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.

Did you know?Explore Trending and Topic pages for more stories like this.
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

reading partial code from external site
Hi,

I am trying to write a script for my website to get an article from an external website.

Last Weeks sDate and eDate.
sDate - Start Date
eDate - End Date

I need to pull two dates for "Last Week" whi

Select all entries from database that include a phrase
I have a database of clubs - one of the categories is meeting time and place
I would like to have

problems with script
I made a small script wich exchanges points in my website:


<?php
session_start

Get relative path from absolute path
How would one go about getting the relative path to a file from its absolute path?

Warning: Cannot modify header information - headers already sent by (output sta
Warning: Cannot modify header information - headers already sent by (output started at /home/praylif

Polymorphism
Was wondering if someone could explain this a little better to me. I had always assumed that it had

Do something every fifth time?
I'm trying to write a loop, but I want it to do something different after every fifth instance. Like

Add_Months not Easy to Understand
Oracle is number 1, very fast and very easy. But....
OK, I think but have a problem, only 1 pro

How to make URL loads only on login
On my page, when a user login he's redirects to user_home.php. I made it also to open the chat scree

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