Rendering a texture of a picture on a mesh

Trying to Render this Opal… In Rhino.
Both Decals and material texture seems to only work in Rendered Mode.
In Raytraced and also in Bella I only get a blank material.

So I tried a different approach; Subdivided the mesh to an approximately the same poly count as the pixels and painted the Opal directly in ZB. [first image]

Then imported as .fbx into rhino. It came with the paint, but looking somewhat dull, less vivd [any idea why?]
And it didn’t make a difference as it still only shows in Rendered mode not in RayTraced or Bella…

What am I missing here?
How to render this Opal…? Preferably in Bella, Surely there must be a way to put the Opal Picture on the mesh so that it works in the render engines
It’s possible to make a composite in PS and use the stone from ZB … But it seems complicated.

thanks a lot

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Have you tried via Adobe Substance textures?

I did not try, I had the Substance subscription for one year… used it very little and didn’t renew.

Can’t do much without a file to investigate or test.

FWIW decals work here just fine

Hi @nathanletwory

file I’m sending to the upload [is too large]. here’s the picture of the Opal

here with Decal on a low res mesh

and here with a high res mesh painted in ZB [PolyPaint so each face = a pixel of the Opal image].

the 3rd stone in the file is an attempt use a file texture material… I admit I have little understanding how this should be done…

thanks a lot


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You can upload using Rhino - Upload to Support - I will get a message when the upload is ready.

Btw, in case you’re using a custom material: switch it to PBR, that should work. I have an item (RH-76999) to fix decals on custom materials.

Thank you @nathanletwory

I have uploaded the file 3 - 4 hours ago. did you get it?

Trying with a PBR does not work with decals here… I may be doing something wrong?

SysInfo09-10-23.txt (5.8 KB)

You are supposed to assign a PBR material to your stone, just add one, no changes needed, then the decal will show in Raytraced.

thanks a lot
It was assigned… but I guess it didn’t really… so I assigned again and it works now.

It doesn’t look very good though … washed out and quite far from the actual vividness of the stone?
*I had a mother crash as well , trying to change the Gamma value. [other decal crashes were reported in a separate thread ] with crash reports sent. this one I think it didn’t give a rhino crash, it gave an OS report only

Hi @nathanletwory
Raytrace appears to endlessly initializing … what is visible is still a rendered mode display …
any idea what is going on here. [it the same file I sent]
this is the HI-Res mesh… it is sill initializing now over 20 minutes.
gpu and cpu are mostly idle…
I changed to shaded… and rhino crashed. [sending report with link to this thread]

thanks a lot

We just got the crash report, thanks. I believe this is associated with crashes we are seeing when users are switching from raytraced to another display mode. It’s “on the list” of things to tune up.

Had a go in Bella with a really rough render, but the texture can be used, is the bottom line.

I recast the file inside an emissive using the chain:

Bella Emissive → [Color] Bella RGBXform → [Map] Bella File Texture

The RGBXform just allows much better control over the image qualities.

I think I’d recommend not having the top layer of ‘misty’, and retain your colour layer. This would allow you to offset the surface by a tiny amount and use the Bella Dielectric followed with a Bella Scattering node to control this quality in light of the envrionment (or even just a roughness for first approximation). It also prevents the restriction on the lighting angle you can use, due to the fixed limb darkening effect in the material, as well as the problems that causes in the contrast.

The reason for using an Bella Emissive here is easy replication of the irridescent property of the opal. I’m sure many people may disagree, but opals almost look like non-illuminating emissive materials for this application. You can modulate the illumination using a grescale version of your colour image in the Emissive’s opacity channel.

To counter the lack of solidity in the Bella Emissive, I just placed a surface just offset under the stone, so that the transparency is erased (as this is non-physical in approach, I think I can argue this is okay here).

Thanks David

I actually managed something sometime earlier this evening with Bella PBR…
I feel emissive will perhaps not be correct for this type of opal .
I’m sort of ok with it… but do you think perhaps adding a thin film to it may help? to try an give it a higher polished so it will look like #50.000 grit polish…? it now looks more like #8.000. [for non jewelers, that’s a ref to Diamond polishing powder]

I’m sure @jdhill will correct me here, but adding a thin film should only act to detract from anything underneath. You are always losing energy. I can only imagine that thin film will subtract energy from your colour, as you will get a colour blend at different size scales.

To maintain independence of the colours from the somewhat volumetric/milky look, as a solution I used Bella Uber material, and then used a generic opal texture I found loitering.

The milkiness is controlled here by Bella Uber [Thin Medium], which applies a layer over the top of the base colour. However, the vibrancy is somewhat maintained.

Again, Bella Uber [Base] is regulated via a Bella RGBXform, and that allows colour contrast control to pick up losses if needed.

I think that your polish attribute is controlled reasonably by the Bella Uber [Specular] properties, as we can control the {Roughness} and {Anisotropy} aspects of the material.

I would argue that in your image, there is some nice falloff which isn’t quite captured. The only way I can think to emulate this in a physically meaningful way would be to use a volumetric (which, isn’t entirely a lie, perhaps). Perhaps that would get rid of some of the uniformity in the milky [Thin Medium] element I am using here. Another rough render. Not going for realism here, just to demonstrate a possible approach which maintains some sense of physical link to the actual lighting; rather than forcing the issue by overlaying it onto the stone.

My problem with maintaining this forced lighting is that there may well be angles where the lack of physicality is easily revealed.

Opal: It’s really hard, and I must say that I’m not all that impressed with my own result. But I think it can be equally made to work.

Thanks a lot @David53

It very interesting , and I’m trying to follow what you did but I’m not getting anywhere past a grey blob with the Uber…
Does it not allow to use png…? selecting assign PBR texture, it keep loading a bmp image that I’m not selecting instead of the png that is selected… very strange.
So I assigned the png to the color under transmission, [with a Bella file texture node]
but I still only get a grey blob…?
[never used then Uber before]

  • Edit. : managed to Get the picture on with file texture assigned to the base color …
    I’ll try to follow the other steps .

*Edit 2 : I’m not really understanding what the sliders Specular area do…
I PS the white spot on the image, and perhaps PS editing the shadow area can help so at least the light direction won’t be so obviously fixed in the image… about the play of fire when rendering from different directions… maybe some PS editing can help to make a few random variations so the stone don’t look exactly the same from different angles …?

thanks again

Hi Akash.

Okay, so to try and give you my result, or part of it, I have created a minimum file for you to have a look at, and you can see if it is any use. All the files should be embedded.

As I said, it’s not great, but it may just about work from a reasonable jewellery render distance with tweaks. You will know much better than I. At least it survived a change in angle and environment.

File in PM.

The Bella Uber[Specular] {weight} and {Roughness} control the presence of the specularity and, in this case, the spread.

For this, I set the [Specular] {Roughness} to 5. However, you can see a drastic difference in how the light diffuses through the surface by changing to a value like 35%.

Also, look at the [Thin Medium] settings, particularly with respect to the {Albedo} and {Anisotropy}. These are also values to play around with to affect the milk-like topcoat. The grey-like colouring can be adjusted in the [Thin Medium] {Color} aspect, by say dropping the HSV Color Wheel “Value” to 90.

In reality, we know it’s not a Thin Medium, but we can fake this effect using the Thin Medium, until I or someone much more intelligent thinks of a better way of self-contained representation of this problem.

It would be nice to get better limb-darkening type effects that you get at higher tangency to the stone, but I’m unsure how to resolve this right now without resorting to utterly cheating using a volumetric somehow.

One of the really wicked things about doing it this way is the awesome way you can change the dominant tone of the opal using the [Thin Medium]{Scattering} colour:

The previews are so fast, I left them for 1 second, and snapshot them, as I can already see a preview of what will happen.

Scatter to Red:

Scatter to Green:

Scatter to Purple:

So you can sort of get different types of opal using the same base colour map, and adjust using the Scattering. Seems neat!

Sorry for the bad spelling, it is way past time for bed here! I’m also sure, every time I look, I am implying bella is doing something that it isn’t (it is doing something, but not what/how I am telling). But you get the idea hopefully.

I’m very grateful for the help and the explanations. You have shared a lot of good knowledge here.
Currently studying these settings, and experimenting with them.

I’m very clear what volumetric means though…? Bella uses a lot of pro terms that are not readily comprisable to non English natives/ pro photographers .

Q: XForm is it necessary…? I seems to deform the image at the surface pols
can I use just regular planer mapping?
Q2: the inner object What does it do… and I wonder why have you added the scratch node?
with thanks a best regards

Hi Akash.

Volumetric is just usually a semi-transparent materials, typically used for cloud-like features. In Vray, the simple equivalent is “Environment Fog”. It’s very out of context here, and becomes a tool rather than something that is physical (of sorts).

Q1: XForm does no UV mapping. The UV mapping is done by a Bella File Texture settings, which of course you can change. The XForm is there merely to regulate the colour properties of the texture.

Above, it is the OpalTexForm which is doing the work to regulate the deployment of the mapping. However, the mapping itself is controlled at the level of OpalColourFile:


You can change the mapping there to planar. However it will change how OpalTexForm acts on that UV mapping.

Q2: Now I am not using an emissive, the inner object does nothing now, and you can delete this. There is no opacity to this Bella Uber either, so it is no longer partially transparent.

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