 3D Glossary

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Sub-categories:

  1. Theory

Answers in this category:

  1. How do I make blender draw distant object?
  2. What are nurbs?
  3. What is flocking?
  4. Additive Color Model
  5. Aliasing
  6. Alpha Channel
  7. Anti-aliasing
  8. Aspect ratio
  9. Bezier Spline

1 - How do I make blender draw distant object?

Contributed by Matt Hilliard.

The trouble with distant objects disappearing is based on the far clipping plane of a camera being set too close, or small. The far clipping plane should be adjusted to a greater value when rendering distant objects. Setting extrememly large values for the it can cause roundoff errors and may cause artifacts with objects rendered close to the camera.

The procedure to change the clipping plane in blender is as follows:

1. Select the camera in the 3d window
2. Go to editbuttons (f9)
3. Adjust the ClipEnd setting to a distance sufficiently long enough between the camera, and the object you need to appear.
3a. (optional) Toggle the showlimits button to show the distance between the front and back clipping planes, while modelling, to ensure the objects within the scene are within the clipping area.

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2 - What are nurbs?

Contributed by type-r.

NURBS (non plural) are Non-Uniform Rational B-Slines. They can be used to to matematically describe any surface composed of nurbs curves. If you would like to learn about nurbs in depth follow links found at https://www.rhino3d.com

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3 - What is flocking?

Contributed by Daniel Jircik.

The following from the following (verbatim) about sums it up.
https://www.blender.nl/showitem.php?id=133

Flocking is a very famous teqnique for simulating group behavior. I'd like to quote the good description about it from "Game
Programming Gems" (Charles River Media):

Flocking (sometimes called swarming or herding) is a technique first put forth by Craig Reynolds in a 1987 paper he did for SIGGRAPH,
"Flock, Herd, and Schools: A Distributed Behavioral Model." In that paper, Reynolds proposed a series of three simple rules, which,
when taken together, gave group of automous agents (also called boids) a realistic form of group behavior simular to flocks of boids,
schools of fish, or swarms of bees. These rules, which Reynolds refer to as steering behaviors, are:

Separation. Steer to avoid crowding local flockmates.
Alignment. Steer toward the average heading of local flockmates.
Cohesion. Steer move to toward the average position of local flockmates.
In later implementation and papers, Reynolds added what has sometimes been referred to as the "fourth rule" of flocking:
Avoidance. Steer to avoid running into local obstacles or enemies.
Note that the steering behavior say nothing about state information or about a given agent maintaining knowledge of the flock, its
environment, where it:s headed, or the like. Flocking is a stateless algorithm in that no information is maintained from update to update;
each boid reevaluates its environment at every update cycle. (written by Steven Woodcock)

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4 - Additive Color Model

Contributed by anonymous.

In the additive color model, red, green, and blue (RGB) are the primary colors, and mixing them together creates white. This is the way light blends together-- shine a red, a green, and a blue spotlight in the same place, and it will make white light.

You add to get white. To get a lighter color use more of each color, or to get a darker color use less of each color. Additive is the color model used to display graphics on your computer screen, where all the colors are just combinations of the colors red, green and blue. Also called RGB space.

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5 - Aliasing

Contributed by anonymous.

When edges look jagged instead of smooth, and moiré patterns develop in fine parallel lines. The problem is most prevalent in diagonal lines. Aliasing happens when the engine tries to display an image on a portion of the screen where the resolution is too low to display its details correctly. This is solved with anti-aliasing, MIP mapping, or texture filtering.

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6 - Alpha Channel

Contributed by anonymous.

An optional channel in the texture file that usually defines the transparency of the texture’s pixels, but can also be used for other things like a height map. The alpha can be anywhere from 1bit up to 8bits, depending on the amount of detail you need. Generally, the lower the bit depth you use, the more memory you save, but the lower the image quality of the transparency.

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7 - Anti-aliasing

Contributed by anonymous.

Anti-aliasing removes the stair-stepping or jaggies which occur at the edges of polygons or between the texels on the polygons. It works by interpolating the pixels at the edges to make the difference between two color areas less dramatic. See also aliasing, MIP mapping, texture filtering.

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8 - Aspect ratio

Contributed by anonymous.

A number that describes the shape of a rectangular texture, whether it's tall or wide. To get the aspect ratio, either divide the width by the height, or write it out as width:height. Aspect ratio helps you decide what kinds of changes need to be done to an image to get it to display correctly, like when you have to scale the image. Aspect ratio gets kind of complex when you have to deal with non-square pixels and other oddities-- not very important to the artist.

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9 - Bezier Spline

Contributed by anonymous.

Another way to make a curved line with very few points. Named after the French mathematician Pierre Bézier (pronounced BEZ-ee-ay), these curves employ at least three points to define a curve. The two endpoints of the curve are called anchor points. The other points, which define the shape of the curve, are called handles, tangent points, or nodes. Attached to each handle are two control points. By moving the handles and the control points, you end up having a lot of control over the shape of the curve. Different from b-splines, which use control points that don't necessarily touch the curve.

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This Blender FAQ was generated on September 24, 2001, 8:40 am. For the most recent version and for searching the tutorial database, please visit the on-line version at https://helium.homeip.net/support