An annotation batch is a container for a set of annotations, which will all be
"batched" and send to the GPU together. This improves performance
by reducing the number of draw calls.
Annotation batches all share a set of supporting primitives. Each time any
annotation in the batch changes, they must be regenerated if they have been
drawn already. It is best to group annotations that are likely to change together
into the same batch.
Annotation batches support "transforms" which modify the current value of the render
context when drawing. This allows us to specify annotations in coordinates other than
equatorial (e.g. in alt/az) and only need to do this transformation once for the batch.
These transforms can either be static matrices, or functions with the signature
(context: RenderContext) => Matrix3d
to facilitate coordinate frames that are time-varying relative to equatorial, such as
horizontal coordinates.
We provide convenience functions for generating annotation batches in horizontal coordinates,
and for drawing annotations that are world-space "overlays", meaning that their position is
static relative to the viewport center, but their sizing is zoom-aware.
An annotation batch is a container for a set of annotations, which will all be "batched" and send to the GPU together. This improves performance by reducing the number of draw calls. Annotation batches all share a set of supporting primitives. Each time any annotation in the batch changes, they must be regenerated if they have been drawn already. It is best to group annotations that are likely to change together into the same batch.
Annotation batches support "transforms" which modify the current value of the render context when drawing. This allows us to specify annotations in coordinates other than equatorial (e.g. in alt/az) and only need to do this transformation once for the batch. These transforms can either be static matrices, or functions with the signature (context: RenderContext) => Matrix3d to facilitate coordinate frames that are time-varying relative to equatorial, such as horizontal coordinates. We provide convenience functions for generating annotation batches in horizontal coordinates, and for drawing annotations that are world-space "overlays", meaning that their position is static relative to the viewport center, but their sizing is zoom-aware.