Sculpt Mode

Blender's "Sculpt" mode is something I am slowly learning about, and so I thought worth a blog post. I will probably add to it as I learn more. It allows you to modify a mesh by, well, sculpting it.

You can go into Sculpt mode using the drop down at top left where Object and Edit mode can be selected, but I think a better way is to go to the Sculpt tab. Either way, whilst in Sculpt mode, you can press tab to go into Edit mode.

I recommend applying scale before sculpting, otherwise it can be skewed along one axis.

Vertices

If you start with the basic cube, go into Sculp mode, and try to edit it, not much will happen. By default, Blender will try to apply the tool to the existing vertices, and you only have six. There are three ways around this.

Lots of Vertices - If you subdivide the cube a lot, then when you sculpt it, Blender will have plenty to work with, and you will see something happening.

Density - You can use the density tool (fifth down on the left) to increase the nodes in one region.

Dyntopo - Alternatively you can turn on "Dynamic Topology". This is a check box towards the top right. When Dyntopo is turned on, Blender will simply create new vertices as and when needed.

Dyntopo has two issue. The first is that it will generate a lot of fine geometry, which will take a lot of processing power, which is a bad thing if you are creating for a video game, but generally not a issue when 3d printing. However, it is likely that the Boolean modifier will struggle with objects that have been sculpted like this.

The second issue is that you will lose UV data. This tells blender how to apply a texture - and again not relevant to 3d printing.

So why mention them? To put in context why Dyntopo will always default to off. Whenever you go into Sculpt mode, Dyntopo will be off, even if you just turned it on for this very object. And it will give you a warning, and ask it you are sure every time! You can disable the warning on a per object basis by going to the Data tab in the properties panel, finding UV Maps, selecting the default, called UVMap, and clicking the minus sign to the right, but you will still need to tick the box every time.

Objects

Sculpting will only apply to the currently selected object - just like Edit mode. To quickly swap to another object, hover over it and do [Alt]-Q. You should see it flash (if not in X-ray). Remember to turn Dyntopo on again!

Tools on the left

In Sculpt mode, a set of brushes  appears across the bottom, and a set of tools on the left. We start with the tools on the left. The five at the bottom on the left are the same as in Object mode, so we can skip them.

Brush - This is the one to select when sculpting. It will apply your selected sculpt brush to the object.

Paint - Makes the object darker. Seems to be just a surface effect, I guess to apply shadows. Hold down [CTRL] while painting to erase.

Mask - At first glace this is like paint, but not as dark. However, areas painting will not get altered by the sculpt tools. Again use [CTRL] to reverse. You can reverse a mask with [CTRL]-I.

Draw face set - Face sets are kind of like masks but you can have many of them. There is a menu for working with face sets, and an option to use them as masks in the auto-masking widget, top-centre. I cannot find aw away to get rid of face sets. Not something I anticipate ever using...

Density - Increases the nodes, as mentioned earlier

Box... - These four tools apply to a rectangle you create by dragging - like box select in Object and Edit modes. The first applies a mask (or removes with [CTRL]), the second hides part of the object ([ALT]-H to unhide as usual), the third applies a face set. The four deletes that section of the model.

All four can be used in modes other than box, such as lasso, by clicking and holding.

There are a further six that are even more esoteric.

Brushes at the bottom

With the tool set to "Brush" you can use these brushes. There are a lot; you can drag up from the top of the toolbar to see three rows of them.

Many of the brushes work in reverse if you are holding down [SHIFT].

Setting for brushes appear at the top. The radius is relative to the view, so if you zoom in closer, you will be working at a smaller scale. Strength determines how much it does it. I find the defaults are good for me and have never bothers to change them.

There are a lot of brushes, and it feels like not much difference between some of them. Two to call out:

Crease sharp is good for chips and nicks in stone.

Elastic grab pulls out a vertex and lets you move it around, nearby ones follow. Elastic snake hook is similar, but more so!

Remesh

If you are not using Dyntopo you can use Remesh to have Blender create more vertices if they are getting too stretched out. Remesh is just right of Dyntopo, or you can do [CRTL]-R.