Arc interpolated Shape

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I tried to rebuild the awesome arc interpolated shaped tool that Ahmidou Lyazidi did in Softimage a long time ago. This is very useful to remove the linear motion of face shapes without a complex rig setup.

I just need to find a more elegant way to display the vectors, as well as isolating all the shape points from the static ones to group them.

Please have a look and let me know how I can improve this.

Here is the old video by Ahmidou
https://vimeo.com/groups/ice/videos/8637260 [vimeo.com]

Attachments:
Arc_Interpolate_101_wz.zip (21.2 KB)
Arc_Interpolate_Shape.jpg (164.8 KB)

Werner Ziemerink
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Little update…Now the height of the vector is driven by the distance the points travel. Much better.

Attachments:
Arc_Interpolate_102_wz.hipnc (139.7 KB)
Arc_shape_102.png (140.3 KB)

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Testing on a mesh…

Attachments:
arc_interpolated_shape.gif (10.9 MB)

Werner Ziemerink
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Is there any way to display Visualisation lines like in Softimage?
Basically it works like markers to show path deformation in this case.

Attachments:
Display_Lines.jpg (43.9 KB)

Werner Ziemerink
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Not a “visualization” per se but have you tried the Trail SOP ?
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There are a few ways to create guides in the viewport.

First I took your file and as Edward suggested, implemented the Trail SOP along with the Timeshift SOP both set to $RFEND which returns the last (relative) frame in the current player. Much more robust that resorting to POPs and far fewer SOPs.


You need to decide where this tool will be used at object level or in SOPs.

If in SOPs, you can set the template flag on the SOP with your guides. This will show the guides as template geometry. Note that display of template flags is only within the geometry SOP context view and not at the Object level.


If this tool is meant to be used by animators at the Object level, it is easy to create a Null Object with an Object Merge SOP that pulls your guides out of the main object with the geometry you wish to view. Object Merge pointing at that SOP and set to Transform to this object. Then set your Null to be non-selectable and then control the display through it's display flag.



This tool is begging to be turned in to an HDA (Houdini Digital Asset). Again you have to decide if the asset is used at the Object Level or the SOP level.

With Digital Assets, there is an option to specify an Object or SOP as a template guide in the Nodes tab of the Edit Operator Type Properties dialog. This is the best way to show templates in the viewport.

With SOP HDA's, the templates are only visible in the geometry SOP context and only if that HDA is selected. Even setting the template flag won't work as this doesn't display a SOPs guides.

If it is an object level HDA, then you see the guides at the Object level all the time when that object is on for display. Just do what I mentioned above about a Null Object fetching your guides and set that as your Guide target in the HDA Operator Type Properties dialog. If you want guides off, you need to add a switch to a Null SOP and raise a toggle to the top level of the asset.

See your attached file modified with the trail SOP approach, and with a SOP asset version of your tool with the Guide Geometry set to the path in the Operator Type Properties.

Attachments:
arc_interpolate_102_wz_143-2_jw.hipnc (214.0 KB)

There's at least one school like the old school!
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Hi,

I have experimented with your example. I remembered there was also a spherical Interpolation method “slerp”, which interpolates two points, which have the same length, on an arc through both points with center 0.
So I've modified your example a little bit, where you can now use the slerp-method as well, but it is very experimental. If interested, you can check out the method. In slerp mode the Offset will be the center of the sphere and the ramp can be used to add radial distance along the angle.

Attachments:
Arc_Interpolate_101_wz_mod.hipnc (176.5 KB)

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Thanks Jeff and Aizatulin. I appreciate your time.

Jeff - I would use this tool at the SOP level as it would mostly be used during the character setup stage. Animators would almost never touch the inner workings.
This has saved me a couple of times in Softimage if we needed quick and nasty facial shapes but wanted a little more control (fake skin sliding over muscles of cheeks or eyelids).

I've created a Digital Asset, but have other problems getting it to work with my limited knowledge of Houdini. I need to be able to ad more than one ‘shape’ at a time, and manual setting up of groups to isolate behaviour is not the way to go. I need a way to get point groups out of the edit and sculpt SOPs (with Soft radius points included) to make it easier to use.
I used subtraction of point positions in VOPs to isolate only points that gets affected by the new shape, but it becomes messy when new shapes are added later.

When working with shapes in Softimage, the edited points gets put in a cluster(group) by default, and makes it easy to pull into ICE and add them together. This would be very handy as an option in Houdini. Maybe I'm missing something here. Any help would be welcome.

Another question…is it possible to have more than 4 inputs on an AttribVop node?

Aizatulin - I will have a look at your example and give feedback asap. Thanks for taking the time.
Werner Ziemerink
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Great stuff Werner
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