Using group instances !!!

In this quick tutorial I will describe how we are using group instances, pilule in a way to decrease our poly count.

For this example we are going to use a table model as shown below:


Original Model:

At this point the table has 125k poly’s which is too many for our purpose (which is just one half or the table).

When this table was created, see only one half of it was modeled and the mirror modifier was applied to it to project the other half.

Since we applied the mirror modifier we have doubled the poly count and it’s all calculated when we render.

What we need is a solution to decrease poly count a bit more, but not to use mirror modifier (since that solution only gave us a double count). Instead of that we are going to use what is called group instances.

Set up:

As you can see our table is essentially the same on all sides.  Now since we have 1/2 of the table, we are going to delete half of that, which leaves us with 1/4 of the table.

We now have around 35k poly’s which is a good poly count for our purpose.

Now let’s make a instances of this 1/4 table shall we ūüôā¬†


Group instances:

1. First select  the table and make it a group (Ctrl + G),  I named it table_front

Now that it is a group, we can add instances of it to create other sides of the table.


2. To add our first  instance of the table go to  Add (Shift A) > Group instance > table_front


The table outline color is green (when we created the group) which indicates it is the original mesh and it is red for the instance.


3.  Since the instance is now placed on top of our original model, we must change their duplication direction.

We can do that (with the instance selected) by going to the Object tab > Transform.

In the field for Scale, enter -1 for X value .

 Now the instance is placed on the opposite side.


4. With our first  instance still selected, create a duplicate by pressing  Shift + D

then go back into a the Object tab > Transform and enter  -1  for Y scale value.

 Now we have 3/4 of the table created.


5. Finally, we will repete this process for the last part of the table.  

Create a duplicate (Shift + D) from the last (third) instance and go back into a Object tab > Transform and enter 1  for X scale value.

(NB: Be sure to use a positive 1 this time!)


Closing note:

The good thing about using group instances instead of using mirror or array…  is that group instances don’t count in memory while rendering.  With  mirror or array this is not the case.

We ¬†now we have a table with 35k instead of previously 125k poly’s.

I hope you learn something useful from this tutorial…



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