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Custom Transfer Function Transparency
12-09-2014, 05:09 PM (This post was last modified: 12-09-2014 05:12 PM by Matthew Turner.)
Post: #1
Custom Transfer Function Transparency
I had a strange issue that I talked to Alex about at the end of today's lecture. When using the custom transfer function, I noticed that even when assigning all 256 scalars an alpha value of 255 and an arbitrary color, the resulting cube doesn't appear to take up the entire rendering space (though it comes close). The points close to the boundary appear to be slightly transparent, despite hard-coding what should be an opaque color. This behavior does not appear to arise when using the default step function.

I was wondering if anyone else observed similar behavior or can offer an explanation of why this occurs.

I attached an image of the problem with the step function on the left and the custom function on the right.


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12-09-2014, 10:52 PM
Post: #2
RE: Custom Transfer Function Transparency
I noticed this also and believe that it is attributed to the "Density" parameter.

When comparing results between transfer function widgets, I noticed that I had to increase the density parameter to be able to produce the same rendering as the step function when using my custom widget.
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12-10-2014, 12:35 PM
Post: #3
RE: Custom Transfer Function Transparency
(12-09-2014 10:52 PM)u0923385 Wrote:  I noticed this also and believe that it is attributed to the "Density" parameter.

When comparing results between transfer function widgets, I noticed that I had to increase the density parameter to be able to produce the same rendering as the step function when using my custom widget.

Good catch! I didn't realize the controls from the step function would still have an effect on the rendering after switching to the custom function. The results look much better after increasing the density. Thanks for your help.
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