VRML surface conic projection

How can i do a conic projection of a surface in VRML format ?

[darova]

What about THIS?

[andre padilla]

My need is a little bit different:

(1) i already have a surface in VRML 2 format

(2) i want to do a conic projection of that surface

How to do that ?

A+

[darova]

Try to search HERE

This is what google found for me. Is this correct?

[andre padilla]

Yes is a conic projection of the earth surface

But how to do that in MATLAB starting from another surface in VRML format ?

A+

[darova]

Is this correct?

Do you know how the cone is situated?

[andre padilla]

Yes of course

i know where the cone is situated and what is its solid angle

and the distance from its top to the geometrical center of the surface

A+

Answer 1

[darova]

Here is an idea:

• Projection onto cone: if your data in cartesian system - convert it to polar ()

New radius of projected data

• Create flat projection:

New limits of angle:

New limits or radius:

See also HERE and HERE

Answer 2

[andre padilla]

May be i did not sufficiently esplain the problem.

I generated in another software a colored surface of an arbitrary shape model (its not a sphere or an an ellipsoide ...)

This surface is in VRML 2 format.

I was wondering how it is possible to use a MATLAB function to generate a conic projection of this colored model surface.

Seems that existing MATLAB functions may produce conic projections of spheres or may be flatened spheroides

So these are not applicable for a random shaped objject. And one other problem is that those geographic MATLAB

functions do not read VRML format.

A+

[darova]

Where do you see a sphere?

[andre padilla]

Do you think that i can use this kind of strategy

MATLAB commands :

landareas = shaperead('landareas.shp','UseGeoCoords',true);

axesm ('eqaconic', 'Frame', 'on', 'Grid', 'on');

geoshow(landareas,'FaceColor',[1 1 .5],'EdgeColor',[.6 .6 .6]);

tissot;

Of course i have to convert

my_object_surface.wrl to my_object_surface.shp

How to do that ?

A+

[darova]

Can you attach the data?

Answer 3

[andre padilla]

Yes of course.

the file need to be renamed to .gz and gunziped

A+

[darova]

Please don't post new answer. Use existing one

[darova]

I uploaded this program to read your file: LINK

Inside the program i changed this line (someone in comments to this script did the same)

keynames=char('Coordinate','point','coordIndex','color');

Then used this script to import to MATLAB and make a projection

[nel,w3d,infoline] = read_vrml1('myscene.wrl');
%%
cla
pts = w3d(1).pts;
fv.vertices = pts;
fv.faces = w3d(1).knx;
patch(fv,'facecolor','g')

a = 60;
[X,Y] = meshgrid(-20:20);           % grid for cone
Z = 40-1/tand(a)*sqrt(X.^2+Y.^2);   % Z coordinate of cone
surface(X,Y,Z,'facecolor','none','edgecolor','y')

[td,rd] = cart2pol(pts(:,1),pts(:,2));  % convert data to polar system
L0 = rd*sind(a) + (40-pts(:,3))*cosd(a); 
r0 = L0 * sind(a);                      % new radius
zd = 40-L0 * cosd(a);                   % new Z coordinate
[xd,yd] = pol2cart(td,r0,pts(:,3));     % conert to cartesian

fv1.vertices = [xd yd zd];
fv1.faces = fv.faces;

patch(fv1,'facecolor','r')

light
axis vis3d equal

Unfortunately i didn't find a way to import colors

Honestly: looks like

Is it you wanted? Or you wanted flat projection?

[andre padilla]

thanks,

that is a first way i will try to find to get the colors

Many thanks

A+