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ogt_vox: handle _frm_t and _frm_r as found in mv 0.99.7.2 #90

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Merged
mgerhardy merged 1 commit into from
Oct 6, 2026
Merged

ogt_vox: handle _frm_t and _frm_r as found in mv 0.99.7.2 #90

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32 changes: 23 additions & 9 deletions src/ogt_vox.h
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Original file line number Diff line number Diff line change
Expand Up @@ -393,7 +393,7 @@
typedef struct ogt_vox_instance
{
const char* name; // name of the instance if there is one, will be NULL otherwise.
ogt_vox_transform transform; // orientation and position of this instance on first frame of the scene. This is relative to its group local transform if group_index is not 0
ogt_vox_transform transform; // base orientation and position of this instance (may differ from animation keyframes). This is relative to its group local transform if group_index is not 0
uint32_t model_index; // index of the model used by this instance on the first frame of the scene. used to lookup the model in the scene's models[] array.
uint32_t layer_index; // index of the layer used by this instance. used to lookup the layer in the scene's layers[] array.
uint32_t group_index; // this will be the index of the group in the scene's groups[] array. If group is zero it will be the scene root group and the instance transform will be a world-space transform, otherwise the transform is relative to the group.
Expand All @@ -414,7 +414,7 @@
typedef struct ogt_vox_group
{
const char* name; // name of the group if there is one, will be NULL otherwise
ogt_vox_transform transform; // transform of this group relative to its parent group (if any), otherwise this will be relative to world-space.
ogt_vox_transform transform; // base transform of this group relative to its parent group (if any), otherwise world-space; may differ from animation keyframes.
uint32_t parent_group_index; // if this group is parented to another group, this will be the index of its parent in the scene's groups[] array, otherwise this group will be the scene root group and this value will be k_invalid_group_index
uint32_t layer_index; // which layer this group belongs to. used to lookup the layer in the scene's layers[] array.
bool hidden; // whether this group is hidden or not.
Expand Down Expand Up @@ -491,13 +491,13 @@
// sample the model index for a given instance at the given frame
uint32_t ogt_vox_sample_instance_model(const ogt_vox_instance* instance, uint32_t frame_index);

// samples the transform for an instance at a given frame.
// samples the animation transform for an instance at a given frame, or its base transform if no keyframes exist.
// ogt_vox_sample_instance_transform_global returns the transform in world space (aka global)
// ogt_vox_sample_instance_transform_local returns the transform relative to its parent group
ogt_vox_transform ogt_vox_sample_instance_transform_global(const ogt_vox_instance* instance, uint32_t frame_index, const ogt_vox_scene* scene);
ogt_vox_transform ogt_vox_sample_instance_transform_local(const ogt_vox_instance* instance, uint32_t frame_index);

// sample the transform for a group at a given frame
// samples the animation transform for a group at a given frame, or its base transform if no keyframes exist.
// ogt_vox_sample_group_transform_global returns the transform in world space (aka global)
// ogt_vox_sample_group_transform_local returns the transform relative to its parent group
ogt_vox_transform ogt_vox_sample_group_transform_global(const ogt_vox_group* group, uint32_t frame_index, const ogt_vox_scene* scene);
Expand Down Expand Up @@ -1614,11 +1614,19 @@
// _name: string
// _hidden: 0/1
// _loop: 0/1
// _frm_r: base packed rotation (optional)
// _frm_t: base translation (optional)
_vox_file_read_dict(&dict, fp);
char node_name[NAME_MAX_LEN];
_vox_strcpy_static(node_name, _vox_dict_get_value_as_string(&dict, "_name", ""));
bool hidden = _vox_dict_get_value_as_bool(&dict, "_hidden", false);
bool loop = _vox_dict_get_value_as_bool(&dict, "_loop", false);
// MagicaVoxel can store a base pose separately from the animation frames.
// Decode it now: reading frame dictionaries below replaces dict's storage.
const char* base_rotation = _vox_dict_get_value_as_string(&dict, "_frm_r");
const char* base_translation = _vox_dict_get_value_as_string(&dict, "_frm_t");
bool has_base_transform = base_rotation != NULL || base_translation != NULL;
ogt_vox_transform base_transform = _vox_make_transform_from_dict_strings(base_rotation, base_translation);

// get other properties.
uint32_t child_node_id = 0, reserved_id = 0, layer_id = 0, num_frames = 0;
Expand Down Expand Up @@ -1651,7 +1659,7 @@
transform_node->node_type = k_nodetype_transform;
transform_node->u.transform.child_node_id = child_node_id;
transform_node->u.transform.layer_id = layer_id;
transform_node->u.transform.transform = keyframes[0].transform;
transform_node->u.transform.transform = has_base_transform ? base_transform : keyframes[0].transform;
transform_node->u.transform.hidden = hidden;
transform_node->u.transform.num_keyframes = num_frames;
transform_node->u.transform.keyframe_offset = keyframe_offset;
Expand Down Expand Up @@ -2559,16 +2567,16 @@
_vox_sprintf(value_str, sizeof(value_str), "%f", value);
_vox_file_write_dict_key_value(fp, key, value_str);
}
static void _vox_file_write_dict_transform(_vox_file_writeable* fp, const ogt_vox_transform* transform) {
static void _vox_file_write_dict_transform(_vox_file_writeable* fp, const ogt_vox_transform* transform, const char* rotation_key = "_r", const char* translation_key = "_t") {
char t_string[65];
char r_string[65];
t_string[0] = 0;
r_string[0] = 0;
uint8_t packed_rotation_bits = _vox_make_packed_rotation_from_transform(transform);
_vox_sprintf(t_string, sizeof(t_string), "%i %i %i", (int32_t)transform->m30, (int32_t)transform->m31, (int32_t)transform->m32);
_vox_sprintf(r_string, sizeof(r_string), "%u", packed_rotation_bits);
_vox_file_write_dict_key_value(fp, "_r", r_string);
_vox_file_write_dict_key_value(fp, "_t", t_string);
_vox_file_write_dict_key_value(fp, rotation_key, r_string);
_vox_file_write_dict_key_value(fp, translation_key, t_string);
}

static void _vox_file_write_chunk_nTRN(_vox_file_writeable* fp, uint32_t node_id, uint32_t child_node_id, const char* name, bool hidden, const ogt_vox_transform* transform, uint32_t layer_id, const ogt_vox_anim_transform* transform_anim)
Expand All @@ -2588,11 +2596,17 @@
_vox_file_write_uint32(fp, node_id);

// write the node dictionary
uint32_t node_dict_keyvalue_count = (name ? 1 : 0) + (hidden_string ? 1 : 0) + (loop_string ? 1 : 0);
// Preserve a distinct base pose without changing the animation keyframes. Emit both
// components, including identity/zero, so the reader does not fall back to frame zero.
bool write_base_transform = transform_anim->num_keyframes != 0 &&
memcmp(transform, &transform_anim->keyframes[0].transform, sizeof(ogt_vox_transform)) != 0;
uint32_t node_dict_keyvalue_count = (name ? 1 : 0) + (hidden_string ? 1 : 0) + (loop_string ? 1 : 0) + (write_base_transform ? 2 : 0);
_vox_file_write_uint32(fp, node_dict_keyvalue_count); // num key values
_vox_file_write_dict_key_value(fp, "_name", name);
_vox_file_write_dict_key_value(fp, "_hidden", hidden_string);
_vox_file_write_dict_key_value(fp, "_loop", loop_string);
if (write_base_transform)
_vox_file_write_dict_transform(fp, transform, "_frm_r", "_frm_t");

// write other properties.
_vox_file_write_uint32(fp, child_node_id);
Expand Down
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