The attribute node already allows accessing attributes associated
with objects and meshes, which allows changing the behavior of the
same material between different objects or instances. The same idea
can be extended to an even more global level of layers and scenes.
Currently view layers provide an option to replace all materials
with a different one. However, since the same material will be applied
to all objects in the layer, varying the behavior between layers while
preserving distinct materials requires duplicating objects.
Providing access to properties of layers and scenes via the attribute
node enables making materials with built-in switches or settings that
can be controlled globally at the view layer level. This is probably
most useful for complex NPR shading and compositing. Like with objects,
the node can also access built-in scene properties, like render resolution
or FOV of the active camera. Lookup is also attempted in World, similar
to how the Object mode checks the Mesh datablock.
In Cycles this mode is implemented by replacing the attribute node with
the attribute value during sync, allowing constant folding to take the
values into account. This means however that materials that use this
feature have to be re-synced upon any changes to scene, world or camera.
The Eevee version uses a new uniform buffer containing a sorted array
mapping name hashes to values, with binary search lookup. The array
is limited to 512 entries, which is effectively limitless even
considering it is shared by all materials in the scene; it is also
just 16KB of memory so no point trying to optimize further.
The buffer has to be rebuilt when new attributes are detected in a
material, so the draw engine keeps a table of recently seen attribute
names to minimize the chance of extra rebuilds mid-draw.
Differential Revision: https://developer.blender.org/D15941
This replaces the direct shader uniform layout declaration by a linear
search through a global buffer.
Each instance has an attribute offset inside the global buffer and an
attribute count.
This removes any padding and tighly pack all uniform attributes inside
a single buffer.
This would also remove the limit of 8 attribute but it is kept because of
compatibility with the old system that is still used by the old draw
manager.
This is a new implementation of the draw manager using modern
rendering practices and GPU driven culling.
This only ports features that are not considered deprecated or to be
removed.
The old DRW API is kept working along side this new one, and does not
interfeer with it. However this needed some more hacking inside the
draw_view_lib.glsl. At least the create info are well separated.
The reviewer might start by looking at `draw_pass_test.cc` to see the
API in usage.
Important files are `draw_pass.hh`, `draw_command.hh`,
`draw_command_shared.hh`.
In a nutshell (for a developper used to old DRW API):
- `DRWShadingGroups` are replaced by `Pass<T>::Sub`.
- Contrary to DRWShadingGroups, all commands recorded inside a pass or
sub-pass (even binds / push_constant / uniforms) will be executed in order.
- All memory is managed per object (except for Sub-Pass which are managed
by their parent pass) and not from draw manager pools. So passes "can"
potentially be recorded once and submitted multiple time (but this is
not really encouraged for now). The only implicit link is between resource
lifetime and `ResourceHandles`
- Sub passes can be any level deep.
- IMPORTANT: All state propagate from sub pass to subpass. There is no
state stack concept anymore. Ensure the correct render state is set before
drawing anything using `Pass::state_set()`.
- The drawcalls now needs a `ResourceHandle` instead of an `Object *`.
This is to remove any implicit dependency between `Pass` and `Manager`.
This was a huge problem in old implementation since the manager did not
know what to pull from the object. Now it is explicitly requested by the
engine.
- The pases need to be submitted to a `draw::Manager` instance which can
be retrieved using `DRW_manager_get()` (for now).
Internally:
- All object data are stored in contiguous storage buffers. Removing a lot
of complexity in the pass submission.
- Draw calls are sorted and visibility tested on GPU. Making more modern
culling and better instancing usage possible in the future.
- Unit Tests have been added for regression testing and avoid most API
breakage.
- `draw::View` now contains culling data for all objects in the scene
allowing caching for multiple views.
- Bounding box and sphere final setup is moved to GPU.
- Some global resources locations have been hardcoded to reduce complexity.
What is missing:
- ~~Workaround for lack of gl_BaseInstanceARB.~~ Done
- ~~Object Uniform Attributes.~~ Done (Not in this patch)
- Workaround for hardware supporting a maximum of 8 SSBO.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D15817
