DrawIndirect doesn't work well in iOS or macOS, since you can only submit one draw at a time referencing the buffer and offset above. There's also no stride to store additional instance data, or drawIndirectCount like in Vulkan, where the GPU supplies the count of things to draw. So it's not really saving much over making the draw calls themselves. If you can target A9 which is where DrawIndirect started, then look into IndirectCommandBuffer which can then supply a range of draw calls which is the only way to submit a batch of commands as one submission.

That's not exactly going to work. Terrain system using R16Unorm for the precision, and it's the only format storable in PNG which only has 8u and 16u. Photoshop has been using 16u for a long time to store color, so I'm a little shocked that it's not exposed on desktop even if the Apple Silicon can't handle it. R16Float is only 10-bits of precision, and R16Uint doesn't often support filtering. But worst case, the PNG data could be read into R16Uint. The Apple sample code should reflect valid use cases though. If this is suddenly a per-format query, then Metal needs a call to query whether read-write support is possible on every format. Those docs are helpful, but runtime query is needed. Otherwise, how would an app test that R16Unit is supported and not R16Unorm.

Seems to be a bad bug in the Metal validation layer. It flags this texture RG16Unorm as unsupported, but it is supported. Turning off Metal validation for me fixes that sample app.

This is happening in Apple's own terrain sample code on macOS on the latest 16" Intel MBP with AMD 5500m. The Metal texture loader somehow loads an L16 png into an RG16Unorm texture since it provides no control over the MTLPixelFormat. Then when you click to modify the terrain with the mouse, the app crashes in the validation. The textures say they support All, function texture read-write is true, and readWriteTexture support is Tier2. If Apple can't write a correct example that works, then we probably can't either. MTLTextureDescriptor *texDesc =       [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:         MTLPixelFormatRG16Unorm         //MTLPixelFormatR16Unorm <- should be this                                 width:heightMapWidth                                height:heightMapHeight                               mipmapped:NO];      2021-08-18 22:43:41.385581-0700 DynamicTerrainWithArgumentBuffers[46069:3553941] sample running on: AMD Radeon Pro 5500M validateComputeFunctionArguments:854: failed assertion `Compute Function(TerrainKnl_UpdateHeightmap): Shader uses texture(heightMap[0]) as read-write, but hardware does not support read-write texture of this pixel format.' validateComputeFunctionArguments:854: failed assertion `Compute Function(TerrainKnl_UpdateHeightmap): Shader uses texture(heightMap[0]) as read-write, but hardware does not support read-write texture of this pixel format.'