OpenCL Acceleration for V-HACD

Since I don’t expect to have time in the near future to work on V-HACD , I am writing this post to keep track of the performance improvements obtained after the latest optimizations I added. The source code is available here.

Experimental Evaluation
Table 1 compares the computation times (cf. Section "Machine description") of V-HACD 2.0 and V-HACD 2.2 obtained by using the configuration described below (cf. Table 2). These results show that V-HACD 2.2 is an order of magnitude faster than V-HACD 2.0. The gains are mainly obtained thanks to the convex-hull approximation (cf. Section "Updates"). The OpenCL acceleration provides 30-50% lower computation times when compared to the CPU-only version of V-HACD 2.2. 

The code is still not fully optimized and more improvements could be expected!

	V-HACD 2.0 (CPU only)	V-HACD 2.2 (CPU+GPU)
army_man	650s	65s
block	220s	26s
Bunny	317s	30s
Camel	388s	34s
Casting	744s	79s
Chair	408s	42s
Cow1	314s	30s
Cow2	349s	32s
deer_bound	411s	34s

Table 1: Computation times: V-HACD 2.0 vs V-HACD 2.2 

Parameter	Config. 1
resolution	8000000
max. depth	20
max. concavity	0.001
plane down-sampling	4
convex-hull down-sampling	4
alpha	0.05
beta	0.05
gamma	0.0005
delta	0.05
pca	0
mode	0
max. vertices per convex-hull	64
min. volume to add vertices to convex-hulls	0.0001
convex-hull approximation	1

Table 2: Tested configuration 

Updates

V-HACD 2.2 include the following updates:

1. OpenCL acceleration to compute the clipped volumes on the GPU
2. Convex-hull approximation to accelerate concavity calculations
3. Added local concavity measure to clipping cost calculation
4. Changed command line parameters

To do
When I'll find time (probably not soon), I need to do the following:

• Test the code and build executables for different platforms (i.e., Linux, Mac OS), and 
• Update the Blender add-on to make it work with the new command line parameters.

Machine description

• OS: Windows 8.1 Pro 64-bit
• CPU: Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz (8 CPUs), ~3.4GHz
• GPU: NVIDIA GeForce GTX 550 Ti
• Memory: 10240MB RAM