Converting an Interior Scene to Arnold

Rollover image for wireframe

 

This tutorial is a breakdown of the workflow required to convert an interior scene that has been setup for another renderer for rendering with Arnold. Scene setup and rendering should take no longer than an hour. The scene used in this example is part of this collection of architectural interiors.

Lighting 

  • The scene is lit very simply with Quad lights positioned outside of the windows of the room. The Color Temperature has been set to that of daylight (5500). Leave the default light Samples setting at 1. For final rendering, increase this value to 4 to reduce any noise in the shadows.
  • Increase the Exposure of the light to around 20.
  • Use a Directional light to simulate sunlight coming through the far window. Increase the Angle slightly to around 0.2. This will give the sunlight a softer edge to the shadow on the floor. You may need to increase the Directional light's Samples if you do (3 should suffice). Enable Color Temperature and choose a slightly warmer temperature like 5000.

Scene lit with Quad lights outside of the windows and a Directional light representing sunlight

To preview how the lighting will affect the scene, you can apply a default Standard shader override to the scene. This effectively creates a 'chalk preview' of your render and allows you to focus purely on lighting without being concerned about shading.

Reducing the Diffuse samples to 0 will effectively disable indirect lighting. This is useful when you want to test render direct lighting in the scene and will also be quicker to render.

Diffuse Samples: 0 (disables indirect lighting)


Shading

Floor Shader

  • Connect the diffuse color map to the Diffuse Color of an Standard shader.
  • Connect the bump map to the Bump attribute. Reduce the Bump Depth to a small amount like 0.03.
  • Increase the Specular Weight to 0.3 and reduce the Specular Roughness to 0.1 to give the floor a glossy appearance.
  • Enable Fresnel and increase the Reflectance at Normal to around 0.1. Fresnel is important for creating believable materials such as a shiny floor for example.

More information about the importance of Specular Fresnel can be found here.

Mirror

We will use Reflectivity and not specularity for the mirror. This is because reflectivity gives a perfectly sharp and mirror-like reflection.

  • Assign a Standard shader to the mirror and rename it 'Mirror'.
  • Reduce the Diffuse Weight to 0.
  • Increase the Reflection to 1.

Curtain

Here, we will use Backlighting to provide the effect of translucency with the curtain being lit from behind.

  • Assign a Standard shader to the curtain and rename it 'curtain'.
  • Increase the Backlighting to around 0.6.

Rollover image to see the effect Backlighting has on the curtain

Glass Door

Any glass surfaces will need to have Opaque disabled, otherwise any shadows cast by the object will always be solid and not pick up the refraction color or density of the shader.

Ensure that the polygon face normals are all facing in the right direction (especially important when rendering glass surfaces with Arnold). 

  • Select the window geometry and disable Opaque.
  • Assign a Standard to the glass door and rename it 'Glass'.
  • Reduce the Diffuse Weight to 0.
  • Increase the Specular Weight to 1.
  • Increase Refraction Weight to 1 (this makes the glass transparent).
  • Increase the Index of Refraction (IOR) to 1.5 (glass).
  • Enable Fresnel Use IOR. This will automatically calculate Fresnel based on the IOR value we entered in the previous step.
  • You can also add a tint to the glass very easily by adding a subtle hue to the Transmittance color. 
Render Settings

Sampling

  • For the final render, the Camera (AA) settings were increased to 6
  • The Diffuse Samples were also increased to 6 to reduce noise in indirectly lit areas of the room. The images below show the difference between rendering 2 (default) Diffuse samples and 6.

Rollover image to see difference between 2 and 6 Diffuse Samples

Care should be taken when increasing this value as your render times will increase dramatically.

More information and tutorials about removing noise can be found here.

Ray Depth

Diffuse Ray Depth

The images below were rendered using a Diffuse Ray Depth of (default) and (rollover image). You can notice a clear difference in the amount of bounced light around the curtain for example.

Rollover image to see difference between Diffuse Ray Depth 1 (default) and 4

Note that render times will linearly increase with regards to the number of ray diffuse bounces and therefore care should be taken when increasing this value.

Refraction Ray Depth

You can 'clearly' see the difference in the glass vases when increasing the Refraction Ray Depth in the images below.

More information about rendering glass surfaces can be found here.

 

That concludes this tutorial on converting an interior scene for rendering with Arnold. 

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