Requires Vulkan 1.0
Shahbaz Youssefi syoussefi
- Last Modified Date
Shahbaz Youssefi, Google
Piers Daniell, NVIDIA
Jason Ekstrand, Collabora
Jan-Harald Fredriksen, Arm
This extension adds support for a new query type to match OpenGL’s
GL_PRIMITIVES_GENERATED to support layering.
1) Can the query from
VK_EXT_transform_feedback be used instead?
While the query from VK_EXT_transform_feedback can produce the same results
as in this extension, it is only available while transform feedback is
GL_PRIMITIVES_GENERATED query is independent from transform
Emulation through artificial transform feedback is unnecessarily
VK_QUERY_PIPELINE_STATISTIC_CLIPPING_INVOCATIONS_BIT be used
RESOLVED: It could, but we prefer the extension for simplicity.
Vulkan requires that only one query be active at a time.
If both the
GL_PRIMITIVES_GENERATED and the
GL_CLIPPING_INPUT_PRIMITIVES_ARB queries need to be simultaneously
enabled, emulation of both through
VK_QUERY_PIPELINE_STATISTIC_CLIPPING_INVOCATIONS_BIT is inconvenient.
3) On some hardware, this query cannot be implemented if
How will this be handled?
RESOLVED: A feature flag is exposed by this extension for this. On said hardware, the GL implementation disables rasterizer-discard and achieves the same effect through other means. It will not be able to do the same in Vulkan due to lack of state information. A feature flag is exposed by this extension so the OpenGL implementation on top of Vulkan would be able to implement a similar workaround.
4) On some hardware, this query cannot be implemented for non-zero query indices. How will this be handled?
RESOLVED: A feature flag is exposed by this extension for this.
If this feature is not present, the query from
can be used to the same effect.
5) How is the interaction of this extension with
RESOLVED: Disallowed for non-zero streams. In OpenGL, the rasterization stream is always stream zero.
For more information, see the Vulkan Specification
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