Using OSL Shaders in V-Ray for 3ds max

Software:
3ds max 2020 | V-Ray next

V-Ray for 3ds max supports compiling and rendering OSL shaders,
And also offers some handy shaders for download on the V-Ray documentation website.
Note:
OSL shaders are supported only in V-Ray Advanced and not in V-Ray GPU.

 

To load an external OSL shader:

  1. For a material (color closure) shader, create a:
    Materials > V-Ray > VRayOSLMtl
    For a texture shader create a:
    Maps > V-Ray > VRayOSLTex
  2. In the VRayOSLMtl or VRayOSLTex‘s General properties,
    Click the Shader File slot-button to locate and load the *.osl file.
  3. Provided that the shader has loaded and compiled successfully,
    You will now be able to set it’s custom parameters in its Parameters section:
    Annotation 2020-05-25 200439
  4. If compile errors will be found you’l be able to read the error messages in the V-Ray messages window:
    Annotation 2020-05-25 200625

 

To write an OSL shader:

  1. To write a material shader (color closure) create a:
    Materials > V-Ray > VRayOSLMtl
    To write a texture shader create a:
    Maps > V-Ray > VRayOSLTex
  2. Expend the Quick Shader section of the node’s properties,
    And check the Enable option.
  3. Write you’r OSL code, and press Compile.
    Annotation 2020-05-25 204835
  4. Provided that the shader compiled successfully,
    You will now be able to set it’s custom parameters in its Parameters section:
    Annotation 2020-05-25 205225
  5. If compile errors will be found you’l be able to read the error messages in the V-Ray messages window.

 

Related:

  1. What are OSL shaders?
  2. Using OSL shaders in Arnold for maya 
  3. Using OSL shaders in Blender & Cycles

What are OSL shaders?

OSL is an acronym for Open Shading Language.
Developed Originally at Sony Pictures Imageworks for the Arnold render engine, Open Shading language is a C like programming language with which custom material, textures and shading effects can be developed OSL shaders (*.osl files), that are supported many by popular render engines.

OSL allows development of complex texturing and shading effects using scene input parameters like the shading point’s world position vector, normal vector, UV coordinates etc., and optical ray-tracing  functions – BSDF*’s or “Color Closures” as they are called in OSL, like Diffuse, Glossy, Refraction light scattering etc. that can be combined with C  logic and math programming.

*.osl files are compiled to *.oso file for rendering.
Most render engines supporting OSL shaders ship with an OSL compiler.

 

Useful OSL shader libraries found on the web:

> OSL Shaders for download on the Chaos Group website:
https://docs.chaosgroup.com/display/OSLShaders/OSL+Shaders+Home

> OSL Shaders for download at the Autodesk Developer Network Github repository:
https://github.com/ADN-DevTech/3dsMax-OSL-Shaders
These are the OSL shaders that ship with 3ds max 2019 or newer, and are providing texture and pattern processing tools, but not materials.
* Material shaders or “Closures” as they are referred to in OSL are not supported by 3ds max’s native implementation of OSL.

> A library of OSL shaders collected by Shane Ambler:
https://github.com/sambler/osl-shaders

 

Notes:

  1. In general, OSL shaders are supported only in CPU Rendering, but not supported by GPU renderers. There are some attempts to develop OSL support for GPU renderers, But as far as I know they are limited.
  2. Some OSL shaders will work on one or more render engines, and not work as expected on other render engines. the reason being that each render engine has it’s own implementation of OSL.
    These differences may show in a different rendered result and also compile failure.

 

Basic example:
The following example renders show how a combination of two basic OSL shaders iv’e written, one of which is a dielectric material shader, and the other a color/angle blend procedural texture, produce fairly consistent results when rendered in different render engines.
* note the difference in specular glossy roughness interpretation for the same 0.1 value..

> You’r welcome to download these two basic OSL shaders here.

Arnold for Maya:
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V-Ray for 3ds max:
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Cycles for Blender:
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Related:

  1. Using OSL shaders in Arnold for Maya
  2. Using OSL shaders in V-Ray for 3ds max
  3. Using OSL shaders in Blender & Cycles

3ds max & V-Ray to UE4 – Datasmith workflow basics and tips

Software:
3ds max 2020 | V-Ray Next | Unreal Engine 4.25

This post details basic steps and tips for exporting models from 3ds max & V-Ray to Unreal Engine using the Datasmith plugin.
The Datasmith plugin from Epic Games is revolutionary in the relatively painless workflow it enables for exporting 3ds max & V-Ray architectural scenes into Unreal Engine.
Bear in mind however, that Datasmith‘s streamlined workflow can’t always free us from the need to meticulously prepare models as game assets by the book (UV unwrapping, texture baking, mesh and material unifying etc.) (especially if we need very high game performance).
That being said, the Datasmith plugin has definitely revolutionized the process of importing assets into Unreal, making it mush more convenient and accessible.

 

Preparation:
Download and Install the Datasmith exporter plugin compatible with your modeling software and Unreal Engine version:
https://www.unrealengine.com/en-US/datasmith/plugins

 

In 3ds max & V-Ray:

  1. Make sure all materials are VRayMtl type (these get interpreted relatively accurately by Datasmith)
  2. Make sure all material textures are properly located so the Datasmith exporter ill be able to export them properly.
  3. In Rendering > Exposure Control:
    Make sure Exposure control is disabled.
    Explanation:
    If the Exposure Control will be active it will be exported to the Datasmith file, and when imported to Your Unreal Level/Map a “Global_Exposure” actor will be created with the same exposure settings.
    Sounds good, right? So what’s the problem?
    The problem with this is that these exposure setting will usually be compatible with photo-metric light sources like a VRaySun for example, but when imported to Unreal, the VRaySun does not keep its photo-metric intensity. (in my tests it got 10lx intensity on import). the result is that the imported exposure settings cause the level to be displayed completely dark.
    Of-course you can simply delete the “Global_Exposure” actor after import, but honestly, I always forget its there, and start looking for a reason why would everything be black for no apparent reason…
    * If your familiar with photo-metric units, you can set the VRaySun to its correct intensity of about 100000lx, and also adjust other light sources intensity to be compatible with the exposure setting.
  4. Annotation 2020-05-12 192439
  5. Select all of the models objects intended for export,
    And File > Export > Export Selected:
    * If you choose File > Export > Export you’l still have an option to export only selected objects..
    Annotation 2020-05-12 192506
  6. In the File Export window,
    Select the export location, name the exported file,
    And in the File type drop-down select Unreal Datasmith:
    Annotation 2020-05-12 192550
  7. In the Datasmith Export Options dialog,
    Set export options, and click OK.
    * Here you select whether to export only selected object or all objects (again)
    Annotation 2020-05-12 192654
  8. Depending on the way you prepared your model,
    You may get warning messages after the export has finished:
    Explanation:
    Traditionally, models intended for use in a game engine should be very carefully prepared with completely unwrapped texture UV coordinates and no overlapping or redundant geometry UV space.
    Data-smith allows for a significantly forgiving and streamlined (and friendly) workflow but still warns for problem it locates.
    In many cases these warnings will not have an actual effect (especially if Lightmap UV’s are generated by Unreal on import), but take into account that if you do encounter material/lighting issues down the road, these warnings may be related.
    Annotation 2020-05-12 192730
  9. Note that the Datasmith exporter created both a Datasmith (*.udatasmith) file, and a corresponding folder containing assets.
    It’s important to keep both these items in their relative locations:
    Annotation 2020-05-12 204541

 

In Unreal Editor:

  1. Go to Edit > Plugins to open the Plugins Manager:
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  2. In the Plugins Manager search field, type “Datasmith” to find the Datasmith Importer plugin in the list, and make sure Enabled checked for it.
    * Depending on the project template you started with, it may already be enabled.
    * If the plugin wasn’t enabled, the Unreal Editor will prompt you to restart it.
    Annotation 2020-05-12 192901
  3. In the Unreal project Content, create a folder to which the now assets will be imported:
    * You can also do this later in the import stage
    Annotation 2020-05-12 193030
  4. In the main toolbar, Click the Datasmith button to import your model:
    Annotation 2020-05-12 193043
  5. Locate the the *.udatasmith file you exported earlier, double click it or select it and press Open:
    Annotation 2020-05-12 193129
  6. In the Choose Location… dialog that opens,
    Select the folder to which you want to import the assets:
    * If you didn’t create a folder prior to this stage you can right click and create one now.
    Annotation 2020-05-12 193301
  7. The Datasmith Import Options dialog lets you set import options:
    * This can be a good time to raise the Lightmap resolution for the models if needed.
    Annotation 2020-05-12 193326
  8. Wait for the new imported shaders (materials) to compile..
    Annotation 2020-05-12 193408
  9. The new assets will automatically be placed into the active Map\Level in the Editor.
    All of the imported actors will be automatically parented to an empty actor names the same as the imported Datasmith file.
    In the Outliner window, locate the imported parent actor, and transform it in-order to transform all of the imported assets together:
    * If your map’s display turns completely dark or otherwise weird on import, locate the “Global_Exposure” actor that was imported and delete (you can of-course set new exposure setting or adjust the light settings to be compatible)
    Annotation 2020-05-12 193517

 

 

Related:

  1. Unreal – Architectural glass material
  2. Unreal – Camera animation

Understanding Transparency Render Settings

In theory, all clear* refractive surfaces should have their shadow calculated using a refractive caustics calculation in-order to render the refractive lensing** effect correctly, have their transparency color calculated as volumetric absorption of light through the medium in-order to render the color correctly for areas of different thickness, and have not only external reflections, but also internal reflections calculated, in-order to render the interaction between light and the transparent body correctly.
However, for thin surfaces of even thickness, like window glazing and car windshields, these optical effects can be rendered in much cheaper (non physical) methods, with very little compromise on final image quality or look, and even have an easier setup in most cases.
For this reason most popular render engines have object (mesh) and material (shader) parameters that allow configuration of the way these transparency effects will be rendered.
In this short article we’ll cover the different methods for rendering transparency effects, the reasoning behind them and the way to configure these settings in different render-engines.

In the comparison images below (rendered with Cycles), the images on the left were rendered with physically correct glass settings, 8192 samples + denoising,
And the images on the right were rendered with “flat” transparency settings and 1024 samples + denoising.
> See the shader settings below
Note that while for the monkey statue, the fast flat transparency settings produce an unrealistic result, the window glazing model loses very little of its look with the flat fast settings:

Transparency_Settings

Lensing, caustics and transparent shadows:

3D-Rendering-of-glassware

It’s a common intuitive mistake, that transparent objects don’t cast shadows, but they actually do. they don’t block light, they change its direction. light is refracted through them, gets focused in some areas of their surroundings (caustics) but can’t pass through them directly, so a shadow is created.
A good example of this would be a glass ball, acting like a lens, focusing the light into a tiny area, and otherwise having a regular elliptical shadow. if we tell the render-engine to just let direct light pass through the object we won’t get a correct realistic result, even if the light gets colored by the object’s transparency color.
There is however one case where letting the direct light simply pass through the object can both look correct and save a lot of calculations, and that is when the object is a thin surface with consistent thickness like window glazing.
So in many popular render-engines, when rendering an irregular thick solid transparent body like a glass statue or a glass filled with liquid, we have to counter-intuitively set the object or material to be opaque for direct light and let the indirect refracted light (caustics) create the correct lensing effect (focused light patterns in the shadow area)
> physically, light passing through a material medium is always refracted, i.e. indirect light. but for thin surfaces with even thickness like glazing, the lensing effect is insignificant, and can be completely disregarded by letting light pass directly through the object and be rendered as ‘transparent shadow’.
So the general rule regarding calculating caustics (lensing) vs casting transparent shadows (non physical), is that if the transparent object is a solid irregular shape with varying thickness like a statue or a bottle of liquid it should be rendered as opaque for direct light but with fully calculated caustics i.e. refracted indirect light.

Transparency color:

Cola_Test_ODED_ERELL_3D_Crop_signed

Physically, the color of transparency*** is always created by volumetric absorption of light traveling within the material medium. as light travels further through a material, more and more of it’s energy gets absorbed in the medium**** (converted to heat), therefore the thicker the object, less light will reach its other side, and it will appear darker. this volumetric absorption of light isn’t consistent for all wave lengths (colors) of light so the object appears to have a color.
For example, common glass, absorbs the red and blue light at a higher rate than green light, and therefore objects seen through it will appear greenish. when we look at the thin side of a common glazing surface we see a darker green color because we see light that has traveled through more glass (through a thicker volume of glass) because of refraction bending the light into the length of the surface. tea, in a glass, generally looks dark orange-brown, but if spilled on the floor it will ‘lose’ its color, and look clear like water because spilled on the floor, it’s too thin to absorb a significant amount of light and appear to have a color.
Most render engines allow setting the transparency (“refraction”/”transmission”) color of the material both as a ‘flat’ non physical filter color, and as a physical RGB light absorption rate (sometimes referred to as ‘fog’ color), that can in some cases be more accurately tuned by additional multiplier or depth parameters.
Setting an object’s transparency color using physical absorption (fog) usually requires more tweaking because in this method, the final rendered color is dependent not only on the color we set at the material/shader, but also on the model’s actual real world thickness.*****
In general, the transparency color of thick, solid, irregularly shaped objects (with varying thickness) must be set as a physical absorption rate color, and not as a simple filter color, otherwise the resulting color will not be affected by the material thickness, and look wrong.
For thin surfaces with consistent thickness, like window glazing, however, it’s more efficient to setup the transparency color as a ‘flat’ filter color, because it’s more convenient and predictable to setup, and produced a correct looking result.
For example, if we need to render an Architectural glazing surface that will filter exactly 50 percent of the light passing through it, it’s much simpler to set it up using a simple 50% grey transparency filter color, because this method disregards the glass model’s thickness. This approach isn’t physical, but for an evenly thick glazing surface, the result has no apparent difference from a physical volumetric absorption approach to the same task.

Internal reflections:

Diamond-close-up-inspection

It’s not intuitive to think that the air surface itself has reflections when seen through a transparent material volume like water or glass.
Viewed from under water, the air surface above, acts like a mirror for certain angles, reflecting objects that are under water. a glass ball lit by a lamp has a very distinct highlight, which is the reflected image of the light source itself (specular reflection), but it also has an internal highlight appearing on inside where the glass volume meets the air volume. we can easily ‘miss’ this internal highlight because in many cases it’s appearance converges with the bright focused light behind the ball, caused lensing (refractive caustics). the distinctly shiny appearance of diamonds, for example, is very much dependent on bright internal reflections, diamond cutting patterns are specifically designed to reflect a large percentage of light back to the viewer and look shiny, and if we wish to create a realistic rendering of diamonds, we will not only have to setup the correct refractive index for the material, but also model the geometric shape of the diamond correctly, and of course, set the material to render both external (“regular”******) reflections and internal reflections.
Your probably already guessing what I’m about to say next..
For thin surfaces with even thickness, the internal reflection is barely noticeable, because it converges with the main surface reflection, an for this reason, when rendering window glazing, car windshields, and the like, we can usually turn the internal reflections calculation off to save render time.

Underwater_31.12.18

Render Settings:

Simplified settings summary table:

Flat (Glazing) Physical (irregular volume)
Shadow Transparent Caustics
Color Filter Volumetric Absorption
Reflections External only External and Internal

Example Cycles (Blender) shaders:
> The Flat glazing shader is actually more complex to define since it involves defining different types of calculations per different type of rays being traced (cheating).
In general, for Shadow and Diffuse rays that shader is calculated as a simple Transparent shader and nor a refraction shader, and when back-facing, the shader is calculated as pure white transparent instead of glossy to remove the internal reflections.
> While the flat glazing shader is only connected to the Surface input of the material output, the physical glass shader has also a Volume Absorption BSDf node connected to the Volume input of the material output node.
> Note that a simple Principled BSDF material will have flat transparency and physical shadow (caustics) by default.
> For caustics to be calculated, the Refractive Caustics option has to be enabled in the Light Path > Caustics settings in the Cycles render settings.

Cycles

Example V-Ray Next for 3ds max material settings:
>
In V-Ray for 3ds max (and Maya) the Affect Shadows parameter in the VrayMtl Refraction settings determines weather the shadows will be fake transparent shadows suitable for glazing or (on) or opaque (off) which is the suitable setting for caustics.
> The caustics calculation is either GI Caustics which is activated by default in the main GI settings or a dedicated Caustics calculation that can be activated, also in the GI settings.
> For flat glazing the color is defined as Refraction Color and for physical glass the Refraction color is pure white and the glass color is set as Fog color.

V-Ray_Glass

Example Arnold for Maya settings:
> In Arnold 5 for Maya the Opaque setting in the shape node Arnold attributes must be unchecked for transparent shadows, and checked for opaque shadows suitable for caustics.
> For rendering refractive caustics in Arnold for Maya more settings are needed.
> When the Transmission Depth attribute is set to 0 the Transmission Color will be rendered as flat filter color, and when the Transmission Depth attribute is a value higher than 0 the transparency color will be calculated as volumetric absorption reaching the Transmission Color at the specified depth.

ArnoldMaya

General notes:

> in Brute Force Path Tracers like Cycles and Arnold the Caustics calculation is actually a Diffuse indirect light path. this seems un-intuitive, but the light pattern appearing on a table surface in the shadow of a transparent glass is actually part of the table surface’s diffuse reflection phenomenon.

> what we refer to as ‘Diffuse Color’ in dielectric (non-metals) is actually a simplification of absorption of light scattered inside the object volume (SSS).

* Optically all dielectric materials (non-metals) are refractive, but not all of them are also clear, the is, most of them actually have micro particles or structures within their volume, that scatter and absorb light that travels through them, creating the effects we’re used to refer to as “Subsurface Scattering” (SSS) and in the higher densities “Diffuse reflection”.

** Lensing is a term used to describe the effect of a material medium bending light, focusing and dispersing it, and so acting as a lens.

*** Actually all color in dielectric (non metallic) materials is created by Volumetric Absorption.

**** Light isn’t only absorbed as it travels through medium, it’s also scattered.

***** Volumetric shading effects usually use the model original scale (the true mesh scale), so to avoid unexpected results it’s best that the object’s transform scale will be 1.0 (or 100% depending on program annotation)

Related Posts:
>
Cycles Nested Transparencies
>
Arnold for Maya Refractive Caustics
> Arnold for Maya Transmission Scattering
> Understanding Fresnel Reflections
> Advanced Architectural Glazing shader for Blender
> V-Ray Underwater Rendering

3ds max & V-Ray – Furry Carpet

Software:
3ds max 2019 | V-Ray Next

A simple example of using VRayFur in 3ds max to create a furry carpet.

Download the example file here

51812013_2489032567792734_5880346472070774784_o.jpg

The VRayFur is grown on a beveled surface, that has no bottom side surface to avoid growing fur at the bottom, and also because it’s unneeded.
The surface is beveled at the edges so that the fur there will grow to the sides,
And a noise modifier is applied to the surface to break its uniformity and give it a more organic shape.
* You could have a bottom surface set the fur not to grow on the bottom polys.Annotation 2019-11-22 185652.jpg

cartpet.jpg

A combination of 3 procedural Noise maps (for each of the RGB channels) is used to create a direction map for the fur threads. the maps are added together using a VRayCompTex map.
The reason the pattern is separated to it’s RGB channels is that it allows more control.
A VRayFur direction map works like a normal map in tangent-space and this means we can’t have the blue channel be less than a value of 0.5 because that would cause the fur to grow down into the surface.

Annotation 2019-11-22 191756.jpg

For the fur material, a VRayFastSSS2 is used to achieve a ‘fluffy’ organic look combined with a VRayDirt map to accentuate the shadows between the fur threads.

Related posts:
Simple snow material in V-Ray
Wood floor material in V-Ray

V-Ray for 3ds max Wood Floor Material

Software:
3ds max 2019 | V-Ray Next

An example of varnished wood floor material in V-Ray and 3ds max.
The material uses a VRayBlendMtl with 2 connected VRayMtl sub materials to simulate a natural wood base layer coated by a glossy varnish layer.

51026299_2476404122388912_8157106964938096640_o

Explanation of the material node graph:50770279_2476404922388832_853261524695777280_o.jpg

  1. The wood color (Diffuse texture)
  2. The wood black and white detail texture (used to add reflection detail)
  3. The wood bump texture (actually the same as the reflection texture just color corrected to whiten most details except the lines separating the wood planks)
  4. The reflection texture is color corrected to to intensify it prior to it being connected to the base wood layer material:
    Untitled-1
  5. The reflection texture is color corrected to to decrease its intensity prior to it being connected to the varnish coat blend:
    Untitled-1
  6. The base layer natural wood material with the Diffuse, Reflect and Bump textures connected to it:
    Untitled-2.jpg
  7. The varnish coat material with the Bump texture connected to it:
    * Note the Fresnel Reflections is turned off because the Fresnel reflection is calculated by the Falloff map (8)
    Untitled-2.jpg
  8. The Falloff map that defines the amount with which the varnish coat material covers the base wood material,
    A combination of Fresnel reflection intensity/Angle with the pre-processed reflection detail map (5):
    Untitled-3.jpg
  9. The final VRayBlendMtl combining the base wood material with the varnish coat material using the Fresnel Falloff blend map:
    Untitled-1.jpg

 

Related posts:

  1. Fresnel Reflections

Simple Snow Material in VRay for 3ds max

Software:
3ds max 2019 | V-Ray Next

A simple way to create a snow material in V-Ray for 3ds max is to combine a VRayFastSSS2 material with a VRayFlakesMtl using a VRayBlendMtl.
The VRayFastSSS2 creates the soft translucent shading for the snow, and the VRayFlakesMtls adds sparkling highlights.

  • Note that depending on the scene and view scale,
    The VRayFlakesMtls ‘flake glossiness’, ‘flake density’ and ‘flake size’ have to be tweaked to achieve the wanted result.

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