Add parent/child

src/dusk/entity/component.c

@@ -87,7 +87,7 @@ entityid_t componentGetEntitiesWithComponent(
     componentid_t used = ENTITY_MANAGER.entitiesWithComponent[
       type * ENTITY_COUNT_MAX + i
     ];
-    if(used == 0xFF) continue;
+    if(used == COMPONENT_ID_INVALID) continue;
     assertTrue(
       ENTITY_MANAGER.components[componentGetIndex(i, used)].type == type,
       "Component type mismatch in entitiesWithComponent lookup"

src/dusk/entity/component/display/entityposition.c

@@ -7,6 +7,33 @@
 
 #include "entity/entitymanager.h"
 
+// Lazily recompute worldTransform from the parent chain.
+static void entityPositionUpdateWorld(entityposition_t *pos) {
+  if(!pos->dirty) return;
+
+  if(pos->parentEntityId == ENTITY_ID_INVALID) {
+    glm_mat4_copy(pos->localTransform, pos->worldTransform);
+  } else {
+    entityposition_t *parent = componentGetData(
+      pos->parentEntityId, pos->parentComponentId, COMPONENT_TYPE_POSITION
+    );
+    entityPositionUpdateWorld(parent);
+    glm_mat4_mul(parent->worldTransform, pos->localTransform, pos->worldTransform);
+  }
+
+  pos->dirty = false;
+}
+
+void entityPositionMarkDirty(entityposition_t *pos) {
+  pos->dirty = true;
+  for(uint8_t i = 0; i < pos->childCount; i++) {
+    entityposition_t *child = componentGetData(
+      pos->childEntityIds[i], pos->childComponentIds[i], COMPONENT_TYPE_POSITION
+    );
+    entityPositionMarkDirty(child);
+  }
+}
+
 void entityPositionInit(
   const entityid_t entityId,
   const componentid_t componentId
@@ -18,7 +45,12 @@ void entityPositionInit(
   glm_vec3_zero(pos->position);
   glm_vec3_zero(pos->rotation);
   glm_vec3_one(pos->scale);
-  glm_mat4_identity(pos->transform);
+  glm_mat4_identity(pos->localTransform);
+  glm_mat4_identity(pos->worldTransform);
+  pos->dirty = false;
+  pos->parentEntityId = ENTITY_ID_INVALID;
+  pos->parentComponentId = COMPONENT_ID_INVALID;
+  pos->childCount = 0;
 }
 
 void entityPositionLookAt(
@@ -31,8 +63,9 @@ void entityPositionLookAt(
   entityposition_t *pos = componentGetData(
     entityId, componentId, COMPONENT_TYPE_POSITION
   );
-  glm_lookat(eye, target, up, pos->transform);
+  glm_lookat(eye, target, up, pos->localTransform);
   entityPositionDecompose(pos);
+  entityPositionMarkDirty(pos);
 }
 
 void entityPositionGetTransform(
@@ -43,7 +76,19 @@ void entityPositionGetTransform(
   entityposition_t *pos = componentGetData(
     entityId, componentId, COMPONENT_TYPE_POSITION
   );
-  glm_mat4_copy(pos->transform, dest);
+  entityPositionUpdateWorld(pos);
+  glm_mat4_copy(pos->worldTransform, dest);
+}
+
+void entityPositionGetLocalTransform(
+  const entityid_t entityId,
+  const componentid_t componentId,
+  mat4 dest
+) {
+  entityposition_t *pos = componentGetData(
+    entityId, componentId, COMPONENT_TYPE_POSITION
+  );
+  glm_mat4_copy(pos->localTransform, dest);
 }
 
 void entityPositionGetPosition(
@@ -115,6 +160,54 @@ void entityPositionSetScale(
   entityPositionRebuild(pos);
 }
 
+void entityPositionSetParent(
+  const entityid_t entityId,
+  const componentid_t componentId,
+  const entityid_t parentEntityId,
+  const componentid_t parentComponentId
+) {
+  entityposition_t *pos = componentGetData(
+    entityId, componentId, COMPONENT_TYPE_POSITION
+  );
+
+  // Remove from old parent's child list.
+  if(pos->parentEntityId != ENTITY_ID_INVALID) {
+    entityposition_t *oldParent = componentGetData(
+      pos->parentEntityId, pos->parentComponentId, COMPONENT_TYPE_POSITION
+    );
+    for(uint8_t i = 0; i < oldParent->childCount; i++) {
+      if(
+        oldParent->childEntityIds[i] == entityId &&
+        oldParent->childComponentIds[i] == componentId
+      ) {
+        oldParent->childCount--;
+        for(uint8_t j = i; j < oldParent->childCount; j++) {
+          oldParent->childEntityIds[j]    = oldParent->childEntityIds[j + 1];
+          oldParent->childComponentIds[j] = oldParent->childComponentIds[j + 1];
+        }
+        break;
+      }
+    }
+  }
+
+  pos->parentEntityId    = parentEntityId;
+  pos->parentComponentId = parentComponentId;
+
+  // Register with new parent.
+  if(parentEntityId != ENTITY_ID_INVALID) {
+    entityposition_t *parent = componentGetData(
+      parentEntityId, parentComponentId, COMPONENT_TYPE_POSITION
+    );
+    if(parent->childCount < ENTITY_POSITION_CHILDREN_MAX) {
+      parent->childEntityIds[parent->childCount]    = entityId;
+      parent->childComponentIds[parent->childCount] = componentId;
+      parent->childCount++;
+    }
+  }
+
+  entityPositionMarkDirty(pos);
+}
+
 entityposition_t *entityPositionGet(
   const entityid_t entityId,
   const componentid_t componentId
@@ -125,57 +218,56 @@ entityposition_t *entityPositionGet(
 }
 
 void entityPositionRebuild(entityposition_t *pos) {
-  glm_mat4_identity(pos->transform);
+  glm_mat4_identity(pos->localTransform);
-  glm_translate(pos->transform, pos->position);
+  glm_translate(pos->localTransform, pos->position);
-  glm_rotate_x(pos->transform, pos->rotation[0], pos->transform);
+  glm_rotate_x(pos->localTransform, pos->rotation[0], pos->localTransform);
-  glm_rotate_y(pos->transform, pos->rotation[1], pos->transform);
+  glm_rotate_y(pos->localTransform, pos->rotation[1], pos->localTransform);
-  glm_rotate_z(pos->transform, pos->rotation[2], pos->transform);
+  glm_rotate_z(pos->localTransform, pos->rotation[2], pos->localTransform);
-  glm_scale(pos->transform, pos->scale);
+  glm_scale(pos->localTransform, pos->scale);
+  entityPositionMarkDirty(pos);
 }
 
 void entityPositionDecompose(entityposition_t *pos) {
   // Translation: column 3
-  pos->position[0] = pos->transform[3][0];
+  pos->position[0] = pos->localTransform[3][0];
-  pos->position[1] = pos->transform[3][1];
+  pos->position[1] = pos->localTransform[3][1];
-  pos->position[2] = pos->transform[3][2];
+  pos->position[2] = pos->localTransform[3][2];
 
   // Scale: length of each basis column (xyz only)
   pos->scale[0] = sqrtf(
-    pos->transform[0][0] * pos->transform[0][0] +
+    pos->localTransform[0][0] * pos->localTransform[0][0] +
-    pos->transform[0][1] * pos->transform[0][1] +
+    pos->localTransform[0][1] * pos->localTransform[0][1] +
-    pos->transform[0][2] * pos->transform[0][2]
+    pos->localTransform[0][2] * pos->localTransform[0][2]
   );
   pos->scale[1] = sqrtf(
-    pos->transform[1][0] * pos->transform[1][0] +
+    pos->localTransform[1][0] * pos->localTransform[1][0] +
-    pos->transform[1][1] * pos->transform[1][1] +
+    pos->localTransform[1][1] * pos->localTransform[1][1] +
-    pos->transform[1][2] * pos->transform[1][2]
+    pos->localTransform[1][2] * pos->localTransform[1][2]
   );
   pos->scale[2] = sqrtf(
-    pos->transform[2][0] * pos->transform[2][0] +
+    pos->localTransform[2][0] * pos->localTransform[2][0] +
-    pos->transform[2][1] * pos->transform[2][1] +
+    pos->localTransform[2][1] * pos->localTransform[2][1] +
-    pos->transform[2][2] * pos->transform[2][2]
+    pos->localTransform[2][2] * pos->localTransform[2][2]
   );
 
-  // Normalize columns to isolate the rotation matrix
+  // Normalize columns to isolate the rotation matrix.
   float invS0 = pos->scale[0] > 0.0f ? 1.0f / pos->scale[0] : 0.0f;
   float invS1 = pos->scale[1] > 0.0f ? 1.0f / pos->scale[1] : 0.0f;
   float invS2 = pos->scale[2] > 0.0f ? 1.0f / pos->scale[2] : 0.0f;
 
   mat4 r;
   glm_mat4_identity(r);
-  r[0][0] = pos->transform[0][0] * invS0;
+  r[0][0] = pos->localTransform[0][0] * invS0;
-  r[0][1] = pos->transform[0][1] * invS0;
+  r[0][1] = pos->localTransform[0][1] * invS0;
-  r[0][2] = pos->transform[0][2] * invS0;
+  r[0][2] = pos->localTransform[0][2] * invS0;
-  r[1][0] = pos->transform[1][0] * invS1;
+  r[1][0] = pos->localTransform[1][0] * invS1;
-  r[1][1] = pos->transform[1][1] * invS1;
+  r[1][1] = pos->localTransform[1][1] * invS1;
-  r[1][2] = pos->transform[1][2] * invS1;
+  r[1][2] = pos->localTransform[1][2] * invS1;
-  r[2][0] = pos->transform[2][0] * invS2;
+  r[2][0] = pos->localTransform[2][0] * invS2;
-  r[2][1] = pos->transform[2][1] * invS2;
+  r[2][1] = pos->localTransform[2][1] * invS2;
-  r[2][2] = pos->transform[2][2] * invS2;
+  r[2][2] = pos->localTransform[2][2] * invS2;
 
   // Extract XYZ euler angles (R = Rx * Ry * Rz, column-major)
-  // r[2][0] = sin(Y), r[2][1] = -sin(X)*cos(Y), r[2][2] = cos(X)*cos(Y)
-  // r[0][0] = cos(Y)*cos(Z), r[1][0] = -cos(Y)*sin(Z)
   float sinBeta = glm_clamp(r[2][0], -1.0f, 1.0f);
   pos->rotation[1] = asinf(sinBeta);
   float cosBeta = cosf(pos->rotation[1]);
@@ -184,7 +276,7 @@ void entityPositionDecompose(entityposition_t *pos) {
     pos->rotation[0] = atan2f(-r[2][1], r[2][2]);
     pos->rotation[2] = atan2f(-r[1][0], r[0][0]);
   } else {
-    // Gimbal lock: pin Z to 0, recover X from the remaining degree of freedom
+    // Gimbal lock: pin Z to 0, recover X.
     pos->rotation[2] = 0.0f;
     pos->rotation[0] = (sinBeta > 0.0f)
       ? atan2f(r[0][1], r[1][1])

src/dusk/entity/component/display/entityposition.h

@@ -8,18 +8,24 @@
 #pragma once
 #include "entity/entitybase.h"
 
+#define ENTITY_POSITION_CHILDREN_MAX 8
+
 typedef struct {
-  mat4 transform;
+  mat4 localTransform;
+  mat4 worldTransform;
   vec3 position;
   vec3 rotation;
   vec3 scale;
+  bool dirty;
+  entityid_t parentEntityId;
+  componentid_t parentComponentId;
+  uint8_t childCount;
+  entityid_t childEntityIds[ENTITY_POSITION_CHILDREN_MAX];
+  componentid_t childComponentIds[ENTITY_POSITION_CHILDREN_MAX];
 } entityposition_t;
 
 /**
  * Initialize the entity position component.
- * 
- * @param entityId The entity ID.
- * @param componentId The component ID.
  */
 void entityPositionInit(
   const entityid_t entityId,
@@ -27,13 +33,13 @@ void entityPositionInit(
 );
 
 /**
- * Transforms the entity's position to look at a target point.
+ * Transforms the entity's local transform to look at a target point.
  *
- * @param entityId The entity ID.
+ * @param entityId    The entity ID.
  * @param componentId The component ID.
- * @param target The target point to look at.
+ * @param target      The target point to look at.
- * @param up The up vector for the look at transformation.
+ * @param up          The up vector.
- * @param eye The position of the camera/eye for the look at transformation.
+ * @param eye         The eye/camera position.
  */
 void entityPositionLookAt(
   const entityid_t entityId,
@@ -44,11 +50,11 @@ void entityPositionLookAt(
 );
 
 /**
- * Gets the transform matrix of the entity position component.
+ * Gets the world-space transform matrix, recomputing it lazily if dirty.
  *
- * @param entityId The entity ID.
+ * @param entityId    The entity ID.
  * @param componentId The component ID.
- * @param dest The destination matrix to write the transform to.
+ * @param dest        Destination matrix.
  */
 void entityPositionGetTransform(
   const entityid_t entityId,
@@ -57,11 +63,20 @@ void entityPositionGetTransform(
 );
 
 /**
- * Gets the cached position of the entity.
+ * Gets the local transform matrix (does not include parent transforms).
  *
- * @param entityId The entity ID.
+ * @param entityId    The entity ID.
  * @param componentId The component ID.
- * @param dest The destination vec3 to write the position to.
+ * @param dest        Destination matrix.
+ */
+void entityPositionGetLocalTransform(
+  const entityid_t entityId,
+  const componentid_t componentId,
+  mat4 dest
+);
+
+/**
+ * Gets the cached local position.
  */
 void entityPositionGetPosition(
   const entityid_t entityId,
@@ -70,11 +85,7 @@ void entityPositionGetPosition(
 );
 
 /**
- * Sets the position of the entity and rebuilds the transform matrix.
+ * Sets the local position and marks the world transform dirty.
- *
- * @param entityId The entity ID.
- * @param componentId The component ID.
- * @param position The new position.
  */
 void entityPositionSetPosition(
   const entityid_t entityId,
@@ -83,11 +94,7 @@ void entityPositionSetPosition(
 );
 
 /**
- * Gets the cached euler rotation (XYZ, radians) of the entity.
+ * Gets the cached local euler rotation (XYZ, radians).
- *
- * @param entityId The entity ID.
- * @param componentId The component ID.
- * @param dest The destination vec3 to write the rotation to.
  */
 void entityPositionGetRotation(
   const entityid_t entityId,
@@ -96,12 +103,7 @@ void entityPositionGetRotation(
 );
 
 /**
- * Sets the euler rotation (XYZ, radians) of the entity and rebuilds the
+ * Sets the local euler rotation (XYZ, radians) and marks the world transform dirty.
- * transform matrix.
- *
- * @param entityId The entity ID.
- * @param componentId The component ID.
- * @param rotation The new euler rotation in radians.
  */
 void entityPositionSetRotation(
   const entityid_t entityId,
@@ -110,11 +112,7 @@ void entityPositionSetRotation(
 );
 
 /**
- * Gets the cached scale of the entity.
+ * Gets the cached local scale.
- *
- * @param entityId The entity ID.
- * @param componentId The component ID.
- * @param dest The destination vec3 to write the scale to.
  */
 void entityPositionGetScale(
   const entityid_t entityId,
@@ -123,11 +121,7 @@ void entityPositionGetScale(
 );
 
 /**
- * Sets the scale of the entity and rebuilds the transform matrix.
+ * Sets the local scale and marks the world transform dirty.
- *
- * @param entityId The entity ID.
- * @param componentId The component ID.
- * @param scale The new scale.
  */
 void entityPositionSetScale(
   const entityid_t entityId,
@@ -136,13 +130,24 @@ void entityPositionSetScale(
 );
 
 /**
- * Returns a direct pointer to the entity position component data.
+ * Sets the parent of this entity's position component.
- * After modifying position, rotation, or scale directly, call
+ * Pass ENTITY_ID_INVALID / COMPONENT_ID_INVALID to detach from any parent.
- * entityPositionRebuild() to update the transform matrix.
  *
- * @param entityId     The entity ID.
+ * @param entityId          The child entity ID.
- * @param componentId  The component ID.
+ * @param componentId       The child component ID.
- * @return Pointer to the entity position component data.
+ * @param parentEntityId    The parent entity ID.
+ * @param parentComponentId The parent component ID.
+ */
+void entityPositionSetParent(
+  const entityid_t entityId,
+  const componentid_t componentId,
+  const entityid_t parentEntityId,
+  const componentid_t parentComponentId
+);
+
+/**
+ * Returns a direct pointer to the entity position component data.
+ * After modifying localTransform directly, call entityPositionMarkDirty().
  */
 entityposition_t *entityPositionGet(
   const entityid_t entityId,
@@ -150,15 +155,18 @@ entityposition_t *entityPositionGet(
 );
 
 /**
- * Internal function to rebuild the transform matrix of the entity position
+ * Rebuilds the local transform matrix from the cached position/rotation/scale,
- * component based on the current position, rotation, and scale.
+ * then marks this node and all descendants dirty.
  */
 void entityPositionRebuild(entityposition_t *pos);
 
 /**
- * Decomposes the transform matrix back into the position, rotation (XYZ euler,
+ * Marks this node and all descendants as having a stale world transform.
- * radians), and scale cache fields. Call after any direct matrix modification.
+ */
- *
+void entityPositionMarkDirty(entityposition_t *pos);
- * @param pos Pointer to the entity position component data.
+
+/**
+ * Decomposes the local transform matrix back into the position, rotation
+ * (XYZ euler, radians), and scale cache fields.
  */
 void entityPositionDecompose(entityposition_t *pos);

src/dusk/entity/entity.c

@@ -22,7 +22,7 @@ void entityInit(const entityid_t entityId) {
   ) {
     ENTITY_MANAGER.entitiesWithComponent[
       compType * ENTITY_COUNT_MAX + entityId
-    ] = 0xFF;
+    ] = COMPONENT_ID_INVALID;
   }
 
   ent->state |= ENTITY_STATE_ACTIVE;
@@ -52,7 +52,7 @@ componentid_t entityAddComponent(
   }
 
   assertUnreachable("Entity has no more component slots available");
-  return 0xFF;
+  return COMPONENT_ID_INVALID;
 }
 
 componentid_t entityGetComponent(
@@ -62,7 +62,7 @@ componentid_t entityGetComponent(
   componentid_t compId = ENTITY_MANAGER.entitiesWithComponent[
     type * ENTITY_COUNT_MAX + entityId
   ];
-  if(compId == 0xFF) return compId;
+  if(compId == COMPONENT_ID_INVALID) return compId;
   assertTrue(
     ENTITY_MANAGER.components[componentGetIndex(entityId, compId)].type == type,
     "Component type mismatch"
@@ -80,7 +80,7 @@ void entityDispose(const entityid_t entityId) {
     componentDispose(entityId, i);
     ENTITY_MANAGER.entitiesWithComponent[
       ENTITY_MANAGER.components[compInd].type * ENTITY_COUNT_MAX + entityId
-    ] = 0xFF;
+    ] = COMPONENT_ID_INVALID;
   }
   
   ent->state = 0;

src/dusk/entity/entity.h

@@ -35,7 +35,7 @@ componentid_t entityAddComponent(
 
 /**
  * Gets the ID of the component of the given type on the entity with the given
- * ID, or 0xFF if the entity lacks the component.
+ * ID, or COMPONENT_ID_INVALID if the entity lacks the component.
  * 
  * @param entityId The ID of the entity to get the component from.
  * @param type The type of the component to get.

src/dusk/entity/entitybase.h

@@ -11,6 +11,9 @@
 #define ENTITY_COUNT_MAX 20
 #define ENTITY_COMPONENT_COUNT_MAX 8
 
+#define ENTITY_ID_INVALID     0xFF
+#define COMPONENT_ID_INVALID  0xFF
+
 typedef uint8_t entityid_t;
 typedef uint8_t componentid_t;
 typedef uint16_t componentindex_t;

src/dusk/entity/entitymanager.c

@@ -15,7 +15,7 @@ entitymanager_t ENTITY_MANAGER;
 void entityManagerInit(void) {
   memoryZero(&ENTITY_MANAGER, sizeof(entitymanager_t));
   memorySet(
-    ENTITY_MANAGER.entitiesWithComponent, 0xFF,
+    ENTITY_MANAGER.entitiesWithComponent, COMPONENT_ID_INVALID,
     sizeof(entityid_t) * COMPONENT_TYPE_COUNT * ENTITY_COUNT_MAX
   );
 
@@ -33,7 +33,7 @@ entityid_t entityManagerAdd() {
     return i;
   }
   assertUnreachable("No more entity IDs available");
-  return 0xFF;
+  return ENTITY_ID_INVALID;
 }
 
 void entityManagerDispose(void) {

src/dusk/script/module/entity/component/moduleentityposition.h

@@ -97,7 +97,11 @@ moduleBaseFunction(moduleEntityPositionSetScale) {
 
 moduleBaseFunction(moduleEntityPositionLookAt) {
   if(argc < 1) return moduleBaseThrow("Expected at least 1 argument");
-  entityposition_t *pos = moduleEntityPositionGet(callInfo);
+  componenthandle_t *h = scriptProtoGetValue(
+    &MODULE_ENTITY_POSITION_PROTO, callInfo->this_value
+  );
+  if(!h) return jerry_undefined();
+  entityposition_t *pos = entityPositionGet(h->eid, h->cid);
   if(!pos) return jerry_undefined();
   vec3 target;
   if(!moduleVec3AnyCheck(args[0], target)) {
@@ -107,8 +111,37 @@ moduleBaseFunction(moduleEntityPositionLookAt) {
   if(argc >= 2 && !moduleVec3AnyCheck(args[1], up)) {
     return moduleBaseThrow("expected Vec3 up");
   }
-  glm_lookat(pos->position, target, up, pos->transform);
+  entityPositionLookAt(h->eid, h->cid, target, up, pos->position);
-  entityPositionDecompose(pos);
+  return jerry_undefined();
+}
+
+moduleBaseFunction(moduleEntityPositionGetParent) {
+  componenthandle_t *h = scriptProtoGetValue(
+    &MODULE_ENTITY_POSITION_PROTO, callInfo->this_value
+  );
+  if(!h) return jerry_undefined();
+  entityposition_t *pos = entityPositionGet(h->eid, h->cid);
+  if(!pos || pos->parentEntityId == ENTITY_ID_INVALID) return jerry_null();
+  componenthandle_t ph = { .eid = pos->parentEntityId, .cid = pos->parentComponentId };
+  return scriptProtoCreateValue(&MODULE_ENTITY_POSITION_PROTO, &ph);
+}
+
+moduleBaseFunction(moduleEntityPositionSetParentProp) {
+  componenthandle_t *h = scriptProtoGetValue(
+    &MODULE_ENTITY_POSITION_PROTO, callInfo->this_value
+  );
+  if(!h) return jerry_undefined();
+
+  if(argc < 1 || jerry_value_is_null(args[0]) || jerry_value_is_undefined(args[0])) {
+    entityPositionSetParent(h->eid, h->cid, ENTITY_ID_INVALID, COMPONENT_ID_INVALID);
+    return jerry_undefined();
+  }
+
+  componenthandle_t *ph = scriptProtoGetValue(
+    &MODULE_ENTITY_POSITION_PROTO, args[0]
+  );
+  if(!ph) return moduleBaseThrow("expected EntityPosition");
+  entityPositionSetParent(h->eid, h->cid, ph->eid, ph->cid);
   return jerry_undefined();
 }
 
@@ -147,4 +180,9 @@ static void moduleEntityPOSITION(void) {
     &MODULE_ENTITY_POSITION_PROTO, "lookAt",
     moduleEntityPositionLookAt
   );
+
+  scriptProtoDefineProp(
+    &MODULE_ENTITY_POSITION_PROTO, "parent",
+    moduleEntityPositionGetParent, moduleEntityPositionSetParentProp
+  );
 }