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

Automatic Webpage ??
I have a page www.mysite.com/test.php with a
<form>
<textarea name=&q

Table trouble
i have been reading the forum for a few weeks and decided to join. i like the format and the advice

noob cURL help
I have a pretty basic form that I need to cURL post to a file in my includes folder (includes/login.

Product categories for registration
Dear all,

We are going live with the Supplier registered next week. At standard, the 'sel

Weekly Calendar
Hi, I am looking at creating a weekly calendar. The calendar will read from Monday - Sunday. Does an

$_POST variable un-useable
I'm trying to use a $_POST variable in a mysql update statement but i can't use it for some unknown

Problem with a select distinct
I have a problema with a select distinct, I have the next sql:

select distinct a,b,c,d fr

Post PHP form to non-existing page
The company that I work for host their PHP code on IIS on a Windows server, no Apache, so no mod_rew

Undefined variables
hi
----------------------------------------------------------------------------------------------

Session login issue
I'm wondering how to fix a problem I'm having with a session-based login system

Say I go to h