Alpha blending or opacity by data value
It would be great to set the opacity by a certain data value or set an alpha blending respectively.
E.g. you have a 3D object with a discrete density distribution. The density is illustrated by color. Every density value was determined with a certain accuracy. Now it would be great to illustrate cells with good accuracy opaque and cells will fade more and more by increasing errors.
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Leon Foks commented
Correct, we can already do this using the same variable. But mapping the colour by variable 1 and the opacity by variable 2 would be very useful. For example, the density value of each cell varies spatially but so too does the accuracy that we obtained those values. So both high and low values may or may not need to be transparent. In a stochastic framework we might have a variance for each density value, the higher the variance, the more transparent the density value.
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Alan commented
So, to elaborate, you want an opacity set by one data variable, and the color by a different data variable? If you can use the same variable, ParaView will do this. Edit/ Color Editor/ Enable Opacity Mapping for Surfaces
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Leon Foks commented
This would be fantastic for Bayesian inversions, where a confidence is given to your parameters. It serves as a direct way to say to your audience, "we are less certain about these values" without having to generate a new image.
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lub commented
I would also love this feature, very useful for volumerendering