From eb8b44981754ba5f13be3caa0de63b18937554b4 Mon Sep 17 00:00:00 2001
From: sfan5 <sfan5@live.de>
Date: Mon, 24 Feb 2025 18:45:23 +0100
Subject: [PATCH] Fix shadow performance regression due to force update

broken by: b861f0c5c59546b64e937fdf384634175df4a372
---
 src/client/shadows/dynamicshadows.h         |  1 +
 src/client/shadows/dynamicshadowsrender.cpp | 18 ++++++------------
 src/client/shadows/dynamicshadowsrender.h   |  1 +
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/src/client/shadows/dynamicshadows.h b/src/client/shadows/dynamicshadows.h
index 640a5479f..70135ea69 100644
--- a/src/client/shadows/dynamicshadows.h
+++ b/src/client/shadows/dynamicshadows.h
@@ -85,6 +85,7 @@ public:
 		return mapRes;
 	}
 
+	/// If true, shadow map needs to be invalidated due to frustum change
 	bool should_update_map_shadow{true};
 
 	void commitFrustum();
diff --git a/src/client/shadows/dynamicshadowsrender.cpp b/src/client/shadows/dynamicshadowsrender.cpp
index b213cf12a..9898b08e6 100644
--- a/src/client/shadows/dynamicshadowsrender.cpp
+++ b/src/client/shadows/dynamicshadowsrender.cpp
@@ -254,17 +254,14 @@ void ShadowRenderer::updateSMTextures()
 	if (!m_shadow_node_array.empty()) {
 		bool reset_sm_texture = false;
 
-		// detect if SM should be regenerated
+		// clear texture if requested
 		for (DirectionalLight &light : m_light_list) {
-			if (light.should_update_map_shadow)
-				m_force_update_shadow_map = true;
+			reset_sm_texture |= light.should_update_map_shadow;
 			light.should_update_map_shadow = false;
 		}
 
-		if (m_force_update_shadow_map) {
+		if (reset_sm_texture || m_force_update_shadow_map)
 			m_current_frame = 0;
-			reset_sm_texture = true;
-		}
 
 		video::ITexture* shadowMapTargetTexture = shadowMapClientMapFuture;
 		if (shadowMapTargetTexture == nullptr)
@@ -273,7 +270,7 @@ void ShadowRenderer::updateSMTextures()
 		// Update SM incrementally:
 		for (DirectionalLight &light : m_light_list) {
 			// Static shader values.
-			for (auto cb : {m_shadow_depth_cb, m_shadow_depth_entity_cb, m_shadow_depth_trans_cb})
+			for (auto cb : {m_shadow_depth_cb, m_shadow_depth_entity_cb, m_shadow_depth_trans_cb}) {
 				if (cb) {
 					cb->MapRes = (f32)m_shadow_map_texture_size;
 					cb->MaxFar = (f32)m_shadow_map_max_distance * BS;
@@ -281,12 +278,9 @@ void ShadowRenderer::updateSMTextures()
 					cb->PerspectiveBiasZ = getPerspectiveBiasZ();
 					cb->CameraPos = light.getFuturePlayerPos();
 				}
+			}
 
-			// set the Render Target
-			// right now we can only render in usual RTT, not
-			// Depth texture is available in irrlicth maybe we
-			// should put some gl* fn here
-
+			// Note that force_update means we're drawing everything one go.
 
 			if (m_current_frame < m_map_shadow_update_frames || m_force_update_shadow_map) {
 				m_driver->setRenderTarget(shadowMapTargetTexture, reset_sm_texture, true,
diff --git a/src/client/shadows/dynamicshadowsrender.h b/src/client/shadows/dynamicshadowsrender.h
index 9bc4f6b94..5854dc4ed 100644
--- a/src/client/shadows/dynamicshadowsrender.h
+++ b/src/client/shadows/dynamicshadowsrender.h
@@ -68,6 +68,7 @@ public:
 	void removeNodeFromShadowList(scene::ISceneNode *node);
 
 	void update(video::ITexture *outputTarget = nullptr);
+	/// Force shadow map to be re-drawn in one go next frame
 	void setForceUpdateShadowMap() { m_force_update_shadow_map = true; }
 	void drawDebug();