[Bf-python] OpenGL drawing for render engines

[Dalai Felinto]

Hi Matt,

I ran into a similar situation and struggled a little to make my peace with
the POST_VIEW callback. Campbell told me that it was still quite
experimental so I got it working for my project (with a modal operator to
be re-activated from time to time) and let it go of it. Would love to see a
reliable way of using it though.

> I'd also suggest that a good way to implement this would be as a custom
object drawing callback

I used it to draw a background plate, so in my case I don't know if a
per-object solution would help. I would prefer an option to have a callback
in the 3dview editor. If I have 100 3dview editors opened so be it, the
code will run 100x. Though one thing doesn't exclude the other, and having
either one I think both results (what I need and what you want) can be
achieved).

--
Dalai

for the records, this is my use of it (see the edit.py) :
http://www.dalaifelinto.com/ftp/impa/ibltoolkit.zip

2012/6/26 Matt Ebb <matt at mke3.net>

> Hi,
>
> I'm looking to do some custom drawing in the 3D View as part of a
> render API plugin. In this particular case, it's to visualise lights,
> for example spot light cone angles/sizes/etc.
>
> Working around this, trying to force the render engine's lights to
> mimic blender's existing light properties is not adequate for several
> reasons, the most significant being that what's built in to blender
> doesn't encompass the range of functionality provided by other
> renderers, such as orthographic shadow maps on distant lights. It
> would be great to be able to draw this info into the 3D View myself,
> depending on the custom engine-specific data attached to the object.
>
> I've done some testing, and using the region POST_VIEW callback, I can
> successfully draw custom OpenGL, looping over all lights in bpy.data
> but the problem is the user experience around it, especially in the
> case of a render plugin, is not good. I've tried a few things and as
> far as I can tell, this is only really possible as part of an
> operator, that must be manually run. On top of this, it's only valid
> for a certain area/region, which means if a user adds a new 3D View,
> the operator must be run again.
>
> If anyone has any hacks/ideas for how this can be worked around or
> improved, I'd love to hear. While I'd be happy with something that
> just works for my use case, I'd also suggest that a good way to
> implement this would be as a custom object drawing callback
> (disclaimer: I have no idea how easy this would be to create).
>
> It's quite commonplace in other applications to allow plugins to do
> custom openGL drawing per object - in many pipelines this is used to
> represent custom object/geometry types that the host application
> doesn't natively support, or to display a representation of geometry
> that will be loaded or generated at render time, without having to
> load that geometry into the host application's scene database. It'd
> also be useful for render engines of course! Something like this would
> probably be a better longer term solution.
>
> Anyway, any thoughts/ideas/hacks welcome!
>
> thanks,
>
> Matt
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