# How can I create 2D projections from a 3D object?

67 visualizaciones (últimos 30 días)
Eric el 10 de Mayo de 2016
Comentada: Seung Jae Lee el 5 de Abr. de 2023
I know I can use "radon" for creating 1D projections from 2D, but how can I get 2D projections from 3D objects (such as from a 3D file like an STL file).
##### 0 comentariosMostrar -2 comentarios más antiguosOcultar -2 comentarios más antiguos

Iniciar sesión para comentar.

### Respuestas (2)

Mike Garrity el 10 de Mayo de 2016
One approach is the technique I showed in answers to this question, and this question.
The basic idea is that you take keep the faces of your geometry, but project the vertices onto the plane. That does mean that you've got multiple conincident polys, so it's not good for things like area computation. But if you just want the visual result, it works well and it's simple.
##### 2 comentariosMostrar NingunoOcultar Ninguno
Thomas Cornew el 10 de Mayo de 2018
Hello Mike,
How would I approach this problem if I was trying to solve for the area of the 2d projection?
Naveen Pathak el 7 de Jun. de 2021
Hi Mike,
I have a simliar problem. Please, could you help me to plot the following:
Thank you.

Iniciar sesión para comentar.

Y.S. el 29 de Mzo. de 2023
2 methods I found that I want to place here for future reference:
[1] fast, but only works for convex shapes. Assuming you have a struct (fvIn) with vertices & faces
fvIn.vertices(:,3)=0; % squash all Z coords
verts = fvIn.vertices;
faces = fvIn.faces;
a = verts(faces(:, 2), :) - verts(faces(:, 1), :); % compute area of all triangles
b = verts(faces(:, 3), :) - verts(faces(:, 1), :);
c = cross(a, b, 2);
area2 = 1/2 * sum(sqrt(sum(c.^2, 2))); % Calculate total area, but this gives double the area because the shape is squashed
Ap = area2/2; %
[2] slow, but works for all shapes
Loop over all triangles, project them on the Z=0 plane, create a polyshape and combine(union) it with the other projected triangles
P = fvIn.vertices(fvIn.faces(1,:),1:2);
psSurfTot = polyshape(P);
for N = 2:size(fvIn.faces,1)
P = fvIn.vertices(fvIn.faces(N,:),1:2);
psSurfTMP = polyshape(P);
psSurfTot = union(psSurfTot,psSurfTMP);
end
% calculate projected area
Ap = area(psSurfTot);
I am still looking for a fast method that works for all shapes, but havent found any
##### 2 comentariosMostrar NingunoOcultar Ninguno
Naveen Pathak el 30 de Mzo. de 2023
Thanks "Y.S." at least you showed a kind gesture.
Matlab people are worth-less to help.
However, I have already solved this problem few months ago :)
Seung Jae Lee el 5 de Abr. de 2023
Hi, Naveen. How could you solve this problem? Can you please share your findings?

Iniciar sesión para comentar.

### Categorías

Más información sobre Map Display en Help Center y File Exchange.

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by