Properties Mantra 9.0 rendering properties

Houdini name	vm_objroot
IFD name	renderer:objroot
Default	("/obj/")

This is set to the “root” of the object tree. In Houdini, this is typically /obj. If object names are specified using relative paths (i.e. “light1” or “subnet1/light1”), this is used to determine the full path. This will be deprecated in the future in favor of category selection.

Houdini name	vm_uvobject
IFD name	renderer:uvobject
Default	("")

Mantra is able to render an object in UV space rather than 3D space. Only one object may be rendered in UV space. This is the name of the object.

Houdini name	vm_uvattribute
IFD name	renderer:uvattribute
Default	("")

The name of the attribute used in UV un-wrapping.

Houdini name	vm_networkqsize
IFD name	renderer:networkqsize
Default	(8)

When performing network rendering, this specifies the number of tiles queued for each remote render.

Houdini name	vm_octreestyle
IFD name	renderer:octreestyle
Default	(1)

Tunes ray-tracing acceleration structures. The default is usually reasonable and there is typically no reason to change the value.

Houdini name	vm_kdcrossover
IFD name	renderer:kdcrossover
Default	(100)

Tunes ray-tracing acceleration structures. The default is usually reasonable and there is typically no reason to change the value.

Houdini name	vm_kdcostratio
IFD name	renderer:kdcostratio
Default	(1)

Tunes ray-tracing acceleration structures. The default is usually reasonable and there is typically no reason to change the value.

Houdini name	vm_kdmemfactor
IFD name	renderer:kdmemfactor
Default	(1)

Tunes ray-tracing acceleration structures. The default is usually reasonable and there is typically no reason to change the value.

Houdini name	vm_shadingfactor
IFD name	renderer:shadingfactor
Default	(1)

The shadingfactor setting is a global multiplier on all shading rates in the scene. Each object has a shadingrate property.

The shading rate used for an object is determined by…

shadingrate = object:shadingrate * renderer:shadingfactor

Houdini name	vm_rayshadingfactor
IFD name	renderer:rayshadingfactor
Default	(1)

Mantra allows a separate shadingrate when ray-tracing is performed (compared with scanline rendering). The rayshadingfactor is a global multiplier on all ray-tracing shading rates in the scene. Each object has a rayshadingrate property.

The ray-tracing shading rate used for an object is determined by…

rayshadingrate = object:rayshadingrate * renderer:rayshadingfactor

Houdini name	vm_vexprofile
IFD name	renderer:vexprofile
Default	(0)

VEX profiling provides a tool to do performance analysis of shader execution. Turning on VEX profiling will affect performance of shading adversely. Especially when NAN detection is turned on.

• 0 – No VEX profiling.

• 1 – Performance analysis of VEX execution.

• 2 – Performance analysis of VEX execution with NAN detection.

When NAN detection is turned on, each instruction executed in VEX will be checked for invalid arithmetic operations. This will check for division by 0, numeric overflow, invalid operations. Errors like this will typically result in white or black pixels in the resulting image.

Houdini name	vm_verbose
IFD name	renderer:verbose
Default	(0)

Determines the verbose level of the renderer. Higher values will cause mantra to print out more information about the rendering process. Typically a level of 1 or 2 is sufficient.

Houdini name	vm_threadcount
IFD name	renderer:threadcount
Default	(1)

The number of threads used for rendering.

Houdini name	vm_renderengine
IFD name	renderer:renderengine
Default	(0)

Mantra has several different methods of rendering an image. The rendering engine determines which algorithm will be used to generate the image. Though this token has an integer value, it’s also possible to set the value through a string value.

• micropoly – Micropolygon scanline rendering (default).

• raytrace – All rendering will be performed using ray-tracing.

• pbrmicropoly – Physically Based Rendering using micro-polygon scanline rendering

• pbrraytrace – Physically Based Rendering using ray-tracing only.

• photon – Photon map generation.

• viewpohoton – View dependent photon map generation.

• irradiance – Irradiance cache creation (partially implemented).

• metropolis – Physically Based Rendering using metropolis integration (partially implemented).

Houdini name	vm_geocachesize
IFD name	renderer:geocachesize
Default	(32)

The number of megabytes used for the geometry cache.

Houdini name	vm_texcachesize
IFD name	renderer:texcachesize
Default	(32)

The number of megabytes used for texture caching. This includes all texture caching.

• 2D .rat file caching

• 3D point cloud caching

• 3D volume caching

Houdini name	vm_alfprogress
IFD name	renderer:alfprogress
Default	("false")

Output progress in a format which can be processed by Pixar’s Alfred render queue.

Houdini name	vm_tilecallback
IFD name	renderer:tilecallback
Default	("")

This property specifies a python callback which can be called at the completion of each tile rendered. There is a “built-in” “mantra” module which allows information to be queried. There is a single function available in the mantra module. The “property” function allows querying of any global rendering property as well as some other special properties. The result of the property call is always a list of values.

The special properties queried may be…

• tile:ncomplete – The number of tiles which have been completed.

• tile:ntiles – The total number of tiles in the image.

• tile:laptime – The number of seconds taken to render the last tile.

• tile:totaltime – The total number of seconds to render since the render began. This does not include time to load the scene, but rather is defined as the time since the first tile began rendering.

• tile:coords – The tile bounding box (in pixels).

• tile:memory – The amount of RAM in use by mantra.

import mantra
import sys

tile = mantra.property("tile:ncomplete")(0)
if tile == 1
    print mantra.property("renderer:name")
    print mantra.property("renderer:version")

Houdini name	vm_networkcompress
IFD name	renderer:networkcompress
Default	("true")

Turns on compression when network rendering. This cuts down on network bandwidth significantly. This should not usually be changed.

Houdini name	vm_dsmoptimize
IFD name	renderer:dsmoptimize
Default	("true")

Deep shadow map optimization. This value should not usually be changed.

Houdini name	vm_fogbackground
IFD name	renderer:fogbackground
Default	("true")

Mantra only runs atmosphere shaders after surface shaders have been run. This means that there are no atmosphere shaders run if there are no objects rendered. When this setting is true, a giant box is created surrounding the scene. The box has a matte shader applied. The size of the box is determined by sqrt(1/3) * far_clip (the camera’s far clipping plane).

Houdini name	vm_usemaxthreads
IFD name	renderer:usemaxthreads
Default	("true")

Set renderer:threadcount to the number of CPUs of the rendering machine.

Houdini name	vm_hidden
IFD name	renderer:hidden
Default	("true")

Perform hidden surface removal. When hidden surface removal is disabled, all surfaces in the camera’s frustum will be rendered, regardless of whether they are occluded. This can impact render time significantly.

Houdini name	vm_blurquality
IFD name	renderer:blurquality
Default	("true")

Whether to enable motion blur sampling for scanline rendering.

Houdini name	vm_rayblurquality
IFD name	renderer:rayblurquality
Default	("true")

Whether to enable motion blur sampling for ray-traced rendering.

Houdini name	vm_dofquality
IFD name	renderer:dofquality
Default	("true")

Whether to enable depth of field sampling.

Houdini name	vm_rayquality
IFD name	renderer:rayquality
Default	("true")

Whether to enable ray-tracing. By disabling ray-tracing no ray-traced shadows, reflections, refractions, etc. will be performed.

Houdini name	vm_giquality
IFD name	renderer:giquality
Default	("true")

Whether to enable the irradiance and occlusion VEX functions. This also controls whether irradiance caching will be enabled.

Houdini name	vm_pbrprimarycache
IFD name	renderer:pbrprimarycache
Default	("")

Specifies the method of caching for primary rays in PBR mode. This may be set to either “icache” or “photon”.

Houdini name	vm_pbrsecondarycache
IFD name	renderer:pbrsecondarycache
Default	("")

Specifies the method of caching for secondary rays in PBR mode. This may be set to either “icache” or “photon”.

Houdini name	vm_pbrcausticcache
IFD name	renderer:pbrcausticcache
Default	("")

Specifies the method of caching for caustic rays in PBR mode. This may be set to either “icache” or “photon”

Houdini name	vm_pbrcachedirect
IFD name	renderer:pbrcachedirect
Default	(1)

The cache file will store direct illumination as well as indirect illumination.

Houdini name	vm_pbrpathtype
IFD name	renderer:pbrpathtype
Default	("diffuse")

The type of path tracing to perform in PBR mode.

• diffuse – Only diffuse paths are traced.

• specular – Diffuse & specular paths are traced.

• caustic – Diffuse, specular and caustic paths are traced.

• all – All paths are traced.

Houdini name	vm_pbrreflectlimit
IFD name	renderer:pbrreflectlimit
Default	(10)

The maximum specular bounces allowed in PBR mode.

Houdini name	vm_pbrdiffuselimit
IFD name	renderer:pbrdiffuselimit
Default	(0)

The maximum diffuse bounces allowed in PBR mode.

Houdini name	vm_pbrphotonsamples
IFD name	renderer:pbrphotonsamples
Default	(10)

The number of photon samples in PBR mode.

Houdini name	vm_pbrbias
IFD name	renderer:pbrbias
Default	(0.001)

The ray-tracing bias used when the PBR rendering engines are used.

Houdini name	vm_bucketsize
IFD name	image:bucket
Default	(16)

The tile size of buckets used to render the image.

Houdini name	vm_samples
IFD name	image:samples
Default	(3, 3)

The number of x and y samples per-pixel.

Houdini name	vm_jitter
IFD name	image:jitter
Default	(1)

A floating point value which adds noise to sampling patterns.

Houdini name	vm_subpixel
IFD name	image:subpixel
Default	("false")

Normally, sub-pixel samples are filtered using the pixel filter defined on an image plane. When image:subpixel is true, each sub-pixel is output without any pixel filtering performed. The image:resolution property will be scaled by the image:samples property to determine the actual output image resolution. For example, if image:resolution was (1024,512) and image:samples was (4,6), the image rendered would have a resolution of 4096 by 3072. Each pixel would represent a single unfiltered sub-pixel sample.

Houdini name	vm_samplelock
IFD name	image:samplelock
Default	("true")

This property will “lock” the sampling patterns from frame-to-frame. This minimizes the buzzing caused by noise when rendering animations. The noise is still present, but is more consistent frame-to-frame.

Houdini name	vm_opacitythresh
IFD name	image:opacitythresh
Default	(0)

After shading of a surface, if the Of variable is less than this threshold, mantra will consider that the surface doesn’t exist and samples will be ignored.

Houdini name	vm_opacitylimit
IFD name	image:opacitylimit
Default	(0.995)

When compositing layers of transparent surfaces, when the cumulative opacity of the transparent layers is more than this threshold, the pixel will be considered opaque, allowing mantra to ignore objects which are occluded.

Houdini name	vm_colorlimit
IFD name	image:colorlimit
Default	(1000)

When performing shading, mantra places no limits on values which may be returned. However, when performing Physically Based Rendering, it’s possible to get very large values for some rays. These extrema will show cause color spikes which cannot be smoothed out without sending huge numbers of rays. The color limit is used to clamp the value of the Cf variable to avoid these spikes.

Houdini name	vm_photongfile
IFD name	photon:photongfile
Default	("global.pmap")

When renderer:renderengine is “photon”, this determines the photon map file for diffuse photons (irradiance)

Houdini name	vm_photoncfile
IFD name	photon:photoncfile
Default	("caustic.pmap")

When renderer:renderengine is “photon”, this determines the photon map file for caustic photons (specular bounces)

Houdini name	vm_photoncount
IFD name	photon:photoncount
Default	(100000)

The number of photons sent when renderer:renderengine is set to “photon”.

Houdini name	vm_photongfilter
IFD name	photon:photongfilter
Default	(50)

The number of photons used in pre-filtering the global map.

Houdini name	vm_photoncfilter
IFD name	photon:photoncfilter
Default	(50)

The number of photons used in pre-filtering for the caustic map.

Houdini name	vm_photongradius
IFD name	photon:photongradius
Default	(1)

The search radius when pre-filtering photons for the global map.

Houdini name	vm_photoncradius
IFD name	photon:photoncradius
Default	(1)

The search radius when pre-filtering photons for the caustic map.

Houdini name	vm_photongratio
IFD name	photon:photongratio
Default	(1)

The probability for discarding photons during pre-filtering of the global map.

Houdini name	vm_photoncratio
IFD name	photon:photoncratio
Default	(1)

The probability for discarding photons during pre-filtering of the caustic map.

Houdini name	vm_photongprefilter
IFD name	photon:photongprefilter
Default	("true")

A boolean to determine whether pre-filtering should be performed on the global photon map.

Houdini name	vm_photoncprefilter
IFD name	photon:photoncprefilter
Default	("false")

A boolean to determine whether pre-filtering should be performed on the caustic photon map.

Houdini name	orthowidth
IFD name	camera:orthowidth
Default	(1)

When camera:projection is “orthographic”, this determines the width of the projection.

Houdini name	vm_curvature
IFD name	camera:curvature
Default	(0)

Mantra is able to render using a non-flat projection plane. When the curvature is non-zero, ray-tracing will be used for primary rays. The curvature may either be greater or less than zero to mimic a wide angle or fish-eye lens.

Houdini name	vm_bokeh
IFD name	camera:bokeh
Default	("radial")

Bokeh determines the “quality” of depth of field.

• null – No depth of field.

• box – Box shaped depth of field.

• radial – Radial shaped depth of field.

Most of the geometry properties are set using the ray_detail statement, though it is possible to explicitly set the values.

Houdini name	vm_computeN
IFD name	geometry:computeN
Default	("true")

Whether mantra should compute the N attribute automatically. If the N attribute exists, the value will remain unchanged. However, if no N attribute exists, it will be created. This allows polygon geometry which doesn’t have the N attribute already computed to be smooth shaded.

Not supported for per-primitive material assignment (material SOP).

Houdini name	vm_motiontimescale
IFD name	geometry:timescale
Default	(1)

When the -v option is specified on the ray_detail line, this determines the time scale for velocity based motion blur.

Unless specified, each object property may be attached to a primitive by binding a material object to the primitive using the shop_materialpath attribute.

Houdini name	categories
IFD name	object:categories
Default	("")

The space or comma separated list of categories to which this object belongs.

Currently not supported for per-primitive material assignment (material SOP).

Houdini name	vm_renderable
IFD name	object:renderable
Default	("true")

If this option is turned off, then the instance will not be rendered. The object’s properties can still be queried from within VEX, but no geometry will be rendered. This is roughly equivalent to turning the object into a transform space object.

Houdini name	vm_rmbackface
IFD name	object:rmbackface
Default	("false")

Perform backface removal on surfaces.

Houdini name	vm_rendersubd
IFD name	object:rendersubd
Default	("false")

Render polygons as a subdivision surface. The creaseweight attribute is used to perform linear creasing. This attribute may appear on points, vertices or primitives.

Houdini name	vm_renderpoints
IFD name	object:renderpoints
Default	("false")

Render only the points of the geometry. Two attributes control the point primitives if they exist.

orient	A vector which determines the normal of the point geometry. If the attribute doesn’t exist, points are oriented to face the incoming ray (the VEX I variable).
width	Determines the 3D size of the points (defaults to 0.005).

Houdini name	vm_metavolume
IFD name	object:metavolume
Default	("false")

Render metaballs as volumes as opposed to surfaces.

Houdini name	vm_overridedetail
IFD name	object:overridedetail
Default	("false")

When geometry has shaders defined on a per-primitive basis, this parameter will override these shaders and use only the object’s shader. This is useful when performing matte shading on objects.

Not supported for per-primitive material assignment (material SOP).

Houdini name	vm_refractlimit
IFD name	object:refractlimit
Default	(1)

The maximum refraction bounces.

Houdini name	vm_reflecttlimit
IFD name	object:reflectlimit
Default	(1)

The maximum reflection bounces.

Houdini name	vm_rayweight
IFD name	object:rayweight
Default	(0.001)

As rays propagate through the scene, they contribute less and less to the final color of the surface. When the contribution becomes less than the ray weight, no further rays will be sent. This is similar to the renderer:opacitylimit.

Houdini name	reflectmask
IFD name	object:reflectmask
Default	("~*")

Houdini name	reflectcategories
IFD name	object:reflectcategories
Default	("~*")

These parameters determine the set of objects which will be visible in reflection rays.

Houdini name	refractmask
IFD name	object:refractmask
Default	("~*")

Houdini name	refractcategories
IFD name	object:refractcategories
Default	("~*")

These parameters determine the set of objects which will be visible in refraction rays.

Houdini name	lightmask
IFD name	object:lightmask
Default	("~*")

Houdini name	lightcategories
IFD name	object:lightcategories
Default	("~*")

These parameters determine the set of light sources which are used to illuminate the surface.

Houdini name	vm_biasnormal
IFD name	object:biasnormal
Default	("false")

When biases are used in VEX shaders, the bias can either be performed along the ray direction or along the surface normal. If this parameter is turned on, biasing will be along the surface normal (in the correct direction).

Houdini name	vm_gridedgebias
IFD name	object:gridedgebias
Default	(0.01)

When shading grid edges, this bias will move the edge points slightly away from the actual grid edge. This improves bad shadowing artifacts which might be seen where two primitives meet. This is only used when micro-polygon rendering.

Houdini name	vm_displacebound
IFD name	object:displacebound
Default	(0)

The maximum bounds that the displacement shader will move geometry. This is defined in “camera” space. Note, that the absolute value is used to determine the bounds.

Houdini name	vm_redice
IFD name	object:redice
Default	("false")

With extreme displacement, it’s possible to get micro-polygons which are stretched far out of shape. Turning re-dicing on will cause the geometry to be re-diced after the geometry has been displaced. This will result in micro-polygons which have a much more uniform size and will most likely provide higher quality images. This is more costly since the displacement shader may be run multiple times during the projection process.

Houdini name	vm_binarysplit
IFD name	object:binarysplit
Default	("false")

When splitting primitives, this ensures that primitives are split into grids containing a power of 2 micro-polygons. This minimizes patch cracks.

Houdini name	vm_truedisplace
IFD name	object:truedisplace
Default	("true")

When running displacement shaders when micro-polygon rendering, this option will determine whether the VEX variable P is actually moved or whether bump mapping will be performed.

Houdini name	vm_raytruedisplace
IFD name	object:raytruedisplace
Default	("true")

When running displacement shaders when ray-tracing, this option will determine whether the VEX variable P is actually moved or whether bump mapping will be performed.

Houdini name	vm_raypredice
IFD name	object:raypredice
Default	("false")

When ray-tracing, it’s more efficient to pre-dice all the geometry in the scene, rather than caching portions of the geometry and re-generating the geometry on the fly. This is especially true when global illumination is being computed (since there is less coherency among rays). The object:raypredice property will cause this object to generate all the micro-polygons before the render begins. Ray tracing can be significantly faster at the cost of potentially huge memory requirements.

Currently not supported for per-primitive material assignment (material SOP).

Houdini name	vm_perspective
IFD name	object:perspective
Default	("false")

When micro-polygon rendering, motion can either be sampled in screen space or in 3D space. Turning on object:perspective will cause sampling to occur in perspective projected space. This will not match ray-traced motion blur, which is always done in 3D space.

Houdini name	vm_rayshade
IFD name	object:rayshade
Default	("false")

When micro-polygon rendering, shading normally occurs at micro-polygon vertices at the beginning of the frame. To determine the color of a sample, the corner vertices are interpolated. Turning on object:rayshade will cause the ray-tracing shading algorithm to be invoked. This will cause each sample to be shaded independently. This means that the shading cost may be significantly increased. However, each sample will be shaded at the correct time, and location.

Currently not supported for per-primitive material assignment (material SOP).

Houdini name	vm_smoothcolor
IFD name	object:smoothcolor
Default	("true")

When micro-polygon rendering, shading normally occurs at micro-polygon vertices at the beginning of the frame. This option causes the vertex colors to be Gouraud shaded to determine the color for a sample.

When trying to match a background plate exactly, it’s desirable to eliminate any filtering which might occur on the plate. The Gouraud interpolation will cause a softening of the map, and thus, this option should be turned off.

Houdini name	vm_geometrygroup
IFD name	object:geometrygroup
Default	("")

Each object references a geometry object. Houdini geometry allows multiple primitive groups to be defined. If the object:geometrygroup parameter is set to a string, only the primitives which are members of the named group will be rendered by this instance. This allows multiple objects to instance the same geometry, but render different parts.

Not supported for per-primitive material assignment (material SOP).

Houdini name	vm_shadingquality
IFD name	object:shadingquality
Default	(1)

The shading quality for scanline rendering. A higher quality will generate smaller micro-polygons meaning more shading and sampling will occur, but the quality will be higher.

Houdini name	vm_rayshadingquality
IFD name	object:rayshadingquality
Default	(1)

The shading quality when ray-tracing.

Houdini name	vm_coving
IFD name	object:coving
Default	(1)

Whether crack-prevention will be performed.

• 0 – No coving.

• 1 – Only displaced surfaces and sub-division surfaces will be coved.

• 2 – All primitives will be coved.

See the help for the Coving parameter in the Geometry container object.

Houdini name	vm_motionfactor
IFD name	object:motionfactor
Default	(0)

Increasing the motion factor of an object will dynamically adjust the shading quality based on the rate of motion. This can significantly speed up renderings of rapid moving objects. It also affects depth of field and may improve speed of scenes with deep depth of focus.

Houdini name	vm_flatness
IFD name	object:flatness
Default	(0.1)

This property controls the tesselation levels for nearly flat primitives. By increasing the value, more primitives will be considered flat and will be sub-divided less.

Houdini name	vm_pbrdiffusemask
IFD name	object:pbrdiffusemask
Default	(2)

When PBR samples the diffuse illumination for the surface, this determines how the illumination should be computed.

• none – No illumination

• direct – Direct illumination (from light sources) only

• indirect – Both direct and indirect illumination

Houdini name	vm_pbrglossymask
IFD name	object:pbrglossymask
Default	(2)

When PBR samples the glossy illumination for the surface, this determines how the illumination should be computed.

• none – No illumination.

• direct – Direct illumination (from light sources) only.

• indirect – Both direct and indirect illumination.

Houdini name	vm_pbrspecularmask
IFD name	object:pbrspecularmask
Default	(2)

When PBR samples the specular illumination for the surface, this determines how the illumination should be computed.

• none – No illumination

• direct – Direct illumination (from light sources) only

• indirect – Both direct and indirect illumination

Houdini name	vm_volumestepsize
IFD name	object:volumestepsize
Default	(1)

The step size used when rendering volumes. The size is specified in camera space.

Houdini name	vm_hasshadowstep
IFD name	object:useshadowstep
Default	("false")

Enable the use of a separate step size when computing shadows for volumes.

Houdini name	vm_shadowstepsize
IFD name	object:shadowstepsize
Default	(1)

When computing shadows, use this step size instead of the object:volumestepsize property.

Houdini name	vm_volumefilter
IFD name	object:filter
Default	("box")

Some volume primitives (Image3D, Houdini Geometry Volumes) can use a filter during evaluation of volume channels. This specifies the filter.

• point

• box

• gauss

• bartlett

• blackman

• catrom

• hanning

• mitchell

Houdini name	vm_volumefilterwidth
IFD name	object:filterwidth
Default	(1)

This specifies the filter width for the object:filter property. The filter width is specified in number of voxels.

Houdini name	vm_gienable
IFD name	object:gienable
Default	("false")

Enable irradiance cache generation for this object.

Houdini name	vm_gifile
IFD name	object:gifile
Default	("")

The file to store the irradiance cache. If multiple objects specify the same file, the cache file will contain samples from all objects.

Houdini name	vm_gifilemode
IFD name	object:gifilemode
Default	("")

The read-write mode for the file.

• r – Read only.

• w – Write only.

• rw – Read and write.

Houdini name	vm_gisample
IFD name	object:gisample
Default	(256)

The default number of samples used to compute irradiance when the shader doesn’t specify it. In most cases, the shader does specify the value.

Houdini name	vm_gierror
IFD name	object:gierror
Default	(0.1)

The error used to determine whether a new irradiance sample needs to be computed. Smaller values will lead to larger, but more accurate irradiance cache files.

Houdini name	vm_giminspacing
IFD name	object:giminspacing
Default	(1.5)

Houdini name	vm_gimaxspacing
IFD name	object:gimaxspacing
Default	(20)

The minimum and maximum number of pixels between nearby irradiance cache samples.

Houdini name	vm_dorayvariance
IFD name	object:dorayvariance
Default	("true")

When ray-tracing VEX functions are invoked, send out additional rays to perform anti-aliasing of ray-traced effects. This will typically generate higher quality ray-tracing. The sampling is determined by image:minraysamples and image:maxraysamples.

Houdini name	vm_variance
IFD name	object:variance
Default	(0.05)

The variance threshold to send out additional anti-aliasing rays. When near-by samples are very similar, fewer anti-aliasing rays will be sent out. When near-by samples are different, more rays will be sent.

Houdini name	vm_minraysamples
IFD name	object:minraysamples
Default	(1)

The minimum number of ray-tracing samples used in variance anti-aliasing.

Houdini name	vm_maxraysamples
IFD name	object:maxraysamples
Default	(9)

The maximum number of ray-tracing samples used when variance anti-aliasing.

Houdini name	vm_traceblur
IFD name	object:traceblur
Default	("false")

Enable or disable raytrace motion blur for micropolygon rendering and photon map generation. By default, raytrace motion blur is disabled. This setting has no effect on the ray tracing rendering engines.

Houdini name	categories
IFD name	fog:categories
Default	("")

The category membership list for the fog object.

Houdini name	lightmask
IFD name	fog:lightmask
Default	("~*")

A pattern of lights (by name) which are used to illuminate the fog object.

Houdini name	lightcategories
IFD name	fog:lightcategories
Default	("~*")

A pattern of lights (by category) which are used to illuminate the fog object.

Houdini name	categories
IFD name	light:categories
Default	("")

The category membership list for the light object

Houdini name	shadowmask
IFD name	light:shadowmask
Default	("~*")

The pattern of object names which are considered for ray-traced shadows.

Houdini name	shadowcategories
IFD name	light:shadowcategories
Default	("~*")

The pattern of object categories which are considered for ray-traced shadows.

Houdini name	vm_activeradius
IFD name	light:activeradius
Default	(-1)

The active radius of the light source can be used to optimize renders. When illuminating a surface, only surfaces within the active radius will be considered.

Example: Consider a car tunnel with lights every 10 meters. If the light has a sharp falloff, then it’s possible to have thousands of lights and still render in a reasonable amount of time. No shaders will be run (neither the illumination nor the shadow shader).

Houdini name	vm_nondiffuse
IFD name	light:__nondiffuse
Default	("false")

When true, the light will not contribute to diffuse() calls.

Houdini name	vm_nonspecular
IFD name	light:__nonspecular
Default	("false")

When true, the light will not contribute to specular() calls.

Houdini name	vm_nondirect
IFD name	light:__nondirect
Default	("false")

When true, the light is only used on secondary GI bounces.

Houdini name	vm_areashape
IFD name	light:areashape
Default	("")

The shape of an area light.

• point – No area shape

• line – Line light (unit line along x-axis)

• grid – Grid light (unit square in XY plane)

• disk – Circle shaped light (radius 0.5 in XY plane)

• sphere – Sphere shaped light (radius 0.5)

• environment – Sphere shaped light (infinite radius)

Houdini name	vm_areasize
IFD name	light:areasize
Default	(0, 0)

The size of the area light. The sizes are interpreted slightly differently for each shape.

• line – Only the X size is used

• grid – The X & Y size of the grid

• disk – The X & Y radii of the circle

• sphere – The average of the sizes is used as the radius

• environment – Ignored

Houdini name	vm_areasamples
IFD name	light:areasamples
Default	(16)

The number of illumination samples to be used for the light source.

Houdini name	vm_areafullsphere
IFD name	light:areafullsphere
Default	("false")

For the environment light, whether the light source represents the full sphere or the upper hemisphere

Houdini name	vm_areausemap
IFD name	light:areausemap
Default	("false")

Only used for the environment light. This determines whether the the light:areamap parameter will be used.

Houdini name	vm_areamap
IFD name	light:areamap
Default	("")

Only used for the environment light. This specifies an environment map which is used for illuminating the scene. The map may be an HDRI map.

See how to create an environment/reflection map.

Houdini name	vm_pbrsampled
IFD name	light:pbrsampled
Default	("true")

If this is true, the map attached to the environment area light will be analyzed to determine the best sample locations for illumination points. This should be turned on for maps which have very sharp discontinuities in illumination levels. For maps which are fairly uniform in color, the toggle should be turned off. With the toggle turned off, the sphere geometry will be used (which provides less noise for smooth maps).

Houdini name	vm_photontarget
IFD name	light:photontarget
Default	("~*")

When sending photons from this light source, this is the category expression to determine which objects will receive photons.

These properties control the conversion of mantra pixels into the chosen output file format.

Generally these are only useful on render drivers and cameras. Properties such as vm_image_rat_makemipmaps could be applied to light sources and objects to control the generation of mipmaps in shadow and reflection/environment maps, but it’s probably not a good idea.

These Houdini properties will be included in the IFD as plane properties named similarly to the format options described in the output of the iconvert utility, for example TIFF.compression.

Houdini name	vm_image_artist
Default	("username")

The name of the image creator. By default uses the current user’s log in name.

Houdini, TIFF, PNG formats

Houdini name	vm_image_comment
Default	("")

A text comment to include in the output file.

Houdini, OpenEXR, PNG formats

Houdini name	vm_image_hostname
Default	("hostname")

The name of the computer where this image was created.

Houdini format

Houdini name	vm_image_tiff_compression
Default	("LZW")

Type of image compression to use in TIFF files. Possible values are "None", "LZW", "AdobeDeflate", "Deflate", "PackBits", "JPEG", "PixarLog", "SGILog", "SGILog24".

Houdini name	vm_image_tiff_predictor
Default	("auto")

Parameter to TIFF compressor. Leave this set to “auto”. Possible values are "auto", "none", "horizontal".

Houdini name	vm_image_rat_compression
Default	("deflate")

Type of image compression to use in RAT (Houdini texture) files. Possible values are "deflate", "none".

Houdini name

vm_image_rat_makemips

Enable generation of MIP MAPS when creating RAT files

Houdini name	vm_image_jpeg_quality
Default	(75)

JPEG Quality, integer from 10 to 100.

Houdini name	vm_image_cineon_space
Default	("lin")

Color space for Cineon format images. Possible values are "log" (unconverted), and "lin" (linear).

Houdini name	vm_image_cineon_lut
Default	("")

Filename of a Look Up Table file to use for display of Cineon images in MPlay.

Houdini name	vm_image_cineon_whitepoint
Default	(685)

White point for Cineon format images, integer from 0 to 1023.

Houdini name	vm_image_cineon_gamma
Default	(0.6)

White point for Cineon format images, from 0.001 to 4.0.

Houdini name	vm_image_exr_compression
Default	("piz")

Compression type for EXR format images. Possible values are "none", "rle", "zips", "zip", "piz", "pix".

Houdini name	vm_image_exr_storage
Default	("scan")

Storage method for EXR format images. Possible values are "scan" (scanline) and "tile".

Houdini name	vm_image_png_frompremult
Default	("premult")

Whether to pre-multiply PNG format images. Possible values are "premult" or "unpremult".

Houdini name	vm_image_mplay_rendermode
Default	("current")

Controls how MPlay deals with new frames. Possible values are "current" (add rendered frames to MPlay’s current sequence) or "new" (have MPlay start a new sequence).

Houdini name	vm_image_mplay_framemode
Default	("append")

Controls how MPlay inserts new frames into the current sequence. Possible values are "append" (add new frames on to the end of the current sequence), or "match" (replace frames with the same number in the current sequence).

Houdini name	vm_image_mplay_direction
Default	("middle")

How MPlay renders the image. Possible values are "middle" (middle out), "top" (top down), or "bottom" (bottom up).

Houdini name	vm_image_mplay_gamma
Default	(0.0)

Display gamma for MPlay, from 0.0 to 4.0.

Houdini name	vm_image_mplay_lut
Default	("")

Filename of a Look Up Table file for MPlay.

Houdini name	vm_matte
Default	("false")

Replaces any shaders with the default matte shader. This property is not available in IFD, because it works by changing what is written to the IFD file.

These properties exist in IFD scene description files, but do not have equivalents in the Houdini property UI.

Houdini name	mplay:port
IFD name	renderer:houdiniportnum
Default	("0")

When Houdini starts a render, it creates a “port” which allows mplay or other applications to communicate information back. This is the port number that Houdini opened. This setting will be deprecated in the future and be passed as an image device option.