give color to volume and then remove a part of it

[CatherineKan]

Hello,

The visualization I want to achieve is to color my sphere volume shells by shells, which was successful by using a color node and using programming to modify its parameters; then, I want to cut a quater or a half of the sphere (it was achieved by Vexpression shown in screenshot 1) so that the shells of color contrast can be more obvious to be seen, like seeing a cross section.

However, what I noticed was that the color seems to be set again based on the new volume obtained after removing a part of the sphere by using volume wrangle node. This was noticed from the second screenshot attached, there should be half of the shells with bright color just like the color ramp gradient shows.

Could someone provide another way to achieve my visualization?

Thanks in advance!!

[Andrea]

Try to see if this is the kind of visualization you are looking for. With volumes is better to use the volume visualization SOP and the Cd field

sphere_volume_colors.hipnc

 

Which expression are you trying to use for the blue component in the color node? 

[CatherineKan]

6 hours ago, Andrea said:

Try to see if this is the kind of visualization you are looking for. With volumes is better to use the volume visualization SOP and the Cd field

sphere_volume_colors.hipnc

 

Which expression are you trying to use for the blue component in the color node? 

Thanks so much!

I tried with the help of your workflow settings, it works for my color. The expression I used for color attributes were set in python source panel, as I attached in screenshot.

There is only one defect I found, that the final sphere is covered by white color outside, I do not know which parameter I should adjust, I tried to move black color on diffuse ramp in volume visualization node, it becomes better. But I noticed your sphere's outer look is smooth, could you help to take a look?

Thank you~

aerosol water loss final version.hipnc

[Andrea]

That's because of how volumes are generated using the "surface attribute" from VDB from polygons.

This method should be better aerosol water loss final version_fix.hipnc

[CatherineKan]

On 2020-06-17 at 8:23 AM, Andrea said:

That's because of how volumes are generated using the "surface attribute" from VDB from polygons.

This method should be better aerosol water loss final version_fix.hipnc

Yes, it looks better, but there are still grids can be seen on the surface. I am wondering why there is no grids on your "sphere volume colors" file? Thanks!