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actor: Clean up transform_stage_point()
Use double precision floats for the intermediate computations, to avoid loss of precision, and don't convert too integer when unnecessary, to avoid rounding errors.
This commit is contained in:
Emmanuele Bassi
parent
4b9e672bc1
commit
6cd24faaa5
@ -15112,11 +15112,12 @@ clutter_actor_transform_stage_point (ClutterActor *self,
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gfloat *y_out)
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{
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ClutterVertex v[4];
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float ST[3][3];
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float RQ[3][3];
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int du, dv, xi, yi;
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float px, py;
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float xf, yf, wf, det;
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double ST[3][3];
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double RQ[3][3];
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int du, dv;
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double px, py;
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double det;
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float xf, yf, wf;
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ClutterActorPrivate *priv;
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g_return_val_if_fail (CLUTTER_IS_ACTOR (self), FALSE);
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@ -15137,20 +15138,18 @@ clutter_actor_transform_stage_point (ClutterActor *self,
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* function calls have been unrolled, and most of the math is done in fixed
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* point.
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*/
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clutter_actor_get_abs_allocation_vertices (self, v);
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/* Keeping these as ints simplifies the multiplication (no significant
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* loss of precision here).
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*/
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du = (int) (priv->allocation.x2 - priv->allocation.x1);
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dv = (int) (priv->allocation.y2 - priv->allocation.y1);
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du = ceilf (priv->allocation.x2 - priv->allocation.x1);
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dv = ceilf (priv->allocation.y2 - priv->allocation.y1);
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if (!du || !dv)
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if (du == 0 || dv == 0)
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return FALSE;
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#define UX2FP(x) (x)
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#define DET2FP(a,b,c,d) (((a) * (d)) - ((b) * (c)))
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#define DET(a,b,c,d) (((a) * (d)) - ((b) * (c)))
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/* First, find mapping from unit uv square to xy quadrilateral; this
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* equivalent to the pmap_square_quad() functions in the sample
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@ -15160,47 +15159,43 @@ clutter_actor_transform_stage_point (ClutterActor *self,
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px = v[0].x - v[1].x + v[3].x - v[2].x;
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py = v[0].y - v[1].y + v[3].y - v[2].y;
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if (!px && !py)
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if ((int) px == 0 && (int) py == 0)
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{
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/* affine transform */
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RQ[0][0] = UX2FP (v[1].x - v[0].x);
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RQ[1][0] = UX2FP (v[3].x - v[1].x);
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RQ[2][0] = UX2FP (v[0].x);
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RQ[0][1] = UX2FP (v[1].y - v[0].y);
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RQ[1][1] = UX2FP (v[3].y - v[1].y);
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RQ[2][1] = UX2FP (v[0].y);
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RQ[0][2] = 0;
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RQ[1][2] = 0;
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RQ[0][0] = v[1].x - v[0].x;
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RQ[1][0] = v[3].x - v[1].x;
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RQ[2][0] = v[0].x;
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RQ[0][1] = v[1].y - v[0].y;
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RQ[1][1] = v[3].y - v[1].y;
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RQ[2][1] = v[0].y;
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RQ[0][2] = 0.0;
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RQ[1][2] = 0.0;
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RQ[2][2] = 1.0;
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}
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else
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{
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/* projective transform */
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double dx1, dx2, dy1, dy2, del;
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double dx1, dx2, dy1, dy2;
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dx1 = UX2FP (v[1].x - v[3].x);
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dx2 = UX2FP (v[2].x - v[3].x);
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dy1 = UX2FP (v[1].y - v[3].y);
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dy2 = UX2FP (v[2].y - v[3].y);
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dx1 = v[1].x - v[3].x;
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dx2 = v[2].x - v[3].x;
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dy1 = v[1].y - v[3].y;
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dy2 = v[2].y - v[3].y;
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del = DET2FP (dx1, dx2, dy1, dy2);
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if (!del)
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det = DET (dx1, dx2, dy1, dy2);
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if ((int) det == 0)
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return FALSE;
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/*
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* The division here needs to be done in floating point for
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* precisions reasons.
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*/
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RQ[0][2] = (DET2FP (UX2FP (px), dx2, UX2FP (py), dy2) / del);
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RQ[1][2] = (DET2FP (dx1, UX2FP (px), dy1, UX2FP (py)) / del);
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RQ[1][2] = (DET2FP (dx1, UX2FP (px), dy1, UX2FP (py)) / del);
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RQ[0][2] = DET (px, dx2, py, dy2) / det;
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RQ[1][2] = DET (dx1, px, dy1, py) / det;
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RQ[1][2] = DET (dx1, px, dy1, py) / det;
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RQ[2][2] = 1.0;
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RQ[0][0] = UX2FP (v[1].x - v[0].x) + (RQ[0][2] * UX2FP (v[1].x));
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RQ[1][0] = UX2FP (v[2].x - v[0].x) + (RQ[1][2] * UX2FP (v[2].x));
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RQ[2][0] = UX2FP (v[0].x);
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RQ[0][1] = UX2FP (v[1].y - v[0].y) + (RQ[0][2] * UX2FP (v[1].y));
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RQ[1][1] = UX2FP (v[2].y - v[0].y) + (RQ[1][2] * UX2FP (v[2].y));
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RQ[2][1] = UX2FP (v[0].y);
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RQ[0][0] = v[1].x - v[0].x + (RQ[0][2] * v[1].x);
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RQ[1][0] = v[2].x - v[0].x + (RQ[1][2] * v[2].x);
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RQ[2][0] = v[0].x;
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RQ[0][1] = v[1].y - v[0].y + (RQ[0][2] * v[1].y);
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RQ[1][1] = v[2].y - v[0].y + (RQ[1][2] * v[2].y);
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RQ[2][1] = v[0].y;
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}
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/*
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@ -15218,15 +15213,15 @@ clutter_actor_transform_stage_point (ClutterActor *self,
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* Now RQ is transform from uv rectangle to xy quadrilateral; we need an
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* inverse of that.
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*/
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ST[0][0] = DET2FP (RQ[1][1], RQ[1][2], RQ[2][1], RQ[2][2]);
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ST[1][0] = DET2FP (RQ[1][2], RQ[1][0], RQ[2][2], RQ[2][0]);
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ST[2][0] = DET2FP (RQ[1][0], RQ[1][1], RQ[2][0], RQ[2][1]);
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ST[0][1] = DET2FP (RQ[2][1], RQ[2][2], RQ[0][1], RQ[0][2]);
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ST[1][1] = DET2FP (RQ[2][2], RQ[2][0], RQ[0][2], RQ[0][0]);
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ST[2][1] = DET2FP (RQ[2][0], RQ[2][1], RQ[0][0], RQ[0][1]);
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ST[0][2] = DET2FP (RQ[0][1], RQ[0][2], RQ[1][1], RQ[1][2]);
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ST[1][2] = DET2FP (RQ[0][2], RQ[0][0], RQ[1][2], RQ[1][0]);
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ST[2][2] = DET2FP (RQ[0][0], RQ[0][1], RQ[1][0], RQ[1][1]);
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ST[0][0] = DET (RQ[1][1], RQ[1][2], RQ[2][1], RQ[2][2]);
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ST[1][0] = DET (RQ[1][2], RQ[1][0], RQ[2][2], RQ[2][0]);
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ST[2][0] = DET (RQ[1][0], RQ[1][1], RQ[2][0], RQ[2][1]);
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ST[0][1] = DET (RQ[2][1], RQ[2][2], RQ[0][1], RQ[0][2]);
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ST[1][1] = DET (RQ[2][2], RQ[2][0], RQ[0][2], RQ[0][0]);
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ST[2][1] = DET (RQ[2][0], RQ[2][1], RQ[0][0], RQ[0][1]);
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ST[0][2] = DET (RQ[0][1], RQ[0][2], RQ[1][1], RQ[1][2]);
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ST[1][2] = DET (RQ[0][2], RQ[0][0], RQ[1][2], RQ[1][0]);
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ST[2][2] = DET (RQ[0][0], RQ[0][1], RQ[1][0], RQ[1][1]);
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/*
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* Check the resulting matrix is OK.
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@ -15234,19 +15229,16 @@ clutter_actor_transform_stage_point (ClutterActor *self,
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det = (RQ[0][0] * ST[0][0])
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+ (RQ[0][1] * ST[0][1])
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+ (RQ[0][2] * ST[0][2]);
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if (!det)
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if ((int) det == 0)
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return FALSE;
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/*
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* Now transform our point with the ST matrix; the notional w
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* coordinate is 1, hence the last part is simply added.
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*/
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xi = (int) x;
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yi = (int) y;
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xf = xi * ST[0][0] + yi * ST[1][0] + ST[2][0];
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yf = xi * ST[0][1] + yi * ST[1][1] + ST[2][1];
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wf = xi * ST[0][2] + yi * ST[1][2] + ST[2][2];
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xf = x * ST[0][0] + y * ST[1][0] + ST[2][0];
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yf = x * ST[0][1] + y * ST[1][1] + ST[2][1];
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wf = x * ST[0][2] + y * ST[1][2] + ST[2][2];
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if (x_out)
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*x_out = xf / wf;
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@ -15254,8 +15246,7 @@ clutter_actor_transform_stage_point (ClutterActor *self,
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if (y_out)
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*y_out = yf / wf;
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#undef UX2FP
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#undef DET2FP
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#undef DET
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return TRUE;
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}
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