Puzzled by a panic

[jwwalker]

When I use a material with shadingModel : lit, refractionType : thin, and refractionMode : screenspace, I get a fatal error:

utils::PostconditionPanic
in void filament::backend::metal::MetalDriver::createRenderTargetR(Handle<filament::backend::HwRenderTarget>, filament::backend::TargetBufferFlags, uint32_t, uint32_t, uint8_t, backend::MRT, filament::backend::TargetBufferInfo, filament::backend::TargetBufferInfo):248
in file filament/backend/src/metal/MetalDriver.mm
reason: The COLOR0 flag was specified, but no color texture provided.

If I change refractionMode to cubemap and make no other change, there is no error. When the Material Sandbox sample is set to thin refraction with screen space refraction, there is no such error. Any idea what I might be doing wrong? As you can see, I'm using Metal. It's on macOS.

[romainguy]

@bejado Any idea? I confirm that material_sandbox doesn't have the issue. It might be related to other post processing features but I can't find a combination that triggers the crash.

[romainguy]

Actually if I sync with tip of tree material_sandbox crashes on startup with Metal:

Thread 7 Crashed:: FEngine::loop
0 material_sandbox 0x0000000108b33dd8 filament::backend::metal::MetalBuffer::getGpuBufferForDraw(id) + 40

[jwwalker]

True, I wasn't quite up to date. After updating, material_sandbox logs this on startup:

-[MTLVertexDescriptorInternal newSerializedDescriptor]:726: failed assertion `Serialized Descriptor Creation
Attribute at index 2 references a buffer at index 6 that has no stride.
Attribute at index 5 references a buffer at index 7 that has no stride.
Attribute at index 6 references a buffer at index 8 that has no stride.
Attribute at index 7 references a buffer at index 9 that has no stride.
Attribute at index 8 references a buffer at index 10 that has no stride.
Attribute at index 9 references a buffer at index 11 that has no stride.
Attribute at index 10 references a buffer at index 12 that has no stride.
Attribute at index 11 references a buffer at index 13 that has no stride.
Attribute at index 12 references a buffer at index 14 that has no stride.
Attribute at index 13 references a buffer at index 15 that has no stride.
Attribute at index 14 references a buffer at index 16 that has no stride.
Attribute at index 15 references a buffer at index 17 that has no stride.
'

[bejado]

I'll take a look into the crash.

[bejado]

@jwwalker The crash has been fixed. Can you re-sync with main and check if your material works?

[jwwalker]

@bejado No, I still get that error if I try to use refractionMode : screenspace. Not that I really need to right now, I was just experimenting.