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Posted by Merja Roiko-Jokela

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How to simulate light and lighting in computer graphics? How to enhance realism?

Shading (Foley 1994, 430-431):

  1. Visible surfaces of objects can be shaded to increase realism.
  2. The appearance of the surfaces depends on:
    1. types of light sources used for illuminating
    2. the properties of the object – color, texture, reflectance
    3. position of the object
    4. orientation in relation to light sources, viewer, and other surfaces
  3. Ambient light is the easiest form of light source to model, because it isn’t dependent on the position or orientation of the surfaces, but the illumination is uniform on all surfaces. Using only ambient light will result in an unrealistic image.
  4. In addition to ambient light, other light sources can be used:
    1. a point source
    2. a directional source
    3. a distributed, or extended source
  5. Shading information can be computed for each polygon vertex (this is referred to as interpolated shading). This can be used especially for curved surfaces.


Foley, James D. (1994). Introduction to computer graphics. Addison-Wesley cop.

Posted by Merja Roiko-Jokela

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Getting started: Light & Lighting Representations

I decided to prepare for developing our concept by reading the course textbook: Colin Ware’s Information Visualization: Perception for Design. I will summarize the key issues that seem to be most relevant for our topic in Chapters 2, 3, and 4.

I begin with Chapter 2: The Environment, Optics, Resolution, and the Display.

In order to understand how human’s perceive light, we must first get an idea of the relations between evolution and our visual system. Our perception is linked to skills, that have helped us survive, including navigation, food seeking and tool use (Ware, 2000, 36). Our vision can perceive only a small fraction of electromagnetic radiation, whereas some animals are able to see infrared or ultraviolet (Ware, 2000, 37). It appears that it hasn’t hindered us from succeeding as a species.  However, texture is critical to perception. Perception of surfaces helps us navigate and avoid obstacles. We are able to comprehend orientation, layout and shape of objects through the perception of their texture (Ware, 2000, 40-42). Light interacts with surfaces in three ways: 1) lambertian shading, 2) specular shading, and 3) ambient shading (Ware, 2000, 42). Objects also cast shadows and shadows provide us information about the shape of an object, especially the height (Ware, 2000, 43).

Time is the general theme of the course. Time and the human ability to see are connected, as our ability to see deteriorates as we get older. Young children have flexible lenses, which means that they are able to focus on object very close by (Ware, 2000, 49). Also our sensitivity to patterns decreases as we get older (Ware, 2000, 62).


Ware, Colin. (2000). Information Visualization: Perception for Design. Morgan Kaufmann.

Posted by Merja Roiko-Jokela

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