Floating Point Precision Loss

Posted on 16th Feb 2014 07:03 pm by admin

I'm writing a program to draw a three-dimensional cube (with a corner cut off) without using any 3D graphics APIs. The only API call I make is win32's SetPixel()

Everything is going great. I've drawn lines, faces, and even the entire cube. Then rotation came along.

For some reason, when I rotate my cube, it begins to shrink. I became confused, then I realised something. Floating point numbers are truncated.

Here's some code that is fired everytime the user presses 'X' on the keyboard.

Code: p->setY( p->getY() * cos(5.0/180.0*PI) - p->getZ() * sin(5.0/180.0*PI)); p->setZ( p->getY() * sin(5.0/180.0*PI) + p->getZ() * cos(5.0/180.0*PI));

p is a Point object that I created. Here the Y value and the Z value of the Point are being set. The problem is everytime X is pressed, and this code is fired, a small amount of precision is lost. As a result, the cube shrinks.

I'm really completely stumped. I remember when studying assembler that floating point numbers can be truncated or rounded. I think rounding would solve my problem. Since 50% of the time the value would round up, and 50% of the time the value would round down.

Whereas with truncation values are always lost, and never gained.

Your Answer:

Login to answer

Other forums

Referential Integrity problem when inserting into 2 tables at same time
Hello Everyone,

Im relativity new to PHP and MySQL and i have come up against a problem. i h

Saving data from a form into a file
Hey everybody,

Sorry, I am really new to PHP coding and such but a project kind of got thrust

Using two $_POST Function / Switch () statements, second does not work.
Hi all. I’m new to php and am having a problem getting $_POST Function / switch () to work. I

Can you help please? Php file
I have to write this php file to allow users to register their nicknames on nickserv

For an I

getAlexaRank($url) function not working
I have made a function to get alexa rank
the site is here: http://mytestsite.rack111.com/1

private constructor
Hello,

Can we create a constructor as private? If yes, what is the use of it? If no, why can'

Sufficient protection from bad input?
I am writing a simple script to let people upload 'pages' of their own content, be it simply a few b

How to make a mail Form secure?
I want to create an email Form on my web site. How can I make the Form secure so the submitted info

Save cookie to DB
I'm working on a pixel tracking script for an incentive website and I need to use an ASP script to s

How do I create a 2D game "camera" to follow player?
In J2ME programming I'm targeting MIDP 2.0 devices.

I'm using gamecanvas and I was thinking t