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

Display data returned from Ajaxservices!!
I have a question about displaying results using ajax. I have part of the code below.
$.ajax({

Creating an invoice
Using fpdf I am trying to create an invoice to send to clients. The products are sold in pricing tie

Calling All PHPFREAKS Blackberry Users
Are you a member of PHPFreaks and have a blackberry? Well RIM just recently released Blackberry Mes

include
Hi I have this way of licensing my PHP application, and I want to know if you guys can answer some q

How to write on database when a link is clicked?
Hi, I have a list of products in a gridview. When the link is clicked currently it takes to an ext

I need help with formatting date from mysql! with php!
Hello guys

*Note: this is a php question not MySQL question, please do not move it to mysql s

reorder sql query
ok so i have this very simple code:
Code: $query = "SELECT search_keywords, COUNT(search_key

keeps going back to index.html ???????
ok so i started making my site using mostly.html files now i have added a fair chunk of php. My inde

php code generators
All

Whilst enjoying learning a new language i have come accross a number of free code generat

Fatal error: Call to a member function fetchrow() on a non-object in C:xamppht
okay i have this query and everytime i add `item_id`=? to it... it gives me the error in the title..