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

Tree Menu
Hi guys,

Can anyone help me making a tree navigation system? I have a site where I'm allowin

Help with lottery style system?
I'm working on a currency system for forums and it is going to have a type of lottery system built i

How to add an image/C++ OpenGL?
Hi,

I have been trying to look online for this and, so far, I haven't found anything usef

Having problemswith multithreading and prime numbers
I have an assignment when I'm suppose to do the following:

Write a multithreaded Java, Pt

Character Set Setup
Whats the best character set to use if you want every character to work, and also how do you make yo

javascript in php code causes page to display white
Hi All,

Odd one this, I've got the following code (below) which is a simple log in form. The

User feedback after MySQL query has been executed
Hi all, I've just registered on PHPFreaks because I've got a question that I simply can't work out b

Help with captcha script needed
Hello,

I am working on a script where reCAPTCHA or a similar form of CAPTCHA will be used, f

Posting Serialized Data Not Working
I am trying to send an object from one PHP file to another using POST. I serialize the object and th

Timer control causing error
I recently decided to add a timer control to an existing page that uses AJAX on my site. As soon as

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