Alain Martel <kua### [at] videotronca> wrote:
> Le 2020-02-03 à 10:30, Francescodario Cuzzocrea a écrit :
> >
> >
> >
> > Hello !!
> >
> > I'm a Master student in Space Engineering in Politecnico di Milano.
> >
> > I'm using POVRay for my master thesis project and I was really impressed by
> > POVRay rendering capabilities.
> >
> > Specifically, I'm using POVRay to generate images of a spacecraft in random
> > position into a generic orbit, which subsequently I'll analyze with different
> > computer vision algorithms to try to recognize the spacecraft into the scene.
> >
> > The spacecraft has first been modeled with Autodesk Inventor, then it has been
> > imported into Blender to exploit the POVRay addon for Blender capability to
> > generate directly generate POV code.
> >
> > The POV blender code was then manipulated in order to obtain a .inc file
> > containing the "spececraft" object, which is assembled by the "merge"
> > (https://gitlab.com/bosconovic/spacacecraft-pov/blob/master/satellite.inc#L158)
> > of the different spacecraft mesh2 components.
> > I did the merge in order to be able to simply call the "spacecraft" object in my
> > pov
> > file and place it into the scene, with the ability to rotate and translate it by
> > simply manipulating the object's attitude\position matrix (which is randomly
> > generated) :
> > https://gitlab.com/bosconovic/spacacecraft-pov/blob/master/tango_102.pov#L24 .
> >
> > The issue is that, sometimes, for certain combination of spacecraft\camera
> > relative position the spacecraft it is not entirely rendered, and I cannot
> > understand why.
> >
> > Here two pictures of the problem :
> >   - https://gitlab.com/bosconovic/spacacecraft-pov/blob/master/tango_102.png
> >   - https://gitlab.com/bosconovic/spacacecraft-pov/blob/master/tango_30.png
> >
> > In the first one almost half of the spacecraft is cutted, in the second on the
> > left a piece of the solar panel is cutted.
> >
> > Can anyone help me out to understand what I'm doing wrong ?
> > Here is the POV source I'm using along with the Blender model :
> > https://gitlab.com/bosconovic/spacacecraft-pov
> >
> > This is the command I use to generate the images : povray tango_102.pov +H1200
> > +W1920
> >
> >
> >
> >
> If you had used an orthographic camera, that would be expected for any
> part that are behind the camera, but your sample files are using the
> default perspective camera.
>
> Using an union instead of a merge is more effecient and render faster.
> The merge is intended for transparent compound objects where internal
> surfaces should not be visible.
>
> In your case
> #declare Space_Craft = merge{...}
> and
> #declare Space_Craft = union{...}
>
> Will give you the exact same end result, but the second will render faster.


Hi Alain, and thanks for your reply !
Thank for the union tip ! I was using union with split_union off before
(otherwhise the object was splitted up in unpredictable way when
rotated/translated), then I discovered merge and decided to go for it as it
seemed more appropriate, but effectively using union rendering times are a bit
faster :)

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