是什么导致Uncaught TypeError：number不是函数？

Question

As you can tell I'm trying to put together a very simple 3d engine. I'm writing it in javascript. I think it's likely that there is an error in the formula, but for the life of me I can't find it. So now I'm thinking there might be something else I haven't considered yet. The error occurs on line 21 (dx = Math.cos.....)

Here is the relevant part of my code:

// Camera Position in x,y,z
var c = [ 0,0,0 ];

// Viewer position [x,y,z]
var v = [ 0,0,0 ];

// Angle of view [x, y, z]
var a = [ 0.01, 0.01, 0.01 ];

var point =  [ 0,0, 50 ];

dx = Math.cos(a[1])(Math.sin(a[2])(point[1] - c[1]) + Math.cos(a[2])(point[0] - c[0])) - Math.sin(a[1])(point[2] - c[2]);
dy = Math.sin(a[0])(Math.cos(a[1])(point[2] - c[2]) + Math.sin(a[1])(Math.sin(a[2])(point[1] - c[1]) + Math.cos(a[2])(point[0] - c[0]))) + Math.cos(a[0])(Math.cos(a[2])(point[1] - c[1]) - Math.sin(a[2])(point[0] - c[0]));
dz = Math.cos(a[0])(Math.cos(a[1])(point[2] - c[2]) + Math.sin(a[1])(Math.sin(a[2])(point[1] - c[1]) + Math.cos(a[2])(point[0] - c[0]))) - Math.sin(a[0])(Math.cos(a[2])(point[1] - c[1]) - Math.sin(a[2])(point[0] - c[0]));

bx = (dx - v[0])(v[2]/dz);
by = (dy - v[1])(v[2]/dz);

Answer 1

你需要使用*来乘以：

dx = Math.cos(a[1])*(Math.sin(a[2])*(point[1] - c[1]) ... etc

Answer 2

I'm no Javascript expert, but I'm guessing Math.cos(a[1]) returns a number, and doing Math.cos(a[1])(5) is trying to use a number as a function. If you want to multiply two numbers you should use the '*' multiplication operator.

Answer 3

You cannot multiply by writing (a)(b)(c) like you do in math.
This is parsed as two function calls, so you get an error that the (a) isn't a function.

Instead, write a * b * c .

Answer 4

You are leaving out multiplication operator, eg:

x = Math.cos(a[1]) * (Math.sin(a[2]) * (...
-------------------^-----------------^

-- Rob