Well we've reached the midway point of the summer (although you wouldn't know from the weather here!) I've been having some trouble this week with the google website after completing my midterm assessment but hopefully this is not a significant problem and I will find out over the weekend if you are all sufficiently satisfied with my progress to continue.
I have begun this week to work on the Recast and Detour (R&D) part of my project. So far this has mainly consisted of getting familiar with the library and Leonardo's previous work implementing it into CEL. I have committed revision 4928 which updates the library files to r345 of R&D and have since tested them in msvc - they do not yet compile.
A number of changes need now to be made to
cellhpf.h/cpp to accommodate the API changes in R&D since the previous version (187) used in Leonardo's work. In particular I have limited the necessary changes down to the following R&D blog posts:
Once complete I may also need to (re)implement the following changes previous made to fit R&D into CEL:
I intend to work on these updates next week (provided the midterm has been passed successfully) with the aim to have the example apps
apppathfindingtest fully functional with the new plugin and latest R&D library by this time next week.
I have just committed the final deliverable for the behaviour tree (BT) portion of this GSoC project. As of revision 4927 BT's can now be loaded from XML. This functionality is also demonstrated in this revision of appbttest.
As mentioned last week this deliverable is slightly behind schedule, but at only 5 days late and given the significant improvements in the BT code, I hope you all agree that this part of the project has been a relative success - especially given that midterm evaluations are coming up next week! :)
I am taking a slightly long weekend, leaving shortly and returning Monday. Unfortunately I will be offline for all of this time. However please feel free to contact me if there are any suggestions regarding the code or the next stage of the project and I will get back to you asap Monday.
Next week I will begin work on the recast and detour code, but until then I hope you all have a good weekend.
Ocean looked nice with connected meshes but it lacked reflection and refraction. Although Ocean is actually a deep water system thus should have no refraction but I did it anyways. For this implementation i followed this Paper.
It involved 5 basic steps.
1. Create the reflection texture : provided by engine
2. Create the refraction texture : provided by engine
3. Distort the textures according to a dudv-map :- We don't need it as it's used to apply distortion. Normal map worked equally great.
4. Apply bump mapping : not needed since we are using vertex shaders to generate waves.
5. Combine with fresnel effects : no problem :)
and here's the result
-ocean exhibits No caustics. Caustics are already implemented in CS but aren't in ocean
-This shader is *not* shaderwaver. It is regular vertex and fragment program.
-LOD pops out as you move along.
-ocean doesn't entirely covers the island. a possible solution for it could be to increase the cell width and leght and corresponding parameters. so that it covers more area.
-also waves direction appears to be changing between different LOD when viewed from top. implementing inverse FFT could remove it, I think.
So Crystal Space had a Ocean system in which Ocean was made by combining little ocean cells(20x20). These ocean cells would have different Level of Details(LOD) Governed by distance from camera. This distribution of LOD wasn't quite working as distance computed between camera and the cell was actually a *squared* distance and comparison was made with actual distance. Also cells re-positions themselves as camera move parallel to ocean. This re-positioning was causing a jerk. Well, both these bugs are fixed now. :)
Now comes the major issue *aaahhhh*. LOD distribution was working fine but the problem was with adjoining ocean cells of different LOD. for example one cell has LOD 5 and adjoining cell had LOD 4. Now LOD5 has double the vertices at boundaries than LOD4. and since the vertices are moving in waves like patterns so the ocean cells looks unconnected and Thus looked Ugly.
Thanks to Nvidia's ocean demo(and of course my mentor res) I was successfully able to replicate their implementation to rectify this problem. Checkout the wireframe rendering of ocean.
Here's what's happening.
Now have a look at this
Yellow color represents an oceancell.
Blue color represents inner mesh.
Green color represents the division line of outer meshes for a single cell.
there are four outer meshes for each cell.
Red color represents how LOD levels are connected using low res boundaries in higher LOD cell.
The vertices for a cells are computed as usual. The real magic happens in computing the triangle(tris). tris for inner meshes are computed as usual. then 2^4=16 different cells are created for one LOD level and stored in an array.
2^4 where 2 is the resolution ie low/high and 4 are edges Top/right/bottom/left. That's how we got the number 16. Desired cell(out of 16) selection depends upon LOD level adjoining cell.
This week I have switched the previous celBehaviourTree to the dedicated propclass celPcBehaviourTree. There were numerous commits but most importantly, revision 4916 includes a fully functional BT prop class and example usage in appbttest.
These revisions also add the abilities to interrupt or reset a behaviour tree and to set how many nodes per frame are parsed.
With the 1st July rapidly approaching, it is apparent at this time that not all goals of the BT portion of this project will be completed as originally scheduled. My mentor and I have agreed that the best way to proceed will be to continue with BT development for now and complete the load from XML deliverable. I will then move on to the Recast and Detour work hopefully by the end of next week and, therefore, not significantly behind schedule.
Finally, I would like to publicly note my gratitude for all the assistance I have received this week. Thank you all - especially Anthony, Christian and Mat! :)
As intended this week I have focussed on making more use of the behaviour tree(BT) specific return status BT_UNEXPECTED_ERROR. In particular, revisions 4908 and 4910 add the reporting of nodes not having the relevant children, rewards, triggers or parameters specified first with severity notify at the node itself and then again with severity error if the unexpected error is not handled but propagated back to the root of the tree.
Revision 4908 also added the method
void SetName (csString nodeName) so that BT nodes cane be given a name, which is then reported if an unexpected error occurs. This should simplify debugging large trees.
Finally, in revision 4909, I added the method
void MakeLoopInfinite () to the loop decorator allowing the node to be set to run forever whilst the child returns BT_SUCCESS. If the child fails, then so does the loop. This will be useful as a root node for many behaviour trees as often non-player characters will be expected to continuously repeat some set of behaviours.
I have begun now to think about the dedicated BT propclass and loading from XML. I hope to make significant progress next week towards at least one of these desirable deliverables before beginning to work on the recast and detour side of this project which is scheduled to begin after next week (for the original timeline please see this post.)
Well I'm back, had a great conference and have dived into implementing the stack-based behaviour tree I discussed here before leaving.
One design change I found necessary was to add another status, BT_NOT_STARTED, to use in resetting and initialising nodes.
Revision 4907 switches from the previous 2009 method of parsing the entire tree every frame to passing a single node every frame. This will make the method far more scalable and should help with debugging as progress can now be tracked in the behaviour tree's stack. This is a significant revision that is key to this part of the project. If there are any comments in particular on this revision I am very keen to hear them.
In a smaller commit, revision 4906 merged all changes from whilst I was away and since I began coding. I intend to complete these merges at least once a fortnight to make the eventual process of merging my branch to trunk far simpler.
That's all for this week, next week I intend to add more to the debugging tools by making better use of the status BT_UNEXPECTED_ERROR and starting to look into loading from XML and making a dedicated propclass for the behaviour tree. Any suggestions either here, by email/mailing list/irc are always appreciated.
First, to quickly wrap up last week's discussion of the problems with a few apps hanging, I have raised a ticket covering this problem (Ticket 103) and will look to help with a solution later into the summer once I am sure to have met the planned deadlines.
This week work moved on to focus on beginning to implement event driven behaviour trees (BTs). I spent some time studying openly available implementations and have made some initial decisions that I would like to discuss briefly.
The current CrystalSpace BTs parse the entire tree every frame starting from the root node. This will obviously not scale well to large trees or games with many trees. Event driven BTs instead remember where in the tree they have reached and parse only active nodes on each callback.
Therefore, my intention is to add a stack of pointers to BT nodes to the behaviour tree and pass a pointer to this to a node when it is executed. This way parent nodes can push their child nodes to the stack instead of calling their children themselves. Then when the behaviour tree receives it's callback it only needs to execute the top node on the stack.
This will reduce the number of nodes executed per callback to a constant number. It should also help with debugging, as by watching the stack a developer can understand which nodes in the tree are being executed and which path has been taken to reach there.
Furthermore, this should allow me to easily add the function of being able to control the rate of updating a BT as the top node can be executed multiple times per callback (with the callback set to either every frame or by time.) On each execution of the top node the subsequent top node may change and so repeat execution of the top node is effectively parsing through the tree.
Whilst exploring existing implementations and designing our solution I noticed that the easiest milestone to add first was Christian's suggestion of extending the termination statuses. Previously a node would indicate only success or failure on termination, but now (as of revision 4899) a failing node can indicate whether it failed cleanly or whether it has exited unexpectedly. (For more detail on why this is useful please see this article.)
This revision will be used more in the upcoming work on event driven BT's as a parent node will want to check the final status of a child node once the child has terminated and the parent has returned to the top of the stack. To do so I intend to add the current status of a node as a public variable of the iBTNode interface.
Please feel free to comment on this blog, email me on the mailing list or catch me in the IRC channel if you have any comments or suggestions.
As mentioned in my proposal I am now leaving for a conference, and so will not be updating the blog next week nor likely to commit any code. However, I do have my linux laptop with me and the source code checked out, so I may get time to think more about the design and look further into prop classes and existing XML code in CEL (as needed for the later BT milestones.) I will update the blog again Friday 15th June.
See you all in 2 weeks time, Sam.
As the first week of GSoC is coming to an end, I thought it best to update the blog with my progress so far. I intend to (as I did previously during GSoC 2009) post weekly on Fridays with quick updates for anyone interested in following the project.
This week has been mostly occupied by getting bttest to work again. It seems there may be a bug in trunk that is causing bttest (and graphtut, steering and walktut) to hang. I have not solved the problem but I have commited a workaround to my branch in revision 4893. If anyone else is having the problem or has suggestions to fix this please join in the conversation on the mailing list (Archived here.)
Revision 4893 also contains a workaround fix to get plgtcpnetwork to compile as DebugWithDLLs in Windows. Which may also be a general problem at this time in trunk.
The final changes in revision 4893 are what I needed to overcome compilation and linking errors in appelcmtst, plg_guiinventory and plg_guiinventory2 due to CEGUI. I think from the discussion on the mailing list these changes were needed only by me.
Since overcoming these difficulties, I have fixed a minor but significant bug in the bttest app that stopped the tree from being evaluated (see revision 4897.)
I now have a working bttest app, a better understanding of my code from 2009 and am ready to start implementing event driven behaviour trees next week.
A quick update and thank you to all who have helped me out the past couple of weeks. Thanks to the mailing list and in particular Christian's efforts I now have a fully compiled and up to date CS and CEL. I have refamiliarised myself with svn-merge.py (I typically use TortoiseSVN but wanted to stick to the tools other CS developers are using for this project), and with my code from the previous GSoC project on behaviour trees. I now feel ready and keen to start coding next week in time for the official start of GSoC.
I include below my proposed timeline and goals, with priorities labelled 1-3 with 1 being the highest:
-Update to event driven BTs (May 21st – July 1st)
(1) -- Focus on debug tools
(2) -- Allow all termination statuses
(2) -- Add load from XML option
(2) -- Create dedicated propclass (set root node, set update rate)
(1) -- Documentation
-Update to latest version R&D (July 1st – July 29th)
(1) -- Allow iPcSteer to use its methods
(2) -- Partial navmesh loading (with missing sector callback)
(2) -- Make navmesh creation parallel
(3) -- Improve function with portals
(3) -- Optimise debug mesh
(3) -- Optimise Terrain
(1) -- Documentation
-Improve life sim demo (July 29th - August 13th)
(1)-- Make behaviours work (perhaps requiring other new propclasses or
fixes to existing ones)
(1)-- Use new BTs and R&D
During this time, I will have one significant break (as mentioned in my proposal) from June 2nd-12th when I will be attending a conference in Valencia. Other than that I am excited to be back and keen to get started :)
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