EEVEE-Next: HiZ Buffer: New implementation

This new implementation does all downsampling in a single compute shader
dispatch, removing a lot of complexity from the previous recursive
downsampling.

This is heavilly inspired by the Single-Pass-Downsampler from GPUOpen:
https://github.com/GPUOpen-Effects/FidelityFX-SPD
However I do not implement all the optimization bits as they require
vulkan (GL_KHR_shader_subgroup) and is not as versatile (it is only
for HiZ).

Timers inside renderdoc report ~0.4ms of saving on a 2048*1024 render for
the whole downsampling. Note that the previous implementation only
processed 6 mips where the new one processes 8 mips.
```
EEVEE ~1.0ms
EEVEE-Next ~0.6ms
```

Padding has been bumped to be of 128px for processing 8 mips.

A new debug option has been added (debug value 2) to validate the HiZ.

1 files changed, 5 insertions, 1 deletions

diff --git a/source/blender/draw/engines/eevee_next/eevee_light.cc b/source/blender/draw/engines/eevee_next/eevee_light.cc
index dbbf481f3f4..5392816124b 100644
--- a/source/blender/draw/engines/eevee_next/eevee_light.cc
+++ b/source/blender/draw/engines/eevee_next/eevee_light.cc
@@ -452,9 +452,11 @@ void LightModule::debug_pass_sync()
     return;
   }
 
-  debug_draw_ps_ = DRW_pass_create("LightCulling.Debug", DRW_STATE_WRITE_COLOR);
+  DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_CUSTOM;
+  debug_draw_ps_ = DRW_pass_create("LightCulling.Debug", state);
   GPUShader *sh = inst_.shaders.static_shader_get(LIGHT_CULLING_DEBUG);
   DRWShadingGroup *grp = DRW_shgroup_create(sh, debug_draw_ps_);
+  inst_.hiz_buffer.bind_resources(grp);
   DRW_shgroup_storage_block_ref(grp, "light_buf", &culling_light_buf_);
   DRW_shgroup_storage_block_ref(grp, "light_cull_buf", &culling_data_buf_);
   DRW_shgroup_storage_block_ref(grp, "light_zbin_buf", &culling_zbin_buf_);
@@ -490,6 +492,8 @@ void LightModule::debug_draw(GPUFrameBuffer *view_fb)
   if (debug_draw_ps_ == nullptr) {
     return;
   }
+  inst_.info = "Debug Mode: Light Culling Validation";
+  inst_.hiz_buffer.update();
   GPU_framebuffer_bind(view_fb);
   DRW_draw_pass(debug_draw_ps_);
 }