The below pattern will form the basis of this challenge.

     /

     /

     /

    /  

   /    

//      /

/      //

       /

      /

     /

     /

     /

Given an input width and height, each >=1, output the above ASCII art pattern repeated that many times, joining (and overlapping) at the small diamonds.

For example, here is an input with width = 2 and height = 1:

     /        /

     /        /

     /        /

    /        /  

   /        /    

//      //      /

/      //      //

       /        /

      /        /

     /        /

     /        /

     /        /

Here is an input width = 3 and height = 2:

     /        /        /

     /        /        /

     /        /        /

    /        /        /  

   /        /        /    

//      //      //      /

/      //      //      //

       /        /        /

      /        /        /

     /        /        /

     /        /        /

     /        /        /

     /        /        /

    /        /        /  

   /        /        /    

//      //      //      /

/      //      //      //

       /        /        /

      /        /        /

     /        /        /

     /        /        /

     /        /        /

Rules and I/O

• Input and output can be given by any convenient method.


• You can print it to STDOUT or return it as a function result.


• Either a full program or a function are acceptable.


• Any amount of extraneous whitespace is acceptable, so long as the characters line up appropriately.


• 
  Standard loopholes are forbidden.


• This is code-golf so all usual golfing rules apply, and the shortest code (in bytes) wins.

Canvas, 26 25 24 21 18 bytes

４／╬/╬⁰ｒ：⤢ｎ↷⁸｛Ａ×├ｍ↷

Try it here!

-3 bytes by fixing ｍ not repeating canvas

Explanation:

4/╬                 quad-palindromize a 4-long diagonal - big inner diamond

   /╬               quad-palindromize "/" - small diamond

     ⁰r             join the two vertically, centered

       :⤢n          overlap with transpose

           ↷        and rotate the thing clockwise

            ⁸{      for each input

              A×      times 10

                ├     plus 2

                 m    mold the canvas to that width

                  ↷   and rotate clockwise, setting up for the next iteration

JavaScript (ES8), 167 161 159 bytes

^{NB: This is encoding the pattern. See my other answer for a shorter mathematical approach.}

Takes input as (width)(height).

w=>h=>(g=h=>h?g(--h)+`

`+([4106,4016,31305,21504,17010]['0102344320'[h%=10]]+'').replace(/./g,c=>'\/'[c^h>5]||''.padEnd(c-1)).repeat(w+1).slice(8):'')(h*10+2)

Try it online!

How?

We encode the upper half of the pattern with digits:

• 
  $0$ means
  


• 
  $1$ means /
  


• 
  $n=2$ to $7$ means $n-1$ spaces

This gives:

0  ···/·····  -->  [3 spaces] [/] [] [5 spaces]             -->  4106

1  ···/·····  -->  [3 spaces] [] [/] [5 spaces]             -->  4016

0  ···/·····  -->  [3 spaces] [/] [] [5 spaces]             -->  4106

2  ··/······  -->  [2 spaces] [/] [2 spaces] [] [4 spaces]  -->  31305

3  ·/·······  -->  [1 space] [/] [4 spaces] [] [3 spaces]   -->  21504

4  /······/  -->  [/] [6 spaces] [] [/] []                -->  17010

For the lower half, we use the rows $4,3,2,0$ with / and inverted.

Haskell, 179 bytes

k '\'='/'

k '/'='\'

k x=x

f x=take(10*x+2)

w#h=map(f w.cycle).f h.drop 9.cycle$(++).reverse=<<map(map k)$["\/\      /","   \    / ","    \  /  ","     \/   ","     /\   "]

Try it online!

Haskell, 181 bytes

k '\'='/'

k '/'='\'

k x=x

f x=take(10*x+2)

w#h=map(f w.cycle).f h.drop 9.cycle$(++).reverse=<<map(map k)$map t[49200,36058,31630,30010,29038]

t 0=""

t n="\ /"!!mod n 3:t(div n 3)

Try it online!

Charcoal, 24 22 20 bytes

/↘²‖Ｍ↘LＦ⊖ＮＣχ⁰Ｆ⊖ＮＣ⁰χ

Try it online! Link is to verbose version of code. Explanation:

´/↘²

Draw one eighth of the original pattern.

‖Ｍ↘L

Duplicate it three times to complete the original pattern.

Ｆ⊖ＮＣχ⁰

Copy the required number of times horizontally.

Ｆ⊖ＮＣ⁰χ

Copy the required number of times vertically.

JavaScript (ES6), 139 bytes

This is using quite a different approach from my initial answer, so I'm posting this separately.

Takes input as (width)(height).

w=>h=>(g=x=>y>8?` /\

`[a=(x+y*9)%10,d=(x+y)%10,x?(y%10>3&&2*(a==8)|d==5)|(y%10<6&&2*(a==6)|d==7):3]+g(x--?x:--y&&w):'')(w=w*10+2,y=-~h*10)

Try it online!

How?

Given the width $w$ and the height $h$, we draw the output character by character over a grid which is:

• 
  $10w+3$ characters wide


• 
  $10h+2$ characters high

with $x$ going from $10w+2$ to $0$ (left to right) and $y$ going from $10h+10$ to $9$ (top to bottom).

Example for $w=3$ and $h=2$:

$$begin{matrix}(32,30)&(31,30)&dots&(0,30)\
(32,29)&(31,29)&&(0,29)\
vdots&&ddots&vdots\
(32,9)&(31,9)&dots&(0,9)end{matrix}$$

The rightmost cells (at $x=0$) are simply filled with linefeeds.

For all other cells, we compute:

• 
  $a=(x-y)bmod 10$ (constant over anti-diagonals)


• 
  $d=(x+y)bmod 10$ (constant over diagonals)

We draw a "/" if:

$$((ybmod 10)>3text{ and }d=5)text{ or }((ybmod 10)<6text{ and }d=7)$$

 y  | y % 10 | output (w = 3, h = 1)

----+--------+----------------------------------

 20 |    0   | ...../........./........./......

 19 |    9   | ....../........./........./.....

 18 |    8   | ...../........./........./......

 17 |    7   | ..../........./........./.......

 16 |    6   | .../........./........./........

 15 |    5   | /./......././......././......./.

 14 |    4   | ./......././......././......././

 13 |    3   | ......../........./........./...

 12 |    2   | ......./........./........./....

 11 |    1   | ....../........./........./.....

 10 |    0   | ...../........./........./......

  9 |    9   | ....../........./........./.....

We draw a "" if:

$$((ybmod 10)>3text{ and }a=8)text{ or }((ybmod 10)<6text{ and }a=6)$$

 y  | y % 10 | output (w = 3, h = 1)

----+--------+----------------------------------

 20 |    0   | .............................

 19 |    9   | .............................

 18 |    8   | .............................

 17 |    7   | .............................

 16 |    6   | .............................

 15 |    5   | .........................

 14 |    4   | .........................

 13 |    3   | .............................

 12 |    2   | .............................

 11 |    1   | .............................

 10 |    0   | .............................

  9 |    9   | .............................

Or we draw a space if none of these conditions is fulfilled.