PolyTrans-for-Maya - What Entities Does It Convert?

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		Which entities are imported into Maya? Click here.
		Which entities are exported from Maya? Click here.

Entities Imported from PolyTrans into Maya

This section describes which Maya entities are exported to the PolyTrans converters.

Polygon Mesh Geometry

N-sided polygon meshes and thier related geometry will be exported from Maya, along with these mesh attributes:

	Vertex normals.
	Vertex (u,v) texture coordinates
	Vertex colors
	Mesh skinning weights using the 'smooth skinning deformer' (in addition to the associated skeleton of bones/joints)
	'Casts Shadows' flag ('castsShadows' plug of a shapeNode)
	'Hidden' flag ('visibility' plug of a shapeNode)
	Materials, assigned either to the mesh node itself or to individual polygons.

In addition, the exporter will remove any redundant vertex normals, texture coordinates and vertex colors to create a more refined database in PolyTrans.

NURBS Geometry

Trimmed NURBS are output in their natural, umodified form. Alternatively, an export option can be enabled so that all NURBS surfaces become polygonalized.

Cameras

Perspective and orthographic cameras are exported with the following parameters:

Exported Maya Camera Parameters

Look-From location

Look-At location

Look-Up location

Field of view for perspective cameras. Most importantly, the Maya 'filmFit' is taken into account (types: horizontal, vertical, overscan and fill) so that the field of view in the destination animation package encompasses the same field of view as seen in Maya. The frame type in PolyTrans is set to TYPE4.

For orthographics cameras, the PolyTrans window width and height are set equal to the Maya ortho camera window width.

Clipping planes (near and far) from Maya.

Lights

The following light types and light parameters are converted:

Exported Maya Light Parameters

Point light

Directional light

Spot light

Ambient light

Transformation matrix decomposed into shine-from, shine-at locations, or shine-direction in the case of directional lights.

Color

Visibility plug of node

Intensity

Spot light cone angle

Spot light penumbra angle

Spot light drop off angle

'Use ray traced shadows'

'Use depth map shadows', including depth map bias and depth map resolution.

Materials

The following table describes how the Maya material parameters are mapped to equivalent material parameters in PolyTrans:

Exported Maya Material Parameters

As PolyTrans/NuGraf has a rich set of shader parameters itself, these parameters are extracted from these supported Maya shaders: Phong, PhongE, Blinn, Lambert and Anisotropic. Layered shaders are not handled.

Diffuse surface color.

Diffuse shading coefficient

Specular color.

Incadesence color.

The diffuse, specular and incadesence are 're-normalized' so that the largest red, green or blue component is 1.0 (full on); the re-normalizing coefficient is then used as the corresponding PolyTrans diffuse, specular or incadescent shading coefficient. When the shading coefficient and the new color is multiplied together, it results in the original Maya material color.

Phong shininess from Maya roughness or Phong cosine power.

Transparency (inverse of transparency will be assigned to the PolyTrans face and reflected opacity values).

Index of refraction (IOR).

Reflect shader 'reflectivity' (mapped to PolyTrans specular coefficient).

Texture Maps

The following are the various Maya texture modulation methods exported to PolyTrans:

Exported Maya Texture Maps

Ambient color map

Diffuse color map

Specular color map

Incadescense color map

Transparency map

Opacity map (if the 'invert' flag is enabled on the transparency texture node)

Ray traced reflectivity map

Bump map. The bump map strength is divided by 4 (arbitrary) before output.

Diffuse shading coefficient texture map.

Spherical environment map with texture u,v offset and scaling.

Alpha channel modulation is enabled for the ambient, diffuse, specular and incadescense texture maps if this option is enabled on the 'PolyTrans -> Maya' export converter options dialog box.

Only a unique number of Okino 'texture layers' will be created by way of comparing texture map filenames and related sub-parameters.

If the diffuse color texture map was output, but not the ambient color texture map, then the ambient color will be locked to the diffuse color within the PolyTrans material shading system (this makes textured objects look better inside Okino's NuGraf rendering software).

As for the texture definition itself, the following 2d bitmap texture parameters are supported:

Exported Maya Texture Parameters

u & v scaling

u & offset (relative to upper left of texture map).

u & v wrap-around flags

Animation Conversion

Animation conversion is one of the hardest tasks to complete in a converter. This is because most 3d software packages use completly different animation mathematical foundations to represent their data. For example, 3DS MAX uses quaternions (angular math on the surface of a sphere) to represent rotations, whereas Maya and Lightwave use Euler angles (three X, Y and Z explicit rotations). PolyTrans overcomes all of these incompatibilities via keyframe resampling and reduction.

The following are the animation channels are converted from Maya into the PolyTrans raw animation database format:

Exported Maya Object Animation Channels

Scale as explicit X,Y, Z animation channels

Euler rotations as explicit X,Y, Z animation channels.

Translation as explicit X,Y, Z animation channels

Object pivot points

Exported Maya Camera Animation Channels

Translation as explicit X,Y, Z animation channels

Camera look-at as explicit X,Y, Z animation channels

Field-of-view animation channel.

Entities Imported from PolyTrans into Maya

This section describes which PolyTrans database entities are imported into the Maya database:

Polygon Geometry

All PolyTrans geometry, including n-sided polygon meshes with recursive holes, trimmed NURBS surfaces (see next section), bicubic patches and quadric surface will all be imported into Maya as polygons meshes. In addition, object hierarchy will be imported and recreated. If any polygon has a hole in it then the mesh will be triangulated (this is unlikely when importing from most 3D file formats).

The following PolyTrans object attributes will be imported along with the mesh geometry:

	Vertex normals.
	Vertex (u,v) texture coordinates
	Vertex colors
	Mesh skinning weights (in addition to the associated skeleton of bones/joints)
	'Casts Shadows' flag ('castsShadows' plug of a shapeNode)
	'Hidden' flag ('visibility' plug of a shapeNode)
	Materials, assigned either to the transform node or to each group of polygons within a shapeNode.

And these are the currently unsupported PolyTrans geometric attributes:

U/V tangent vectors are not imported. There is no equivalent in Maya.

In addition, the import converter allows the following geometric processing functions to be applied to the imported mesh geometry:

	Flip orientation of all normals.
	Unify the orientation of all polygons and normals.
	Weld all vertex coordinates and vertex normals together using a specified tolerance.

NURBS Geometry

Trimmed NURBS surfaces with uv-space trim curves are imported into Maya either as equivalent trimmed NURBS or as meshed geometry.

Cameras

Perspective cameras are imported with the following parameters:

Imported Maya Camera Parameters

Look-From location

Look-At location

Look-Up location

Field of view

Manual clipping override set to TRUE

PolyTrans automatically selects tight clipping planes

'filmFit' set to horizontal or vertical, depending on TYPE4 or TYPE5 camera frame types in PolyTrans

Camera background color set to the PolyTrans global background color.

Lights

The following light types and light parameters are converted:

Imported Maya Light Parameters

Point light

Directional light

Spot light

Transformation matrix. The directional light is moved to the outer limits of the world space extents.

Color

Visibility plug of node

Intensity

Spot light cone angle

Spot light penumbra angle

Spot light drop off angle

'Use ray traced shadows'

'Use depth map shadows'

Maya's 'ambient' light source is not used by the Polytrans imported. This is because its ambient color output cannot be attenuated by a shader, such as can be done my many other 3d programs. Instead, the PolyTrans global ambient color is multiplied into each new shader's local ambient color.

Materials

The following table describes how the PolyTrans material parameters are mapped to equivalent material parameters in Maya:

Imported Maya Material Parameters

Lambert ambient color is computed as the Polytrans ambient shader color * ambient shader coefficient * global ambient color.

Lambert diffuse color derived from PolyTrans diffuse color directly.

Lambert diffuse coefficient derived from PolyTrans diffuse coefficient directly.

Depending on PolyTrans 'lock specular' flag, reflect shader's specular color is either the PolyTrans specular color multiplied by the specular shading coefficient, or it is the diffuse color multiplied by the specular shading coefficient.

Lambert incadesence color derived from PolyTrans luminous color multiplied by the luminous shading coefficient.

Phong cosine power taken by PolyTrans shininess parameter.

Lambert transparency is 1.0 minus PolyTrans face opacity.

Lambert refractive index taken from PolyTrans IOR

Reflect shader 'reflectivity' taken from PolyTrans reflect shading coefficient.

Texture Maps

The following are the various PolyTrans texture modulation methods imported to Maya

Imported Maya Texture Maps

Ambient color map

Diffuse color map

Specular color map

Incadescense color map

Transparency map

Opacity map

Bump map

Spherical environment map (envSphere), plus rotation angles

As for the texture definition itself, the following 2d bitmap texture parameters are supported:

Imported Maya Texture Parameters

u & v scaling

u & offset (relative to upper left of texture map).

u & v wrap-around flags

When importing a scene which uses 2d bitmap images of a format not understoof by Maya, automatic bitmap conversion can be enabled during import to change these bitmaps into any one of the following supported Maya bitmap file formats:

Supported Maya Bitmap Formats for Automatic Bitmap Conversion

IFF & PIX, BMP, GIF, JPEG, SGI RGB, Softimage PIC, Targa, TIFF and all respective 2D image file formats shown here.

Animation Conversion

Animation conversion is one of the hardest tasks to complete in a converter. This is because most 3d software packages use completly different animation mathematical foundations to represent their data. For example, 3DS MAX uses quaternions (angular math on the surface of a sphere) to represent rotations, whereas Maya and Lightwave use Euler angles (three X, Y and Z explicit rotations). PolyTrans overcomes all of these incompatibilities via keyframe resampling and reduction.

The following are the animation channels converted from other software packages into Maya, via the PolyTrans core animation conversion engine.

Imported Maya Object Animation Channels

Scale as explicit X,Y, Z animation channels

Euler rotations as explicit X,Y, Z animation channels. Proper conversion from angle/axis and quaternion rotations are made to Euler angles via keyframe resampling and reduction.

Translation as explicit X,Y, Z animation channels

Object pivot points

Imported Maya Camera Animation Channels

Translation as explicit X,Y, Z animation channels

Orientation as explicit X,Y, Z Euler rotation animation channels. Proper conversion from angle/axis, quaternion rotations and look-from/look-at/look-up camera notation are made to Euler angles via keyframe resampling and reduction.

Focal length animation channel. Maya animates the focal length while other programs animate the field-of-view. A special resampler was written to convert field-of-view into the inverse focal length animation.