A new type of "Sensor" physics object is available in the GE for advanced
collision management. It's called Sensor for its similarities with the
physics objects that underlie the Near and Radar sensors.
Like the Near and Radar object it is:
- static and ghost
- invisible by default
- always active to ensure correct collision detection
- capable of detecting both static and dynamic objects
- ignoring collision with their parent
- capable of broadphase filtering based on:
* Actor option: the collisioning object must have the Actor flag set to be detected
* property/material: as specified in the collision sensors attached to it
Broadphase filtering is important for performance reason: the collision points
will be computed only for the objects that pass the broahphase filter.
- automatically removed from the simulation when no collision sensor is active on it
Unlike the Near and Radar object it can:
- take any shape, including triangle mesh
- be made visible for debugging (just use the Visible actuator)
- have multiple collision sensors using it
Other than that, the sensor objects are ordinary objects. You can move them
freely or parent them. When parented to a dynamic object, they can provide
advanced collision control to this object.
The type of collision capability depends on the shape:
- box, sphere, cylinder, cone, convex hull provide volume detection.
- triangle mesh provides surface detection but you can give some volume
to the suface by increasing the margin in the Advanced Settings panel.
The margin applies on both sides of the surface.
Performance tip:
- Sensor objects perform better than Near and Radar: they do less synchronizations
because of the Scenegraph optimizations and they can have multiple collision sensors
on them (with different property filtering for example).
- Always prefer simple shape (box, sphere) to complex shape whenever possible.
- Always use broadphase filtering (avoid collision sensor with empty propery/material)
- Use collision sensor only when you need them. When no collision sensor is active
on the sensor object, it is removed from the simulation and consume no CPU.
Known limitations:
- When running Blender in debug mode, you will see one warning line of the console:
"warning btCollisionDispatcher::needsCollision: static-static collision!"
In release mode this message is not printed.
- Collision margin has no effect on sphere, cone and cylinder shape.
Other performance improvements:
- Remove unnecessary interpolation for Near and Radar objects and by extension
sensor objects.
- Use direct matrix copy instead of quaternion to synchronize orientation.
Other bug fix:
- Fix Near/Radar position error on newly activated objects. This was causing
several detection problems in YoFrankie
- Fix margin not passed correctly to gImpact shape.
- Disable force/velocity actions on static objects
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...
Use dynamic linked list to handle scenegraph rather than dumb scan
of the whole tree. The performance improvement depends on the fraction
of moving objects. If most objects are static, the speed up is
considerable. The following table compares the time spent on
scenegraph before and after this commit on a scene with 10000 objects
in various configuratons:
Scenegraph time (ms) Before After
(includes culling)
All objects static, 8.8 1.7
all visible but small fraction
in the view frustrum
All objects static, 7,5 0.01
all invisible.
All objects moving, 14.1 8.4
all visible but small fraction
in the view frustrum
This tables shows that static and invisible objects take no CPU at all
for scenegraph and culling. In the general case, this commit will
speed up the scenegraph between 2x and 5x. Compared to 2.48a, it should
be between 4x and 10x faster. Further speed up is possible by making
the scenegraph cache-friendly.
Next round of performance improvement will be on the rasterizer: use
the same dynamic linked list technique for the mesh slots.
This commit contains a number of performance improvements for the
BGE in the Scenegraph (parent relation between objects in the
scene) and view frustrum culling.
The scenegraph improvement consists in avoiding position update
if the object has not moved since last update and the removal
of redundant updates and synchronization with the physics engine.
The view frustrum culling improvement consists in using the DBVT
broadphase facility of Bullet to build a tree of graphical objects
in the scene. The elements of the tree are Aabb boxes (Aligned
Axis Bounding Boxes) enclosing the objects. This provides good
precision in closed and opened scenes. This new culling system
is enabled by default but just in case, it can be disabled with
a button in the World settings. There is no do_version in this
commit but it will be added before the 2.49 release. For now you
must manually enable the DBVT culling option in World settings
when you open an old file.
The above improvements speed up scenegraph and culling up to 5x.
However, this performance improvement is only visible when
you have hundreds or thousands of objects.
The main interest of the DBVT tree is to allow easy occlusion
culling and automatic LOD system. This will be the object of further
improvements.
* Where possible use vec.setValue(x,y,z) to assign values to a vector instead of vec= MT_Vector3(x,y,z), for MT_Point and MT_Matrix types too.
* Comparing TexVerts was creating 10 MT_Vector types - instead compare as floats.
* Added SG_Spatial::SetWorldFromLocalTransform() since the local transform is use for world transform in some cases.
* removed some unneeded vars from UpdateChildCoordinates functions
* Py API - Mouse, Ray, Radar sensors - use PyObjectFrom(vec) rather then filling the lists in each function. Use METH_NOARGS for get*() functions.
Profiling revealed that the SceneGraph updated every physics object, whether it moved or not, even though the physics object was at the right place. This would cause SOLID to go and update its bounding boxes, overlap tests etc.
This callback handles the special case (parented objects) where the physics scene needs to be informed of changes to the scenegraph.
Added Python attributes (mass, parent, visible, position, orientation, scaling) to the KX_GameObject module.
Make KX_GameObject use the KX_PyMath Python <-> Moto conversion.
(adding)
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
also the Makefile.in's were from previous patch adding
the system depend stuff to configure.ac
Kent
--
mein@cs.umn.edu
