Functions Color Selection Active Material Material Textures Library Test Image Exit

Menu : SCENE

Command: Edit:Materials

Shortcut : None

This command is used to define and assign different material properties to surface objects. After executing the command, an extensive material palette window appears which includes various fields to perform different operations. Any number of materials may be simulated from this material palette and predefined materials may be loaded from a material library. The defined materials can then be assigned to different surfaces or elements.

Click on the picture below for further explantion.

Active material selection

The colors and names of all the currently defined materials are shown in a separate field below the color fields. The currently selected active material is highlighted by a black box surrounding the color.

You may select any of the materials, making it active, by clicking on it with the left mouse button. The rest of the parameters displayed in the box will then change to reflect the properties of this material. Any changes you make to the colors and other properties only affect the currently chosen active material.

Material functions

Above the active material selection, in the center of the window, are five general functions to manage with the materials. These are:

Color selection

The fields at the top left are available for color selection. The color may be defined graphically, or numerically using either the HSV (Hue–Saturation–Value) or RGB (Red-Green-Blue) models.

The color fields are operated with the mouse as follows:

If you need a more exact shade of a particular color, you may zoom into the selected color field by pressing the middle mouse button. This displays more variations of color, which vary slightly around the selected color. Clicking the middle mouse button again returns you to the basic colors.

  • The color-mixing field is located next to the basic color field. This operates much like an artist palette where up to four standard colors can be chosen and mixed together. Each of its corners may be assigned a color. To do this first select a color from the basic color field. Then position the cursor over a corner square in the mixing field and click the right mouse button. The shades inside the mixing field change correspondingly.

If each corner has a different color, four colors are mixed. If two neighboring corners have the same color, three colors are mixed, etc.

The shades in the color-mixing field may also be selected with the left mouse button, and zoomed with the middle button.

  • To the right, shades of the selected color are shown against two backgrounds. By default, these are black and white, but you may change them by clicking the right mouse button in the background area which will assign the currently selected color to that background.

  • Below the basic color and mixing fields, the selected color is displayed numerically as either RGB or HSV values. You may change these values using the sliders next to the values, or by typing in new values. An explanation of these values can be found in most color books.

Material properties

On the extreme right of the window, a series of parameters allow you to adjust the properties of the material. They can be varied by slider or by entering a numeric value. Each explanation below includes a picture of a test ball rendered with the lighting parameter inquestion.

Note that all the other material parameters, such as the diffuse specular and reflection components, are added to the ambient value. With mirroring objects, in particular, the ambient component should be made quite small to avoid objects appearing too bright.

  • Diffuse - This defines the general reflectivity of the surface. Its value ranges from 0.0–1.0. The greater the value, the greater the effect of the light points on the surface. The diffuse factor emphasizes the curvature of surfaces.

  • Specular - This defines the polish of the surface. Its value ranges from 0.0–1.0. This parameter works in conjunction with the hardness parameter. It controls the appearance of highlights on the parameter component. The greater the specular value, the brighter the highlights.

  • Hardness - This defines the hardness of the surface. Its value ranges from 0.0-1.0. It controls the appearance of highlights on the parameter. With small values, the material looks soft and the highlights on the surface appear on large areas. With large values, the highlights are small and sharp. This parameter therefor controls the size of the highlights.For glass and other hard materials, use a large hardness value.

  • Bump - This gives the surface a "bumpy" appearance. The range of the bump values is 0.0 to 1.0. This parameter cannot be used to define large bumps on the surface. It can only produce the appearance of a slight texture on the surface, similar to that found on many plastic injection molded objects.

  • Mirror - This is a switch, which makes the material mirroring, or not. This parameter works in conjunction with the reflect parameter.

The amount of reflected light is added to other material properties. Consequently, you should not use too much ambient or diffuse light on mirroring materials.

With glass, in particular, the amount of reflected light should be proportional to the transparency. As a rule of thumb, a value of reflect equal to 2*(1-transpar) gives good results.

Library materials

The library material field, at the bottom of the window, allows you to load in materials from the material library or from your current model directory. The choice of where to read from is made with the two buttons MATLIB and MODELDIR at the bottom of the area.

The contents of the directories can be seen in a scrollable name list. You may select any library material by pointing and clicking with the left mouse button. The following functions to operate on the selected library material:

  • REPLACE - Replaces the active material with the selected library material, keeping the active material's name.
  • STORE - Stores the active material into the material library. It will be saved under the current name of the material.

Textures

A list of various solid textures can be found in the TEXTURES field, at the bottom left of the window. You may use them to preview there appearance on the test object, however, they are not assigned to the materials. You may later assign such a texture to the objects with the TEXTUREÞArea:New command.

The available textures are shown in a scrollable name list. Pointing and clicking with the left button on a name chooses the textures.

Some textures need two materials. The name of the second material is shown below the VEINS button. You can choose any material by clicking on the VEINS button then selecting by pointing and clicking on the material table. With wood and marble textures the name may be left empty and a default black material is used for the veins.

The X, Y and Z scales adjust the density of the texture in the directions of the three axes. The bigger the value the denser the texture.

Texturing can be removed by selecting the current texture name again.

Test image

A spherical test object can be ray traced with the chosen material properties by pressing the SHOW button in the TESTIMAGE field in the bottom right corner of the window. Pressing the STOP button in the same field can interrupt the rendering.

For transparent or mirroring materials, a chessboard floor automatically appears for these effects to be more clearly seen. The chessboard materials are floor and floor2, likewise, the background is rendered using the background material.

Clicking the button EXTRACE immediately shows the changed materials in the EXTRACE window. This means that you need not exit the Material Palette to see the changes. You can change the materials and immediately check the effect in the ray traced image.

In order to use this button, the ExTrace program must have been started before entering the Material Palette, and the ExTrace picture must not be currently computing. You may always press the STOP button in the ExTrace window to stop its computation.

Thus, the interaction with the materials and ExTrace is typically:

  1. Start ExTrace.
  2. Change a material.
  3. Click STOP in the ExTrace window.
  4. Click EXTRACE in the Material Palette window.
  5. Return to step 2 as often as required.

Exiting

Material editing is exited with the OK or CANCEL buttons at the bottom of the material palette window. The OK button stores all the material changes in the model, and CANCEL rejects them. Materials are actually stored in a special element in the object window called MAT.

Note: the CANCEL button is disabled if you have assigned any material to the objects. To cancel such changes exit and use SettingsÞUNDO.