GPU: New API for clearing SSBOs #105492

New Issue

Jeroen Bakker · 2023-03-06T16:07:59+01:00

Jeroen Bakker commented

2023-03-06 16:07:59 +01:00

Current GPU_storagebuf_clear uses texture format to determine the size of the data to clear. But this results in confusion and additional development inside the gpu backends that isn't actually used.

Proposal would be to have a public function to clear storage buffer based on a int or float with a specific number of elements given to the function.

GPU_storagebuf_clear_int(GPUStorageBuf* ssbo, int32_t* clear_data, int clear_data_len);
GPU_storagebuf_clear_uint(GPUStorageBuf* ssbo, uint32_t* clear_data, int clear_data_len);
~~GPU_storagebuf_clear_float(GPUStorageBuf* ssbo, float* clear_data, int clear_data_len);~~

[x] We should check the actual usage, perhaps the next API should be sufficient and optimum as clearing buffers is only supported for 32bit clear data.
GPU_storagebuf_clear_int(GPUStorageBuf* ssbo, int clear_data);
GPU_storagebuf_clear_float(GPUStorageBuf* ssbo, float clear_data);

This should be done before the metal/vulkan ssbo support as it will reduce the complexity of those code-paths.

Usage

Eevee-next shadow mapping uses a non-uniform clearing of an ssbo and requires the clear_data_len.

 union {
      ShadowTileMapClip clip;
      int4 i;
    } u;
    u.clip.clip_near_stored = 0.0f;
    u.clip.clip_far_stored = 0.0f;
    u.clip.clip_near = int(0xFF7FFFFFu ^ 0x7FFFFFFFu); /* floatBitsToOrderedInt(-FLT_MAX) */
    u.clip.clip_far = 0x7F7FFFFF;                      /* floatBitsToOrderedInt(FLT_MAX) */
    GPU_storagebuf_clear(tilemap_pool.tilemaps_clip, GPU_RGBA32I, GPU_DATA_INT, &u.i);
    ```
 All other usages uses a uniform clear (-1 as uint or int)

Current `GPU_storagebuf_clear` uses texture format to determine the size of the data to clear. But this results in confusion and additional development inside the gpu backends that isn't actually used. Proposal would be to have a public function to clear storage buffer based on a int or float with a specific number of elements given to the function. `GPU_storagebuf_clear_int(GPUStorageBuf* ssbo, int32_t* clear_data, int clear_data_len);` `GPU_storagebuf_clear_uint(GPUStorageBuf* ssbo, uint32_t* clear_data, int clear_data_len);` ~~`GPU_storagebuf_clear_float(GPUStorageBuf* ssbo, float* clear_data, int clear_data_len);`~~ [x] ~~We should check the actual usage, perhaps the next API should be sufficient and optimum as clearing buffers is only supported for 32bit clear data. `GPU_storagebuf_clear_int(GPUStorageBuf* ssbo, int clear_data);` `GPU_storagebuf_clear_float(GPUStorageBuf* ssbo, float clear_data);`~~ This should be done before the metal/vulkan ssbo support as it will reduce the complexity of those code-paths. **Usage** Eevee-next shadow mapping uses a non-uniform clearing of an ssbo and requires the `clear_data_len`. ``` union { ShadowTileMapClip clip; int4 i; } u; u.clip.clip_near_stored = 0.0f; u.clip.clip_far_stored = 0.0f; u.clip.clip_near = int(0xFF7FFFFFu ^ 0x7FFFFFFFu); /* floatBitsToOrderedInt(-FLT_MAX) */ u.clip.clip_far = 0x7F7FFFFF; /* floatBitsToOrderedInt(FLT_MAX) */ GPU_storagebuf_clear(tilemap_pool.tilemaps_clip, GPU_RGBA32I, GPU_DATA_INT, &u.i); ``` All other usages uses a uniform clear (-1 as uint or int)

Jeroen Bakker added the

Type

To Do

label 2023-03-06 16:07:59 +01:00

Jeroen Bakker added this to the EEVEE & Viewport project 2023-03-06 16:08:00 +01:00

Jeroen Bakker added this to the 3.6 LTS milestone 2023-03-06 16:08:51 +01:00

Michael Parkin-White commented

2023-03-06 16:35:10 +01:00

Looks good for Metal, clearing buffers to a set value over a range is quite straightforward using: https://developer.apple.com/documentation/metal/mtlblitcommandencoder/1400761-fillbuffer?language=objc

So this will be fine to implement.

Looks good for Metal, clearing buffers to a set value over a range is quite straightforward using: https://developer.apple.com/documentation/metal/mtlblitcommandencoder/1400761-fillbuffer?language=objc So this will be fine to implement.

Clément Foucault commented

2023-03-06 18:36:52 +01:00

LGTM!

Jeroen Bakker referenced this issue

2023-03-07 09:01:26 +01:00

GPU: Refactor API for Clearing Storage Buffers #105521

Jeroen Bakker referenced this issue

2023-03-08 10:48:09 +01:00

Eevee-next: Use compute shader to clear clipmaps #105560

Jeroen Bakker referenced this issue from a commit

2023-03-09 18:28:16 +01:00

Eevee-next: Use compute shader to clear clipmaps