Multi-view GPU frustum culling

[simwangrui]

Hi,
I'd like to render my own terrain based VSG, which may rendering of multi channels, so l need multi vsg::view.I need to perform terrain tile culling on the GPU, so I need to pass clip planes into my tessellation shader.
Currently, can vsg::ViewDependentState provide view-specific clip planes? Or do I need to subclass ViewDependentState to implement this functionality myself?
Thank you!

[robertosfield]

It may or may not be an advantage for your usage case to perform GPU culling of tiles, this will depend upon a range of factors but as you don't go into any details of your terrain rendering I can't provide any guidance on whether it's appropriate, I would flag up that it might not be the best way to get things running most efficiently.

For tasks like vegetation and heavily instanced objects where there are millions of objects that may need to be rendered then culling on GPU becomes compelling.

For cases where GPU culling is compelling using a compute or mesh shader is possible right now without any modifications to vsg::ViewDependentState or vsg::View. The way to do it is use the project and modelview matrix that are passed as push constants to compute the frustum and then doing the culling from there.

There is one caveat, you'll need to use VulkanSceneGraph-1.1.13 or master when using a compute shader as you'll want to nest the compute shader under the View subgraph and support for this was added in 1.1.13.

Unfortunately there isn't any vsgExamples code that illustrates the above use of compute shader/mesh shader for culling, something for the future.

[simwangrui]

Hi,
Your suggestion was extremely helpful to me. I realized that the view frustum clipping planes could actually be derived by calculating them from the projection matrix and the model-view matrix, rather than passing the clipping planes separately for each vsg::View. I've updated my VSG code to version 1.1.13 and am now experimenting with using nest the compute shader under the View subgraph for culling. Thank you very much!