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Basic 3D Math for ARKit
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KBOY
September 15, 2018
Technology
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Basic 3D Math for ARKit
KBOY
September 15, 2018
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Transcript
Basic 3D Mathematics for ARKit Kei Fujikawa 2018.9.15@Tokyo iOS Meetup
Who?
Who?
Why is ے?
Spajam 2nd Prized Best Body Japan Held ے.swift Showing in Article Smooth-sailing?
Not so easy.
A bunch of ے
ے 4FOHPLV1FSJPE
AR!
Question!
Spajam 2nd Prized Best Body Japan Held ے.swift Showing in Article
I have to ride on this big wave.
So,
I joined AR startup this January
Graffity Inc.
Apps we’re making
I studied ARKit for so much time
Not so easy.
Let’s think about this example.
Place an airplane at the 30cm in front of screen’s
touched point.
None
Looks way too easy
Getting x,y from touch gesture and Z is 0.3?
Finally
None
It does not show
Ideal
None
Real
None
Not so easy
So,
I studied 3D programming.
Books I read for study IUUQTBN[OUP.4V.F( IUUQTBN[OUP1,'Z5
So,
Today I will explain 3D Programming clearly.
Basic 3D Mathematics for ARKit Kei Fujikawa 2018.9.15@Tokyo iOS Meetup
Today’s goal
Place an airplane at the 30cm in front of screen’s
touched point.
None
We will study •Coordinate systems •Method for coordinate transformation
Coordinate system for ARKit
Coordinates World Object Camera Screen Drawn by iPad Pro
World Coordinate system The biggest coordinates In your iPhone
Object Coordinate system Airplane’s own coordinate
Camera coordinate system ΧϝϥͷϩʔΧϧ࠲ඪ
Camera
Screen
Screen
Coordinates World Object Camera Screen Drawn by iPad Pro
Let’s check the Goal
Place an airplane at the 30cm in front of screen’s
touched point.
30cm Get x,y from tap gesture Place the object In
the world. Place at 30cm In front of camera Convert to world ᶃ ᶄ ᶅ Convert to Screen ᶆ ᶄ’ Convert to screen
ᶃPlace at 30cm in front of camera Minus 30cm
None
ᶄConvert to World
Convert from a coordinate to a coordinate
ᶄ’Convert to screen
World <-> Screen
ᶅGet x,y from tap gesture
ᶆPlace in the world
Screen <-> World
At 30cm Tapped position Convert Convert
Calculate at easy coordinate system
By the way
You can do it all in the screen coordinate
30cm Get x,y from tap gesture Place the object In
the world. Place at 30cm In front of camera Convert to world ᶃ ᶄ ᶅ Convert to Screen ᶆ ᶄ’ Convert to screen Removable
Removabl
It looks easier!!
Yes
You can code shorter
None
But
In fact
This 0.996 is Same with 0.3m in camera coordinate
What is 0.996?
Review for coordinate system
0.0 1.0 Screen’s z 0.001m 1000m Camera’s z
Screen’s Z
https://developer.apple.com/documentation/scenekit/scnscenerenderer/1522631-unprojectpoint Z is 0.0~1.0
Camera’s Z?
None
None
None
debug
None
Z is 0.01~1000
Let’s change zNear.
None
0.0 1.0 Screen’s z 0.001m 1000m Camera’s z
Screen’s z vs Camera’s z
http://www.alecjacobson.com/weblog/?p=3835 -0.001 -1000 0.996 screenZ = f(n + cameraZ)/((f −
n)cameraZ) -0.3 screenZ cameraZ
screenZ = f(n + cameraZ)/((f − n)cameraZ) screenZ = 1000(0.001
+ (−0.3))/((1000 − 0.002)(−0.3)) f = 1000 n = 0.001 cameraZ = − 0.3 screenZ = 0.9966...
Way too hassle
Removable?
Must
So,
Understanding Coordinate’s system And..
None
Make sense?
Let’s study more?
Make a airplane Bigger or Rotation
Scale
Rotate by SCNVector4 Axis Degree
Rotate by Euler angle
Rotate by Euler angle x
Rotate by Euler angle Y
Rotate by Euler angle Z
x Y Z
That’s it
One more thing.
Making ARKit 2.0 repository
End