From 7be082f9a8bb6bd46c226d7ef4c42f0fd9fe7314 Mon Sep 17 00:00:00 2001
From: hecktest <42101236+hecktest@users.noreply.github.com>
Date: Fri, 26 Jun 2020 00:06:29 +0200
Subject: Fix bone-attached entities (#10015)

---
 src/client/content_cao.cpp | 38 +++++++++++++++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 5 deletions(-)

diff --git a/src/client/content_cao.cpp b/src/client/content_cao.cpp
index 7f573b5a1..4f949f6b0 100644
--- a/src/client/content_cao.cpp
+++ b/src/client/content_cao.cpp
@@ -162,6 +162,15 @@ static void setBillboardTextureMatrix(scene::IBillboardSceneNode *bill,
 	matrix.setTextureScale(txs, tys);
 }
 
+// Evaluate transform chain recursively; irrlicht does not do this for us
+static void updatePositionRecursive(scene::ISceneNode *node)
+{
+	scene::ISceneNode *parent = node->getParent();
+	if (parent)
+		updatePositionRecursive(parent);
+	node->updateAbsolutePosition();
+}
+
 /*
 	TestCAO
 */
@@ -929,11 +938,6 @@ void GenericCAO::updateNodePos()
 
 void GenericCAO::step(float dtime, ClientEnvironment *env)
 {
-	if (m_animated_meshnode) {
-		m_animated_meshnode->animateJoints();
-		updateBonePosition();
-	}
-
 	// Handle model animations and update positions instantly to prevent lags
 	if (m_is_local_player) {
 		LocalPlayer *player = m_env->getLocalPlayer();
@@ -1143,6 +1147,18 @@ void GenericCAO::step(float dtime, ClientEnvironment *env)
 		rot_translator.val_current = m_rotation;
 		updateNodePos();
 	}
+
+	if (m_animated_meshnode) {
+		// Everything must be updated; the whole transform
+		// chain as well as the animated mesh node.
+		// Otherwise, bone attachments would be relative to
+		// a position that's one frame old.
+		if (m_matrixnode)
+			updatePositionRecursive(m_matrixnode);
+		m_animated_meshnode->updateAbsolutePosition();
+		m_animated_meshnode->animateJoints();
+		updateBonePosition();
+	}
 }
 
 void GenericCAO::updateTexturePos()
@@ -1444,6 +1460,18 @@ void GenericCAO::updateBonePosition()
 			bone->updateAbsolutePosition();
 		}
 	}
+	// The following is needed for set_bone_pos to propagate to
+	// attached objects correctly.
+	// Irrlicht ought to do this, but doesn't when using EJUOR_CONTROL.
+	for (u32 i = 0; i < m_animated_meshnode->getJointCount(); ++i) {
+		auto bone = m_animated_meshnode->getJointNode(i);
+		// Look for the root bone.
+		if (bone && bone->getParent() == m_animated_meshnode) {
+			// Update entire skeleton.
+			bone->updateAbsolutePositionOfAllChildren();
+			break;
+		}
+	}
 }
 
 void GenericCAO::updateAttachments()
-- 
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