# I am trying to draw a pyramid.

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Michael on 7 Dec 2013
Answered: sixwwwwww on 7 Dec 2013
I'm not asking you to do my homework, but guide me through what I am doing wrong. I am trying to create a function that draws a pyramid by accepting 4 inputs. The origin, the length in the x direction, width in the y direction and height in the z direction. If you run my code, you will get a pyramid but with a little extra. You will see what I mean if you run it. I tried defining the x,y, and z arrays that define the 5 faces of the pyramid.
Here's my code:
function [] = pyramid(P,l,w,h) % PYRAMID will accept four inputs. P0 is an array of 3 scalar numbers for % the origin (x, y, and z). l is the length of the box in the x-direction, % w is the width of the box in the y-direction, and h is the height of the % box in the z-direction. The functin will draw a square pyramid. % Input: Four inputs, an array of the point of origin, a length, width, and % height. % Output: A pyramid drawn with a set transparency and different colors for % the faces % Proecessing: The first thing I will do is use the figure funciton in % order to prevent any previous figures from being overwritten.
figure x = [P(1),P(1)+l,P(1)+l,P(1)]; y = [P(2),P(2),P(2)-w,P(2)-w]; z = [P(3),P(3),P(3),P(3)]; face1 = [x;y;z]; surf(face1) fill3(x,y,z,'blue') hold on x2 = [P(1),P(1)+l,P(1) + l/2]; y2 = [P(2),P(2),P(2) - w/2]; z2 = [P(3),P(3),P(3)+h]; face2 = [x2;y2;z2]; surf(face2) fill3(x2,y2,z2,'green') x3 = [P(1)+l,P(1)+l,P(1) + l/2]; y3 = [P(2),P(2)-w,P(2)- w/2]; z3 = [P(3),P(3),P(3)+h]; face3 = [x3;y3;z3]; surf(face3) fill3(x3,y3,z3,'red') x4 = [P(1)+l,P(1),P(1)+ l/2]; y4 = [P(2)-w,P(2)-w,P(2)- w/2]; z4 = [P(3),P(3),P(3)+h]; face4 = [x4;y4;z4]; surf(face4) fill3(x4,y4,z4,'green') x5 = [P(1),P(1),P(1) + l/2]; y5 = [P(2),P(2)-w,P(2)- w/2]; z5 = [P(3),P(3),P(3)+h]; face5 = [x5;y5;z5]; surf(face5) fill3(x5,y5,z5,'red') alpha(0.3) hold off end

sixwwwwww on 7 Dec 2013
Dear Micheal, you don't need to use surf for this purpose just use fill. Below is your corrected code:
function [] = pyramid(P,l,w,h)
% PYRAMID will accept four inputs. P0 is an array of 3 scalar numbers for
% the origin (x, y, and z). l is the length of the box in the x-direction,
% w is the width of the box in the y-direction, and h is the height of the
% box in the z-direction. The functin will draw a square pyramid.
% Input: Four inputs, an array of the point of origin, a length, width, and
% height.
% Output: A pyramid drawn with a set transparency and different colors for
% the faces
% Proecessing: The first thing I will do is use the figure funciton in
% order to prevent any previous figures from being overwritten.
figure
x = [P(1),P(1)+l,P(1)+l,P(1)];
y = [P(2),P(2),P(2)-w,P(2)-w];
z = [P(3),P(3),P(3),P(3)];
fill3(x, y, z ,'blue'), hold on
x2 = [P(1),P(1)+l,P(1)+ l/2];
y2 = [P(2),P(2),P(2)-w/2];
z2 = [P(3),P(3),P(3)+h];
fill3(x2, y2, z2,'green'), hold on
x3 = [P(1)+l,P(1)+l,P(1) + l/2];
y3 = [P(2), P(2)-w,P(2)- w/2];
z3 = [P(3),P(3),P(3)+h];
fill3(x3, y3, z3,'red'), hold on
x4 = [P(1)+l,P(1),P(1)+ l/2];
y4 = [P(2)-w,P(2)-w,P(2)- w/2];
z4 = [P(3),P(3),P(3)+h];
fill3(x4,y4,z4,'green'), hold on
x5 = [P(1),P(1),P(1) + l/2];
y5 = [P(2),P(2)-w,P(2)- w/2];
z5 = [P(3),P(3),P(3)+h];
fill3(x5,y5,z5,'red')
Good luck!