Sign in to follow this  
bushman_IL

Normal Direction Detection

Recommended Posts

Hello,

I am not too familiar with normals so please bare with me. I have meshes that I am trying to rotate so they will lay flush along a line. To give a litle more background, these lines make up the walls of a room. so I know the center point of a room very easily. However, when I get the normal depending on which end of the wall I use first it is possible the normal could be pointing to the outside of the room instead of the inside.

So the fact that I have this normal of the wall and the center point of the room, can someone give me a little help on an efficient way of deternining if I need to flip my normal or if it is indeed pointing to the inside of the room?


I am not sure what other information might be helpful, so let me know if I am leaving anything major out to help better understand the problem I am facing.

Thank you!!

Share this post


Link to post
Share on other sites
I'm not sure if this is efficient, but is it possible to take the equation of the wall/plane, say

x+y+z=3, and given the center point of the room, say (5,5,5), the parallel plane passing through the point is

x+y+z=15

Then, take the parametric equation of the normal line, and find out the respective t-values for where it intersects both planes. Based on a comparison of the two values, either increasing or decreasing, it will tell you which direction the normal is facing.

Share this post


Link to post
Share on other sites
Assuming your mesh is convex (otherwise things are not so simple) then just evaluate dot product between your normal, and (centre of room - any point on the wall) and if the dot product is positive, the normal points towards the centre of the room, otherwise flip it.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this