ICE Interoperability for Maya

This section contains information for Maya users who want to take advantage of ICE using the Softimage interoperability features.

The “Send to” commands let you transfer scene elements from Maya to Softimage, then use ICE to create particle or deformation effects, and finally send the data back to Maya for rendering. You can transfer data back and forth as often as you like as you tweak the results.

 

If you have never run Softimage before you open it from Maya, your interaction model is set to Maya by default. Otherwise, you can change it manually as described in Changing Interaction Preferences [Data Management].

What You Should Select in Maya

You should select the following things in Maya to send to Softimage:

• A user-created camera. This will be the default camera used to view the scene in Softimage.

• Any objects that you want to use to control particle effects in ICE. For example, this includes the emitter objects as well as any collision objects, goal objects, curves to flow along, and so on. Although it is possible to add these in Softimage, in that case they will not be sent back so you will be unable to modify and animate them in Maya.

• Any geometric objects that you want to deform using ICE, plus any objects that you want to use to control the deformation. Again, it is possible to add controllers in Softimage but you will be unable to modify and animate them in Maya.

• If any objects have an animated deformation in Maya, such as a Squash or Twist, you must prepare them before transferring to Softimage. See Preparing Animated Deformations in Maya.

What You Can Expect Back from Softimage

When you send data back from Softimage to Maya, the following are sent:

• An nCache for every point cloud driven by an ICE tree. In Maya, an nParticle object is automatically created and set to read from the nCache.

• A geometry cache for every object sent from Maya that gets deformed by an ICE tree. In Maya, the geometry cache is applied automatically.

• Absolutely nothing else. In particular, the following are not sent back to Maya:

- Any new objects created in Softimage (apart from point clouds). For example, if you want to create a polygon mesh from a particle simulation, you must do the meshing in Maya.

- Any changes to an object’s transformation or animation made in Softimage, or any other modification to an object including new properties such as weight maps and vertex colors. These changes may be lost if objects are re-sent from Maya.

Preparing Animated Deformations in Maya

If any objects have an animated deformation, such as a Squash or Twist, you must prepare them before transferring to Softimage. Although you do not need to do this for Skin deformers, the deformations might not be exactly the same in Softimage if you don’t prepare them.

1. Create a geometry cache for every object with an animated deformation.

2. Add the objects to a set.

3. If you have not sent any data from the current scene to Softimage yet, choose File > Send to Softimage > Preferences to create an ICEFlowAttributes object.

4. In the ICEFlowAttributes’ Extra Attributes, enter the set’s name in Geometry Cache Set for Export.

Remember that you must select the set or the individual objects (or both), as well as any other objects and a camera, to send to Softimage.

Transferring Data Between Maya and Softimage

1. In Maya, set up the scene as desired: objects to emit particles from, objects to deform, other objects to control the effect, and so on.

2. Select the objects to send to Softimage. See What You Should Select in Maya.

3. Choose File > Send to Softimage > Send as New Softimage Scene.

If Softimage is not already running then it starts, or if it is already running then it gets focus and you are prompted to save the current scene as necessary. After that, the objects sent from Maya are imported into a new scene in Softimage. If the Softimage window does not come to the front automatically, then you may need to switch to it manually.

In addition, an ICEFlowAttributes object is created in Maya if it didn’t already exist. The ICEFlowAttributes object stores the settings used in its Extra Attributes. You can see and edit these settings by choosing File > Send to Softimage > Preferences.

A corresponding ICEFlowState property is created on the scene root in Softimage, containing information about the transfer as well as a list of particle attributes to cache and return to Maya. You can see and edit this information by choosing File > Send to Maya > Preferences.

4. In Softimage, set the scene’s start and end frames to the desired values, and then use ICE to create particle and/or deformation effects as described elsewhere in this guide.

5. To send the effect back to Maya, choose File > Send to Maya > Update Current Maya Scene or click Update in the lower left of the Softimage interface. If the Maya window does not come to the front automatically, then you may need to switch to it manually.

 

Note that if the appropriate scene is not already open in Maya, you should first switch to Maya and open it. If you want to open the last Maya scene that was used to send data to the current Softimage scene, you can open the ICEFlowState property editor and click Open Previous Maya Scene.

6. For a particle effect, set the desired Particle Render Type in the nParticle object’s Attribute Editor, and apply the desired material. In the Hypershade view, you can add a particleSamplerInfo node and connect it to drive shader values using particle attributes. Any changes you make to the shading network are preserved even if you re-send data from Softimage.

7. Continue to build and refine the effect until satisfied:

- If you make changes to the sent objects in Maya, for example if you change the animation of the controller objects, choose File > Send to Softimage > Update Current Softimage Scene or click Update in the lower left of the Maya interface. Don’t forget to first regenerate geometry caches if required.

 

- To send additional objects from Maya to Softimage, for example, additional emitters or control objects, select them in Maya and choose File > Send to Softimage > Add to Current Softimage Scene.

- If you no longer need certain control objects, you can manually delete them from both the Maya and Softimage scenes.

- To send the latest results from Softimage to Maya, including the effect of any objects that were changed or added as well as any modifications made in ICE, choose File > Send to Maya > Update Current Maya Scene or click Update in the lower left of the Softimage interface again.

- You can keep multiple versions of the Maya and Softimage scenes as you test different settings by saving the scenes under different names, loading them manually, and updating.

Supported nParticle Attributes

The following tables list the nParticle attributes that can be included in the nCache from Softimage, and the ICE attributes that they correspond to.

Required Attributes

Maya

Softimage

position

PointPosition

id

ID

rgbPP

Color (RGB channels)

opacityPP

Color (Alpha channel)

radiusPP

Size

mass

Mass

count

NbPoints

Optional Attributes

Optional attributes can be set in the ICEFlowState property. Note that ICE attributes must be used in Softimage or they will not be calculated and therefore not cached. See Beware of ICE Optimizations.

Maya

Softimage

velocity

PointVelocity

birthTime (calculated as CurrentTime – Age in Softimage)

Age

lifespanPP

AgeLimit

rotationPP

Orientation

angularVelocityPP

AngularVelocity

Particle Render Type and Shape

Only Points and Spheres are supported in the same way in both Maya and Softimage. If the ICE particles use either of these shapes, the corresponding shape is automatically set as the Particle Render Type in Maya. All other ICE shapes are transferred as points by default.

You can change the Particle Render Type in Maya after updating from Softimage.

Maya nParticles do not support multiple Particle Render Types in the same cloud. If the ICE particle cloud uses multiple shapes, the shape of the first particle is used for all particles in Maya.

If you want to use scene objects as instanced shapes, you need to instance the geometry in Maya after sending the effect back from Softimage.

Notes and Tips

Here are some notes and tips for Maya users working with ICE:

• Objects are sent from Maya to Softimage using the FBX format. Any Maya features that are not supported by FBX, such as Maya subdivision objects, are not transferred.

• Objects in the Maya and Softimage scenes are matched by name. If you change the name of an object in Maya, it will not be included when you update Softimage unless you add it explicitly, and the object with the old name in Softimage will not be automatically updated or deleted. Similarly if you change the name of a point cloud in Softimage, it will be treated as a new nParticle object in Maya and the nParticle object with the old name will not be automatically updated or deleted.

• Particle strands in ICE are not transferred to Maya. nParticles do not support arrays of positions per point.

• If you change the Time working units in Maya, the frame rate in Softimage is automatically updated when you re-send data from Maya.

• If you want to change the start and end frames, you must do so manually in both Maya and Softimage.

• ICE kinematics are not supported for sending to Maya.

 



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