Accurately Converting NSString to GLFloat - iPhone

Question

Say I have some vertice values which I am reading into my app as a NSString :

-7501.6 -6198.2 834.939 -5547.66 -6348.32 2122.65

The values in the source are always 6 figures in length.

I need to pass these exact values to OpenGL. If I try to cast as a float (using NSString floatValue) then, as expected, I get an approximate value for each float due to the inexact nature of a float :

-7501.600098, -6198.200195, 834.939026 -5547.660156, -6348.319824, 2122.649902

Can anyone suggest a way that I can get these values into OpenGL and retain their exact initial integrity ?

Thank you.

But even OpenGL will be using floats/doubles. If these values cannot be represented exactly as floating-point values, then you cannot do this. — Mike Weller, May 31 '12 at 15:53

score 0 · Accepted Answer · edited May 23 '17 at 10:34

0

maybe this: NSString to NSNumber could help.

edited May 23 '17 at 10:34

Community

1
1

answered Feb 21 '12 at 13:26

CarlJ

9,461
3
33
47

score -1 · Answer 2 · answered Feb 21 '12 at 13:17

-1

See 'Getting Numeric Values' paragraph from NSString Documentation (Apple).

[str floatValue]; [str doubleValue];

answered Feb 21 '12 at 13:17

hburde

1,441
11
6

Accurately Converting NSString to GLFloat - iPhone

2 Answers2