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 MtoA. 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.
Another tutorial that demonstrates different ways to approach lighting a room can be found here.
The workflow covers the following topics:
The scene has been exported from 3ds Max as an .fbx file and imported into Maya using the FBX plugin.
- When you import the scene, you will see that the Outliner and Hypershade windows are quite messy. Before you start, Go to File> Optimize Scene to delete any empty group nodes and add the geometry to a group node.
- The scene is lit very simply with a Skydome light and Light Portals positioned outside of the windows of the room. You may need to increase the number of Skydome light samples for final rendering (3 or 4).
- Increase the Exposure of the Skydome light to around 4.
- 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 light portals (with Skydome light) 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 Surface 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. Alternatively, there is a 'Lighting' mode in the Debug Shading in the Arnold RenderView window.
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)
Default Maya scene with Maya Phong shaders visible in the Hypershade window
Select a Phong shader and open the Attribute Editor. Select Phong from the 'Type' scroll down menu and choose Standard Surface. Any diffuse color information will carry over to the Standard Surface shader.
If the Phong shader has textures assigned to the Color, these will automatically be connected to the Base Color of the Standard Surface shader, requiring no extra effort.
A shader conversion script is supplied with MtoA to facilitate the conversion of multiple shaders to Ai Standard.
- Connect the diffuse color map to the Base Color of a Standard Surface 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.
- Assign a Standard Surface shader to the mirror and rename it 'Mirror'.
- Increase the Base Weight to 1.
- Increase Metalness to 1.
Here, we will add some translucency to give the effect that the curtain is being lit from behind.
- Assign a Standard Surface shader to the curtain and rename it 'Curtain'.
- Increase the SSS to around 0.5 and enable Thin Wall.
Rollover image to see the effect Thin Wall and SSS has on the curtain
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' in the Arnold tab of the Attribute Editor.
Opaque switch disabled for non-opaque surfaces such as glass
- Assign a Standard Surface to the glass door and rename it 'Glass'.
- Reduce the Base Weight to 0.
- Increase the Specular Weight to 1.
- Increase Transmission Weight to 1 (this makes the glass transparent).
- Increase the Index of Refraction (IOR) to 1.5 (glass).
- You can also add a tint to the glass very easily by adding a subtle hue to the Transmission color.
- 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.
Diffuse Ray Depth
The images below were rendered using a diffuse_ray_depth of 1 (default) and 4 (rollover image). You can notice a clear difference 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.
Transmission Ray Depth
You can 'clearly' see the difference in the glass vases when increasing the transmission_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.