looks really nice. Do you export the results?

Very nice!
Do you plan to give your command line interface the ability to perform batch processing?

> load fly
> load seth_brundle
> add fly seth_brundle brundlefly
Objects combined at molecular level.

Have you ever heard of Insect Politics?

Not yet because I'm still struggling with DirectX 8 interfaces :-) The final demo will have that ability.

I already have this ability, although it doesn't show from the picture. I plan to include several of these files in the demo so that people can tweak them.

Would be cool to have a mesh class that can encapsulates CSG operations ;-)

Tim

Nah, just add some operators to your meshes.
Works really cool, so you can add meshes, subtract 'em, whatever.

Like

Mesh new_mesh = cube + pyramid;
new_mesh -= cylinder;

Looks cool!

What size of objects can you handle before you start grinding to a halt?

I recently coded a CSG thing, and had it running at around 30fps with 2 objects each around 2-300 faces intersecting.. (just flatshading, on a GeForce2)..

What the hell is a CSG?

I think CSG is Constructive Solid Geometry or something like that

Yup, it is.
Basicly, it's just boolean operators on solid volume descriptions.

Stupid me tried to drag the window in the image to have a better look at the other images underneath..

Anyhow - very cool - how does your engine handle epsillion sized triangle slivers when you've csg'd an object several times? Do you have any plans for a polygon "optimization" pass for this, to remove over tesselation?

Mech game where you can literally melt holes through your opposition - now that'd be sweeeeeet.

Good work man.

i'm very interested into coding boolean operations can anyone say me where i can find tutorial, source code, & all the things i need??
thanks
giuseppe

Actually, I am not descending the BSP tree every frame (not drawing correctly back-to-front), I just draw a static vertex buffer, which is filled by the "show" command. So even thousands of faces draw fast enough (>300fps)

Greets,
Nikolay

I don't handle these ####ing holes (T-junctions or whatever) in any way still, because I don't really know how to :)
I am now working on the code that merges coplanar polygons that are on the same node of the BSP tree. I have left that for the last moment, after I finish with the basic functionality

Greets,
Nikolay

Here is a good place to start (and in fact the only one I know)

http://members.home.net/droyer/tutorials/index.html

I will release the source code to this demo soon. If you have any questions, feel free to ask :)

Greets,
Nikolay

Can your algorithm (naylor) work with objects that have holes?
I'm trying to find an algorithm that doesn't have the contraint of objects need to be solid.
Looking forward to your demo (and the code of course)

- Ron

Yes, there's no problem with objects that have holes in them. Check the link I posted in a previous reply for a tutorial on Naylor's algorithm. Unfortunately, I cannot find an electronic version of the original paper - siggraph 90-something.

Greets,
Nikolay

"Yes, there's no problem with objects that have holes in them."

How can you do CSG with objects that aren't solid? Intuitively what does that mean?

Max

For example look at the yellow cube with the carved sides (small picture). You can add / subtract any primitive... I guess it's not "Solid" geometry anymore, though :)

Greets,
Nikolay

I'd disagree there... it looks like a solid object, as does the rotated cube that seems to have been taken out of the cube to give it...

A non-solid object is a pyramid with no base, or a simple plane...

Back to my computer graphics and programming of graphics knowledge ->

Normal boolean operations on solids are defined as such-
A Union of two objects contains all the points that were contained in the two objects.
An Intersection contains all the points that were contained in both objects, without including planes or points. (so if two cubes of size 2x2x2 were placed at (1,0,0) and (-1,0,0) the intersection would be empty)
A Subtraction contains all the points of the first object, without any that were in the intersection of the two objects.

An important aspect of this is that these operations are CLOSED on solid objects, you cannot get an object that doesn't have a volume - which is why you have to have the careful definition of Intersection.

Another operation that isn't as common is Cut (although it may be known as something else to other people) where you remove any points on the faces of the first object which would lie within the second. It is NOT closed. As an example, take a 4x4x4 cube centered at (0,0,0), if you cut from this a sphere of radius 1 centered at (2,0,0) you get a cube with a circular hole in the top face. It is nolonger a solid object.

I think you've simply got the wrong definition of what a solid object is.

Hi! Lookin' really good!

I'm really looking forward to read the code :o).. I wont be able to run it, cause I'm on NT 4.0...(Opengl rulez *G*)..

cya,
Phil

Hmm,
I guess I was wrong with the definition of a "solid" object indeed. The objects I was talking about are really "non-convex", which means that if you take two points inside them, the line that connects them is not necessarily contained within the object.
I really haven't tested with non-solid objects and I might just as well do that :)

Greets,
Nikolay

Welll ... I can get 1500 fps. Of course, my screen in empty, but it is nicely cleared by any color you want. And yes, blue color looks nice ! it remembers me about win98

Zdrasti Niki,
ami kude sa sorsovete?
imash li web-page?

malkia

My firs post was derived from my impression about your frame rates.
Now about CSG
CSG is cool.
but I use modified CSG approach which is way better than known so far. Well, I plan to use it ... so thanks for more info about that topic. I'll try to understand why programs work so bad to make better one. And most of them works bad, believe me

Heh, yeah, I was hunting for some good CSG info for a while now. Here's what I've found...

www.mr-gamemaker.com was going to put up a tutorial using BSP trees, but odd happened, and now ALL of his great tutorials disapeared. Strange. Now it seems his page is gone, replaced now only by his bbs. That bbs though still is a great source though for CSG info.

Here's Naylor's paper Merging BSP trees yields polyhedral set operations.

and Merging BSP trees yields polyhedral set operations.

Lets see...

here's formal definition of Naylor's merging BSP algorithm.

Cuban has an short, but easy-to-read explanation.

and the last one I got is just a presentation by Naylor.


And that's about all I've found (other than Midnight's here). I wish, though, there were tutorials out there on this stuff. Reading these papers can be rough...

Note, I havent yet figured out how to implement Naylor's second paper. I did get the first one though. If you're interested, I'll post up my source code too.

hey, I posted the link to the papers up a post or so...

:-)
mi sorsovete i web-page kato dovyrsha poslednite raboti deto mi ostanaha - oprostqvaneto i t.n. a tuka edno takova lqtno vreme che edvam se zasedqvam pred komp-a :)

are,
Niki