Generate 3D shapes

Hi all,

I'm struggling to figure out how to create a few 3D shapes, such as a 3D pyramid.

Basically what I want is say for example, in a 25x35 domain, at every point a value between 0 and 1 is produced. And when the 25x35 matrix is plotted using surf for example, a rectangular based pyramid will be plotted.

The following is an example but of a 3D gaussian, and I can't figure out how to do any other shape:

x = linspace(-4,4,25); y = linspace(-4,4,35); [X,Y] = meshgrid(x,y); Z = exp(-X.^2-Y.^2); figure; surf(X,Y,Z);

Thanks very much in advance! Tim

Answer 1

[Jarrod Rivituso]

Looks like you are on the right track and you just need to get the correct equation for the height of the pyramid.

One thing I've found helpful in similar situations is to sometimes define the size of the grid larger than needed and then use NaN to indicate points that I don't want to be drawn. This helps eliminate the need to conform to a square boundary.

Here's a pyramid example

>> x = linspace(-8,8,200);
>> y = linspace(-8,8,200);
>> [X,Y] = meshgrid(x,y);
>> Z = (4-abs(X)) + (4-abs(Y));
>> Z(Z < 0) = NaN;
>> surf(X,Y,Z)

Hope this helps!

[Ayush singhal]

and how to generate sphere, cube,cylinder?

Answer 2

[Nausheen]

We can think of pyramid as a cone. To draw this cone we give it only 4 sides, so it would draw a pyramid. cylinder([1 0],4)