Flipped Normals have donated a studio lighting sample scene for use with rendering in MtoA. I highly recommend the full scene as a quick and easy way to light your models realistically using Arnold for Maya.
More information is available here.
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Flipped Normals Studio Lighting
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Refractive Portrait
In this tutorial we will explore how to create an abstract, painterly effect applied to a head scan model to produce a ghostly looking portrait. In this tutorial we will specifically use the alSurface shader to produce this effect. Arnold can make use of 3rd party shaders such as the alShaders by Anders Langlands. This collection of shaders will need to be installed prior to starting this tutorial. Further examples using this technique can be found here.
This tutorial makes use of this free head scan, kindly provided by Ten24.info.
Head
Head Model
- Start off by opening the head scan model Male_Head_L4.OBJ in Maya. Create a new camera and rename it ‘RenderCam’. Position the camera so that it roughly matches the image at the top of the page. We will talk more about careful positioning of the camera later.
Head Shader
- Assign an alSurface shader to the head model. Create a file texture (with projection).
- Open your texture in the file texture. Be aware that some images work better than others. It helps if you use an image with a lot of contrast. It will give more variation in the refraction which will give the effect that the head is distorting and breaking up more.
- Connect the file texture to the following attributes of the alSurface shader.
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- Diffuse Color
- Opacity
- Specular Color
- SSS Radius Color
- Bump Value
The head model has a projected file texture connected to Backlight Color, Diffuse Color, Opacity, Specular Color and SSS Radius Color attributes of the alSurface shader. Right alSurface shader attributes.
Refractive Plane
- Create a polygon plane and position it so that it intersects the face as in the image below. We will use this plane to refract the rest of the head using the same texture map.
Ensure that you disable ‘Opaque‘ for the polygon plane otherwise the refractive texture will not work correctly.
Poly Plane Normals
The direction that the the plane is facing in can have a large effect on the rendered result. The images below show the difference when rendering with the normals pointing inwards vs outwards.
Normals facing outwards (left). Normals facing inwards (right).
Refractive Plane Shader
- Create another alSurface shader and assign it to the plane.
- Connect the same projection texture map used for the head into the Transmission IOR (andBacklightColor) via a Maya remapHSV node.
The refractive plane has same file texture but is connected to Transmission and Backlight Color.
Texture Projections
In most cases setting the Projection Type to Perspective works best for this effect to work. However, it is also possible to get some interesting results by using some of the other texture projection methods.
None, Ball, Cubic, Spherical.
Remap HSV
You can use a node such as the Remap HSV to give more control over the effect the texture map has on the Transmission IOR. The animation below shows the effect of the Remap HSV ‘Value’ attribute being animated from 1 to 5.
Camera Angle
Careful positioning of the camera should be ensured otherwise the illusion will be broken. This can be seen in the animation below, where the camera has been rotated too far.
Transmission Roughness
Increasing the amount of Transmission Roughness can help to soften the refractive effect. However, increasing this value too much can make the refractive effect appear too soft. Ensure that you have enough Refraction Samples when using Transmission Roughness. In this case a value of 4 was used.
Transmission Roughness: 0, 0.5, 1
Volume Scattering Color
You could also try adding some Volume Scattering to the scene to add some more integration of the head model with the background texture. Be warned however, that this technique can be prone to noise when using bright light sources and high specular values. This can be minimized by increasing the Specular Roughness for the head shader.
Same projected texture map connected to the Volume Scattering Color
Enabled (left). Disabled (right).
Black and White
Converting the final rendered image to black and white in Photoshop (Image> Adjustments> Black and White) can also yield some interesting results. The images below show some of the effects available.
Default, High contrast blue filter, Infrared, Maximum WhiteThat concludes this tutorial on how to create an abstract refractive effect using the alSurface shader. You can also try this technique using different shaders and textures to get many interesting effects. The key is to just experiment with it and see what happens. You may be surprised by the results!
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Happy Holidays!
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Remnant Studios Bed Scan
Daniel Morrison has some great 3D scans available for free here. Below is an Arnold render of his disheveled bed scan (video here).
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Hunter Alien Model by Christophe Desse
This scene is kindly provided by Christophe Desse. Click here to download the scene file (setup for rendering with Arnold for Maya).
The kitchen probe hdr map used for the skydome light in this scene can be downloaded here.
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Arnold Standard Shader: SSS Diffusion Profile
The Standard shader has a new Diffusion Profile called Empirical (the default is Cubic). Empirical is a more physically accurate subsurface scattering profile, that, with a single layer, can capture both surface detail and deep scattering.
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GGX Microfacet Distribution
I thought I would have a go at comparing the new ‘GGX’ Specular attribute in Arnold against ‘Beckmann’ (default).
“GGX is a microfacet distribution. It has a sharper peak and a larger tail than Beckmann. GGX is suitable for modeling light reflection from surfaces more realistically.”
It seems to give a subtle softer highlight that falls off more gradually. The effect seems more obvious on the brighter specular highlights on the metallic surfaces below.
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LUT file’s
The Arnold Render View enables you to open LUT (Lookup Table) files directly in the window.
Below are some tests using some 3D LUT .cube files from this site. There also some free LUT files available here.
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Speckle Effect
How to achieve a specular speckle effect (see video below)? This effect is visible in various places such as car paints, plastic coatings on mobile phones, christmas ornaments, snow etc
It can quite easily be achieved using the alShaders by Anders Langlands. In particular the alFlake shader is required. You need to connect it to the alSurface shader’s Specular Normal attribute.
You can download the shader here – Maya, C4D.
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Space Pirate Model
This toy model is available to download (also contains a studio lighting scene). It is set up for rendering in Arnold.
The Maya scene is available here along with some other learning scene files.
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Queen Nefertit Scan
Apparently some (rather naughty) people went in and scanned the contested Egyptian Queen Nefertit bust at the Nues Museum in Berlin without their permission.
I thought I’d have a go at rendering it with Arnold using the alSurface shader.
The high resolution model is freely available to download here (.obj).
Thanks to Ben Fischler for the story.
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Zoic – Arnold Camera Shader
The extraordinarily talented Zeno Pelgrims has created a rather nifty camera shader for Arnold for Maya capable of simulating optically imperfect lens effects.
Below are some examples using some bokeh images from www.dofpro.com
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Arnold does Emily
Daniel Hennies from http://uglykids.org has created a brilliant video tutorial in Arnold, rendering a photorealistic portrait in Cinema 4D with C4DtoA.
Thanks for the shout-out Arnie!
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Food Scans
_blank | REPOSITORY has some great high quality scans of food that are available to download.
Below is an Arnold render of the avocado scan.
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Solid Angle has joined Autodesk!
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[Arnold] Setting up the Standard shader to be energy conserving
Stephen Blair (Solid Angle support) has posted some great tips on energy conservation when using the Standard shader in Arnold.
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Understanding Physically Based Rendering in Arnold
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Material Studies: Metals
Here are some awesome metal material studies using the Standard shader in Arnold for Houdini by Jarrod Hasenjager.
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Volume Rendering Using Houdini & Arnold
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Converting Mental Ray Scenes to MtoA: Hyperspace Madness Production
Here are a series of tutorials aimed at mental ray users who are using Arnold for Maya for the first time. The tutorials are based on the Hyperspace Madness production over on the Autodesk Area site. You will have to download the assets from this site before starting the tutorials. I recommend downloading the assets as they are a great learning resource to have.
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