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Apply the rotation in Penrose grid descriptions by rotating in the

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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]
This commit is contained in:
Simon Tatham
2011-05-06 17:09:03 +00:00
parent 5619904bcc
commit 4a172274f2
3 changed files with 10 additions and 10 deletions
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13
grid.c
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@ -2472,7 +2472,6 @@ static grid *grid_new_greatdodecagonal(int width, int height, char *desc)
typedef struct setface_ctx
{
int xmin, xmax, ymin, ymax;
int aoff;
grid *g;
tree234 *points;
@ -2488,8 +2487,6 @@ static int set_faces(penrose_state *state, vector *vs, int n, int depth)
setface_ctx *sf_ctx = (setface_ctx *)state->ctx;
int i;
int xs[4], ys[4];
double cosa = cos(sf_ctx->aoff * PI / 180.0);
double sina = sin(sf_ctx->aoff * PI / 180.0);
if (depth < state->max_depth) return 0;
#ifdef DEBUG_PENROSE
@ -2499,8 +2496,8 @@ static int set_faces(penrose_state *state, vector *vs, int n, int depth)
for (i = 0; i < n; i++) {
double tx = v_x(vs, i), ty = v_y(vs, i);
xs[i] = (int)round_int_nearest_away( tx*cosa + ty*sina);
ys[i] = (int)round_int_nearest_away(-tx*sina + ty*cosa);
xs[i] = (int)round_int_nearest_away(tx);
ys[i] = (int)round_int_nearest_away(ty);
if (xs[i] < sf_ctx->xmin || xs[i] > sf_ctx->xmax) return 0;
if (ys[i] < sf_ctx->ymin || ys[i] > sf_ctx->ymax) return 0;
@ -2602,7 +2599,7 @@ static char *grid_validate_desc_penrose(grid_type type, int width, int height, c
static grid *grid_new_penrose(int width, int height, int which, char *desc)
{
int max_faces, max_dots, tilesize = PENROSE_TILESIZE;
int xsz, ysz, xoff, yoff;
int xsz, ysz, xoff, yoff, aoff;
double rradius;
tree234 *points;
@ -2635,7 +2632,7 @@ static grid *grid_new_penrose(int width, int height, int which, char *desc)
sf_ctx.points = points;
if (desc != NULL) {
if (sscanf(desc, "G%d,%d,%d", &xoff, &yoff, &sf_ctx.aoff) != 3)
if (sscanf(desc, "G%d,%d,%d", &xoff, &yoff, &aoff) != 3)
assert(!"Invalid grid description.");
} else {
xoff = yoff = 0;
@ -2654,7 +2651,7 @@ static grid *grid_new_penrose(int width, int height, int which, char *desc)
debug(("penrose: x range (%f --> %f), y range (%f --> %f)",
sf_ctx.xmin, sf_ctx.xmax, sf_ctx.ymin, sf_ctx.ymax));
penrose(&ps, which);
penrose(&ps, which, aoff);
freetree234(points);
assert(g->num_faces <= max_faces);