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Synopsis

convertLightmap( shadingGroup object [shadingGroup object ...] , [bakeSetOverride=string], [camera=string], [content=boolean], [exportPathNames=string], [faceNormals=boolean], [file=string], [help=boolean], [illumOnly=boolean], [miStream=boolean], [normalDirection=string], [notUndoable=boolean], [project=string], [rayDirection=string], [separator=string], [shadows=boolean], [vertexMap=boolean])

Note: Strings representing object names and arguments must be separated by commas. This is not depicted in the synopsis.

convertLightmap is undoable, queryable, and editable.

Calculating global illumination is an expensive and time-consuming task that denies its usage in realtime rendering. As long as the lighting conditions in scenes do not change, illumination on objects can be precomputed and stored in appropriate data structures, like texture maps or vertex colors. These can then be applied in realtime applications like hardware rendering and game engines.
The Lightmap Rendering feature allows to prerender surface color or surface lighting (including global illumination) into file textures and per-vertex colors, respectively, on a per object basis. These file textures can then be used as regular texture maps to speed up subsequent software renderings and to apply the precomputed rendering effects even to hardware rendering.
For the purposes of baking and prelighting, mental ray for Maya supports the convertLightmap command.
Any given shading group must be assigned to (some components) of the given object. Any number of shading group - object combinations can be given. The given object should uniquely identify a single instance of a single shape node. If just a transform name or a shape name is given, the command will try to determine the first child shape or instance parent. If a single object should be baked that has multiple materials assigned (per-face assignment on mesh objects, per-instance assignment on multiply instanced shape nodes) then every shading group has to be provided separately referencing the same object. On the other hand, if the same material has been applied to multiple objects (shared materials) then this shading group needs to be given multiple times for all of the objects.
Besides the command flags, per-object settings are set through bakeset of each object. If an object does not have a bakeset, and -bo flag is not specified, default settings for a bakeset will be used. See node reference of TextureBakeSet and VertexBakeSet

LIMITATION:
The lightmap rendering is done with the render quality currently set in the mental ray render globals. Especially, photon tracing and/or final gathering should be enabled to compute global illumination that will be considered during lightmap generation. But certain limitations apply to the current implementation:

  • motion blur may not appear in lightmaps
  • volumes and fog are not recognized in lightmaps
  • the alpha channel is always rendered into file textures

    • Flags

    bakeSetOverride, camera, content, exportPathNames, faceNormals, file, help, illumOnly, miStream, normalDirection, notUndoable, project, rayDirection, separator, shadows, vertexMap
    Long name (short name) [argument types] Properties
    help(h) boolean query
    Prints a verbose help message.

    In query mode, this flag needs a value.
    vertexMap(vm) boolean create
    Bake illumination into vertices. If not present bake into a light map.
    camera(c) string create
    Which camera to use for computing the direction of the incident ray. Default: current render camera
    shadows(sh) boolean create
    Take shadow into account. If shadow is disabled in the mental ray render globals, mental ray for maya will enable the shadow map, and shadow method segments will be turned on.
    content(co) boolean create
    Specify which information to be baked into the lightmap. If "LightAndColor" or "1", the radiance exiting from the surface is stored into the lightmap. If "OnlyLight" or "2", the lightmap contains both the direct and indirect(photons, final gathering) illumination information. If "OnlyGlobalIllumination" or "3", the lightmap contains indirect illumination only. The default is "LightAndColor".
    faceNormals(fn) boolean create
    Use only face normals for baking. Otherwise, vertex normals are used.
    normalDirection(nd) string create
    Determines in which direction the normals of the object to be baked should be pointing. Supported arguments are "toCamera" (towards the camera), "front" (outwards), and "back" (inwards). Default: "toCamera"
    rayDirection(rd) string create
    Choose direction of the incoming ray. This direction is not well defined for baking. Currently one can select either "fromCamera" (incident ray points from the current render camera to the point being shaded) or "normal" (incident ray hits the surface perpendicularly at the point being shaded). The direction of the incident ray makes a difference when computing specular highlights, ray traced reflections, environment maps, and more.
    notUndoable(nun) boolean create
    If this parameter is given, the command can not be undone.
    project(prj) string create
    Set the project directory. If baking to a light map, light maps will be generated into "lightMap" sub directory in the project. If "lightMap" directory does not exist, the command fails to write light maps. Default: current project root directory
    separator(sep) string create
    If this parameter is given, baking will use this string to separate instance and shape name parts when generating unique file names for complex dag objects (dag instances with multiple shapes, or hierarchical dag entries). Default: no separator.
    bakeSetOverride(bo) string create
    If this parameter is given, the specified bakeset will be used instead of bakeset of each object.
    miStream(mi) boolean create
    If this parameter is given, besides the lightmap rendering, the command generates a mental ray file that can be used with mental ray standalone. -f/-file flag must be specified.
    file(f) string create
    Specifies the absolute file name of the mental ray file to be generated. Effective only if -mi/-miStream flag is present.
    exportPathNames(xp) string create
    Export option for the file references such as : ink library, include mi file, texture file, lightmap, etc.
    The string can specifies an for individual file refs, with each character in the string representing a single file ref entry, with meaning
    0-nochange 1-absolute 2-relative 3-nopath, or
    0-nochange a-absolute r-relative n-nopath.
    The file ref entry is specified in this order :
    link library, include mi file, texture file, lightmap, light profile, output image, shadow map, finalgather map, photon map, demand load object mi file. Effective only if -mi/-miStream flag is present.
    Default: nochange
    For example, "-xp aarrararra" will use absolute path for link libray, include file, light profile, shadow map, demapd load object mi file, and relative path for texture file, lightmap, output image, finalgather map, photon map
    illumOnly(io) boolean create
    OBSOLETE
    Flag can appear in Create mode of command Flag can appear in Edit mode of command
    Flag can appear in Query mode of command Flag can have multiple arguments, passed either as a tuple or a list.

    Return value


    string array
    The command returns an array for string values of exactly the same length as bake combinations have been given. The returned string contains the name of the baked object (either texture file name or vertex bake object) upon success, or the string "error" otherwise.

    Related

    Mayatomr