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

System copy error in RUN ABAP REPORT PHASE
Hi,
I am performing system copy on my test server. I have previously taken export of JAVA + A

Call db table from any PHP file
Hi,

I want to be able to call a database table that will be setup in another file called init

How do I get the row number from from an sql table query
Hi all

I have a table that I query and it returns a number of rows.
mysql_num_rows($query)

compile php5 with DOM
Hi,

I can't manage to compile php 5.3.0 from source on Windows to include DOM,
in spite of

Populate drop down list from table??
Lets say for arguments sake that i have a table which contains the numbers 1 to 10.
How can i get

Inserting into MySQL Newbie
Hi ive got a slight problem where ive made a simple web form where the customer inserts the ammount

Adding Outlook 2007 items via file upload
I am looking for a way to be able to attach an Outlook item (an email message) in an ASP.NET 3.5 app

Dealing with code in db query
I am dealing with C code and I need to make sure it is encoded some how to ensure its integrity and

PHP Mysql Staff Induction System
Hi there, I'm pretty new to PHP and Mysql so could really do with being pointed in the right directi

Best way to cross matching large datasets
Hi,

Im running a script where am I cross matching about 200 000 data sets with each other. Ea