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Render Passes - Krakatoa For Maya

Last Edited on 2012/12/20 @11:45 pm PST

Introduction

Images rendered using Krakatoa are typically composited with other images using 2D compositing applications like Nuke, Fusion or After Effects. Like most other renderers, Krakatoa produces several render passes to assist the compositing artist.

Render Output Formats

While the rendered image could be saved to any file format supported by Maya specified in the Common tab of the Render Settings window, by default Krakatoa MY forces the output to an OpenEXR file.

It is recommended for compositing purposes and to fully preserve the floating point precision of the Krakatoa render output.

When Render Passes have been requested via the Render Output And Passes panel in the Krakatoa Settings tab of the Render Settings dialog, all passes will be saved as layers in the OpenEXR file.

When the Force Output to .EXR option is unchecked, the file format specified in the Common tab of Maya will be used for both the RGBA beauty output and for all Render Passes, producing individual files per pass.

Passes Currently Available in Krakatoa MY

Beauty (RGBA) Pass

The main render output of Krakatoa is an unclamped RGBA Beauty pass. As discussed above, it is recommended to save it to OpenEXR to get the highest quality data for compositing and post-processing.

The Beauty pass is always saved and cannot be turned off by the Krakatoa Settings controls.

The Beauty pass will normally contain the combined result of all particles rendered in the camera view, except when the Save Occluded Particles Pass option is checked. In that case, the Beauty pass will only contain the particles that are completely unoccluded by camera holdouts (matte objects or DTEX maps).

Normal Pass

The Normal Pass contains the vector representation of the ppNormalDir channel of Maya, or of the native Normal channel available in PRT files saved from other applications (e.g. Krakatoa for 3ds Max), or generated by the PRT Volume based on the mesh volume's surface data.

The data stored in this pass will only fully represent the particles closest to the camera. No deep data will be saved by the current implementation.

No filtering will be applied to the particles to avoid distortion of the data, A particle that would normally draw into 2x2, 3x3 or more pixels of the Beauty RGBA pass using Bilinear or Bicubic filering will fully overwrite all 2x2, 3x3 or more pixels.

Velocity Pass

The Velocity pass contains the vector representation of the particle Velocity channel.

The data stored in this pass will only fully represent the particles closest to the camera. No deep data will be saved by the current implementation.

No filtering will be applied to the particles to avoid distortion of the data, A particle that would normally draw into 2x2, 3x3 or more pixels of the Beauty RGBA pass using Bilinear or Bicubic filering will fully overwrite all 2x2, 3x3 or more pixels.

Z-Depth Pass

The Z-Depth pass contains a floating point value describing the distance from the closest particle to the camera's image plane in world units. Thus, looking at this pass as RGBA data in the range from 0.0 to 1.0 would make no sense as the image will typically appear purely white. Sampling the pixels will reveal real-world distances stored in the respective areas.

The data stored in this pass will only fully represent the particles closest to the camera. No deep data will be saved by the current implementation.

No filtering will be applied to the particles to avoid distortion of the data, A particle that would normally draw into 2x2, 3x3 or more pixels of the Beauty RGBA pass using Bilinear or Bicubic filering will fully overwrite all 2x2, 3x3 or more pixels.

Occluded Particles Pass

This special pass is a Background version of the Beauty pass. When enabled, it will contain the RGBA information of all particles partially or fully occluded by matte geometry or a DTEX holdout map. 

Please see this topic to learn more.

Other Passes

More passes including shader passes to split the components of the various Phase Functions like Phong (Diffuse, Specular) etc. are planned for the near future. They are already supported by Krakatoa MX.

Custom Passes

The ability to design custom passes is currently only available in Krakatoa MX via the Magma Channel Editing system, but is planned to be included in Krakatoa MY at a later point.