The most important change here is that we no longer apply the
backend (e.g. Metal/Vulkan) UV transformation before calling the
user's vertex shader. This is an API change for post-process materials
(but they're not public).
Now the user is responsible for using uvToRenderTargetUV() in their
shaders (either in the fragment or vertex as appropriate).
This makes it easier to handle offsets/transforms with all APIs.
Conceptually, the only thing that is needed is to call
uvToRenderTargetUV() just before making a texture call.
This fixes a couple of issues:
- some image shifting in metal/vk
- flare in metal/vk was upside down
We also simplify the DoF code quite a bit now that we can rely on the
rendertargets begin multiple of 16.
We also "fix" SSAO that was working by accident on metal/vk. The UV
correction was applied 3 times 2 of which were canceling each other.
it made it actually more confusing to have two version of the uv
(normalized and not). Also the unnormalized version was computed from
frameUniforms which is not great in the case of post-processing
(it just happened to work).
* Use a clip space that matches our screen space for the z axis
We now set the projection matrix so that the clip space for the z
axis follows the inverted DX convention, i.e.: z_clip between 1 (near)
and 0 (far), which matches our screen space.
Note that the actual clip space in the GPU can revert to the "inverted
GL convention", i.e.: z_clip between -1 and 1, if the clip_control
extension is not present. In that case the precision benefits are
mostly lost.
Also note that there shouldn't be any user facing changes.
The projection matrix at the API level, still follows the GL convention.
Also, currently, the VERTEX_DOMAIN_DEVICE for materials also keeps
the GL convention (this is corrected in the vertex shader).
The gist of this change is to move the "reversed DX" mapping from the
vertex shader to the projection matrix.
* Update shaders/src/getters.vs
Co-authored-by: Ben Doherty <bendoherty@google.com>
Co-authored-by: Ben Doherty <bendoherty@google.com>
This significantly improve the depth-buffer resolution utilization
through the near-infinity range on Metal and Vulkan.
On OpenGL, this benefit is only seen when glClipControl is available.
The user-facing clip plane is unchanged [-1,1], the conversion
happens in filament's vertex shaders.
The bulk of this change consists in:
- invert the clip space's z in the vertex shader
- clear the depth buffer with 0
- invert all depth function comparisons
- fix all screen-space effects, e.g. ssao, DoF
- fix shadows and shadow biases
- use floating-point depth
- add a driver API to query which clip-space is used
- add glClipControl support to the gl backend
If you tried removing `culling: none` from any post-process materials,
everything would be fine in GL but Vulkan would be black because
our full-screen triangle was back-facing.
Continue reading only if you thrive in absurd situations.
- Metal and OpenGL define clip space as Y-up whereas Vulkan is Y-down.
- Metal and Vulkan define tex coords as Y-down whereas OpenGL is Y-up.
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.
