Background

WANNA rendering engine is capable of showing beautiful gems like diamonds or sapphires. Some of this beauty is proprietary and requires special model preparation; this article describes how to achieve the desired effect.

Preparation

1. Set up Substance Painter.
2. Download archive with various gemstone cuts.

Suggested workflow

The best way to model items with repetitive gems is to use instances. Unfortunately not all modeling tools support them, so we suggest the following workflow to work around it.

1. Create base model geometry in any tool of your choice. You don't need to add any gems at this point, they will be added later.
2. Texture 3D model using Substance Painter or any other software.
3. Export textured model to gltf and import into Blender.
4. Add gemstones to the model using samples from the archive and Reset their transformations (this is temporary solution to a problem we uncovered). All gemstones of the same cut should be instances of the same mesh.
   1. Do not bake AO under gems, otherwise black spots will be visible through the gem.
   2. Leave a bit of space between gems and materials that hold them to avoid coplanar meshes.
   3. All gems should be subnodes of the top level main node to correspond with General model requirements for 3D Viewer 
5. Name materials used for gems in a special way:
   • Any diamond-like material with visible dispersion (diamond, cubic zirconia, etc.) should be called wanna_diamond_XXX, where XXX can be replaced with anything. For example, wanna_diamond_1, wanna_diamond_2, etc. Materials for the gems in the archive are pre-set to diamonds.
   • Any other gem material (sapphire, emerald, ruby, etc.) should be called wanna_colored_gem_XXX, where XXX can be replaced with anything.
6. Set base materials parameters to the following for all gems. If you are using cuts from our archive, they are already preset there.

7. Export model to gltf with deactivated Vertex Colors checkbox. 
   
8. Upload it to Wanna Studio, as the rest of the settings will be set there.

9. After model is uploaded press Edit and select Gems Setting tab. 
   
10. First select material you want to edit. 
    
    

11. Number of bounces regulates how many times light will be reflected inside a gem.
     

12. Roughness, metallic and Specular are pretty straightforward.
     

13. IOR - Index of Refraction - use physically accurate value for your gem. https://pixelandpoly.com/ior.html
     

14. KHR Specular regulates Specular Intensity and also lets add a slight color tint to the stone if needed
     

15. Thickness factor - use a real stone thickness in units used when creating a model.
    

    If you are creating different watch sizes for try-on, use the following coefficients:

    Watch size 45 - Thickness factor * 1.512
    Watch size 50 - Thickness factor * 1.361
    Watch size 55 - Thickness factor * 1.237
    Watch size 60 - Thickness factor * 1.134
    Watch size 65 - Thickness factor * 1.047

     

14. Attenuation distance is a way to set color to colored gem. Attenuation distance regulates how deep light needs to go through before it is absorbed (Color intensity). Attenuation color is basically gem color.

17. Press Save all button to save changes into optimized Gltf  model.