From 1afe4876cb8133c5b47fdcfeb07decc5565c4844 Mon Sep 17 00:00:00 2001
From: Omniscient <17525998+omnisci3nce@users.noreply.github.com>
Date: Sun, 17 Mar 2024 14:59:35 +1100
Subject: wip: transform propagation

---
 examples/transforms/ex_transforms.c | 51 +++++++++++++++++++++++++++++++++++++
 src/maths/maths.h                   |  6 +++--
 src/transform_hierarchy.c           | 27 ++++++++++++++++++++
 src/transform_hierarchy.h           |  6 +++--
 xmake.lua                           |  7 +++++
 5 files changed, 93 insertions(+), 4 deletions(-)
 create mode 100644 examples/transforms/ex_transforms.c

diff --git a/examples/transforms/ex_transforms.c b/examples/transforms/ex_transforms.c
new file mode 100644
index 0000000..edb1c21
--- /dev/null
+++ b/examples/transforms/ex_transforms.c
@@ -0,0 +1,51 @@
+#include <glfw3.h>
+
+#include "core.h"
+#include "render.h"
+#include "render_types.h"
+#include "maths_types.h"
+#include "maths.h"
+#include "transform_hierarchy.h"
+
+int main() {
+  core* core = core_bringup();
+
+  // Set up scene
+  vec3 camera_pos = vec3(3., 4., 10.);
+  vec3 camera_front = vec3_normalise(vec3_negate(camera_pos));
+  camera cam = camera_create(camera_pos, camera_front, VEC3_Y, deg_to_rad(45.0));
+
+  model_handle cube_handle =
+      model_load_obj(core, "assets/models/obj/cube/cube.obj", true);
+  model* cube = &core->models->data[cube_handle.raw];
+  // 2. upload vertex data to gpu
+  model_upload_meshes(&core->renderer, cube);
+
+  // Create transform hierarchy
+  transform_hierarchy* transform_tree = transform_hierarchy_create();
+  transform_node* root_node = transform_hierarchy_root_node(transform_tree);
+
+  // Add nodes
+  // -- 4 cubes
+  transform cube1 = transform_create(vec3(-2.0, -2.0, -2.0), quat_ident(), 2.0);
+  transform cube2 = transform_create(vec3(2.0, 2.0, 2.0), quat_ident(), 2.0);
+  transform_hierarchy_add_node(root_node, cube_handle, cube1);
+  transform_hierarchy_add_node(root_node, cube_handle, cube2);
+
+
+  // Main loop
+  while (!glfwWindowShouldClose(core->renderer.window)) {
+    input_update(&core->input);
+    threadpool_process_results(&core->threadpool, 1);
+
+    render_frame_begin(&core->renderer);
+
+    // insert work here
+
+    render_frame_end(&core->renderer);
+  }
+
+  transform_hierarchy_free(transform_tree);
+
+  return 0;
+}
diff --git a/src/maths/maths.h b/src/maths/maths.h
index d832739..390b611 100644
--- a/src/maths/maths.h
+++ b/src/maths/maths.h
@@ -207,8 +207,10 @@ static transform transform_create(vec3 pos, quat rot, f32 scale) {
 }
 
 static inline mat4 transform_to_mat(transform *tf) {
-  // TODO: rotation
-  return mat4_mult(mat4_translation(tf->position), mat4_scale(tf->scale));
+  mat4 trans = mat4_translation(tf->position);
+  mat4 rot = mat4_rotation(tf->rotation);
+  mat4 scale = mat4_scale(tf->scale);
+  return mat4_mult(trans, mat4_mult(rot, scale));
 }
 
 // --- Sizing asserts
diff --git a/src/transform_hierarchy.c b/src/transform_hierarchy.c
index 25ace6c..468be56 100644
--- a/src/transform_hierarchy.c
+++ b/src/transform_hierarchy.c
@@ -117,4 +117,31 @@ void transform_hierarchy_dfs(transform_node* start_node,
     // post-order
     visit_node(start_node, ctx_data);
   }
+}
+
+// Update matrix for the current node
+bool update_matrix(transform_node* node, void* _ctx_data) {
+  if (!node) return true;  // leaf node
+
+  if (node->parent->tf.is_dirty) {
+    node->tf.is_dirty = true;
+  }
+
+  if (node->tf.is_dirty) {
+    // invalidates children
+    mat4 updated_local_transform = transform_to_mat(&node->tf);
+    node->local_matrix_tf = updated_local_transform;
+    if (node->parent) {
+      mat4 updated_world_transform =
+          mat4_mult(node->parent->world_matrix_tf, updated_local_transform);
+      node->world_matrix_tf = updated_world_transform;
+    }
+  }
+
+  return true;
+}
+
+void transform_hierarchy_propagate_transforms(transform_hierarchy* tfh) {
+  // kickoff traversal
+  transform_hierarchy_dfs(&tfh->root, update_matrix, false, NULL);
 }
\ No newline at end of file
diff --git a/src/transform_hierarchy.h b/src/transform_hierarchy.h
index 703baa8..9af8a97 100644
--- a/src/transform_hierarchy.h
+++ b/src/transform_hierarchy.h
@@ -58,8 +58,10 @@ void transform_hierarchy_delete_node(transform_node* node);
  * @param ctx_data An optional pointer to data that is be passed on each call to `visit_node`. Can be used to carry additional information or context.
  *
  * @note The main use-cases are:
-            1. traversing the whole tree to update cached 4x4 affine transform matrices (pre-order)
+            1. traversing the whole tree to update cached 4x4 affine transform matrices (post-order)
             2. freeing child nodes after deleting a node in the tree (post-order)
             3. debug pretty printing the whole tree (post-order)
  */
-void transform_hierarchy_dfs(transform_node* start_node, bool (*visit_node)(transform_node* node, void* ctx_data), bool is_pre_order, void* ctx_data);
\ No newline at end of file
+void transform_hierarchy_dfs(transform_node* start_node, bool (*visit_node)(transform_node* node, void* ctx_data), bool is_pre_order, void* ctx_data);
+
+void transform_hierarchy_debug_print(transform_node* start_node, )
\ No newline at end of file
diff --git a/xmake.lua b/xmake.lua
index 15159ef..0f039e7 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -115,6 +115,13 @@ target("obj")
     add_files("examples/obj_loading/ex_obj_loading.c")
     set_rundir("$(projectdir)")
 
+target("transforms")
+    set_kind("binary")
+    set_group("examples")
+    add_deps("core_shared")
+    add_files("examples/transforms/ex_transforms.c")
+    set_rundir("$(projectdir)")
+
 target("demo")
     set_kind("binary")
     set_group("examples")
-- 
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