Added box mover utility for quick move and slide physics

register_types.cpp

@@ -6,6 +6,7 @@
 #include "voxel_terrain.h"
 #include "voxel_provider_test.h"
 #include "voxel_provider_image.h"
+#include "voxel_box_mover.h"
 #include "transvoxel/voxel_mesher_smooth.h"
 
 void register_voxel_types() {
@@ -20,6 +21,7 @@ void register_voxel_types() {
 	ClassDB::register_class<VoxelProviderTest>();
 	ClassDB::register_class<VoxelProviderImage>();
 	ClassDB::register_class<VoxelMesherSmooth>();
+	ClassDB::register_class<VoxelBoxMover>();
 
 }
 

voxel_box_mover.cpp

@@ -0,0 +1,164 @@
+#include "voxel_box_mover.h"
+#include "voxel_map.h"
+
+static AABB expand_with_vector(AABB box, Vector3 v) {
+
+	if(v.x > 0) {
+		box.size.x += v.x;
+	} else if(v.x < 0) {
+		box.position.x += v.x;
+		box.size.x -= v.x;
+	}
+
+	if(v.y > 0) {
+		box.size.y += v.y;
+	} else if(v.y < 0) {
+		box.position.y += v.y;
+		box.size.y -= v.y;
+	}
+
+	if(v.z > 0) {
+		box.size.z += v.z;
+	} else if(v.z < 0) {
+		box.position.z += v.z;
+		box.size.z -= v.z;
+	}
+
+	return box;
+}
+
+static float calculate_i_offset(AABB box, AABB other, float motion, int i, int j, int k) {
+
+	const float EPSILON = 0.001;
+
+	Vector3 other_end = other.position + other.size;
+	Vector3 box_end = box.position + box.size;
+
+	if(other_end[k] <= box.position[k] || other.position[k] >= box_end[k])
+		return motion;
+
+	if(other_end[j] <= box.position[j] || other.position[j] >= box_end[j])
+		return motion;
+
+	if(motion > 0.0 && other_end[i] <= box.position[i]) {
+		float off = box.position[i] - other_end[i] - EPSILON;
+		if(off < motion)
+			motion = off;
+	}
+
+	if(motion < 0.0 && other.position[i] >= box_end[i]) {
+		float off = box_end[i] - other.position[i] + EPSILON;
+		if(off > motion)
+			motion = off;
+	}
+
+	return motion;
+}
+
+// Gets the transformed vector for moving a box and slide.
+// This algorithm is free from tunnelling for axis-aligned movement,
+// except in some high-speed diagonal cases or huge size differences:
+// For example, if a box is fast enough to have a diagonal motion jumping from A to B,
+// it will pass through C if that other box is the only other one:
+//
+//  o---o
+//  | A |
+//  o---o
+//          o---o
+//          | C |
+//          o---o
+//                  o---o
+//                  | B |
+//                  o---o
+//
+// TODO one way to fix this would be to try a "hot side" projection instead
+//
+static Vector3 get_motion(AABB box, Vector3 motion, const Vector<AABB> &other_boxes) {
+	// The bounding box is expanded to include it's estimated version at next update.
+	// This also makes the algorithm tunnelling-free
+	AABB expanded_box = expand_with_vector(box, motion);
+
+	Vector<AABB> colliding_boxes;
+	for(int i = 0; i < other_boxes.size(); ++i) {
+		AABB other = other_boxes[i];
+		if(expanded_box.intersects(other_boxes[i]));
+			colliding_boxes.push_back(other);
+	}
+
+	if (colliding_boxes.size() == 0)
+		return motion;
+
+	//print("Colliding: ", colliding_boxes.size())
+
+	Vector3 new_motion = motion;
+
+	for(int i = 0; i < colliding_boxes.size(); ++i)
+		new_motion.y = calculate_i_offset(colliding_boxes[i], box, new_motion.y, 1, 0, 2);
+	box.position.y += new_motion.y;
+
+	for(int i = 0; i < colliding_boxes.size(); ++i)
+		new_motion.x = calculate_i_offset(colliding_boxes[i], box, new_motion.x, 0, 1, 2);
+	box.position.x += new_motion.x;
+
+	for(int i = 0; i < colliding_boxes.size(); ++i)
+		new_motion.z = calculate_i_offset(colliding_boxes[i], box, new_motion.z, 2, 1, 0);
+	box.position.z += new_motion.z;
+
+	return new_motion;
+}
+
+Vector3 VoxelBoxMover::get_motion(Vector3 pos, Vector3 motion, AABB aabb, VoxelTerrain *terrain) {
+
+	ERR_FAIL_COND_V(terrain == NULL, Vector3());
+
+	AABB box(aabb.position + pos, aabb.size);
+	AABB expanded_box = expand_with_vector(box, motion);
+
+	Vector<AABB> potential_boxes;
+
+	// Collect collisions with the terrain
+
+	Ref<VoxelMap> voxels_ref = terrain->get_map();
+	ERR_FAIL_COND_V(voxels_ref.is_null(), Vector3());
+	VoxelMap &voxels = **voxels_ref;
+
+	int min_x = int(Math::floor(expanded_box.position.x));
+	int min_y = int(Math::floor(expanded_box.position.y));
+	int min_z = int(Math::floor(expanded_box.position.z));
+
+	Vector3 expanded_box_end = expanded_box.position + expanded_box.size;
+	int max_x = int(Math::ceil(expanded_box_end.x));
+	int max_y = int(Math::ceil(expanded_box_end.y));
+	int max_z = int(Math::ceil(expanded_box_end.z));
+
+	Vector3i i(min_x, min_y, min_z);
+
+	for (i.z = min_z; i.z < max_z; ++i.z) {
+		for (i.y = min_y; i.y < max_y; ++i.y) {
+			for (i.x = min_x; i.x < max_x; ++i.x) {
+
+				int voxel_type = voxels.get_voxel(i, 0);
+				if(voxel_type != 0) {
+					AABB voxel_box = AABB(i.to_vec3(), Vector3(1,1,1));
+					potential_boxes.push_back(voxel_box);
+				}
+			}
+		}
+	}
+
+	// Calculate collisions
+	return ::get_motion(box, motion, potential_boxes);
+}
+
+Vector3 VoxelBoxMover::_get_motion_binding(Vector3 pos, Vector3 motion, AABB aabb, Node *terrain_node) {
+	ERR_FAIL_COND_V(terrain_node == NULL, Vector3());
+	VoxelTerrain *terrain = Object::cast_to<VoxelTerrain>(terrain_node);
+	ERR_FAIL_COND_V(terrain == NULL, Vector3());
+	return get_motion(pos, motion, aabb, terrain);
+}
+
+void VoxelBoxMover::_bind_methods() {
+
+	ClassDB::bind_method(D_METHOD("get_motion", "pos", "motion", "aabb", "terrain"), &VoxelBoxMover::_get_motion_binding);
+}
+

voxel_box_mover.h

@@ -0,0 +1,19 @@
+#ifndef VOXEL_BOX_MOVER_H
+#define VOXEL_BOX_MOVER_H
+
+#include "voxel_terrain.h"
+#include <core/math/aabb.h>
+
+// Helper to get simple AABB physics
+class VoxelBoxMover : public Reference {
+	GDCLASS(VoxelBoxMover, Reference)
+public:
+	Vector3 get_motion(Vector3 pos, Vector3 motion, AABB aabb, VoxelTerrain *terrain);
+
+protected:
+	Vector3 _get_motion_binding(Vector3 pos, Vector3 motion, AABB aabb, Node *terrain_node);
+
+	static void _bind_methods();
+};
+
+#endif // VOXEL_BOX_MOVER_H