Apply the rotation in Penrose grid descriptions by rotating in the

4-vector representation, rather than mucking about with sines and
cosines after grid generation. _Should_ make no difference in the
generated grids (there's a theoretical risk of an unlucky rounding
error just about managing to push some point in or out of bounds, but
I think it's vanishingly small), but simplifies the coordinate-
flattening procedure, and in particular increases its chance of
getting vertical lines actually vertical.

(Prior to this change, the game ID
10x10t12:G2554,-31,108_a3b12h0a212a3d102b2a23a2e3b01b0a2c2a0c0 was
generating a not-quite-vertical edge at top left, in the Java port but
not on Linux; I suspect differences in sin and cos as the cause of the
discrepancy. With the rotation done like this, the points'
x-coordinates are now computed without reference to their
y-coordinates.)

[originally from svn r9168]

1 files changed, 4 insertions, 1 deletions

diff --git a/penrose.c b/penrose.c
index 7adab03..ccde30d 100644
--- a/penrose.c
+++ b/penrose.c
@@ -434,7 +434,7 @@ void penrose_count_tiles(int depth, int *nlarge, int *nsmall)
  * (later mail: this is an overestimate by about 5%)
  */
 
-int penrose(penrose_state *state, int which)
+int penrose(penrose_state *state, int which, int angle)
 {
     vector vo = v_origin();
     vector vb = v_origin();
@@ -444,6 +444,9 @@ int penrose(penrose_state *state, int which)
 
     vb.b = state->start_size;
 
+    vo = v_rotate(vo, angle);
+    vb = v_rotate(vb, angle);
+
     if (which == PENROSE_P2)
         return penrose_p2_large(state, 0, 1, vo, vb);
     else