About 1.5 a years ago I've made my second 3D engine.
The best thing about this engine compared to other is that it displays everything in the correct order and even can deal with intersecting triangles.
It uses Binary Space Partioning to sort triangles and sprites.
This topic is a tutorial for using it.

Everything in this 3d engine is based on 3d objects.
You can control objects from Game sprite.
In Engine sprite the only thing you should change is

define Controls

Game sprite contains lots of custom blocks for interacting with 3d:

Custom block definitions:

broadcast [activate engine v]
broadcast [stop engine v]

Clear all::category custom

Does exactly what you expect

NewObject [type]at(0)(0)(0)visible(1)::category custom

type x y z visibility:
type - is actually an object type. Objects of the same type have the same behavior.
x,y,z - position of the object
visibility - 0-invisible 1-visible

Add triangle(0)(0)(0)(0)(0)(0)(0)(0)(0)color(0)(0)(0)(0)face(0)object(0)::category custom

x1 y1 z1 x2 y2 z2 x3 y3 z3 red green blue transparency face object
x1 y1 z1 x2 y2 z2 x3 y3 z3 - position of the triangle corner
red green blue - color (value from 0 to 255)
transparency - 255-solid 0-invisible
face - 0-visible from both sides 1,-1-visible from one side, everything else-invisible
object - number of element(not a name) containing needed object in the GroupName

Hide(0)::category custom
Show(0)::category custom

object - number of element(not a name) containing needed object in the GroupName

Clear model(0)::category custom

removes all triangles of entered object
object - number of element(not a name) containing needed object in the GroupName

Deleate(0)::category custom

removes object and all triangles of it
object - number of element(not a name) containing needed object in the GroupName

Sprite(0)costume[costume name]::category custom

object costume
object - number of element(not a name) containing needed object in the GroupName
costume - name or id of a costume that is placed inside Engine sprite
puts your costume at the center of an object
does exactly the same thing as:

replace item (object v) of [GroupDisp v] with [costume]

replace item (object v) of [GroupX v] with [0]
replace item (object v) of [GroupY v] with [0]
replace item (object v) of [GroupZ v] with [0]

object position
moves object

replace item (object v) of [GroupVX v] with [0]
replace item (object v) of [GroupVY v] with [0]
replace item (object v) of [GroupVZ v] with [0]

object velocity
sets velocity
purpose can be changed

replace item (object v) of [GroupTmp v] with [costume]

object value
value - has no purpose, you can use it for anything

Variables

(Pheight)

- Height of the player(meters)

(CamX) (CamY) (CamZ)

- position of the feet

(Quality-Speed)

- 1-max quality 10-low quality

(AngleX)

- pitch

(AngleY)

- yaw

(AngleZ)

- roll

(Max walking speed)

(StandOn)

reports a triangle(not an object)
to get object number, you should use

(item ((StandOn) * (3)) of [FO v] :: list)

to get object type, you should use

(item (item ((StandOn) * (3)) of [FO v] :: list) of [GroupName v] :: list)

(Look_Tri)

works the same but can also report looking at sprite, by giving negative value(and in that case it would be group number)

(Look_Dist)

Distance to the place which you are looking at

(Look_X)(Look_Y)(Look_Z)

Coordinates of place which you are looking at

Behavior

Making animated objects.

define Game tick
set [item v] to [0]
repeat (length of [GroupName v] :: list)
change [item v] by (1)
your code 1::color #aaaaaa
replace item (item) of [GroupX v] with ((item (item) of [GroupX v] :: list) + (item (item) of [GroupVX v] :: list))
replace item (item) of [GroupY v] with ((item (item) of [GroupY v] :: list) + (item (item) of [GroupVY v] :: list))
replace item (item) of [GroupZ v] with ((item (item) of [GroupZ v] :: list) + (item (item) of [GroupVZ v] :: list))
end
your code 2::color #aaaaaa

In Your code 1 you describe what would happen with every object in every frame.
Example:

if <(item (item) of [GroupName v]::list)=[samll_tree]> then
    replace item (item) of [GroupTmp v] with ((item (item) of [GroupTmp v] :: list) + (1))
    if<(item (item) of [GroupTmp v] :: list)=(1000)> then
        replace item (item) of [GroupName v] with [tree]
        replace item (item) of [GroupDisp v] with [tree_costume]
    end
end

In Your code 2 you describe what would happen every frame(something you don't need to run for every object).

Thanks I get it a little more now

Each time I read something I understand something different

This is truly incredible!

[/i][/b]
move () steps
pen up

I really dont understand

Still confused