vray

V-Ray – Underwater rendering tip

Posted on December 29, 2018April 11, 2020 by Oded Maoz Erell

Software:
3ds max 2019 | V-Ray Next

I decided to do some test renders for an underwater swimming pool scene with 3ds max and V-Ray,
And happily found out that my initial geeky academic approach to the subject was actually outdated and unnecessary.
> look down at the bottom for the correct sample renders.

In this example there is a VRaySun & VRaySky for the daylight render setup and a Caustics calculation to create the light lensing effects on the under water surfaces.

The wrong way:
Having ancient habits in the subject,
I first flipped the water\air surface’s normals so they’ll point down into the water (towards the camera), And set the water material’s IOR to 0.75 ( 1 / 1.333 ) so instead of being an “air to water” material, it will become a “water to air” material.
This produced a non realistic result.
Viewed from underwater, the air surface should have a very dominant mirror reflection at most angles.

The Correct Way:
It seems that in V-Ray nothing special should be setup in terms of the water material.
You don’t have to create a special water-to-air material like I thought at first.
Its a regular water material, and the water surface is facing upwards like it should,
And when the camera is underwater it renders the water surface correctly as an air surface from withing the water.

The pool water material setup:
Note that Affect Shadows is turned off so the surface will generate caustics and not fake transparent shadows, and that Reflect on back side is turned on to produce more detailed reflections.

This produced the following result in which the reflection/refraction look correct but the water is still too simple:

Improved wave deformation for the water surface, added detail using a Noise bump in the water material and a sense of depth with Volumetric Fog:

Finally remembered to activate Reflect on back side at the water material to add more realistic reflection detail, some basic contrast in the V-Ray VFB,
And a shark because I couldn’t help it…. 😀

V-Ray Next’s PBR’ness

Posted on December 23, 2018July 21, 2020 by Oded Maoz Erell

Software:
3ds max 2019 | V-Ray Next

A quick test of V-Ray Next‘s PBR* workflow,
Namely designing materials while previewing them using V-Ray,
Defining the material properties using the new (to V-Ray) Metalness attribute, and using Roughness rather than Glossiness, shows good results IMO.

* It should be noted that although we got used to referring to the base-color / metallness / Specular material interface as “PBR”, it is actually a principled material interface developed by Disney animations studios.

Results are generally consistent through Blender & Cycles, Maya & Arnold, and UE4.

Related Posts:

Maya – Setting the V-Ray Sun direction according to location, date and time

Posted on August 19, 2018September 9, 2018 by Oded Maoz Erell

Software:
Maya 2018 | V-Ray 3.6

To set the VRaySun photometric light source diretion according to the location in the world, the date and the time:

Select the VRaySun parent node – ‘VRayGeoSun1Transform‘ and rotate it so its Z axis points to the architectural plan’s south.
Select the VRaySun node – ‘VRayGeoSun1‘ and in its attributes un-check Manual Position.
This will make the location / date / time parameters accessible.
Set the GMT zone of you architectural project’s location in the world, the Date and time.
* haven’t found how to set daylight saving time….

V-Ray for Maya toon shading

Posted on July 24, 2018July 24, 2018 by Oded Maoz Erell

Software:
Maya 2018 | V-Ray 3.6

Toon shading in V-Ray consists of two elements:

A VRayToon node that creates a graphic contour effect on the rendered image.
A flat shader that uses surface luminance data to define color areas.
* A VRayLightMtl can be used for that.

Creating the VRayToon node:

Click the Create V-Ray Toon button in the V-Ray toolbar to create a VRayToon node.
In the VRayToon node attributes, set line thickness, color, and more graphic properties.
* if you created a VRayToon node and it’s not selected RMB click the Create V-Ray Toon button in the V-Ray toolbar and choose Select VRayToon node.
* To delete the VRayToon node, select it and press Delete.

Creating the toon shader:

Create a VRayLightMTL node as the object’s surface shader.
Create a Ramp texture node, connect it’s output color to the VRayLightMTL’s color input and delete it’s accompanying 2D placement node.
Create a surfaceLuminance node and connect it’s output to the Ramp node’s V Coord input.
Optional remapValue node between the surfaceLuminance node and the Ramp node to clamp the luminance values.
Optional floatMath node to scale or manipulate the surfaceLuminance output value.

Related:
Arnold for Maya Toon Shading

V-Ray for Maya with XGen

Posted on July 22, 2018July 22, 2018 by Oded Maoz Erell

Software:
Maya 2018 | V-Ray 3.6

The technical steps needed to render XGen hair with V-Ray and a VRayHair3Mtl in Maya:

in the Plugin Manager,
Make sure the xgenvray.py plugin is loaded.
* Needless to say vrayformaya.mll must be loaded too.
Set a Project Folder and save the scene.
In Render Settings, set the Renderer to V-Ray.
Select an object or mesh elements and create an XGen Description.
* This can be done by clicking the Create New Description button in the XGen tab or XGen Window.
In the XGen Output Settings set the Operation to Render and the Renderer to V-Ray.
Edit / Design / Groom your hair.
In the XGen window, Choose File > Export Collections or Descriptions,
And export the hair Collection and Description.
in the XGen window, Choose File > Export Patches for Batch Render,
To export the hair cache abc (alembic) file.
In the Hypershade, create a VRayHair3Mtl shader.
In the Outliner, select the XGen Description.
In the Hypershade Browser window,
RMB click the VRayHair3Mtl and choose Assign Material To Selection.
Make sure there is a light source, and render the scene.

Related:
V-Ray for Maya and nHair

Untitled-1.1.1.jpg

VRayMtl’s new metallic goodness

Posted on July 21, 2018September 23, 2018 by Oded Maoz Erell

Software:
3ds max 2019 | V-Ray Next | V-Ray next GPU

In V-Ray Next (4) for 3ds max, a new Metalness parameter has been added to the Reflect parameters of the VRayMtl material.
This allows for easy creation of realistic metal materials and also effectively enables a PBR workflow with V-Ray.

When the Metalness parameter is set to 1.0, the material becomes completely reflective, the Diffuse color controls the general reflection color, and the Reflect color (which should generally be set to white) controls the reflection color at grazing incidence angle.

The IOR parameter still controls how fast will the main reflection color (set by the Diffuse color) blend into the Reflection color, and I don’t know whether some form of complex Fresnel has been implemented or if it’s just a dielectric simple Fresnel blended over a reflective surface.

An excellent article on the new Feature from the Chaos Group blog:
https://www.chaosgroup.com/blog/understanding-metalness

Related:

Denoising animations in V-Ray for Maya

Posted on May 12, 2018February 22, 2019 by Oded Maoz Erell

Software:
Maya 2018 | V-Ray 3.6

Animated sequences require ‘Temporal Denoising’ in order to achieve a flicker-less result.
‘Temporal Denoising’ means that in addition to taking into account neighboring pixel data, the denoising process also takes into account pixel data from adjacent frames in the animation.
For that reason, the V-Ray Denoiser render Element can’t simply be used during the render process like we can use it when rendering still images,
And the animation sequence is denoised after it has been rendered, and stored with extra data needed for the V-Ray Denoiser to work.

Update:
In V-Ray Next the vdenoise.exe tool has a GUI that allows loading sequences easily.

In versions of V-Ray prior to V-Ray Next the vdenoise tool has to be operated through command line with the following easy steps:

This is a very useful article on the subject from Dabarti studio:
http://dabarti.com/vfx/using-v-ray-denoiser-tool-vdenoise-exe-with-send-to-scripts/

General sequence denoising setup that has to be done just once:

1) Create a command line denoising script batch file, and store it in the Windows ‘Send to’ folder:
Write the following script to a new text file.
* this script is from an article by Tomasz Wyszołmirski – Dabarti Studio.

@echo off
set input=%1
set denoiser_input=%input:~0,-8%????.exr
"C:\Program Files\Chaos Group\V-Ray\Maya 2018 for x64\bin\vdenoise.exe" -inputFile="%denoiser_input%" -useGPU=2 -display=0
pause

Save the file named ‘Denoise Sequence.bat’ in the Windows Send to folder.
* to find the Windows Send to folder quickly open the Windows ‘run’ utility and type: shell:sendto.

Render setup for denoising:

2) In your Maya scene, In the Render Settings window, In Render Elements tab, add a Denoiser Render Element.

3) Select the vrayRE_Denoiser Render Element,
And in the Attribute Editor, under Exta V-Ray Attributes set ‘Mode’ to ‘Only Generate Render Elements’.

4) In Render Settings > Common > Image File Output:
Choose exr (multichannel)

5) Render the Animation.

Denoising the animation:

Right click the first frame of the rendered sequence,
And choose Send to > Denoise Sequence.bat

Architectural Visualization can be both physically correct and aesthetically pleasing

Posted on April 29, 2018April 26, 2020 by Oded Maoz Erell

Thinking we must “cheat” about the real-world lighting conditions of an architectural interior in order to render an aesthetically pleasing image of it is a common misconception in the field of Architectural Visualization.

I have been a professional in the field of digital 3D Visualization and Animation for the past 17 years, and the technologies we use to create synthetic imagery have developed dramatically during this period. The profession that is traditionally named “Computer Graphics”, can today rightfully be named “Virtual Photography”.

At the beginning of my career, photo-realistic rendering was impossible to perform on a reasonably priced desktop PC workstation. Today things are very different. In the early years, the process of digital 3D rendering produced images of a completely graphic nature. No one back than would mistake a synthetic 3D rendering for being a real-world photograph.

About 12 years ago, the development of desktop CPU performance and the advent of 3D rendering software that use Ray-Tracing* processes have made possible a revolution in the ability to render photo-realistic images on desktop PC’s. The term “photo-realistic” simply means that an uninformed viewer might mistake the synthetically generated image for a real-world photo, but it doesn’t mean the image is an accurate representation of the way a photograph of the subject would look if it were really existing in the world. For a computer generated image to faithfully represent how a real-world photo would look, it’s not enough for the rendering to be photo-realistic, it also needs to be physically correct and photo-metric.

https://vimeo.com/171403660

“Physically correct” rendering means the rendered image was produced using an accurate virtual simulation of physical light behavior, and “Photo-Metric” rendering means that the virtual light sources in the 3D model have been defined using real-world physical units and and the rendered raw output is processed in a way that faithfully predicts the image that would result from a real-world camera exposure.

Most contemporary rendering software packages, have the features I described above, and therefore are capable of generating photo-realistic images that are also physically correct and photo-metric, and so faithfully predict how a real world photo of the architectural structure would look.

C_Bath_Room_Dusk+Lights_EV-7.5_Oded_Erell

D_Bath_Room_Night+Lights_EV-7_Oded_Erell

So what’s the problem?

The problem is that when we virtually simulate the optics of a scene using real world physical light intensities, we come across the challenges that exist in real world photography, mainly the challenge of contrast management, or in more geeky terms, handling the huge dynamic range of real-world physical lighting, simply put, we encounter the common photography artifacts like unpleasing “blown out” or “burnt” highlights, light fixtures and windows.

Trying to solve the problem by lowering the camera exposure simply reveals more details in bright areas at the expense of darkening the more important areas of the image. traditional photo editing manipulations don’t do the trick, they might serve as a blunt instrument to darken areas of the image selectively but the result looks unnatural and fake and the traditional approach in interior rendering is to simply give up the realism of the visualization by drastically reducing the intensities of visible light sources and adding invisible light sources, a solution that might produce an aesthetic image but not one that faithfully reflects how a real photograph of the place would look and can be said to be physically correct.

https://vimeo.com/211347494

Fortunately today we have tools and processes, that allow for a much more effective development of physically accurate renders, somewhat similar in approach technologies incorporated into professional digital photography. these techniques involve processing the rendered images using specialized file formats that contain a very high degree of color accuracy and can store the full dynamic range of the “virtual photograph”, a process called “Tone mapping” designed to display an image in a way that mimics the the way are eyes naturally see the world, optically simulated lens effects that mimic the way a real lens woulds react to contrast and high intensities of light.

Incorporating this workflow requires taking a completely different approach to creating and processing 3D rendered images than the traditional methods used in the past decades. we give up some of the direct control we’re used to in computer graphics, but in return we are able to produce physically correct visualization that are both aesthetically pleasing and have a naturally feeling lighting.

In conclusion, with effective usage of today’s imaging technologies, it’s possible to produce 3D visualization that will serve both as a faithful representation of a possible real world photograph of the architectural design, thus aiding the creative design and planning process, and at the same time provide a photo-realistic basis for producing highly aesthetic marketing media.

Thank you for reading! I would love to hear your opinion, discuss the subjects in the article and answer any questions that you may have about it.

* “Ray-Tracing” is a process that simulates the physical behavior of light by tracing the directions it travels as it hits surfaces, reflects of them and refract though them. Ray-Tracing calculations are a key ingredient in photo-realistic rendering.

The author is Oded Erell, photo-realistic rendering specialist and instructor, the 3D visualizations displayed in this article have all been produced CG LION Studio.
Your’e welcome to visit our portfolio website and see more examples of our work.

Related Posts:

V-Ray for Maya IPR Viewport

Posted on April 14, 2018April 14, 2018 by Oded Maoz Erell

Software:
Maya 2018 | V-Ray 3.6

To Activate Viewport IPR with V-Ray for Maya:
In the Viewport menu,
Under Renderer, choose V-Ray IPR

Untitled-3

Rendering an Animation in Maya and V-Ray

Posted on March 29, 2018May 20, 2018 by Oded Maoz Erell

Software:
Maya 2018 | V-Ray 3.6

Set a Project Folder or Image output path.
In Render Settings > Common under Image File Output,
Set a file name and format.
In Render Settings > Common under Animation,
Set Animation to Standard.
Set the Maya UI to Rendering and choose Render > Render Sequence,
Or simply press the Render Button in the toolbar.

Related post:
Denoising animations with V-Ray for Maya