ID 374209 - Preview and Live Render updates in the Monitor tab aren't smooth and may be delayed

Problem summary:

When rendering to the Monitor tab in Katana 3.1, the image in the monitor does not update as smoothly in comparison to the 3.0 line.

This behaviour can be seen in the attached video, which shows the difference before and after the change of behavior occurred in development build Katana 3.1dev#103.

Steps to reproduce (Preview Render with Scanlines):

1. Launch Katana with PRMan 22.1
2. Unzip and open the attached project in: 347209.zip, and preview render from the RenderSettings node named Prman (Note: the bucket size has been edited in a PrmanGlobalStatements node to simulate a scanline render).

Preview render is updated in the Monitor tab smoothly, ie. adding the "scanline" buckets from top to bottom evenly until the initial image is constructed.

Actual behaviour:

Preview render is updated in the Monitor tab unevenly, ie. adding the "scanline" buckets from top to bottom in blocks until the image is constructed.

Steps to reproduce (Live Render Frame Updates):

1. Launch Katana with PRMan 22.1.
2. Open the attached project: bucket_size_incremental.katana
3. Start a Live Render, and move the camera once the render has begun.

Workaround:

Catalog entries use push-based events to update the display, and the number of render draw events that are buffered before an event is pushed can be controlled by the environment variable KATANA_CATALOG_RECT_UPDATE_BUFFER_SIZE. The default value is 256. Setting this to a lower value, e.g. 32, increases the frequency of redraws.

Tested versions/platforms:

• 3.0v6 - Unaffected
• 3.1v1 - Affected

• 3.1dev#99 - Unaffected
• 3.1dev#103 - Affected