implemented rats in new system to verify that it works

src/collision.cpp

@@ -0,0 +1,184 @@
+/*
+Minetest-c55
+Copyright (C) 2010 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "collision.h"
+#include "mapblock.h"
+#include "map.h"
+
+collisionMoveResult collisionMoveSimple(Map *map, f32 pos_max_d,
+		const core::aabbox3d<f32> &box_0,
+		f32 dtime, v3f &pos_f, v3f &speed_f)
+{
+	collisionMoveResult result;
+
+	v3f oldpos_f = pos_f;
+	v3s16 oldpos_i = floatToInt(oldpos_f, BS);
+
+	/*
+		Calculate new position
+	*/
+	pos_f += speed_f * dtime;
+
+	/*
+		Collision detection
+	*/
+	
+	// position in nodes
+	v3s16 pos_i = floatToInt(pos_f, BS);
+	
+	/*
+		Collision uncertainty radius
+		Make it a bit larger than the maximum distance of movement
+	*/
+	f32 d = pos_max_d * 1.1;
+	// A fairly large value in here makes moving smoother
+	//f32 d = 0.15*BS;
+
+	// This should always apply, otherwise there are glitches
+	assert(d > pos_max_d);
+	
+	/*
+		Calculate collision box
+	*/
+	core::aabbox3d<f32> box = box_0;
+	box.MaxEdge += pos_f;
+	box.MinEdge += pos_f;
+	core::aabbox3d<f32> oldbox = box_0;
+	oldbox.MaxEdge += oldpos_f;
+	oldbox.MinEdge += oldpos_f;
+
+	/*
+		If the object lies on a walkable node, this is set to true.
+	*/
+	result.touching_ground = false;
+	
+	/*
+		Go through every node around the object
+	*/
+	for(s16 y = oldpos_i.Y - 1; y <= oldpos_i.Y + 2; y++)
+	for(s16 z = oldpos_i.Z - 1; z <= oldpos_i.Z + 1; z++)
+	for(s16 x = oldpos_i.X - 1; x <= oldpos_i.X + 1; x++)
+	{
+		try{
+			// Object collides into walkable nodes
+			if(content_walkable(map->getNode(v3s16(x,y,z)).d) == false)
+				continue;
+		}
+		catch(InvalidPositionException &e)
+		{
+			// Doing nothing here will block the object from
+			// walking over map borders
+		}
+
+		core::aabbox3d<f32> nodebox = getNodeBox(v3s16(x,y,z), BS);
+		
+		/*
+			See if the object is touching ground.
+
+			Object touches ground if object's minimum Y is near node's
+			maximum Y and object's X-Z-area overlaps with the node's
+			X-Z-area.
+
+			Use 0.15*BS so that it is easier to get on a node.
+		*/
+		if(
+				//fabs(nodebox.MaxEdge.Y-box.MinEdge.Y) < d
+				fabs(nodebox.MaxEdge.Y-box.MinEdge.Y) < 0.15*BS
+				&& nodebox.MaxEdge.X-d > box.MinEdge.X
+				&& nodebox.MinEdge.X+d < box.MaxEdge.X
+				&& nodebox.MaxEdge.Z-d > box.MinEdge.Z
+				&& nodebox.MinEdge.Z+d < box.MaxEdge.Z
+		){
+			result.touching_ground = true;
+		}
+		
+		// If object doesn't intersect with node, ignore node.
+		if(box.intersectsWithBox(nodebox) == false)
+			continue;
+		
+		/*
+			Go through every axis
+		*/
+		v3f dirs[3] = {
+			v3f(0,0,1), // back-front
+			v3f(0,1,0), // top-bottom
+			v3f(1,0,0), // right-left
+		};
+		for(u16 i=0; i<3; i++)
+		{
+			/*
+				Calculate values along the axis
+			*/
+			f32 nodemax = nodebox.MaxEdge.dotProduct(dirs[i]);
+			f32 nodemin = nodebox.MinEdge.dotProduct(dirs[i]);
+			f32 objectmax = box.MaxEdge.dotProduct(dirs[i]);
+			f32 objectmin = box.MinEdge.dotProduct(dirs[i]);
+			f32 objectmax_old = oldbox.MaxEdge.dotProduct(dirs[i]);
+			f32 objectmin_old = oldbox.MinEdge.dotProduct(dirs[i]);
+			
+			/*
+				Check collision for the axis.
+				Collision happens when object is going through a surface.
+			*/
+			bool negative_axis_collides =
+				(nodemax > objectmin && nodemax <= objectmin_old + d
+					&& speed_f.dotProduct(dirs[i]) < 0);
+			bool positive_axis_collides =
+				(nodemin < objectmax && nodemin >= objectmax_old - d
+					&& speed_f.dotProduct(dirs[i]) > 0);
+			bool main_axis_collides =
+					negative_axis_collides || positive_axis_collides;
+			
+			/*
+				Check overlap of object and node in other axes
+			*/
+			bool other_axes_overlap = true;
+			for(u16 j=0; j<3; j++)
+			{
+				if(j == i)
+					continue;
+				f32 nodemax = nodebox.MaxEdge.dotProduct(dirs[j]);
+				f32 nodemin = nodebox.MinEdge.dotProduct(dirs[j]);
+				f32 objectmax = box.MaxEdge.dotProduct(dirs[j]);
+				f32 objectmin = box.MinEdge.dotProduct(dirs[j]);
+				if(!(nodemax - d > objectmin && nodemin + d < objectmax))
+				{
+					other_axes_overlap = false;
+					break;
+				}
+			}
+			
+			/*
+				If this is a collision, revert the pos_f in the main
+				direction.
+			*/
+			if(other_axes_overlap && main_axis_collides)
+			{
+				speed_f -= speed_f.dotProduct(dirs[i]) * dirs[i];
+				pos_f -= pos_f.dotProduct(dirs[i]) * dirs[i];
+				pos_f += oldpos_f.dotProduct(dirs[i]) * dirs[i];
+			}
+		
+		}
+	} // xyz
+	
+	return result;
+}
+
+