Is it true there is no smoothing groups/vertex normals in Houdini? I did a google search and a couple posts said Houdini doesn't have/need smoothing groups, and its because it doesn't have vertex normal? Someone suggested using more polygons, which isn't really the greatest option.

How do I set a poly/edge/vertex to a certain world position? Like if I want a face to be on Z 0, how do I do that? All I can find is Local Space coordinates, and near it is a check box for Local Only, but before its checked its already in local space.

How do I change the axis/direction to move vertices? Example, when I select a single vertex on a cube, its gizmos point off to the corners instead of straight up, forward or left. Its nice to have this, but how do I switch it back to moving directly on the X, Y, Z? Sorry having a hard time explaining this.

How do I break the object stack down? So every time I use a bevel/edge loop/poly split/etc. the nodes get added to the stack. How do I “finalize” the changes so there isn't a stack of tool modifiers?

How do I change the vertex colours? Not for changing the material, but in Unity some shaders I write access the vertex colours, which is really handy for grouping them together if you only want to access certain parts of a model.

How do I select a loop of polys? In 3ds max you can select 2 polys, then hit a button and it will select everything adjacent from them.

Sorry if its hard to understand, I had a hard time explaining some things. I can get screenshots if need be.

Thanks!

LittleRain
Is it true there is no smoothing groups/vertex normals in Houdini?

It has vertex normals. It doesn't need smoothing groups, because it has vertex normals, which are more general. You can select a group of primitives and append a Normal SOP with Cusp Angle set to 180 if you want that patch to be smooth with a cusped edge loop around it.

LittleRain
How do I set a poly/edge/vertex to a certain world position?

I'm not an imperative modeller, so when I want to do stuff like that, I tend to be okay with using an Attribute Wrangle with @P.z = 0;. Other people probably have better approaches than me. Maybe something with snapping to a construction plane? I'm not sure.

LittleRain
How do I change the axis/direction to move vertices? Example, when I select a single vertex on a cube, its gizmos point off to the corners instead of straight up, forward or left.

Right-click on the handle, Align Handle > World. Alternatively, if you want it in the object's space, you can select Object, instead of World.

LittleRain
How do I break the object stack down? So every time I use a bevel/edge loop/poly split/etc. the nodes get added to the stack. How do I “finalize” the changes so there isn't a stack of tool modifiers?

You can right-click on a node, Flags > Lock/Unlock, to lock the node's output geometry, then you can delete the input nodes if you want to. It's a good idea to lock the end nodes of imperative modelling chains when switching major versions of Houdini, but we try to avoid the need to do that between builds of the same major version, so most people don't do that and just keep all of the nodes. It's quite often useful to keep the nodes if you need to change something upstream later, though point and primitive numbers may change between different major versions, (though we do try to keep that to a minimum, too), so imperative modelling chains using manual selections may or may not work after upgrading to a new major version.

LittleRain
How do I change the vertex colours?

You can set either vertex colours or point colours using a Color SOP. (Points are shared between vertices.) You can also use Attribute Wrangle if you want to do something fancy.

LittleRain
How do I select a loop of polys?

When in polygon selection mode, it looks like you can select one, hold A, and middle-mouse click on the next one to select a loop of polygons in that direction.

Hopefully that covers most of what you were looking for.