The Rest of the Appearance... Form

If you look back at the appearance form, there are several other quantities which will now be discussed. Realize that these all are attributes which are assigned to either surfaces or an entire part. These are Color, Shading Type, Radiant Light, Isoline Density, Texture/Decal, Translucency and Precedence. Each are discussed as follows:

Color

Color is self-explanatory. You can select any color that is defined in the model file and apply it to whatever is selected. Color is self-explanatory. You can select any color that is defined in the model file and apply it to whatever is selected.

Shading Type

Shading Type refers to what happens to a surface or part when it is shaded. There are two options; Smooth and No_Shading. Smooth is what is set by default and is what is most needed. In effect, Smooth means "use the display model". No_Shading means that the surfaces selected should always be displayed at 100% of their color regardless of any consideration of light source, surface curvature or any of the other characteristics of shape and environment which affect how we perceive things. The following pictures illustrate the difference:

Isoline Density

Isoline Density will not be discussed in this document. It has to do with the display of the NURB surfaces. Although it can have an impact on shaded displays since it will alter the manner in which tessellation is performed (to be discussed later), there are more direct methods of controlling tessellation which do not result in as much of a performance hit as modifying Isoline Density. This should only be changed for very specific needs which do not generally have anything to do with shaded displays. Isoline Density will not be discussed in this document. It has to do with the display of the NURB surfaces. Although it can have an impact on shaded displays since it will alter the manner in which tessellation is performed (to be discussed later), there are more direct methods of controlling tessellation which do not result in as much of a performance hit as modifying Isoline Density. This should only be changed for very specific needs which do not generally have anything to do with shaded displays.

Texture/Decal

The Texture/Decal capability is only available with Shading Hardware and Shading Hardware and will not be discussed in this document.

Translucency

Translucency is a percentage between 0% and 100%. 0% translucent is opaque surfaces. 100% translucent is "invisible" surfaces. Anything in between is that level relative of "invisibility" for the surface. Notice that the word "surface" is used and not "part". The evaluation of translucency is applied on a surface-by-surface basis. In the following display, the sphere has a hole cut through it. Note that where the hole surface appear, the blocks behind the sphere are harder to see. That is because the images of the block must pass through four levels of translucent surfaces whereas elsewhere the block images have to pass through only two levels of surfaces. In the first picture the surfaces have all been made 35% translucent; in the second they are 60% translucent.

Translucency does not support refraction, that is, the bending of light through the part because of a density difference between media. In that sense, I-DEAS Translucency, therefore, is not a particularly "accurate" rendering of real-world translucency.

Precedence

Precedence is a characteristic that "piggybacks" off Translucency, i. e., Precedence changes will not be invoked unless Translucency is also turned on and assigned a non-zero value. In the Precedence display below, the following appearance attributes have been set: Precedence is a characteristic that "piggybacks" off Translucency, i. e., Precedence changes will not be invoked unless Translucency is also turned on and assigned a non-zero value. In the Precedence display below, the following appearance attributes have been set:

Sphere Translucency = 1 and On, Precedence = 75 and On
Green Block Translucency = 0, Precedence = 100
Other Blocks Translucency = 0, Precedence = 50

The purpose of Precedence is to change the natural "precedence" of display, i. e., that parts behind other parts are not visible; the closer parts take "precedence" in display over the parts that are behind. Precedence allows the user to decide that "something behind" has higher Precedence for display than something in front. Even though the Precedence value must be between 0 and 100, it is not evaluated like a percentage. Precedence is evaluated purely on a greater-than or less-than basis. The Green Block has a higher Precedence value than the Sphere, so it is displayed even though it is behind the Sphere. All the other blocks have Precedence values less-than the Sphere, so the Sphere takes precedence over the other blocks.

It was desirable that the sphere appear opaque, but the Translucency of 1% for the sphere is necessary or Precedence will not work. A very small value is essentially opaque. If more complicated Precedence displays are desired (and I don't know why they would be considering that the result of using Precedence is to create an image which has no real-world analog), then setting some of the other parts to having some level of Translucency may also be necessary. Finally, Precedence only works in "Shaded Software" mode, it does not work in "Ray Tracing" mode.

Radiant Light

Radiant Light was left until last because it segues into the next topic to discuss which will be the Lighting Options under Lighting. There is a setting in that form (Ambient) which will have similar characteristics to Radiant Light (at least in what its settings do to the shaded display), but the purpose of the two are different. Radiant Light was left until last because it segues into the next topic to discuss which will be the Lighting Options under Lighting. There is a setting in that form (Ambient) which will have similar characteristics to Radiant Light (at least in what its settings do to the shaded display), but the purpose of the two are different.

First, Radiant Light is a factor between 0% and 100% which identifies how much of the part's color is visible even when there is no light source being used. In effect, this is a factor which indicates how much the part "glows". Now take a look at the I-DEAS standard defaults for this quantity. It is 15%. That means that if you do not change the Radiant Light value from the standard default, every part you have ever created "glows" to 15% of its color. That is a bizarre virtual world to be "living" in. The following three images show the difference between 0% Radiant Light, 15% Radiant Light and 50% Radiant Light set for just the sphere.

Radiant Light seems to be a useful characteristic to apply to things like LED displays and lighted buttons on control panels. However, it makes no real sense to make every part every created "glow" just a little bit.