Boundin box

sader · Post by **sader** » Thu Oct 11, 2007 3:41 pm

Not sure how update bounding boxes so that it would be roteted scaled and positioned right. Is it possible overall?

Couldn't find function in aabbox3d class or ISceneNode

I am drawing box like this

Code: Select all

g_Driver->draw3DBox(Node->getTransformedBoundingBox());

and this is what I get

correct
wrong

hybrid · Post by **hybrid** » Thu Oct 11, 2007 3:52 pm

Why not just enabling the debug mode to draw bbox? But for drawing a 3d box you will have to set a proper material and projection matrix to avoid interference with former draw calls.

sader · Post by **sader** » Thu Oct 11, 2007 4:17 pm

Cool

I enabled debug mode for my node and it looks is everything fine

but anyway interesting why draw method doesn't draw box like it should

vitek · Post by **vitek** » Thu Oct 11, 2007 5:08 pm

The problem is that the transformed bounding box from getTransformedBoundingBox() is wrong when a scene node is rotated. It is very efficient compared with the correct method, but it is still wrong. I have commented on this many times.

http://irrlicht.sourceforge.net/phpBB2/ ... hp?p=94967

Here is an image that illustrates the different bounding boxes that you can get for a single rotated cube.The green one is axis aligned in object space, the red one is axis aligned in world space. The blue one is just wrong as it doesn't even enclose the entire object. Once you have the incorrectly transformed bounding box from getTransformedBoundingBox(), there is no way to get something useful out of it without undoing the bad transform [which would be silly].

If you want the correct world space bounding box, try the following.

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core::aabbox3df box = Node->getBoundingBox();
Node->getAbsoluteTransformation().transformBoxEx(box);

If you just want to render the meshes bounding box, it is easier to use the debug mode flag as suggested by hybrid [assuming you want to use that color].

Travis

sader · Post by **sader** » Thu Oct 11, 2007 5:39 pm

that very good explanation

but then goes question is this function getTransformedBoundingBox() usefull somehow/somewhere

vitek · Post by **vitek** » Thu Oct 11, 2007 7:08 pm

If you know absolutely that the object is aligned with the world axes, then it gets the same results as calling transformBoxEx(), except that it is more efficient. I don't believe that is a very good reason to keep it. Other than that I haven't really found a good reason for it to exist. Maybe someone could provide a reason.

Travis