From c961568b969dc138e912b844b4d9949b05558fa4 Mon Sep 17 00:00:00 2001
From: SeanOMik <seanomik@gmail.com>
Date: Fri, 19 Jul 2024 16:07:40 -0400
Subject: [PATCH] render: update the shadow filting poisson disc when shadow
 settings are modified

---
 lyra-game/src/render/graph/passes/shadows.rs | 49 ++++++++++----------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/lyra-game/src/render/graph/passes/shadows.rs b/lyra-game/src/render/graph/passes/shadows.rs
index e4e1b61..cd217e7 100644
--- a/lyra-game/src/render/graph/passes/shadows.rs
+++ b/lyra-game/src/render/graph/passes/shadows.rs
@@ -12,7 +12,7 @@ use lyra_ecs::{
 use lyra_game_derive::RenderGraphLabel;
 use lyra_math::{Angle, Transform};
 use rustc_hash::FxHashMap;
-use tracing::warn;
+use tracing::{debug, warn};
 use wgpu::util::DeviceExt;
 
 use crate::render::{
@@ -356,10 +356,8 @@ impl ShadowMapsPass {
 
     /// Generate and write a Poisson disc to `buffer` with `num_pcf_samples.pow(2)` amount of points.
     fn write_poisson_disc(&self, queue: &wgpu::Queue, buffer: &wgpu::Buffer, num_samples: u32) {
-        //let num_points = num_samples.pow(2);
         let num_floats = num_samples * 2; // points are vec2f
         let min_dist = (num_floats as f32).sqrt() / num_floats as f32;
-        //let min_dist = (num_samples as f32).sqrt() / num_samples as f32;
         let mut points = vec![];
 
         // use a while loop to ensure that the correct number of floats is created
@@ -439,12 +437,11 @@ impl Node for ShadowMapsPass {
             Some(SlotValue::Buffer(Arc::new(settings_buffer))),
         );
 
-        let def_settings = ShadowSettings::default();
         node.add_buffer_slot(
             ShadowMapsPassSlots::PcfPoissonDiscBuffer,
             SlotAttribute::Output,
             Some(SlotValue::Buffer(Arc::new(
-                self.create_poisson_disc_buffer(device, "buffer_poisson_disc_pcf", def_settings.pcf_samples_num),
+                self.create_poisson_disc_buffer(device, "buffer_poisson_disc_pcf", PCF_SAMPLES_NUM_MAX),
             ))),
         );
 
@@ -452,7 +449,7 @@ impl Node for ShadowMapsPass {
             ShadowMapsPassSlots::PcssPoissonDiscBuffer,
             SlotAttribute::Output,
             Some(SlotValue::Buffer(Arc::new(
-                self.create_poisson_disc_buffer(device, "buffer_poisson_disc_pcss", def_settings.pcss_blocker_search_samples),
+                self.create_poisson_disc_buffer(device, "buffer_poisson_disc_pcss", PCSS_SAMPLES_NUM_MAX),
             ))),
         );
 
@@ -465,25 +462,26 @@ impl Node for ShadowMapsPass {
         world: &mut lyra_ecs::World,
         context: &mut crate::render::graph::RenderGraphContext,
     ) {
-        {
-            // TODO: Update the poisson disc every time the PCF sampling point number changed
-            if !world.has_resource::<ShadowSettings>() {
-                let def_settings = ShadowSettings::default();
-                let buffer = graph.slot_value(ShadowMapsPassSlots::PcfPoissonDiscBuffer)
-                    .unwrap().as_buffer().unwrap();
-                self.write_poisson_disc(&context.queue, &buffer, def_settings.pcf_samples_num);
+        world.add_resource_default_if_absent::<ShadowSettings>();
+        if world.has_resource_changed::<ShadowSettings>() {
+            debug!("Detected change in ShadowSettings, recreating poisson disks");
 
-                let buffer = graph.slot_value(ShadowMapsPassSlots::PcssPoissonDiscBuffer)
-                    .unwrap().as_buffer().unwrap();
-                self.write_poisson_disc(&context.queue, &buffer, def_settings.pcss_blocker_search_samples);
-            }
+            let settings = world.get_resource::<ShadowSettings>();
+            // convert to uniform now since the from impl limits to max values
+            let uniform = ShadowSettingsUniform::from(*settings);
+
+            let buffer = graph.slot_value(ShadowMapsPassSlots::PcfPoissonDiscBuffer)
+                .unwrap().as_buffer().unwrap();
+            self.write_poisson_disc(&context.queue, &buffer, uniform.pcf_samples_num);
+
+            let buffer = graph.slot_value(ShadowMapsPassSlots::PcssPoissonDiscBuffer)
+                .unwrap().as_buffer().unwrap();
+            self.write_poisson_disc(&context.queue, &buffer, uniform.pcss_blocker_search_samples);
 
-            // TODO: only write buffer on changes to resource
-            let shadow_settings = world.get_resource_or_default::<ShadowSettings>();
             context.queue_buffer_write_with(
                 ShadowMapsPassSlots::ShadowSettingsUniform,
                 0,
-                ShadowSettingsUniform::from(*shadow_settings),
+                uniform,
             );
         }
 
@@ -811,12 +809,12 @@ impl LightShadowMapAtlas {
 pub struct ShadowSettings {
     /// How many PCF filtering samples are used per dimension.
     /// 
-    /// A value of 16 is common.
+    /// A value of 25 is common, this is maxed to 128.
     pub pcf_samples_num: u32,
     /// How many samples are used for the PCSS blocker search step.
     /// 
     /// Multiple samples are required to avoid holes int he penumbra due to missing blockers.
-    /// A value of 16 is common.
+    /// A value of 25 is common, this is maxed to 128.
     pub pcss_blocker_search_samples: u32,
 }
 
@@ -829,6 +827,9 @@ impl Default for ShadowSettings {
     }
 }
 
+const PCF_SAMPLES_NUM_MAX: u32 = 128;
+const PCSS_SAMPLES_NUM_MAX: u32 = 128;
+
 /// Uniform version of [`ShadowSettings`]
 #[repr(C)]
 #[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
@@ -840,8 +841,8 @@ struct ShadowSettingsUniform {
 impl From<ShadowSettings> for ShadowSettingsUniform {
     fn from(value: ShadowSettings) -> Self {
         Self {
-            pcf_samples_num: value.pcf_samples_num,
-            pcss_blocker_search_samples: value.pcss_blocker_search_samples,
+            pcf_samples_num: value.pcf_samples_num.min(PCF_SAMPLES_NUM_MAX),
+            pcss_blocker_search_samples: value.pcss_blocker_search_samples.min(PCSS_SAMPLES_NUM_MAX),
         }
     }
 }