[Bf-committers] Blender success story, a couple of potential bugs and a feature request.

[Jonathan Merritt]

Forgot to mention...

I'm using the current CVS version of Blender, running on a customized 
Intel Linux system, but with very recent versions (< 3 months since last 
update from source) of all of the dependencies.

> Hi Everyone,
>
> I recently put Blender to use on an animation that was shown at 
> Equitana, which is a big commercial horse show that was held here in 
> Melbourne over the last weekend.  I gave Blender a big plug, pointing 
> out that the animation would not have been possible without the 
> efforts of Free Software programmers all over the world.  Here's a 
> single frame:
>    http://www.warpax.com/temp/forelimb-frame.png
> The animation showed a moving horse limb (animated with real 
> kinematics data that I pulled out of a refereed publication), and 
> illustrated the function of one of the ligaments of the limb in 
> storing elastic energy.  I'm reluctant to post the full animation at 
> this stage, since there are a few things that need to be fixed, and 
> among them are the bugs listed below.
>
> The limb is an animated armature (animated by rotation and location 
> keyframes, not by an IK solver).  It has a basic animation that is set 
> to repeat by having a cyclic extend mode.  In order to control the 
> speed of the animation, the armature object has a Time IPO curve, 
> whose slope varies through the animation to slow the limb down for a 
> while before moving it back up to full speed.
>
> I discovered that the rendering of objects parented by the "Use 
> Armature" method seems to have a bug after the first frame, when 
> motion blur is used.  The following is an example:
>    http://www.warpax.com/temp/forelimb-ghost.png
> Here, the ligament at the back of the bones is rendered in entirely 
> the wrong place for just *one* of the motion blur frames (the others 
> may be out of place as well, but I can't tell).  Note that this bug 
> *does not* show up in the *first* rendered frame, only in subsequent 
> frames, and does not appear in Blender itself when an animation is 
> played using Alt-AKEY.  Hence, you can't observe the bug by rendering 
> a single frame - it will only appear in the second frame of a rendered 
> animation.
>
> Also, the amount of blur applied to the animation does not seem to 
> respect the relative progression of time indicated by the Time IPO 
> curve.  Hence, even when I slowed the Time IPO curve to a complete 
> halt (ie: horizontal line in the IPO window), the rendered objects 
> were still being motion-blurred.  Is this the desired behaviour?
>
> Finally, an option to render a flat mirror reflection map (as opposed 
> to a cube-face environment map) would be really wonderful.  In this 
> instance, with a heavily set-up scene, I was able to reflect things 
> manually only by painstakingly selecting everything except the bone 
> mesh objects and reflecting them in the ground plane.  This was quite 
> a hassle, considering the simplicity of the effect from a technical 
> point of view.
>
> Jonathan Merritt.
> PhD Student in Equine Biomechanics,
> Faculty of Veterinary Science,
> The University of Melbourne.
>
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