VR: shots fly along the aim, not above it

A shot fired from the muzzle of the weapon in the hand was kept inside the
level by the game's test of the line from the eyes to it, which in VR runs
down through the player's own body: the test hit it and moved the shot up
towards the eyes, from where it flew parallel to the aim, a few centimetres
above the crosshair and the laser (measured: up to 7 cm at 3 m). In VR the
line is tested against the level alone (a hand through a wall still does
not fire through it); measured after: the impacts on their rays, on
average within a millimetre.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

source/items/weapons.c

@@ -231,6 +231,7 @@ symbols in this file:
 #include "units/units.h"
 #ifdef HALO_ANDROID
 #include "halo_vr.h"
+#include "physics/collisions.h"
 #endif
 
 /* port/linux/game/pal_tags.c's */
@@ -2205,6 +2206,10 @@ static void trigger_create_projectiles(
 		long target_object_index= NONE;
 		long projectile_definition_index;
 		short projectile_count;
+#ifdef HALO_ANDROID
+		/* VR: fired from the muzzle of the weapon in the hand */
+		boolean vr_from_muzzle= FALSE;
+#endif
 
 		if (!TEST_FLAG(trigger_definition->flags, _weapon_trigger_projectiles_cannot_be_aimed_bit) &&
 			unit &&
@@ -2282,6 +2287,7 @@ static void trigger_create_projectiles(
 						origin.x = vr_origin[0];
 						origin.y = vr_origin[1];
 						origin.z = vr_origin[2];
+						vr_from_muzzle = TRUE;
 					}
 				}
 #endif
@@ -2383,6 +2389,26 @@ static void trigger_create_projectiles(
 						real_point3d camera_position;
 
 						unit_get_camera_position(owner_object_index, &camera_position);
+#ifdef HALO_ANDROID
+						if (vr_from_muzzle)
+						{
+							/* VR: from the eyes down to the hand the line runs through
+							the player's own body, which the game's test hits, moving the
+							shot up towards the eyes (it then flies parallel to the aim,
+							above it): only the level stops it, a hand through a wall */
+							struct collision_result collision;
+							struct object_datum *projectile_object= object_get(projectile_object_index);
+
+							if (collision_test_line(FLAG(_collision_test_structure_bit) | FLAG(_collision_test_front_facing_surfaces_bit),
+									&camera_position, &projectile_object->object.position, owner_object_index, &collision) &&
+								collision.location.cluster_index!=NONE)
+							{
+								object_translate(projectile_object_index, &collision.point, &collision.location);
+								object_compute_node_matrices(projectile_object_index);
+							}
+						}
+						else
+#endif
 						object_force_inside_bsp(projectile_object_index, &camera_position);
 					}
 					if (target_object_index!=NONE)