From ddf16392dab7ecae0e56ab9861f7fc92e60e3ebe Mon Sep 17 00:00:00 2001
From: FatalErr42O <58855799+FatalError42O@users.noreply.github.com>
Date: Thu, 21 Dec 2023 13:41:33 -0800
Subject: [PATCH] made read frames offset by -1 to match irrlicht behavior

---
 README.md           | 1 +
 modlib/read_b3d.lua | 3 ++-
 nodes.lua           | 4 ++--
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 571d500..fd4ec34 100644
--- a/README.md
+++ b/README.md
@@ -17,5 +17,6 @@ features:
 todo:
 * allow use of `get_node_by_name()` without CPML. (move to b3d_reader or set alias?)
 * document b3d table contents (I already wrote most of the documentation in modlib's wiki...)
+* finish b3d writer (NOTE: must offset "frame" by +1 as the reader is modified to match irrlicht)
 
 Without Appgurue's Modlib this would not be possible, and while I personally have my issues with it, it still provides useful tools, and it's worth looking into for libraries.
diff --git a/modlib/read_b3d.lua b/modlib/read_b3d.lua
index 459e932..3e482a0 100644
--- a/modlib/read_b3d.lua
+++ b/modlib/read_b3d.lua
@@ -275,7 +275,8 @@ function mtul.b3d_reader.read_from_stream(stream, ignore_chunks)
 			}
 			while content() do
 				local frame = {}
-				frame.frame = int()
+				--minetest uses a zero indexed frame system, so for consistency, we offset it by 1
+				frame.frame = int()-1
 				if position then
 					frame.position = vector3()
 				end
diff --git a/nodes.lua b/nodes.lua
index 1dcda54..588b627 100644
--- a/nodes.lua
+++ b/nodes.lua
@@ -56,8 +56,8 @@ function b3d_nodes.get_animated_local_trs(node, target_frame)
     local frames = node.keys
     local key_index_before = 0 --index of the key before the target_frame.
     for i, key in ipairs(frames) do
-        --pick the closest frame we find that's less then the target
-        if key.frame < target_frame then
+        --pick the closest frame we find that's less then the target. Also allow it to pick itself if this is an option.
+        if (key.frame <= target_frame) then
             key_index_before = i
         else
             break --we've reached the end of our possible frames to use.