CODEWITHSUNDEEP
c#unity-game-engineruntime
Eduardo Corona
Eduardo Corona

Reputation: 1332

Unity flips x coordinate in obj using importer at runtime

I'm creating a .obj file importer at runtime in Unity3D.

The problem is that when I import a .obj file, it comes with the x coordinate flipped; by "flipped" I mean that if the x coordinate in a vertex in the file says -12, then unity reads a 12 and vice versa.

The logged coordinates look like this:

-42.4 -6.608938 -1.6
-42   -6.579293 -1.6
-42.4 -6.652683 -1.2
-42.4 -6.608938 -1.6

Whereas my original .obj file had vertices like this:

v 42.4000015258785 -6.60893774032594 -1.60000002384146
v 42.4000015258785 -6.65268325805652 -1.20000004768452
v 42.0000000000008 -6.57929277420054 -1.60000002384146
v 42.0000000000004 -6.57929277420055 -1.60000002384106

So, the question is, how can I prevent Unity from changing the signs of my coordinates?

Upvotes: 1

Views: 325

Answers (1)

Lews Therin
Lews Therin

Reputation: 3777

I found a similar question on gamedev.stackexchange.com. From one of the answers there:

  1. The actual OBJ file format specification declares that, "A right-hand coordinate system is used to specify the coordinate locations."

  2. Unity uses a left-hand coordinate system.

  3. Conversion from right-handed to left-handed is accomplished by negating the coordinates on any axis (it doesn't matter which one).

  4. Unity negates the X-coordinates to convert the right-handed OBJ data to left-handed data.

Upvotes: 3

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