This commit extend the technique of dynamic linked list to the mesh
slots so as to eliminate dumb scan or map lookup. It provides massive
performance improvement in the culling and in the rasterizer when
the majority of objects are static.
Other improvements:
- Compute the opengl matrix only for objects that are visible.
- Simplify hash function for GEN_HasedPtr
- Scan light list instead of general object list to render shadows
- Remove redundant opengl calls to set specularity, shinyness and diffuse
between each mesh slots.
- Cache GPU material to avoid frequent call to GPU_material_from_blender
- Only set once the fixed elements of mesh slot
- Use more inline function
The following table shows the performance increase between 2.48, 1st round
and this round of improvement. The test was done with a scene containing
40000 objects, of which 1000 are in the view frustrum approximately. The
object are simple textured cube to make sure the GPU is not the bottleneck.
As some of the rasterizer processing time has moved under culling, I present
the sum of scenegraph(includes culling)+rasterizer time
Scenegraph+rasterizer(ms) 2.48 1st round 3rd round
All objects static, 323.0 86.0 7.2
all visible, 1000 in
the view frustrum
All objects static, 219.0 49.7 N/A(*)
all invisible.
All objects moving, 323.0 105.6 34.7
all visible, 1000 in
the view frustrum
Scene destruction 40min 40min 4s
(*) : this time is not representative because the frame rate was at 60fps.
In that case, the GPU holds down the GE by frame sync. By design, the
overhead of the rasterizer is 0 when the the objects are invisible.
This table shows a global speed up between 9x and 45x compared to 2.48a
for scenegraph, culling and rasterizer overhead. The speed up goes much
higher when objects are invisible.
An additional 2-4x speed up is possible in the scenegraph by upgrading
the Moto library to use Eigen2 BLAS library instead of C++ classes but
the scenegraph is already so fast that it is not a priority right now.
Next speed up in logic: many things to do there...
Realtime modifiers applied on mesh objects will be supported in
the game engine with the following limitations:
- Only real time modifiers are supported (basically all of them!)
- Virtual modifiers resulting from parenting are not supported:
armature, curve, lattice. You can still use these modifiers
(armature is really not recommended) but in non parent mode.
The BGE has it's own parenting capability for armature.
- Modifiers are computed on the host (using blender modifier
stack).
- Modifiers are statically evaluated: any possible time dependency
in the modifiers is not supported (don't know enough about
modifiers to be more specific).
- Modifiers are reevaluated if the underlying mesh is deformed
due to shape action or armature action. Beware that this is
very CPU intensive; modifiers should really be used for static
objects only.
- Physics is still based on the original mesh: if you have a
mirror modifier, the physic shape will be limited to one half
of the resulting object. Therefore, the modifiers should
preferably be used on graphic objects.
- Scripts have no access to the modified mesh.
- Modifiers that are based on objects interaction (boolean,..)
will not be dependent on the objects position in the GE.
What you see in the 3D view is what you get in the GE regardless
on the object position, velocity, etc.
Besides that, the feature is compatible with all the BGE features
that affect meshes: armature action, shape action, relace mesh,
VideoTexture, add object, dupligroup.
Known problems:
- This feature is a bit hacky: the BGE uses the derived mesh draw
functions to display the object. This drawing method is a
bit slow and is not 100% compatible with the BGE. There may
be some problems in multi-texture mode: the multi-texture
coordinates are not sent to the GPU.
Texface and GLSL on the other hand should be fully supported.
- Culling is still based on the extend of the original mesh.
If you have a modifer that extends the size of the mesh,
the object may disappear while still in the view frustrum.
- Derived mesh is not shared between replicas.
The derived mesh is allocated and computed for each object
with modifiers, regardless if they are static replicas.
- Display list are not created on objects with modifiers.
I should be able to fix the above problems before release.
However, the feature is already useful for game development.
Once you are ready to release the game, you can apply the modifiers
to get back display list support and mesh sharing capability.
MSVC, scons, Cmake, makefile updated.
Enjoy
/benoit
