I have been fighting with Blender on one particular point.
I am trying to animate the motion a deflection of a flexible object. I have started by creating a lattice around the object and using the actions sliders to create various kinds of deformation and motion. For instance I have one slider to squash the object and another to make it go up and down. THe idea is to make the object look like soft rubber which is bouncing up and down. This all works great up to a particular point.
If I try to make a slider so that the lattice rotates (so that the bouncing object can flip over whilst in the air) the rotating lattice causes the object to rotate and shrink! This is especialy so at about 90 degrees of rotation where the object shrinks to almost nothing. By 180 degrees it is back to its original size.
I have come across similar problems in the past in structural analysis packages. Rotation is not realy animated only the cartesian deflection. This means that when the deflection is ‘amplified’ the graphics engine simply extrapolates the motion linearly instead of displaying a greater angle.
If I rotate the object itself (animate rigid body motion without the rubbery deflections) it works fine but then the lattice no longer matches the position of the object.
Can I use the lattice method or must I modify the vertex positions manualy for each individual frame?
Select the lattice object. In the Editing buttons, set the interpolation mode to Linear (i.e. select the three Lin buttons). This should make the rotation work as you expect. However, it may make your other deformations behave strangely.
Is there a reason you can’t parent the lattice to the object so you can animate the rotation of the object and have the lattice follow?
thanks guys, the parenting tip was bang on. I am kicking myself that such a simple solution didn’t occur to me. It is probably my structural analysis background wich ‘prevented’ me from useíng a circular reference.
Blender does recognise that the object and lattice have a circular reference but it still gets on and does the job anyway!
However, it is a bit peculiar now that the state of the object in the 3D editing window now ‘lags’ behind the time frame during editing. I have to jiggle the frame back and forth a few times until the object catches up to the IPO curve and the lattice deformation. THis is probably because blender needs to iterate a few times around the circular refernce until everything has more or less converged. Its not a big problem but it does make manual fine positioning a bit tedious.