Doesn't the scene graph of qt3d use the instancing and sort the draw calls to reduce the number of state changes? In our engine the win was big when I add the sort to reduce calls of glUniform* and glBindTexture,... especially on Android and Windows. We don't use instancing for the moment because it's hard for us to maintain the backend, it's one of reasons I am planning the migration to qt3d.
In my opinion for qt3d the API have to expose a flag on entity to allow or not automatic batching. Else the automatic batching could be applied on meshes that doesn't have a transformation and don't require to be rendered in a particular order (like those with alpha). I'll made some tests on our engine to evaluate the performance win, it may be insignificance due to the sort. 2016-09-25 11:55 GMT+02:00 Sean Harmer <sean.har...@kdab.com>: > Hi Xavier, > > On 23/09/2016 17:13, Xavier Bigand wrote: > >> Hi, >> >> Does qt3d backend capable to batch geometries to reduce the number of >> draw calls? >> >> In our case this optimization should improve performances a lot, because >> we generate dynamically geometries that doesn't change often and are >> created in world coordinates (no transformations applied). >> > > Qt 3D does not yet do batching automatically. However we do support stuff > that may help you. > > * You can use instancing if you have GL 3.2 or newer > * You can do your own batching by putting such geometry into a single > buffer, either > > ** to be rendered as a single entity if you don't need interaction with > the individual parts or > ** to be rendered as separate entities with GeometryRenderer's all > referencing the same Buffer. > > The latter doesn't reduce the draw call count but does minimise the state > changes related to binding different buffers. > > We hope to add automatic batching in the future but we're still looking > into a nice API to expose this without reducing the control the user has > over organising their data. > > Cheers, > > Sean > > >> >> >> -- >> Xavier >> >> >> _______________________________________________ >> Interest mailing list >> Interest@qt-project.org >> http://lists.qt-project.org/mailman/listinfo/interest >> >> > -- > Dr Sean Harmer | sean.har...@kdab.com | Managing Director UK > KDAB (UK) Ltd, a KDAB Group company > Tel. +44 (0)1625 809908; Sweden (HQ) +46-563-540090 > Mobile: +44 (0)7545 140604 > KDAB - Qt Experts > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest > -- Xavier
_______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
