Below are the current options and their defaults.

Name
Type
Default
Description
bucket:orderstringhorizontalRender bucket order. Supported values are: horizontal, vertical, zigzag-x, zigzag-y, spacefill, random, spiral, circle.
bucket:orderorigininteger[2]-1 -1First bucket for "spiral" and "circle" order. Image center is [-1 -1].
checkpoint:asfinalinteger0When enabled, this keeps the extra channels and the checkpoint tag when writing the final image for the render. The final image will be identical to any other checkpoint, rather than a slimmed down image. This means that once your image has reached the quality you've set and it completes, it can always be restarted by the user later.
checkpoint:commandstringemptySystem command to be called after checkpoint. If system calls are enabled, then after a checkpoint has been written, the specified command will be called. This is synchronous; the rendering threads are quiescent while this runs and will not resume again until the process returns, avoiding possible race conditions if the command takes a token %i will be replaced with the current increment, zero-padded to 5 digits. The token %e will be replaced with the elapsed time in seconds, zero-padded to 6 digits. The token %r will be replaced with the reason for this update to the checkpoint files (either completely `finished`, `exiting` early due to exitat option, or a normal `checkpoint`). Literal % characters may be inserted with %%.
checkpoint:exitatstringemptyHow long render should run before writing a final checkpoint and terminating. Value can also be a string such as "10m" or "0.5h". Set to 0 or empty to disable.
checkpoint:intervalstringemptyWrite framebuffers to disk every N progressive steps. If value is positive the units will be interpreted as seconds. If value is negative its units will be interpreted as increments. Value can also be a string such as "10m" or "0.5h". Setting option to 0 or empty will disable checkpoints.
checkpoint:keepfilesinteger0If set to true then prman will write to a new, numbered image for each checkpoint. Note: This will disable the final write of a checkpoint file which means the render cannot be recovered using the 'recover' option.
curve:minwidthfloat0Minimum curve width in raster coordinates.
deep:flagvolumesinteger1Off [0], auto (off for dtex, on otherwise) [1], or on [2]
dice:offscreenmultiplierfloat1Dicing rate multiplier for objects outside the viewing frustum.
dice:trianglestringtrimThe method used for dicing "triangles". The default method "trim" renders triangles by trimming a quad. The "blp" method renders a quad with two points being coincident.
hider:adaptallinteger0Enable adaptive sampling of all AOVs. When enabled, all channels (beauty pass + AOVs) are considered when deciding if a pixel is converging. The default (off) will ignore the AOVs and only the beauty pass is considered for pixel convergence. So turning off "adaptall" may speed up your render if some of your AOVs never reach the specified variance threshold.
hider:darkfallofffloat0.025De-prioritize low luminance samples in the adaptive sampler. Use this parameter to avoid oversampling dark areas while maintaining overall image quality. Higher values cull more samples, speeding up render time while increasing noise in darker areas.
hider:extrememotiondofinteger0Enable improved sampling accuracy. In some cases where a large amount of motion blur is used with depth of field, sampling artifacts could cause an undesirable result. This flag causes a slower but more accurate sampling method to be used to alleviate the artifacts. Due to the performance degradations of this sampling method, this flag should only be used when necessary.
hider:incrementalinteger0Enables the progressive display of results (rather than bucketed results).
hider:maxsamplesinteger0An explicit limit for the number of samples. If maxsamples is equal to its default then the maximum number of samples will be set equal to 64. Note that minsamples defaults to the square root of the maxsamples setting.
hider:minextrasamplesinteger-1This is the minimum number of extra samples that a pixel should continue shooting with after a sample fails to meet its convergence test with the adaptive sampler. Defaults to matching minsamples.
hider:minsamplesinteger-1Specifies the minimum number of samples for adaptive sampling. The default value is the square root of maxsamples.
hider:pixelfiltermodestringweightedSpecifies how pixel filtering of camera samples is performed. "Weighted" is the standard method and blends together samples from neighboring pixels. "Importance" warps the samples in screen space around the pixel center and does not share samples between pixels. It may be noisier, but is needed by some postprocessing algorithms. It is also needed to produce variance AOVs.
hider:samplemotioninteger1This option toggles the sampling of motion blurred micropolygon in the hider, and is thus only meaningful if motion blur is being used in your scene. By default, this hider option is enabled (set to 1), meaning that micropolygons will be blurred and sampled in the hider. When disabled (set to 0), micropolygons will no longer be blurred before sampling; however, the dPdtime variable will still be computed for all objects. This variable can be output into a separate image using an arbitrary output variable (aov) and used to perform motion blur as a postprocess.
hider:sampleoffsetinteger0This allows several images to be rendered in parallel (with different sampleoffset values) and then combined. With non-adaptive sampling: Let's say you render four images with 256 samples each, with sampleoffsets 0, 256, 512, and 768. If you combine those four images, you'll get exactly the same image as if you had rendered a single image with 1024 samples. With adaptive sampling: Let's say you again render four images, each with "maxsamples" 256, with sampleoffsets 0, 256, 512, and 768. Let's say that due to adaptive sampling, some given pixel only gets 64 pixel samples in each of the four images. Then the combined image has been rendered with sample numbers 0-63, 256-319, 512-575, and 768-831. Due to the stratification of the samples, this is not quite as good as if you had rendered a single image with 256 consecutive samples. However, it is still better than rendering a single image with only 64 samples.
hider:typestringraytraceRender mode. Supported values are: raytrace, bake.
lighting:selectionlearningschemeinteger0Employs a machine learning algorithm to more accurately importance sample lights, taking into account occlusion and light filters.
limits:brickmemoryinteger2097152Brickmap cache size in kB.
limits:bucketsizeinteger[2]16 16Size of render buckets in pixels.
limits:deepshadowerrorfloat0.01Control lossy compression scheme to reduce file size of deep output. Setting to a high value will result in lower numbers of samples stored for each pixel.
limits:geocachememoryinteger2097152Geometry cache size in kB.
limits:gridsizeinteger289
limits:matrixcachememoryinteger0Matrix cache in kB.
limits:nurbcurvaturedicefactorinteger3NURBs max curvature multiplier.
limits:octreememoryinteger20480None cache size in kB.
limits:opacitycachememoryinteger1048576Opacity cache in kB (1024 MB).
limits:othresholdfloat[3]0.99609375 0.99609375 0.99609375Opacity Culling: When rendering scenes with a large number of semi-transparent layered objects (e.g. hair), the opacity culling threshold can be set for a significant time and memory savings. Essentially, a stack of visible points whose accumulated opacity is greater (in each channel) than the specified limit will be considered fully opaque by the hider, and objects behind the stack will be culled.
limits:pointmemoryinteger20480Point cache size in kB (20 MB).
limits:proceduralbakingclumpsizeinteger0
limits:ptexturemaxfilesinteger128
limits:ptexturememoryinteger32768PTex cache size in kB.
limits:rendermemoryfloat0Memory limit as percentage of machine memory.
limits:rendertimeinteger0Maximum render time in minutes.
limits:shadesizeinteger289The maximum number of vertices, not grid (17 x 17 = 289).
limits:texturememoryinteger2097152Texture cache size in kB (2048 MB).
limits:textureperthreadmemoryratiofloat0.5
limits:threadsinteger0Set the number of threads that the renderer uses. If a value of 0 is specified then all CPUs will be utilized for rendering. If a negative value '-N' is specified then prman will use all but N CPUs for rendering.
procedural:splitmodeinteger0Split on demand [0], up front [1], or hybrid [2].
Ri:CropWindowfloat[4]0 1 0 1Crop window [left right top bottom] in NDC space.
Ri:FormatPixelAspectRatiofloat1Device pixel aspect ratio.
Ri:FormatResolutioninteger[2]640 480Output image resolution.
Ri:Frameinteger0Frame number.
Ri:FrameAspectRatiofloat-1Output image aspect ratio.
Ri:PixelVariancefloat0.001Controls adaptive sampling. This sets the upper bound on the acceptable estimated variance of the pixel values from the true pixel values.
Ri:ScreenWindowfloat[4]0 0 0 0Screen window [left right top bottom] in screen space.
Ri:Shutterfloat[2]0 0Scene motion shutter.
ribparse:varsubststringemptyRIB parse only.
scenedump:filenamestringemptyPath to dump RIB scene for rendermode "catrib".
searchpath:archivestringemptySearch path for Rib archives and DelayedReadArchive.
searchpath:dirmapstringemptySearch path remapping.
searchpath:displaystringemptySearch path for display plug-ins.
searchpath:proceduralstringemptySearch path for DynamicLoad procedural plug-ins.
searchpath:rifilterstringemptySearch path for Rif plug-ins.
searchpath:rixpluginstringemptySearch path for shading plug-ins.
searchpath:shaderstringemptySearch path for OSL pattern plug-ins.
searchpath:texturestringemptySearch path for texture files.
shade:debuginteger0Shading debug level.
shade:derivsfollowdicinginteger1
shade:frequencyframetimefloat-infShading time for frequency "frame".
Shutter:offsetfloat0Offset shutter open/close.
statistics:displace_ratiosfloat[2]0.1 1Suppress reporting of displacements that, when divided by the max displacement, fall in the specified range.
statistics:filenamestringemptyFile name for summary statistics reported in plain text.
statistics:iotracefilenamestringempty
statistics:levelinteger0Enable statistics reporting.
statistics:maxdispwarningsinteger100Modify the maximum reported displacement issues. If the value is set to 0, then all displacements issues are reported.
statistics:shaderprofilestringempty
statistics:stylesheetstringemptyStylesheet for XML detailed statistics.
statistics:texturestatslevelinteger0
statistics:trackassetobjectsinteger0
statistics:xmlfilenamestringemptyFile name for detailed statistics reported as XML.
stitch:refwarninginteger1Enable stitch warnings.
trace:depthmodestringseparateIntegrators track diffuse/specular depth "separate" or "combined".
trace:maxdepthinteger25Maximum ray depth.
trace:worldoffsetfloat[3]0 0 0Used as the origin when the worldorigin option is set to "worldoffset".
trace:worldoriginstringcameraSet a new world origin to give better floating point precision. Supported values are: world, worldoffset, camera.