Display _very far_ objects

gbrinon · Post by **gbrinon** » Thu Oct 15, 2009 2:04 pm

Hi,

I have a question, i suppose it's not specific to irrlicht, but i'am working with it so...

I try to display a large space. If and object is near the player's ship, i display it. But if something is very far, i want to display a little sign. (just as eve online do http://linuxoutlaws.com/files/eve-online.jpg )

I thought i had to use LOD but the sign must always have the same size however the distance between the object and the ship.

How can I do such a thing ?

P.S : Sorry for my English (I'm french)

FuzzYspo0N · Post by **FuzzYspo0N** » Thu Oct 15, 2009 2:57 pm

These little icons are generally done in 2d, there is a function in the collision manager to get a screen coordinate from a 3d position, just draw an icon at the position in 2d, and fade its alpha in based on a distance factor

gbrinon · Post by **gbrinon** » Thu Oct 15, 2009 3:00 pm

.... good idea, i should have thought to that

I'll try to find this function.

If i don't want to display the objects whitch are too far (in order to replace them with the 2d image), i use the LOD ?

Thanks a lot

Lonesome Ducky · Post by **Lonesome Ducky** » Thu Oct 15, 2009 7:16 pm

Also, if you have a lot of objects you may want to think about calculating the distance every 100 ms or so instead of every frame, as sqrt() isn't exactly the fastest function.

Halifax · Post by **Halifax** » Thu Oct 15, 2009 7:52 pm

Lonesome Ducky wrote:Also, if you have a lot of objects you may want to think about calculating the distance every 100 ms or so instead of every frame, as sqrt() isn't exactly the fastest function.

You could always fade based on magnitude squared.

lymantok · Post by **lymantok** » Fri Oct 16, 2009 4:30 am

Hi,

It looks like the function you want to use in Irrlicht 1.6 is:

virtual core::position2d< s32 > getScreenCoordinatesFrom3DPosition (core::vector3df pos, ICameraSceneNode *camera=0)=0
Calculates 2d screen position from a 3d position.

From:

http://irrlicht.sourceforge.net/docu/cl ... nager.html

gbrinon · Post by **gbrinon** » Fri Oct 16, 2009 8:03 am

Thank you very much !!!

I'll try this one. I hope it exists on irrlicht 1.3.1, actually i'm using jirr, so i cannot use the newest irrlicht version.

But thanks a lot

JP · Post by JP » Fri Oct 16, 2009 9:06 am

could you not use one of the text scene nodes or text billboard scene node things... one of those displays text at 3D positions always at the same size.

gbrinon · Post by **gbrinon** » Fri Oct 16, 2009 12:46 pm

All your ideas works well. Thanks a lot again

Now i just have to use a LOD to make the models disapear when they are too far.

The problem will be to compute all the distances everytime (or maybe all the 100ms or more like Lonesome Ducky said)