Comments for Piko3D

Comment on libPNG Tutorial: Loading PNG files from streams by Wracky

Wracky — Mon, 19 Dec 2011 12:36:27 +0000

Hi Benson, and thanks for posting!

The pUInt is actually one of our own typedefs. It guarantees a 32 bit int, same as the PNG one.
I thought I’d removed all our own types for the sake of this tutorial, but I guess this one slipped by, so thanks!

Regards,
Wracky.

Comment on libPNG Tutorial: Loading PNG files from streams by Benson

Benson — Sun, 18 Dec 2011 01:33:19 +0000

Out of curiosity, should

pUInt q = (imgHeight- i – 1) * stride;

actually be:

png_uint_32 q = (imgHeight- i – 1) * stride;

Comment on Space Partitioning Tutorial: Piko3D’s Dynamic Octree by Wracky

Wracky — Mon, 07 Nov 2011 10:54:36 +0000

Hi Everyone!

Thanks Ganaboy, glad you like the article!

khayman218: Thanks for posting, and sorry for the late reply.
To answer your question: Octrees are basically structures fit for fast spacial queries. In your case the question is: What query do I want to do ? if you are implementing an AI and want to find nearby entities, you’d have to specify the range in which you want to look. Finding “Nearby” Entities would mean defining what you think is “nearby”, defining a volume that describes that nearby space, and query the octree with it to find out what objects fall within it.

Hope that helps!
Regards,
Wracky.

Comment on Space Partitioning Tutorial: Piko3D’s Dynamic Octree by Ganaboy

Ganaboy — Mon, 07 Nov 2011 06:56:39 +0000

Thanks you so much for sharing this. I am just beginning to think of scene management and was feeling overwhelmed with same exact problems you have described here.

Thanks,
Mr Ganaboy

Comment on libPNG Tutorial: Loading PNG files from streams by Chris Arena

Chris Arena — Sat, 03 Sep 2011 16:26:26 +0000

Thanks for the tutorial!!

BTW, you don’t have to check for non-NULL before doing:

delete [] rowPtrs;
or
delete ptr;

The delete operator accepts NULL gracefully.

Cheers!!

Comment on Space Partitioning Tutorial: Piko3D’s Dynamic Octree by khayman218

khayman218 — Thu, 18 Aug 2011 21:17:32 +0000

How do you handle the situation where an entity could be very close to the boundary of its partition? This is not relevant for collisions, but more for AI trying to discover other nearby entities.

Do you do a range check and then include the entities in the nearby partition in your query?

Comment on Space Partitioning Tutorial: Piko3D’s Dynamic Octree by Paramike

Paramike — Wed, 29 Jun 2011 11:19:15 +0000

Hi Adi!

Thanks for your reply!

We currently have not tackled this problem; however, we do have support for custom memory management by overloading the ‘new’ and ‘delete’ operators in a base class that is the parent or great-parent of all classes We aim to implement a thread safe (hopefully lock-free) memory pool, but that is of later concern.

Also note that the splitting and merging in the movie is a worst-case scenario: A large number of objects moving through space with no other objects in the same scene graph. Also, the amount of splits and merges can be minimized by adjusting the thresholds for splitting and merging.

Cheers,

Paramike

Comment on Space Partitioning Tutorial: Piko3D’s Dynamic Octree by Paramike

Paramike — Wed, 29 Jun 2011 11:18:39 +0000

Hi Ian!

Thanks for your reply! We like to hear from you when you succeed If anything is unclear, please tell us, so we can improve this article.

Cheers,

Paramike

Comment on Space Partitioning Tutorial: Piko3D’s Dynamic Octree by Adi Jurca

Adi Jurca — Wed, 29 Jun 2011 10:49:24 +0000

Hi. really great tutorial
What I wanted to ask is how did you overcome the fact that “new” and “delete” operations are very expensive. I mean if you use C++ and do as many splits, merges and creations or destructions as you describe, during run-time, doesn’t it affect your frame rate?
do you use some kind of memory manager? do you create your octree in some static way?
I’m working on something similar and your article helped me very much until now.
thanks

Comment on Space Partitioning Tutorial: Piko3D’s Dynamic Octree by Ian

Ian — Thu, 23 Jun 2011 02:33:24 +0000

You, sir, just blew my mind.

I’d been doing the “rebuild the whole damn octree if there are too many objects outside it” thing. Planning to implement your growing/shrinking scheme tonight.

Many thanks