You can change the material properties of the selected shape(s) in the dedicated dialog box. This dialog box can be invoked from the context popup menu using "Material properties" item:
In this dialog box you can:
The material is specifed by several attributes of the lighting model. More details can be found in the documentation related to the OpenGL programming, for example here: http://www.glprogramming.com/red/chapter05.html.
In the OpenGL lighting model, the light in a scene comes from several light sources; the light sources have an effect only when there are surfaces that absorb and reflect light. Each surface is assumed to be composed of a material with various properties. A material might emit its own light (like headlights on an automobile), it might scatter some incoming light in all directions, and it might reflect a portion of the incoming light in a preferential direction like a mirror or other shiny surface.
The OpenGL lighting model considers the lighting to be divided into four independent components: emissive, ambient, diffuse, and specular. All four components are computed independently and then added together.
Ambient illumination is the light that has been scattered so much by the environment that its direction is impossible to determine - it seems to come from all directions. Backlighting in a room has a large ambient component, since most of the light that reaches your eye has first bounced off many surfaces. A spotlight outdoors has a tiny ambient component; most of the light travels in the same direction, and since you're outdoors, very little of the light reaches your eye after bouncing off other objects. When ambient light strikes a surface, it is scattered equally in all directions.
The diffuse component is the light that comes from one direction, so it is brighter if it comes squarely down on a surface than if it barely glances off the surface. Once it hits a surface, however, it's scattered equally in all directions, so it appears equally bright, no matter where the eye is located. Any light coming from a particular position or direction probably has a diffuse component.
Finally, the specular light comes from a particular direction, and it tends to bounce off the surface in a preferred direction. A well-collimated laser beam bouncing off a high-quality mirror produces specular reflection by almost 100 percent. Shiny metal or plastic has a high specular component, and chalk or carpet has almost none. You can think of specularity as shininess.
Although a light source delivers a single distribution of frequencies, the ambient, diffuse, and specular components might be different. For example, if you have a white light in a room with red walls, the scattered light tends to be red, although the light directly striking objects is white. OpenGL allows you to set the red, green, and blue values for each component of light independently.
The dialog box consists of two parts:
The following properties of the material model can be specified:
If the material model is specified as a physical one (like Gold, for instance), this means that the color of the shape (more precisely its ambient color) can not be modified. If you assign a physical material model to the shape, the "Color" menu item will not be available in the popup menu.
If the model is non-physical (artificial), the color can be changed to any appopriate one, only other attributes will be constant. In the dialog box you will be able to modify the color of the shape via the "Color" button. "Ambient color" button becomes disabled to signalize that this attribute of the model is ignored. Also, it will be possible to modify the color of the shape via the corresponding popup menu command.
All available predefined material models are shown in the list box of the Color and Material Properties dialog:
The buttons "Add material" and "Remove material" in the lower part of the dialog box can be used to create or remove custom material models. The same commands are also available via the popup menu that is shown if the user presses right mouse button in the materials list box. An additional "Rename material" command, available in popup menu, can be used to change the name of material model.
Examples:
Different materials in OCC viewer
Different materials in VTK viewer
The default material model is specified via the preferences of Geometry module.