vertex shader interpolants are interpolated at pixel centers by the GPU,
but we were doing our own "pixel-center" adjustment, so we ended-up with
"vertex_uv" at a pixel corner instead of center.
with this change, the vertex shader always compute vertex_uv in
fractional texels and the conversion to texture coordinates is done
in the fxaa code.
The half-pixel adjustment is removed.
This leads to sharper looking images because in addition to shifting
everything by 0.5 pixels, this was essentially applying a box-filter
to the whole picture -- kind of like taking 1 mip level down.
By removing the Fresnel term (often ommitted from fabric/cloth BRDFs)
we can store the DG term for the cloth BRDF in the 3rd channel of the
existing DFG LUT.
In the public docs and materials API, Filament "variables" are custom
interpolants (outputs of VS, inputs of FS). However we internally used
"variables" to also refer to built-in VS inputs.
CodeGenerator had a generateVariable method and a generateVariables
method, which did something completely different. :)
* Fix FXAA computations in mediump
UV coordinates computed in highp should be passed to the FXAA function
in highp as well. This change also fixes a potential division by 0 which
was causing dir1 to have components set to inifinity, thus breaking the
texture sampling calls below. We fix this with an early exit when a
potential division by 0 is detected. The original code contained a bias
to try to avoid this problem but that bias was not always enough. It
was frequent in mediump to cancel out the bias.
* Update shaders/src/fxaa.fs
Co-Authored-By: romainguy <romainguy@curious-creature.com>
This calculates the modulo of the user time by a given value, using
the high precision user time. This is useful for animations without
having to worry about resetting the time.
THIS CHANGE BREAKS MATERIALS.
This adds getUserTime() in shaders/materials, which returns the time
in second since Renderer::resetUserTime() was called.
Two values are provided, the time in second encoded as a float and
the difference between that and the double value, which together allows
to perform high precision time computation when needed.
This change allows longer running animations in materials. Using only
the float value, give millisecond resolution for more than 4h.
(1)
Generating the C file (only used for WebAssembly) causes slowness in the
build so this makes it into an option. Also, we were flushing too often,
which made it even slower.
(2)
Using "static" in a header was causing symbol duplication.
Recall that Vulkan has a right-handed NDC system. Currently, our Vulkan
backend is not handling VERTEX_DOMAIN_DEVICE correctly, but we didn't
notice because the culling mode is not honored yet (a separate PR is on
the way for that).
To fix this, we considered adding a shader-based fixup only for the
device domain and keeping our Vulkanish projection matrix as-is.
However, this would cause the skybox shader to compute an incorrect
wrong eye vector due to in the inconsistent definition of clip space.
After discussion with Mathias and Ben, we decided that the most elegant
fix is for Filament to have only one canonical clip space, which for
now is the clip space that OpenGL requires.
Ben pointed out that spirv-cross has a flag for injecting shader-based
fixups. However we don't invoke spirv-cross for the Vulkan target, and
it's easy just to do this on our own.
This is achieved by pre-scaling the normals
transform so that the resulting normal doesn't have
any large component allowing to do the normalize()
in the fragment shader in mediump.
This must be done for skinning too.
because the shadow map can be “focused”, its
texture coordinates can end-up very large, which
in turn can cause overflows in the calculation of
the PCF positions. Unfortunately some GPUs
abort in that situation, which causes artifacts.
Fix Bug 111455153
This remapping can be confused with roughness, because
linear_roughness = roughness*roughness and
lod = sqrt(linear_roughness)
so the value of lod is roughness, but conceptually
it’s not.
