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

Simultaneous select/update/insert
Hi

How would I need to go about when 2 users update a single row simultaneous? And how would

Print 'a' to 'z' via for loop
A very simple problem..
How Can I print a to z NOT a to y ?
It is a part of a code where
<

Display thumbnails as square while retaining aspect ratio
I am trying to figure out a way to make an image display as a square, for example 80x80 pixels, when

jquery validation in codeIgniter
hai i need to add client side validation to my fiels which are selected in a forloop.the fields are

PHP and Javascript
Hi Guys,

Im trying to load the contents of an html file into a text area for editing, this is

TimeZoneOffset
Hello,

Please i need your help. I have a system that users can use to punch in and out. This

listcube issue
Hi
I have a virtual cube ZREMOTE. I use Tcode "listcube" to retrieve contents. I use of the

Problem with array max size.
Hi to everyone,
I've got a homework about filling a bidimensional array un spiral shape, I alre

calendar dates and hours compare problem
i have a calendar in wordpress, everything works great except that i can make 2 meetings at the same

Displaying Multidimensional Arrays...about to put my head in a vice, PLEASE HELP
I am fairly new to PHP and MySQL and I have a problem which I have been trying to resolve for days.