#### Archived

This topic is now archived and is closed to further replies.

# Plotting a 3d point in 2d space

This topic is 5530 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I have a plane defined in terms of 3 points in space (a,b,c). I have another point (d) that is on this same plane. What I am trying to do is basically plot d in 2d coordinates (which i''m assuming I can do since all points are on the same plane) using a as the origin, and b defining the X-axis, and c defining the Y-axis. I''m not sure if this is even possible, or how to begin going about this. If I have not provided enough information, I apologize... I''m not really sharp on this type of math. Is there a way I can go about doing this that is not incredibly heavy on the math? Any help anyone can provide would be greatly appreciated. Thanks in advance!

##### Share on other sites
Could you describe better your problem ?
do you eed to get the u and v componet form the plane equation ?

##### Share on other sites
Yes. I am trying to map a texture onto a polygon, and the texture is being described as being on a plane (a,b,c), with (a) being the top left of the texture, (b) being the top right, and (c) being the bottom left. (d) is a point on my polygon that i am trying to map this texture onto. so I am trying to solve to the u,v texture coordinates that i need to assign to point (d). Does this help at all?

##### Share on other sites
So, the way I see it, your U coordinate would be:

U = DotProduct(d - a, b - a)

And V would be:

V = DotProduct(d - a, c - a)

Some assumptions were made. First, I assumed that your texture's u direction is aligned with the plane's x axis, and the v direction is aligned with the plane's y axis. Second, I assumed that b-a and c-a are unit length. Or that they are scaled as necessary based on the texture scale. Third, I assumed that (u,v) = (0,0) sits at location a on the plane.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

[edited by - grhodes_at_work on June 2, 2003 2:27:06 PM]

##### Share on other sites
All valid assumptions, Graham. Thanks for the help. It looks like that is generating the correct U,V coordinates for me. I appreciate the help, a lot!

1. 1
2. 2
Rutin
19
3. 3
4. 4
5. 5

• 10
• 14
• 30
• 13
• 11
• ### Forum Statistics

• Total Topics
631782
• Total Posts
3002332
×