Hi,
I just bought Trestle and Scrim and have been playing around with the combo.
My first animated test has a flicker at each end.
http://www.geocities.com/aziz_cg/TSflicker/tsflicker.mov
I’m using three trestle contruction profiles. There’s a linear wave deform applied to the object. The Scrim mesh is dense enough, I think.
Would appreciate any suggestions on what I’m doing wrong. Thanks.
Judging from your wireframe you’re attempting to animate adaptive geometry. Adaptive geometry modifies itself depending on the amount of curvature in the spline between cross sections. Normally that isn’t a problem… however it can be an issue if you haven’t triangulated your mesh.
So… try this for me:
Activate triangulation.
Make sure your U Topology Mode is set to “By Indicies”.
(Best for identical cross sections)
Since you’re using identical cross sections, there’s really no need for adaptive geometry in the Spline V direction so deactivate it by setting the adaptive angle to -1. Are you using adaptive geometry in the U direction?
Upload some screen shots of your Trestle Cross section and your Scrim settings.
Hi Brian,
Thanks for replying. I did try a test with triangulation activated but the flicker still occured.
Screenshots of my trestle and scrim settings:
I’ll try a render with your suggested settings.
Ah Ha!
Since all your cross sections are identical, switch to a U-Topology mode of “By Indicies” instead of “By Positions”. Secondly, set an adaptive angle for Spline V to -1.
“By Positions” causes scrim to project cross sections with different numbers of CV points onto each other in order to smooth the loft. Since your cross sections are all the same, “By Indicies” is better choice for animated surface geometry. All of your U and V lines will match point by point with each vertex on the cross section.
Finally, since this is a simple uniform loft, there’s no need for adaptive geometry in the Spline V direction. Change the adaptive angle to -1 to turn that function off.
More on adaptive geometry.
The adaptive angle analyzes the amount of curvature betwen cross sections and inserts additional geometry between each uniform step in Spline V. The greater the curve, the more geometry is inserted. The adaptive angle value sets the threshold on how much curve is needed in order to insert geometry. The ends of your loft are affected the most because they are going through the greatest range of motion. Thus geometry is constantly being insert or subtracted depending upon the angle. Uniform geometry wont suffer from this problem and if you’re intending on animating a surface in this matter, additional uniform steps for greater mesh resolution is preferrable than adaptive resolution. Polygons wont be popping on and off.
And Finally… (after reproducing your set up here)… you’re applying a deformation region over your Scrim geometry to obtain the wave right? Well make sure your deformation region extends past the geometry of the scrim object a little, just to make sure your deformation isn’t effecting the ends… just in case.
Here’s a sample:
Hurrah! Everything works well now. Thanks Brian :).
That extra secret ingredient about extending the deformation region helps a lot. Must remember that for future projects.
I did some tests with adaptive geometry and was able to obtain non flickering animation. The flickering you’re experiencing, I’m pretty certain now, is due to the deformation region on the scrim surface being exactly the size of the geometry. My theory of polys popping on and off with adaptive geometry is not the case when applying a deformation region on the resulting scrim surface. Adaptive geometry topology is only modified when the cross sections are animated, not by deforming the resulting scrim surface.
Here is a much lower resolution model using adaptive geometry. No popping polys, and the mesh is stable. The deformation region, however, is slightly extended past the scrim surface.
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