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.

No comments posted yet

Your Answer:

Login to answer
213 Like 53 Dislike
Previous forums Next forums
Other forums

New to PHP and just trying to understand a little code.
I hope I'm not annoying anyone or breaking the rules but I was wondering about this bit of code righ

A little help needed passing hidden values to next page
I have a page that has hidden values in a form.

example
Code: <input name='signupID

A WBS element with the name XXX already exists in version FREI_VERSION
Hi.
When I am trying to insert WBS element in a project, error occurs:

"A WBS eleme

PHP mail() rejected by SMTP
I'm currently working on a newsletter application which is installed on a windows 2003 server runnin

why does my session end?
my connect.php starts the session just so you know
i can navigate arround my site fine except whe

This must be easy , pulling the last record of the day, every day, from a txt
I have a txt file logging weather data every minutes (so 1 record per minute). I want to extract the

same querie, or a new one??
Hi guys,

I'm still working on this drop down list. I've got the actual drop down list to wor

problem with sql querry in php script
Hello guys,

What I want to do is I want to read out a csv file and then but te conent ot the

ASP.NET Validation Event Cycle
Hi,
I have asp button as follow:

Running External Scripts
I am very new to PHP and am not even sure what I'm asking is possible. I have just installed mediaW

Sign up to write
Sign up now if you have flare of writing..
Login   |   Register
Follow Us
Indyaspeak @ Facebook Indyaspeak @ Twitter Indyaspeak @ Pinterest RSS



Play Free Quiz and Win Cash