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The illustrations in this article are fairly old; so they were all done in Strata StudioPro 2.5, which was the application I was using at the time. However, the basic principals hold true no matter what application you use. You will need to know where to find the various attributes in your own app, of course.
There are three things the control the actual transparency that you will see in your finished render, as shown in the table below.
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Transparency Recursions 3, Reflection 1. |
Transparency Recursions 15, Reflection 10. |
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Transparency Recursions 3, Reflection 1. |
Transparency Recursions 15, Reflection 10. |
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Transparency Recursions 3, Reflection 1. |
Transparency Recursions 15, Reflection 10. |
The first, of course, is the opacity of the material itself.
This is usually set with a slider or in a text field, and will be labeled something like "Transparency" or "Opacity". Normally, it's expressed as a percentage. Its use should be clear, if you'll pardon the pun. The two diagrams at the top in the table above are set to 100% opacity, just to show the effect of the other settings.
The second is the amount of diffuse and/or ambient light the shader will accept.
Once again, you can normally find this right in the shader dialog, as a percentage slider or text field. The more light your object will accept, the cloudier it will appear. In the diagrams below, the ones in the middle are set to accept 95% of the light (both diffuse and ambient,) while the ones on the bottom are set to accept 0%. (The brass bell is also set for 92% and 8%, respectively. As you can see, the light also affects how shiny metallic surfaces will appear.) In this particular program, setting a high transparency and a high acceptance of light causes objects to appear to glow. This doesn't happen in all applications. You might want to experiment with yours to see exactly what effect you can expect.
The third, and perhaps most important setting is the amount of transparency recursion in the render.
This is generally hidden in an "expert settings" dialog box someplace. Basically, it lets you choose how many levels of things are transparent before the renderer stops trying to look through things, and either just gives them their base color or makes them black, depending on the application.
Each time a light ray goes through something, that counts as one level. So a glass bottle, like this one, would have one for the front of the first wall, and one for the back of that wall. Then it would have another for the front of the back, and one for the back. So if you want to see the whole way through the glass, you need at least 4 levels of transparency.
Reflectivity recursion is a related value, probably found in the same place, which determines how many times the renderer tries to follow a reflection before it gives up. In the examples below, the bell is reflected in the bottle. But that reflection has a reflection of the bottle in the bell, and so on, bouncing back and forth.
In the diagrams above, the ones on the left have low values for these two variables, and the ones on the right have high values. Look specifically at the shadows of the bottle on the wall if you want to see what this does. In fact, in your own pictures, if there seem to be opaque shadows from things you wanted to be transparent, I suggest that you increase these values.
With both of these, the more you have the more realistic your rendering will be (in the real, analog world light never does give up!) But also the longer it will take to render. There is a point of diminishing returns where the things you see through the bottle, or the reflections get to small to be visible anyway! So my advice is not to overdo it here. Count it out, have fun, and get the render done!
And in case you thought that some of the images above are identical; they're not. And here's an animated GIF that steps through them, to prove it!
