Darter
01-19-2008, 07:51 AM
Here's an updated version of the Theo Jansen mechanism scene posted earlier in the main forum.
It's probably of more interest from an XPresso/COFFEE perspective than of practical use, so I'll share my discoveries here.
The previous version was still a work-in-progress and as such was a bit flaky.
When undoing a viewport position change, the geometry would not immediately refresh in the viewport. This was caused by the Condition nodes responsible for matching objects and points with their positions. The reference objects had been placed in the AM input fields of the nodes. The solution was to connect Object nodes to the Condition node inputs instead. (Works with either Link or Object Data Type).
When using an Align To Spline tag with non-uniform paths, the animation speed of the mechanism was incorrect. This was due to an error in the COFFEE SDK, which says "Use UniformToNatural() if you want to get a uniform distribution" and later gives the correct usage. Had I paid attention to the function name, common sense would have prevented this error.
Finally, the addition of controls to slow down the mechanism revealed jerkiness at certain points in the cycle. This was remedied by offsetting the output crank angle so that it didn't cross the 0 degree threshold.
Included in the updated scene is a control null which can be dragged freely in the viewport. The mechanism object will target and follow the null as if being dragged around. User Data are on the XPresso tag. The owner of the tag is automatically set as the control object and the follower object is set via the tag's link field.
It's probably of more interest from an XPresso/COFFEE perspective than of practical use, so I'll share my discoveries here.
The previous version was still a work-in-progress and as such was a bit flaky.
When undoing a viewport position change, the geometry would not immediately refresh in the viewport. This was caused by the Condition nodes responsible for matching objects and points with their positions. The reference objects had been placed in the AM input fields of the nodes. The solution was to connect Object nodes to the Condition node inputs instead. (Works with either Link or Object Data Type).
When using an Align To Spline tag with non-uniform paths, the animation speed of the mechanism was incorrect. This was due to an error in the COFFEE SDK, which says "Use UniformToNatural() if you want to get a uniform distribution" and later gives the correct usage. Had I paid attention to the function name, common sense would have prevented this error.
Finally, the addition of controls to slow down the mechanism revealed jerkiness at certain points in the cycle. This was remedied by offsetting the output crank angle so that it didn't cross the 0 degree threshold.
Included in the updated scene is a control null which can be dragged freely in the viewport. The mechanism object will target and follow the null as if being dragged around. User Data are on the XPresso tag. The owner of the tag is automatically set as the control object and the follower object is set via the tag's link field.