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When converting from double to fixed, round carefully. 

This reduces the matrix representation error after inverting a
transformation matrix (although it doesn't eliminate it entirely).

Perhaps we should extend Render to include 64-bit floating point transforms...
This commit is contained in:
Keith Packard 2008-03-18 15:15:40 -07:00
parent 6d3a9e40a4
commit 97ab0c6eff
1 changed files with 4 additions and 3 deletions
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7
render/matrix.c
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@ -72,9 +72,9 @@ PictureTransformPoint3d (PictTransformPtr transform,
return FALSE; return FALSE;
result.vector[j] = (xFixed) v; result.vector[j] = (xFixed) v;
} }
*vector = result;
if (!result.vector[2]) if (!result.vector[2])
return FALSE; return FALSE;
*vector = result;
return TRUE; return TRUE;
} }
@ -286,7 +286,8 @@ from_doubles (PictTransformPtr t, double m[3][3])
double d = m[j][i]; double d = m[j][i];
if (d < -32767.0 || d > 32767.0) if (d < -32767.0 || d > 32767.0)
return FALSE; return FALSE;
t->matrix[j][i] = pixman_double_to_fixed (d); d = d * 65536.0 + 0.5;
t->matrix[j][i] = (xFixed) floor (d);
} }
return TRUE; return TRUE;
} }
@ -294,7 +295,7 @@ from_doubles (PictTransformPtr t, double m[3][3])
static Bool static Bool
invert (double r[3][3], double m[3][3]) invert (double r[3][3], double m[3][3])
{ {
double det, norm; double det;
int i, j; int i, j;
static int a[3] = { 2, 2, 1 }; static int a[3] = { 2, 2, 1 };
static int b[3] = { 1, 0, 0 }; static int b[3] = { 1, 0, 0 };