Category: General

2010-08-17

Last day of the Summer of Code

Permalink 02:54:10 am, Categories: General  

So, today is the last day of this year's Google Summmer of Code (although the date on the post will say it's August 17, it's still August 16 where I am =]). Time surely has flown by! I was really worried at the beginning of the program, there was a lot of code I had to get used to, and I still didn't know exactly how some things had to be done. But in the end, everything worked out, and I believe this project was a great success.

I was able to finish all the tasks that were on the original proposal, with minimal adaptations. I also documented everything as well as I could, both with comments in the code and posting the details in this blog. There are two demo applications as well, to show how the API should be used.

I would like to thank everyone from CrystalSpace for the opportunity, specially my mentor Andrew. People have been very helpful and friendly since our first contacts, during the GSoC applications period. I hope the code produced during this program can be put to good use.

Please feel free to contact me at anytime by mail. I will also stick around the IRC channel.

Best regards,
Leonardo

Last week's changes

Permalink 02:44:16 am, Categories: General  

This last week I have made a few changes to the code, and I thought it would be good to make one post to talk a little about them.

First and most important, I found a problem with the demo application (not exactly a bug, more of a map misbehavior). If you plot a path going from the stairs in the basement01 sector to the basement03 sector, near the basement-dungeon sector, the path is likely to go below the stairs and through a wall. After careful examination, I realized this was actually caused by some parts of navigation meshes that were created below the stairs, due to the level geometry. Since Detour searches for the polygon nearest to the path's starting point, one of the polygons in this disconnected piece of mesh was being chosen, which caused the problem. In order to fix this, I altered the portal's polygon position for the portals that connect basement01 and basement03 in the world xml file, moving them up a little (the portal polygons were going below the stair level).
Here is the modified world file: link.

Second, I changed the DebugRender methods to return a list of csSimpleRenderMesh instead of drawing the structures directly using OpenGL. Notice that now you don't have to (read you shouldn't) call those methods every frame, only when the structure being drawn changes (you have to ask the iGraphics3D plugin to draw the meshes every frame, however).

Finally, I added another hotkey to the pathfindingtest application. Upon pressing 't', a path will be calculated between two predetermined points. This path will then be compared to a path previously calculated, and an error message will be displayed if they differ. If the paths are equal, nothing will happen.

2010-08-11

PolygonSearchBox parameter

Permalink 01:26:11 am, Categories: General  

I have added a new parameter to the iCelNavMeshParams class, polygonSearchBox. Here is a detailed description (copied from the parameter values post):

"Before creating a path, Detour finds the closest polygons in the navigation mesh to the origin and destination points. This parameter determines the dimensions of the bounding box where Detour will look for the closest polygons. The bounding box is represented by two vertices: (center + polygonSearchBox) and (center - polygonSearchBox), where center is the point one wants to find the closest polygon to.

This parameter is also used to determine if a low level path that was calculated by Detour reaches it's intended destination (Detour always returns a path, either to the destination or the closest possible point). If the distance between the two points, in each of the coordinates, is less then this parameter, then they are considered to be close enough for this purpose."

One simple way to understand this parameter using the demo application is clicking on a point that is not exactly on the navigation mesh. For example, consider clicking on the walls: the greater the y coordinate of the polygonSearchBox, the higher you can click on the wall and still have the path traced.

Updating navigation structures

Permalink 12:37:23 am, Categories: General  

If some object changes position in a map, instead of rebuilding the whole navigation structure, one can update it using the iCelHNavStruct::Update() method. This method takes a bounding box and a pointer to a sector as parameters (although the sector is optional): the bounding box describes the area of the navigation mesh that one wishes to update, and the sector determines which sector should be updated. If no sector is specified, then the bounding box will be collided with each of the sectors navigation meshes' bounding boxes to determine what sectors have to be updated.

Note that this should probably not be used for objects that are on constant movement (npcs for example), since it's not very fast. This can be seen on the apppathfindingtest application by pressing 'y' (check last modifications to the demo application on this post).

Although updating a navigation structure takes some time, it is still way faster then rebuilding it.

2010-07-26

Hierarchical pathfinding demo

Permalink 02:03:59 am, Categories: General  

I created a new demo application to test the HPF algorithm (it's the pathfindingtest app). In this application, there is a player controled actor (Cally), which can be moved around by the arrow keys. The map used in this demo is the Castle map, from CrystalSpace.

Here is a list of hotkeys for this application:

  • b: Build the navigation structure.
  • l: Load a previously built navigation structure.
  • s: Save the current navigation structure.
  • c: Clear the navigation structure, as well as the current path, if there is one.
  • 1: Toggle navigation structures debug rendering.
  • 2: Toggle destination point debug rendering.
  • 3: Toggle path debug rendering.

Once a navigation structure is either built or loaded, the mouse can be used to create paths. A left click will create a path between the actor's current position and the clicked position.

For the path following code, I used the pcmove.mover property, modified so the curves are sharp and precise instead of smooth. If the old smooth behaviour was used, there would be no guarantee that the actor would not walk out of the navigation meshes. The new behavior can be activated in any application that uses pcmove.mover, all that has to be done is set iPcMover::SetSmoothMovement() to false (the old behaviour is the default one).

I made a video of the actor moving around, being controled by the mouse, you can check it clicking here or in the image below (unfortunately, I was unnable to embed the video).

Path following
Path following

2010-06-08

Introduction

Permalink 06:44:51 am, Categories: General  

Hello everyone!

My name is Leonardo, and I am one of this year's GSoC students.
I am currently a M.S. student in Computer Science at UNICAMP (University of Campinas), Brazil. I don't have any prior experience with CrystalSpace and CEL, but I believe I won't have much problem, since everything looks organized and the community has been very friendly and helpful so far.

This summer (although it's technically a winter for me), I will be working into integrating the Recast and Detour toolsets into CEL.

The main topics of my project will be the following:

  • Build a navigation mesh from a sector, using Recast.
  • Build a hierarchical navigation structure from a map.
  • Build a navigation mesh from a height map.
  • Allow changes to the navigation meshes during runtime.

I plan on posting on this blog updates about my progress and any problems I come across, so people can use it as reference for this work.

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