Random rotation of instances

Question

I am trying to use geometry nodes to build a wall, where the stones of every second layer are offset to create a brick-like pattern. I tried using mesh lines to points for more control, so that I could access every line separately. I instantiate a vertical mesh line for the vertical dimension, then a horizontal one for every point on the vertical one, then convert the whole thing to points and instantiate the original brick on every point.

The problem is I want to add a slight variation of scale and rotation to every instance of the original brick. All advice recommends simply plugging in a random value to the "instance on points" node, but when using the double mesh lines approach the result looks like this:

I know I can simply use a grid mesh, as it seems to make all the points "equal" and randomization of rotation works just fine:

Unfortunately I do not know how to offset every second horizontal line of points in a grid mesh. So my question is twofold: is it possible to achieve an actually random rotation for every instance in the first approach, and/or is it possible to offset every second line of points in the second one?

Answer 1

First of all, you can instance objects on the Mesh Line points without having to convert them with Mesh to Points.

The next thing is: when you use the Grid for Instance on Points, on each point of the grid is created a new instance with its own index in X and Y direction. So each instanced cube is rotated individually.

When you instance the vertical lines on the horizontal line, the points on each line instance and the instanced cubes are indexed 0, 1, 2, 3. So they all share the same indices according to their position on the line and so they get the same random value.

To change that the more complicated way you could use a Capture Attribute node to get the indices of the line instances and add them to the cubes indices to make them all have different values or the easier way is to Realize Instances after the second Instance on Points node, so that each point of each line has an individual index.

By the way, I do not know if this is on purpose: you are using random Float values instead of Vector values. This way, each of the three axes is rotated by the same random values. With a vector output each axis on each cube would get an individual random value, so instead of a random (0.3°, 0.3°, 0.3°) for example it could be (0.3°, 4.2°, 1.8°).