what is the definition of a 'unit ' in 3D

Blitz3D Forums/Blitz3D Beginners Area/what is the definition of a 'unit ' in 3D

rod54(Posted 2008) [#1]
Is it a fix'd distance in pixels or a fixed measurement such as 1 meter ?


Pretty dumb question I suppose.


rod54(Posted 2008) [#2]
What I am asking this for is it doesn't seem that the documentation for blitz 3D doesn't cover this to someone new to 3D

There is only links for command reference and I can't find the info
that explains it there.

There is a link for tutorials which explains movement and rotation and describes that you are moving the rocket .05 units but doesn't explain what a unit really is in distance.

Seems that someone new to 3D would like to know this.

.05 units seems to move the rocket a fair distance on the screen

Also when he describes rotation, he states the the rotation in units
should that not be degrees ?

I know these are probably dumb questions but I am only taking this
from the perspective of some one new just buying the language and not knowing anything about 3D.


Robert Cummings(Posted 2008) [#3]
A unit is what you make it. This is the official response. So 1 unit can mean 1 inch or 1 mile if you want to. It is all about how you use it in relation to your other objects.

In my engine I choose 1 meter = 1 unit because its simple.

Don't go too high like 1 unit = 1 mile because it can throw things off whack if you want to zoom out too far or zoom in too close (clipping etc).

As a general rule 1 meter for 1 unit is good.


rod54(Posted 2008) [#4]
so is there a command to set how far a unit is in relation to your screen
resolution ?

Can you then change this to make 1 unit will to a meter then again to make
1 unit = to 1 foot ?


Gabriel(Posted 2008) [#5]
so is there a command to set how far a unit is in relation to your screen resolution ?

No, because it obviously depends on where the camera is. If the camera is miles away from it, the screen size is going to be a lot smaller than if it's right next to it.

Can you then change this to make 1 unit will to a meter then again to make 1 unit = to 1 foot ?

There's nothing to change. As Rob told you, it is whatever you want it to be. If you treat it like it's a meter, it will be. If you treat it like it's a foot, it will be. You can treat it like it's one thing and then another thing, providing you clean up in between. You can't treat it like it's more than one thing at a time though, so pick a scale and stick to it or you'll bury yourself in confusion.


Rob Farley(Posted 2008) [#6]
so pick a scale and stick to it or you'll bury yourself in confusion.
Excellent advice. My early projects I just made things up and then had to mess around with scaleentity for hours trying to make things look right against each other.

I too use 1 unit = 1 metre.

Of course if you're creating something huge or something tiny this probably isn't appropriate.

But personally I'd stick to metric and 10s... So for making something small use 1unit = 10cm or 1unit = 1cm and big 1unit = 1km etc etc... This way you just scale by 10s or 100s, makes life simple!


Beaker(Posted 2008) [#7]
1 unit = 1 metre for me too.

Rotations are always in degrees (not radians, not units).


rod54(Posted 2008) [#8]
Appreciate your help ...


GfK(Posted 2008) [#9]
There's no golden rule here. While 1 unit = 1 metre might be fine for some games, for others it would be preposterous, i.e. a snooker or chess game.

1 unit = whatever is suitable for what you're doing.

Obviously you'll want to stick to the same scale throughout your project, unless you like bashing your head on the desk.


D4NM4N(Posted 2008) [#10]
1:1M here too.


rod54(Posted 2008) [#11]
Makes sense... just that sometimes (usually I dont)


Santiworld(Posted 2008) [#12]
i allways try to find the best scale to the game..

if i´m going to make spaceships games, with planets, with large camerarange, is the same engine? maybe for some ranges, the game runs faster....

if i do a car game, with a track, i have 10km visibility range, but in a naval simulator, you have 100km visibility range, and in the space, you have 1.000.000 km range...

big games, like Armed assault, reduce the scale of all units and scenary, because they found a best performance doing all smaller...

1 unit? what is the best? using the camerarange that i need for my game? or in the case of blitz, is the same any range?


GfK(Posted 2008) [#13]
I have no idea what you just said. (well, beyond the first line)


Ross C(Posted 2008) [#14]
Looks like a google/altavista translation. When will these programs convert the grammar too? :o)


Ice9(Posted 2008) [#15]
This site explains most of the "units"
http://www.hobbyprojects.com/dictionary_of_units.html


Ice9(Posted 2008) [#16]
Just remember 3D sound is the big stricter on your unit size.


Gabriel(Posted 2008) [#17]
What's a "big stricter"? ( If it's something Max Mosley pays through the nose for, no need to tell me. )


Vertigo(Posted 2008) [#18]
3D Sound is fine until you get into REALLY big scales... but then again, why would you want to do that... When you create the listener for the 3d sound, just decrease that first parameter relative to your scene.


John Blackledge(Posted 2008) [#19]
1 unit = 1 metre here too.

3rd engine on, I found it too confusing not knowing what size to model people or scenery, then always having to rescale after loading.
At least now, with 1 unit = 1 metre I just make models created in other packages conform to this standard.