Add a basic API to Volume to track what data is currently needed to draw the image given the state of the viewer, and use it to enable context-aware single-slice loading (!!).
Volume gets new properties: loader, channelLoadCallback, and loadSpecRequired. The first two of these allow Volumes to issue load requests all by themselves. loadSpecRequired is a second loadSpec that tracks the subset of data which is necessary to display the current image.
Volume gets a new method: updateRequiredData. This applies changes to loadSpecRequired, and issues a load request when new data is needed.
View3d's setTime method now makes use of updateRequiredData
VolumeRenderImpls call updateRequiredData to allow single-slice loading: Atlas2DSlice calls it on construction and when z-slice changes to request a single z-slice, and all other implementations call it on construction to reset the required data to the full extent of the volume.
To accommodate Volume's new data loading responsibilities, IVolumeLoader gets a new API: callbacks for when single channels load are passed into createVolume, rather than loadVolumeData, so that Volume can store them. It is still possible to pass a callback to loadVolumeData, in which case both will run. But only the callback passed to createVolume will be run when a volume decides to load new data via updateRequiredData, which should almost always be the right behavior for such a callback.
Add a basic API to
Volumeto track what data is currently needed to draw the image given the state of the viewer, and use it to enable context-aware single-slice loading (!!).Volumegets new properties:loader,channelLoadCallback, andloadSpecRequired. The first two of these allowVolumes to issue load requests all by themselves.loadSpecRequiredis a secondloadSpecthat tracks the subset of data which is necessary to display the current image.Volumegets a new method:updateRequiredData. This applies changes toloadSpecRequired, and issues a load request when new data is needed.View3d'ssetTimemethod now makes use ofupdateRequiredDataVolumeRenderImpls callupdateRequiredDatato allow single-slice loading:Atlas2DSlicecalls it on construction and when z-slice changes to request a single z-slice, and all other implementations call it on construction to reset the required data to the full extent of the volume.Volume's new data loading responsibilities,IVolumeLoadergets a new API: callbacks for when single channels load are passed intocreateVolume, rather thanloadVolumeData, so thatVolumecan store them. It is still possible to pass a callback toloadVolumeData, in which case both will run. But only the callback passed tocreateVolumewill be run when a volume decides to load new data viaupdateRequiredData, which should almost always be the right behavior for such a callback.