Apply volume to a spherical texture?

Question

I have a quick texture applied on a UV Sphere. It is meant to be a spherical nebulae that I animate by keyframing the nodes settings (mostly color ramp, noise textures and color dodge mix shaders).

Here is a screen :

From here, I need 3 things :

• Making my camera fly through this sphere to discover what is inside
• Make the black areas completely transparent
• Blur the limits of the sphere (it is too round now)

To do this, my though was to make this texture a volumed texture, keeping the sphere empty inside. Is it possible ? Like if I had a spherical smoke domain with this exact texture, but Blender cannot handle it as far as I know. Plus, I'm a nood with volumetric textures.

Here is a quick reprensation:

Is there any way to achieve this ? Or, do you have any idea on how I can meet the results I need ?

Answer 1

You could try something like this.

The object I used for this is a simple UV sphere (I scaled mine up in edit mode to make it bigger - this might affect mapping values, I'm not sure - just be warned you may need to adjust those). Anyway, for the material, the main objective is to make 2 "spheres" using Gradient textures. You need to make a large one and a smaller one - The large sphere will be your Volume, and the smaller one will be used as a Mix Factor to "subtract" from the larger one. In the image below where I show the smaller sphere, I inverted it just for the image example - The regular (non-inverted) output is what makes the mix factor, it just doesn't display well in a 2D image because it's a volume.

You can see from the mix with a Transparent BSDF (or Volume absorption if you want a "void" in the center), that the center sphere is "missing". It's a bit faint in the photo, but this is due to the nature of volumetrics.

The last thing I did was make a "noise volume", colored similarly to the colors in your image. You can use whatever texture you already have (as a volume).

Lastly, I multiplied those values with the large sphere's "color" to transfer the dark (absent) areas and the colors. The final result looks like this (In my image, I added the values to themselves a couple of times with an add shader to make them brighter - you may or may not want to do this).

Answer 2

Ok so, thanks to Christopher Bennett, I managed to create some kind of "volumed & voided nebulae" (by voided I mean with a hole inside). Using two gradient texture to artificially split the sphere in two was the good call ! Thanks Christophe, and to anyone : please check his comment where he explains everything :)

A little note here : I used an Emission node instead of the Volume Scatter node.

As I understand it, the Volume Scatter node is able to provide a high quality render, but alters a lot the colors you choose with the color ramp (especially if you scale up your sphere !), adds a lot of noise in the texture, and ask for a high level of CPU/GPU ressources.

So I used an Emission node, which provides a simpler texture I guess (but it is enough for me), and is processed wayyyy faster in Cycles.

Anyway it looks pretty cool for what I need to do (fly through it, and discover what's inside the "voided area" of the nebulae).