Displacement: Killamari wip

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In this tutorial we will cover how to convert a scene that has been setup for use with the mental ray renderer to MtoA. We will cover how to shade the Killamari character character using the Ai Standard shader. We will cover Override Sets to add subdivision to create a smooth looking mesh. We will also cover using vector displacement on the leg and tentacle objects.

The original Maya scene files for this series of tutorials can be downloaded from Autodesk's Hyperspace Madness production page here.


This tutorial will cover the following topics:

Displacement: Killamari wip

Displacement: Killamari wip

Vector Displacement

Feature Overrides

Displacement: Killamari wip

 

Subdivision

  • Start off by opening the Killamari model in Maya. You will notice that it is a low poly model. We can add geometry detail by increasing the number of Subdivision Iterations using Arnold's Subdivision settings. We will also need to add subdivisions to the leg and tentacle models as we will be adding displacement to them.

 

Override Sets

Rather than having to change the number of Subdivisions for each model we can add any changes to a Maya Set and override that set.

  • Select the body geometry (not the tentacles) and create a Maya Set for them.
  • Select the Set and go to the Arnold tab. Click on Add to open the Add Override Attribute window.
  • We want to create a smooth surface for our model, so add Ai SubdivType and change it to Catclark.
  • We will also want to add some subdivision iterations to smooth the model. Add Ai Subdiv Iterations to the Set and increase them to 2.

Subdivision Overrides assigned to body Set

Bear in mind that each subdivision iteration quadruples the number of polygons. If your object has 2 levels of subdivision iterations set and 4 additional iterations set in Arnold, that's 6 subdiv iterations total and therefore 426936 * 4^6 = 426936 * 4096 = 1.7 Billion polygons.

The number of iterations / levels of subdivision. With Catmull-Clark subdivision, increasing the number of iterations produces a smoother mesh.

Care should be taken when increasing Arnold's subdivision iterations in combination with Maya's Smooth Mesh Preview (3 on the keyboard). Arnold will also render this preview smoothed state in the final image. This may result in a subdivided mesh that far exceeds the necessary amount of polygons required and will result in longer export/render times.

Displacement

We can add more detail to the leg and tentacle models by using a vector displacement map.

  • Repeat the above steps by adding another Override Set to the leg and tentacle geometry. However this time, increase the number of Ai Subdiv Iterations to 6. We will need these extra subdivisions to see the fine detail from the displacement map on the model.

Override Set for leg and tentacle geometry

 

  • Assign an Ai Standard shader to the Killamari and rename it Killamari_body.
  • Select the Shading Engine for this shader and connect a displacement shader to the Vector Displacement attribute.
  • Select the displacement shader and connect the 'killamari_merged_appendages_vdm' vector displacement map to the Vector Displacement.

Displacement texture connected to Shading Group of Hair shader

The Utility shader can be useful for diagnosing issues when rendering displacement maps. The leg and tentacles appear black because they have subdivision iterations set to 6 whereas the rest of the body has only 2. You can also use Feature Overrides if you need to disable rendering of displacement in the scene (useful for scene diagnosis purposes).


Utility shader. Shade mode set to 'ndoteye'. Rollover to disable subdivision (Feature Override).

 

 

 

 

Rendering

Displacement: Killamari wip

  • Open the Render Settings window and go to Environment. Connect the Physical Sky we created earlier here by clicking and holding on the  icon to the right. It should appear in the drop down menu.

Physical Sky connected to Background

 

Sampling

Open up Sampling in the Render Settings Window. For test rendering Camera (AA) samples at 3 is fine. However, for final frame rendering you will want to increase it to at least 5.

A simple guide to sampling can be found here.

Displacement: Killamari wip

When rendering scenes with MtoA it is a good idea to get familiar with the Arnold Log in the Diagnostics tab of the Render Settings window. This log file will show you any warnings and statistics which will help you diagnose your scene file.

A guide on how to read a render log can be found here.

 

 

Thats it. Congratulations, you have successfully converted a scene from mental ray to MtoA! Now go out there and explore new worlds of rendering!

 

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