Add implicit instancing support to AlembicAssembly

[Narann]

As its name states, this commit add implicit instancing in AlembicAssembly using IObject::getPropertyHash() on poly mesh.

The weird part of the code review will be that a tiny refacto appear: I created a do_extract_polymesh() method that put the content of the Alembic IPolyMesh into the appleseed MeshObject. This obfuscate the diff but it make the whole logic easier to read.

[Narann]

I also think I should provide some test scene but I have no idea where I should put them. sandbox/samples/cpp/alembicassembly looks weird to me.

[dictoon]

I also think I should provide some test scene but I have no idea where I should put them. sandbox/samples/cpp/alembicassembly looks weird to me.

A testscenes/ subdirectory in sandbox/samples/cpp/alembicassembly/ sounds perfectly acceptable to me.

[Narann]

Thanks, I try to use relative paths in the appleseed XML file:

<parameter name="file_path" value="alembics/xform_ogawa.abc" />

This path is relative to the scene but I suspect I have to resolve it as I'm in bin/Ship when I run appleseed.studio.

Any hint, in the code, where a similar problem is solved?

[Narann]

2019-02-22T20:08:03.968452Z <003>   165 MB info    | time_offset: 0.000000
2019-02-22T20:08:03.968452Z <003>   165 MB info    | verbose: true
2019-02-22T20:08:03.969460Z <003>   167 MB warning | invalid archive: alembics/xform_ogawa.abc
2019-02-22T20:08:03.973803Z <001>   167 MB info    | rendering finished in 0 ms.

It's my code logging this: https://github.com/Narann/appleseed/blob/master/sandbox/samples/cpp/alembicassembly/alembicassembly.cpp#L450

So I need to "interpret" a relative file path. Once again, I'm sure you guys already had to deal with that.

[Narann]

Reading other scenes, it looks like .obj are always passed relative to the .appleseed scene:

                <object name="Sphere" model="mesh_object">
                    <parameter name="filename" value="meshes/Sphere.obj" />
                </object>

But the obj parser doesn't seems to do anything to convert to absolute path:

appleseed/src/appleseed/foundation/mesh/objmeshfilereader.cpp

Line 574 in 9c6daf3

if (!impl.m_lexer.open(m_filename))

appleseed/src/appleseed/foundation/mesh/objmeshfilelexer.h

Line 78 in 96c4992

bool open(const std::string& filename)

So I suspect the working directory used when rendering test scenes must be the place where scenes are.
Am I good ?

[dictoon]

So I suspect the working directory used when rendering test scenes must be the place where scenes are.

That's correct: relative paths aren't relative to the project's directory, they're relative to the current directory. You could add . as a search path: relative assets would then be resolved with respect to the project's directory, regardless of the current directory.