Trying to render some animations with OpenSCAD 2016.04.06.

For roundtravel of view I use:

$vpr = [70, 0, $t*360];

but this produces some unwanted height changes in outputted frame sequence.
This is the effect: https://www.youtube.com/watch?v=NA3Zcl2nfVA

This is the frames and their sizes:
http://forum.openscad.org/file/n17657/Ani.png

Any idea? Is this a known bug?

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Rudolf,

I think everything works right if you set $vpt = [0,0,h] for any h. If you
don't set $vpt, the z movement depends on the initial $vpt value which may
be changed by interaction. I understand that $vpt is the center of the
rotation set by $vpr.

Ronaldo

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I traced it down. Was somehow homemade. I had a typo when naming colors and
ignored the warnings issued.

This reproduces it. Use >1 timesteps ;-)

if ($t<0.5) color("golden") cube([10, 20, 10]);

You can see in the status line, how the size is jumping.

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So it's actually any warning being issued. This IS a bug!

cube([1,1,1]);
if ($t<0.5)
max(x);

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As I wrote: any warning issued during animation will change the size of the
frame - by 30 pixels.

max() is a built-in function and should be known. But x is unknown and this
issues a warning.

First I thought it was the $vpr. Found the simple but nasty reason now:
Stacked upon the output window there is a panel shown, that indicates the
warning - and thus alters the frame height.

So its more a feature then a bug. But it should be switched off during
animations.

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You are both perfectly right. I used just something unknown to generate a
warning.

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