[Bf-committers] Bringing Freestyle back to Blender 2.8

[Tamito KAJIYAMA]

Hi Brecht,

Many thanks for the detailed replies, and excuse me for the delayed reply.

I agree that the first thing to do to keep Freestyle functional in the 
Blender 2.8 code base is the removal of Freestyle's dependency to the 
object/mesh data structures of the Blender Internal.  Freestyle in 
Blender 2.7x and earlier receives a bunch of tris/quads through the 
Render::instancetable (that is, a linked list of ObjectInstanceRen 
data).  Freestyle doesn't really have to care about many details of 
Blender scene data, mesh modifiers, animation, render settings, and so 
on---instead, the ObjectInstanceRen data allow Freestyle to simply deal 
with a final set of polygons resulting from all the rendering related 
details already addressed by the Blender Internal and Cycles.  If there 
is a convenient way to do the same in 2.8, then I expect the dependency 
removal would be straightforward.  Otherwise, the work might be a bit of 
hassle.

As to the material system, Freestyle currently relies on static (not 
node-based) material properties such as diffuse color, specular color, 
and some other props.  In addition, there are a few Freestyle-specific 
static material properties such as line color, line alpha transparency, 
and line priority (plus, line thickness is to be added in the future). 
Freestyle employs static colors as solid line colors no matter how the 
material is lit by various light sources and seen by the camera.  If 
everything is defined by material nodes in 2.8, then a few extra nodes 
specific to Freestyle are necessary.  At the moment Freestyle doesn't do 
anything with material nodes when retrieving material props.  So, again 
everything in nodes might imply a substantial amount of work on the 
Freestyle side.

As far as Eevee gives Freestyle a render buffer to which line components 
are composited, that's fine and I expect very little work there. 
Freestyle performance is far from real time, so I would say Freestyle 
rendering in the viewport is out of scope in short- and mid-term ranges.

Best regards,

-- 
KAJIYAMA, Tamito <rd6t-kjym at asahi-net.or.jp>


On 2017/08/01 9:47, Brecht Van Lommel wrote:
> Hi Tamito,
> 
> Blender internal and its material system have not been removed yet, but
> they are planned to be replaced by Eevee. I don't think anyone has actually
> gone though what that entails in detail, since there is indeed code like
> Freestyle and the texture system that rely on it even when not rendering
> with BI.
> 
> I expect the first thing to keep things functional would be to stop relying
> on the BI object/mesh data structures, and rather get geometry directly
> from the Blender object/mesh data structures. This should be easier now
> than it was when Freestyle was initially implemented, since there are now
> functions like BKE_mesh_new_from_object to get a mesh from any type of
> object. Some of this stuff will likely still evolve some as the dependency
> graph is being worked on.
> 
> Materials I think would all be defined using node graphs, which should
> already work with Freestyle? But for NPR work is needed to get back some
> functionality from Blender Internal. There is no design for that yet as far
> as I know, would be interesting to get some idea which extra nodes Eevee
> needs.
> 
> In terms of integrating with render buffers, I hope the way it works with
> Cycles as an external engine can also work for Eevee. So Eevee could
> deliver render buffers the same way as Cycles and freestyle could composite
> on top of them in the same way. Beyond that it would of course be really
> cool if Freestyle could work in realtime on top of Eevee, showing OpenGL
> accelerated line drawing in the viewport, but I guess that would be almost
> a full rewrite of Freestyle.
> 
> Regards,
> Brecht.
> 
> 
> On Mon, Jul 31, 2017 at 4:26 PM, Tamito KAJIYAMA <rd6t-kjym at asahi-net.or.jp>
> wrote:
> 
>> Hi,
>>
>> I would like to discuss with the viewport team what precisely would be
>> necessary to bring Freestyle back to Blender 2.8.  I was informed that
>> the old material system and the Blender Internal renderer have been
>> removed so that Freestyle won't work anymore.  The idea is to have a
>> development plan of what needs to be done and until when.  Thoughts and
>> suggestions are much welcome.  Thanks in advance for the input.
>>
>> Best regards,
>>
>> --
>> KAJIYAMA, Tamito <rd6t-kjym at asahi-net.or.jp>
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