This applet shows how the form factor between two patches varies in magnitude depending on the relative geometry of the patches. The cosine relationships based on relative patch rotation and the 1/r^2 relationship based on distance are plotted on a graph as the geometry is manipulated.
This applet was developed for use in an undergraduate computer graphics programming course. A familiarity with the topic of radiosity is helpful so that the motivation for the form factor calculation is apparent. The applet is appropriate for computer science students studying graphics or for any graphics programmer.
Select a relationship to examine using the radio buttons. For the Cos(theta_i) relationship click the point on the red patch to drag the patch and vary theta_i. You will see the form factor as it changes with the angle plotted on the graph. The cosine relationship should become apparent as the graph plots points over a range of theta_i. For the Cos(theta_j) relationship click the tip of the red vector to change the orientation of the patch and vary theta_j. For the distance relationship click the point on the red patch to vary the distance between the patches. The camera can be moved by clicking the right mouse button and dragging.
The camera can be moved by clicking the right mouse button and dragging. If you click near the center of the scene you can zoom in and if you click near the edge of the scene you can rotate the camera about the center of the scene.