368fa2bf39
it was incorrectly mapping the equirect image to a cubemap due to a typo in our overload of atan2 which was swapping its parameters. atan2 is now removed, and we use atan(y,x) instead. Also modified the code slightly so it matches almost exactly cmgen's. FIXES=[320856413]
IBL Prefilter
This library can be used to generate the reflections texture used by filament's IndirectLight
class. It is similar to the cmgen tool except that all computations are performed on the GPU and
are therefore significantly faster. cmgen however offers more functionalities.
IBL Prefilter is designed entirely as a client of filament, that is, it only uses filament
public APIs.
Library and headers
The library is called libfilament-iblprefilter.a and its public headers can be found in
<filament-iblprefilter/*.h>.
Performance
Expect a total processing time of about 100ms to 300ms for a 5-levels 256 x 256 cubemap with 1024 samples.
Example
#include <filament/Engine.h>
#include <filament-iblprefilter/IBLPrefilterContext.h>
using namespace filament;
Engine* engine = Engine::create();
// create an IBLPrefilterContext, keep it around if several cubemap will be processed.
IBLPrefilterContext context(engine);
// create the specular (reflections) filter. This operation generates the kernel, so it's important
// to keep it around if it will be reused for several cubemaps.
IBLPrefilterContext::SpecularFilter filter(context);
// launch the heaver computation. Expect 100-100ms on the GPU.
Texture* texture = filter(environment_cubemap);
IndirectLight* indirectLight = IndirectLight::Builder()
.reflections(texture)
.build(engine);