9. Cameras and Lights

Describing the objects in a scene doesn't serve much purpose unless you can see the objects when they are rendered. Open Inventor tries to guess at some workable viewing defaults so that you can see a scene, but you will usually be better off controlling this yourself. The two concepts that determine how you view a scene are camera and lighting.

9.1 Camera Classes

Cameras describe where you are viewing the scene from, and as such have various fields to control characteristics like camera position and orientation. There are two camera classes in Open Inventor:

• PerspectiveCamera. A PerspectiveCamera shows you the scene and applies foreshortening to give you a better impression of distance.

      PerspectiveCamera {
          viewportMapping  ADJUST_CAMERA
          position         0 0 1
          orientation      0 0 1  0
          aspectRatio      1
          nearDistance     1
          farDistance      10
          focalDistance    5
          heightAngle      0.785398
      }
  

• OrthographicCamera. A OrthographicCamera shows you the scene but doesn't apply any foreshortening.

      OrthographicCamera {
          viewportMapping  ADJUST_CAMERA
          position         0 0 1
          orientation      0 0 1  0
          aspectRatio      1
          nearDistance     1
          farDistance      10
          focalDistance    5
          height           2
      }
  

One interesting way to create a walk-through-like animation would be to animate the camera instead of animating the objects in a scene. This would be useful, for example, to let somebody know what it would look like to walk through a building.

9.2 Lighting Classes

• DirectionalLight. A DirectionalLight node provides a light source that illuminates the entire scene. Use this to model lighting from a distance source, like the Sun.

      DirectionalLight {
          on         TRUE
          intensity  1
          color      1 1 1
          direction  0 0 -1
      }
  

• PointLight. A PointLight node provides light that emanates in all directions from a single point source of light. Use this to model lighting from small sources like a candle flame or an unshaded light bulb.

      PointLight {
          on         TRUE
          intensity  1
          color      1 1 1
          location   0 0 1
      }
  

• SpotLight. A SpotLight node has properties of both the previous lighting methods. The light comes from a particular source, but is directed in a cone. Use this for modelling (what else?) spotlights.

      SpotLight {
          on           TRUE
          intensity    1
          color        1 1 1
          location     0 0 1
          direction    0 0 -1
          dropOffRate  0
          cutOffAngle  0.785398
      }
  

More Information

More information about cameras and lighting in Open Inventor is available in chapter 4 of Inventor Mentor.