The user can now choose amongst 3 specular AO methods:
- None, specAO is off
- Simple, specAO is inferred from roughness and diffuse AO
- Bent normals, specAO is computed accurately from cone intersections
The last method is more expensive but produces the best results.
This change also fixes a few issues:
- Rename materialRefraction() and materialRefractionType() for
consistency
- Fixes user time in shaders
On metals (made only of specular light), specular AO can
create large black spots. This change simply kills specular
AO to avoid this artifact. In practice we should take into
account multiple bounces but this is rasterization...
* Add support for bent normals
Bent normals can be enabled via the bentNormal property of a material.
When specular occlusion is enabled, bent normals improve the quality
of the computation.
* Save a couple of multiplications in bent specular AO
- handle heightFalloff=0 (i.e. fog doesn't depend on height) correctly,
previously, a divide-by-zero on the cpu side would get in the way.
The fix is to clamp heightFalloff to a small-enough value, and to
make sure that this is handled correctly in the shader.
- default fog distance is 0 instead of 1m
- inScatteringSize parameter should be allowed to be large in samples
* Add support for screen-space contact shadows
This CL adds support and always enables it.
toggles and setting in the next CL (same PR).
* Plumb settings for screen-space contact shadows
screen-space contact shadows is handled like a shadow option,
parameters (including on/off) are set in the LightManager, using
the existing ShadowOptions API.
Additionally there is a per-renderable toggle.
Both toggles are off by default.
* Allow contact shadows when shadowing is auto-disabled
Shadowing can be auto-disabled when for instance there are no
shadow casters in the scene. We still allow contact shadows in
that case.
This would allow for instance, to make the vegetation on a terrain
not shadow-casting, and still get some shadowing there by using
contact shadows instead.
* apply micro-shadowing after contact shadows
also, don't compute contact shadows when we know we're fully shadowed.
- minor uniform optimizations (saves ~0.1ms)
- fix some missing highp precision qualifers
- make it easier to tweak the blur filter
- make sure samples's radius goes from 0 to 1
- update comments
We now use a fixed-size kernel (right now 17), for each mip-level.
And we workout the mapping from roughness to such mip.
This improves performance by reducing significantly the number of taps
per mip, however, we don't control how much blur is actually applied
at each level. This gives a mip-chain that is proportional to
'roughness'.
It's now easier to tune quality vs. speed by tweaking the kernel's width
as well as how we map 'sigma' to a the kernel width.
With this PR screen-space refraction is functional.
Caveats:
The blur passes for supporting rough refractive materials is quite
heavy and increases with the resolution.
SSR uses a gaussian approximation for the brdf and therefore doesn’t
match perfectly cubemap-based refraction and IBL.
The use of MSAA with screen-space effects, while working, is going
to incur a large cost, especially on tilers.
We were conflating two concepts in our comments about the roughness
remapping, which was confusing. Also changed the remapping so it
matches a log2 mapping in our default configuration.
If spherical harmonics are not specified in IndirectLight (i.e.
omitted entirely), we instead use the roughness==1 LOD in the shader.
This produce much better results with absolute HDR environment, and
generally works better more often.
This is now the preferred solution.
For cases where spherical harmonicas are better or preferred, they
can simply be supplied as before.
The thin roughness remapping only makes sense for thin surfaces, it was
a mistake to apply it to solids. It assumes that a ray will go
undisturbed though the thin surface with an ior of 1.
We now take into account the light bouncing between the two interfaces
of the materials. We can do this because we assume thin surfaces,
meaning that the light will exit where it entered and with the same
direction that the specular.
This strengthen the specular at grazing angles (and reduces the transmission).
When dealing with thin objects we really have two thicknesses to
consider, the thickness in the direction of the normal, which
corresponds to the value used for solid objects, and the thickness of
the object's walls, which generally is a constant.
Reusing thickness in the later case is problematic for assets that have
a thickness map, but are rendered hollow.
In the future we can even imagine handling double-sided hollow objects
by using the thickness information -- e.g. a hollow cube.
this is because for solids we're also handling both interfaces in one
go (as opposed to calculate the actual btdf), and roughness should
depend on the ior.
Also rename some variables for less confusion (we now use
incident(I)/refracted(R)).
We also now assume a thickness of 0, if it's not set in the material.
We don't want to assume any particular thickness, because it depends
on the scene's scale.
Also clamp the remapped roughness.
Normally the IOR is deduced from the reflectance, but now we allow to
specify the IOR instead or in addition to the reflectance.
In the later case, it's possible to create physically impossible
materials, but this can be useful for artistic reasons.
Romain Guy
Pixelflinger
Mathias Agopian
Ben Doherty