Fix: EEVEE-Next: No shading from lights for volume only scenes

The issue was that the shadow module was never setup by any
other pipeline before the volume lighting pass.

Fix #121971

source/blender/draw/engines/eevee_next/eevee_pipeline.hh

@@ -308,7 +308,7 @@ class DeferredLayer : DeferredLayerBase {
 
   bool is_empty() const
   {
-    return closure_count_ != 0;
+    return closure_count_ == 0;
   }
 
   /* Returns the radiance buffer to feed the next layer. */
@@ -369,6 +369,11 @@ class DeferredPipeline {
 
   void debug_draw(draw::View &view, GPUFrameBuffer *combined_fb);
 
+  bool is_empty() const
+  {
+    return opaque_layer_.is_empty() && refraction_layer_.is_empty();
+  }
+
  private:
   void debug_pass_sync();
 };

source/blender/draw/engines/eevee_next/eevee_view.cc

@@ -139,7 +139,7 @@ void ShadingView::render()
 
   inst_.gbuffer.release();
 
-  inst_.volume.draw_compute(main_view_);
+  inst_.volume.draw_compute(main_view_, extent_);
 
   // inst_.lookdev.render_overlay(view_fb_);
 

source/blender/draw/engines/eevee_next/eevee_volume.cc

@@ -377,11 +377,23 @@ void VolumeModule::draw_prepass(View &main_view)
   DRW_stats_group_end();
 }
 
-void VolumeModule::draw_compute(View &main_view)
+void VolumeModule::draw_compute(View &main_view, int2 extent)
 {
   if (!enabled_) {
     return;
   }
+
+  if (inst_.pipelines.deferred.is_empty()) {
+    /* This assume the volume are computed after deferred passes. This is needed to avoid broken
+     * lighting and shadowing as the lights are not setup otherwise (see #121971). */
+    inst_.hiz_buffer.swap_layer();
+    inst_.hiz_buffer.update();
+    inst_.volume_probes.set_view(main_view);
+    inst_.sphere_probes.set_view(main_view);
+    inst_.shadows.set_view(main_view, extent);
+    printf("here\n");
+  }
+
   scatter_tx_.swap();
   extinction_tx_.swap();
 

source/blender/draw/engines/eevee_next/eevee_volume.hh

@@ -139,7 +139,7 @@ class VolumeModule {
   /* Render material properties. */
   void draw_prepass(View &main_view);
   /* Compute scattering and integration. */
-  void draw_compute(View &main_view);
+  void draw_compute(View &main_view, int2 extent);
   /* Final image compositing. */
   void draw_resolve(View &view);