Surfacing - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 191

Take a look at the Transparency panel of the Material
properties, shown in Figure 7.24 . The two methods of
rendering transparency are ray tracing and a technique called
Z Transparency . Ray tracing is slower, but produces
more realistic results. Z Transparency (Ztransp) is very fast
but cannot generate refraction, which is the way that light
changes direction when passing between two transparent
substances such as glass and air. In many cases, Ztransp is
sufficient (regular windows, small unimportant objects). For
rounded objects that will be the focus of attention though,
ray tracing is hard to do without.

As we're already using ray tracing on a couple of lamps and
the reflective surface of the table, let's skip it on the vase.
Having ray tracing interacting with ray tracing can drasti-
cally raise your render times. So, enable Transparency and
make sure that the Z Transparency button is selected. For
uniform transparency across an object, use the Alpha
control. 1.0 equals 100% opacity; 0.0 is 0% opaque, or
completely transparent. Glass, however, also exhibits the
Fresnel effect we mentioned with reflection. Start to adjust
the Fresnel control, which is found to the right of the Alpha slider. The material preview, when set to
either the Sphere or Monkey, shows the effect, like Figure 7.24 . The rule of halves makes the first attempt
set to 2.5, which seems to work pretty well.

Figure 7.24 The Transparency panel and Fresnel
preview.

One thing conspicuously missing from the material is reflection. Glass reflects, and without it the vase
looks horribly unconvincing. A trick that will often suffice is to use a fake reflection map.

Add a new texture channel, setting the Mapping coordinates to Relection. Reflection mapping pretends
that the texture is in a ball all around the object, and the texture is mapped to the object as though it
were perfectly reflected on its surface. Set the texture's style to Blend . Figure 7.25 shows the texture
properties for this channel, including the color ramp.

Build the color ramp according to the sidebar instructions from earlier in the chapter. On the Blend
control panel, set it to Vertical so the resulting texture runs up and down, as opposed to side to side.
Notice how the colors in the ramp in the figure are configured to provide a kind of generic outdoor
reflection. While this isn't realistic, the map is going to be fairly light, not the subject of close scrutiny,
and will provide an appropriate look for the vase. Set the Diffuse Color influence of the texture to around
0.6. The effect is immediately apparent in the material preview. Once again, this is not realistic, and close
examination will break the illusion. However, when you just need a suggestion of reflection, the fake
reflection blend can save you hours of render time. Figure 7.26 shows the vase, rendered with these set-
tings. Notice how believable everything is beginning to look—so much so that the nonsurfaced flowers
stick out noticeably and horribly.