Dr. Easton's rule 2

Using more than one of the bump, transparency, or reflective properties at the same time dramatically increases render time. This rule can have a really big impact on your rendering time! Read on.

For this test I used a variation of the reflective sphere picture. I placed 21 sphere randomly all within the field of view of the camera, Figure 2.

I then set each property like so:

Diffusion 80%
Ambience 20%
Specularity 20%

These were left the same for each test. I then varied the use of the bump, (blue bump), transparency, and reflection properties as outlined in Table 1.

Table 1 Effect of property on render time.
Property	min. (+/- 0.01)
Transparency 100%	0:31
Reflection 100%	0:31
Reflection 100% bump 30%	1:25
Reflection 100% Transparency 30%	1:38
Reflection 100% Transparency 100% Bump 100%	2:45

Figure 1

Figure 2

As you can see adding just one of the three properties (bump, transparency, & reflection) does not really affect the render time. However when you use two or more of these properties it produces a big impact on render time. The moral? Use only what you need!

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