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# Environment Variables

ParaView looks for a few environment variables that can be used to modify its behavior. Environment variables are only accessed from the first process which contains the user interface. ParaView is responsible for broadcasting the effects of the modifications to all processes.

## PV_INTERFACE_PATH

This variable is used for adding custom VTK filters to ParaView's user interface. It should point to the directory which contains the XML descriptions of the additional filters or sources.

## PV_OFFSCREEN

This environment variable is important only when running with multiple processes. It determines whether off screen rendering will be used for the satellite processes. The default behavior is for each node to map a window and use hardware rendering. When the assigned processors do not have access to a display, this environment variable should be set to "True" (any value will do). When this variable is set, ParaView only maps the render window of the first process. Software render will be used for the other processes. Of course, using software rendering will affect ParaView's rendering performance.

It is important to note that currently, you must link against Mesa's OpenGL libraries to get off-screen rendering on Unix systems.

## PV_SEPARATE_RENDER_WINDOW

Setting this environmant varible to "True" (or any value) will cause ParaView to create a render window separate from its main interface window.

## PV_DISABLE_COMPOSITE_INTERRUPTS

Since still renders can take a substantial amount of time, ParaView has the ability to interrupt a long render when another event comes along. Although this is relativly straight forward when rendering with a single processes, interrupting multiple processes during rendering and compositing is tricky. The parallel implementation of this feature uses asynchronous send and receives. Setting this environment variable will disable the interrupt feature. This option is used primarily for debugging purposes.

## PV_USE_TRANSMIT

Many sources and readers in VTK cannot break up their output into pieces. In order to parallize subsequent operations, ParaView breaks up the data after it has been generated/loaded. Unfortunately, this can be inefficient. ParaView's default behavior is to have each process load the entire data set, and then throw away the portions they do not need. This means every process will be accessing the same file at the same time.

Setting this environment variable to "True" causes ParaView to use a more efficient strategry. The first process reads the entire data set, and then transmits pieces of the data set to the satellite processes. Unfortunately, there are some VTK pipeline issues that have not been completely resolved with this strategy. All processes must execute or a deadlock will occur. Although most of the time ParaView can use this strategy without incident, there is a small possiblilty that ParaView might hang. I can currently only get ParaView to hang when using a vtkCleanPolyDataFilter with result invariance on. Until this issue is resolved, this feature is turned off by default.

## PV_DEBUG_HALF

This environment variable fools ParaView into thinking it has twice as many processors than it actually has. When it is set to "True", only half of any data set is processed and rendered. This option is primarly used for debugging purposes.

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Last modified: Mon Dec 3 13:25:35 EST 2001