This tutorial explains the steps to create a gemstone material with the help of VRayMtl’s translucency features.


Overview

In this tutorial, we show you how to make a green gemstone material using the versatile VRayMtl material, particularly its translucency parameters. We explore the interaction between the translucency and the Reflection Glossiness to determine respectively how opaque the object is and how rays interact with the object’s surface. All three translucency modes offered by the VRayMtl are shown.

The new modes require GI with minimum 16 bounces (brute force or light cache). They also require that the Affect shadows option of the material is enabled.

We use a fish figurine geometry for the purposes of thе tutorial. Chaos Cosmos Assets are also used to give the scene some final touches. The sofa and pots from our Cosmos 3D content library give depth to the image. Also the camera's depth of field is enabled for a more artistic look.

The images are rendered on CPU with V-Ray for 3ds Max 2022, update 1.3. The scene files provided are saved with 3ds Max 2018. In the "Start" scene file, the figurine is shaded with a default VRayMtl and respectively in the "End" file it's shaded with a ready made gemstone material.





Step 1: Create a VRayMtl

Let’s start with creating a VRayMtl material and assigning it to our fish figurine.

Open the Material Editor and drag-and-drop а VRayMtl in the active view.

Select the fish geometry in the viewport.

Then, in the Material Editor right-click on the new VRayMtl and select Assign Material to Selection.

We need to slightly tweak the basic parameters to give the material a gemstone look.

Set the Reflection Color close to white or very light grey to make the material more reflective. Here, we use RGB (190, 190, 190).

Also set the Refraction Color close to white or very light grey to make it slightly transparent as a gemstone. Here, we again use RGB (190, 190, 190).

We need glossy and more blurry reflections, so reduce the Reflection Glossiness to 0,85 to reduce reflections sharpness.

Gemstones’ IORs vary between 1.34 and 3.2, depending on the stone type. For example, gemstones like sodalite, obsidian, chrysocolla, or jade are on the lower spectrum of IORs, i.e. less than 1.65. Let’s set the Fresnel IOR here to 1.45.




The figurine does not have a color yet. We are going for a greenish look, so we need to add color with the help of textures.



Step 2: Add Diffuse, Reflection Glossiness, and Fog Color textures

Let’s first assign a VRayBitmap to the Diffuse map slot of the VRayMtl and load the gem_diffuse.jpg texture. This gives a color and a more detailed appearance to our figurine.

Create another VRayBitmap and load the gem_refl_gloss.jpg texture to provide more detailed appearance of the reflection glossiness. Then link it to the VRayMtl's Reflection glossiness slot.

Now, add a third VRayBitmap and load the gem_fog.jpg texture to the VRayMtl's Fog color slot. This allows us to control the attenuation of light as it passes through the material. We aim to simulate a more transparent appearance where the figurine is less thick and vice versa, and at the same time take advantage of the detail provided by the texture.

All textures used for this tutorial can be found in the attached archive at the top of the page.




The color and texture intensity are too strong and the glossy effect is almost lost. We need to adjust the maps a bit.




Reduce the Reflection Glossiness map to 45% from the VRayMtl’s Maps rollout. This brings back a more pure glossy reflections effect.

Lower the Fog color map as well to about 45%.

Leave the Translucency mode to None.

Set a green color for the Fog color. Here, we use RGB (12, 20, 5).

Increase the Depth to 3 to slightly reduce the effect of the fog. This lowers the opaqueness a little.




The glossiness is brought back and we’ve achieved a gemstone look.

Notice that with the None mode, there is no Subsurface scattering.

Render time and resolution: 9 min, 50 sec, 800х1280px.

We can enrich the gemstone look effect by tweaking the Translucency settings.


Translucency is set to None


Step 3: Control Translucency

Set the Translucency to Volumetric. It works together with the Refraction color of the material to scatter light inside the object. This mode is useful for liquids and other highly transparent materials. In this case the SSS amount parameter controls the amount of scattering versus plain absorption and the value means the amount of blending between full scattering and pure refraction. The Fog color parameter controls the absorption of the material.

Keep the same green color for the Fog color RGB (12, 20, 5).

Change the Scatter color to lighter green. Here we use RGB (91, 150, 38) for the overall look of the material.

Lower the SSS amount to around 0.8.




Here’s our fish figurine.

Render time and resolution: 16 min, 38 sec, 800х1280px.


Translucency is set to Volumetric



Let’s see how the material will turn with SSS mode.

Set the Translucency to SSS mode. This mode is useful for skin, wax, marble and other relatively opaque materials. Its SSS amount parameter reduces the diffuse component of the material and replaces it with the sub-surface scattering effect.

The green color for the Scatter radius remains the same: RGB (12, 20, 5). That applies also for the SSS color: RGB (91, 150, 38). This parameter controls how far each of the red/green/components travels inside the volumе.

The Scale's value remains 3 cm to boost the sub-surface scattering effect.

Keep the SSS amount to 0.8.


  


Here’s our green gemstone figurine.

Render time and resolution: 17 min, 22 sec, 800х1280px.


Translucency is set to SSS


Final Images


Here are the final images showing the translucency modes applied on the same object for better visual representation with the help of a slider.

Note that all three renders use the same colors and values for the translucency parameters to best demonstrate the differences between the three translucency modes.



Translucency mode set to None

Translucency mode set to Volumetric

Translucency mode set to SSS