lib/gamnit flat: rotation follows the right hand rule on the Z axis

[nit.git] / lib / gamnit / flat.nit

diff --git a/lib/gamnit/flat.nit b/lib/gamnit/flat.nit
index b489f1c..b74da82 100644 (file)
--- a/lib/gamnit/flat.nit
+++ b/lib/gamnit/flat.nit
@@ -52,7 +52,7 @@ class Sprite
        # Position of this sprite in world coordinates
        var center: Point3d[Float] is writable
 
-       # Rotation on the Z axis
+       # Rotation on the Z axis, where 0.0 points right and `0.5*pi` points up
        var rotation = 0.0 is writable
 
        # Mirror `texture` horizontally, inverting each pixel on the X axis
@@ -95,7 +95,7 @@ class Sprite
                        else texture.texture_coords, 2)
                simple_2d_program.coord.array(texture.vertices, 3)
 
-               simple_2d_program.rotation.uniform new Matrix.rotation(rotation, 0.0, 0.0, 1.0)
+               simple_2d_program.rotation.uniform new Matrix.rotation(rotation, 0.0, 0.0, -1.0)
 
                glDrawArrays(gl_TRIANGLE_STRIP, 0, 4)
        end