Retopoflow 4: clean up, close, and creatures

Start here

These are lessons four to eight of Retopoflow 4: the core flows. That page covers orientation, the PolyStrips skeleton and the Strokes fill.

Relax and Tweak: clean up

Goal: Even out the quads and fix lumpy spots without redoing anything.

A patch of quads. Tweak (Ctrl Shift drag) pulls two vertices out of place and the distorted quads tint orange. Relax (Shift drag) sweeps across and evens them out. A pinned vertex stays where it was.

Concept

Both are brushes that only affect the geometry under the brush.
Relax evens out spacing and angles while staying on the source surface. It isn't a plain smooth [8].
Tweak pushes vertices around. The default brush is Nudge; Alt toggles loop mode in Nudge [9] [10].
You can reach both from any other Retopoflow tool without switching.

Clicks and keys

From any Retopoflow tool, hold Shift and left-drag over vertices: Relax.
Hold Ctrl Shift and left-drag: Tweak.
In the Relax or Tweak tool itself, left-drag applies the brush. Select with Shift + click, box select with B, or lasso with Ctrl + right-drag [9].
Brush size is F, strength Shift F, falloff Ctrl F.
Masking: Boundary (Exclude, Slide, Include) keeps the outer edge from drifting. Selected (Exclude, Only, All) limits the brush to or away from the selection.
Pin vertices you like: select them and use Pin Selected in the tool settings (Shift P); unpin with Alt P [8] [10]. Pins only show in vertex select mode.
For a whole selected loop, use the Relax operator (Shift R) or Even (Shift Alt R) in Edit Mode [5] [10].

Exercise: on your sculpt's new mesh, drag a few vertices out of place with Tweak on purpose, then Shift-drag Relax over the area and watch the quads recover. Then pin a sharp corner and Relax across it. It shouldn't move.

Common mistakes

Relaxing sharp corners flat. Pin them, or mask Corners.
Turning up Iterations, when Strength is the setting to try first [8].
Expecting a plain click to select inside the brush tools.

Time target: novice 20 min, competent 8 min, fluent 3 min.

Good enough when

Quad sizes change gradually, except where you chose otherwise.
Corners and ridges you want sharp didn't soften.

Caps and fills: closing the top and bottom

Goal: Close the open holes at the top and bottom of the mesh.

A rock with an open top. With only half the rim selected, F makes nothing. With the whole rim loop selected, F fills the top with quads. The buried bottom is left open.

Concept

F is an auto fill: it tries to fill the selected boundary with quads [5] [4].
The Patches tool also fills when you press Enter or Ctrl + click.
Check your version: in Retopoflow 4.2.2 the toolbar's Patches tool is the older "legacy" one, because the newer one is switched off in the code [2]. The manual describes the newer tool, so check its exact settings (Solution, Offset, step width) by eye. F, Enter and Ctrl + click should work in both.

Clicks and keys

Select the edges of the hole. Loop select is Alt + click, or double-click on an edge [3].
Tap F. A filled patch appears.
If it looks wrong, open the Adjust Last Operation panel. The Solution and Offset sliders (and Ctrl Scroll and Shift Scroll while the preview is up) cycle through other fills [4].
For holes with sharp corners, toggle which vertices count as corners with Ctrl + click on a selected boundary vertex [4].
Plain Blender fallback: select the boundary loop, then Edge > Grid Fill. It needs an even number of edges around the loop; if the count is odd, add or remove a vertex first.
If a hole won't fill cleanly, F with the loop selected makes a single n-gon [4].

Exercise: take the slab from earlier with its top and bottom open. Close the top with F and leave the bottom open. Then redo the top with Grid Fill and compare the face counts in the Statistics overlay.

Common mistakes

Selecting only part of the boundary loop.
Fighting for an all-quad bottom that nobody will see.
Forgetting that Grid Fill needs an even edge count around the loop.

Time target: novice 15 min, competent 5 min, fluent 2 min.

Good enough when

There are no holes anywhere the camera can see.
The top fill has no long, thin triangles.
The face count didn't jump by more than about 15 percent (a starting value to test).

PolyPen: fix corners and single faces

Goal: Place or fix vertices one at a time where the other tools get it wrong.

PolyPen: a plain click makes nothing; four Ctrl+clicks make a vertex, an edge, a triangle and then a quad.

Concept

PolyPen gives vertex-by-vertex control, built for low-poly game models [11].
Insert Method decides what a click makes. Tri / Quad is the precise default: a vertex, then an edge, then a triangle, then a quad.
It also works as a knife, cutting into existing faces.
It expects vertex and edge selection, not face selection.

Clicks and keys

Pick PolyPen. Deselect all. Ctrl + click on the source: one vertex.
Keep it selected. Ctrl + click again: an edge. Again: a triangle. Again: the fourth corner makes it a quad.
To bridge two edges with a quad: select one edge, then Ctrl + click on the second edge.
To cut: deselect all, Ctrl + click on an edge, then Ctrl + click on another edge of the same piece. Partial loops and quad junctions are toggles in the tool options (Knife Loop Cuts, Knife Junctions).
Drag any vertex, without Ctrl, to tweak it. Hold Shift while dragging to move in small steps [10].
Set Insert Method to Quad for one-click quads.

Exercise: on the slab, delete one corner quad and rebuild it with PolyPen in Tri / Quad mode.

Common mistakes

Clicking without Ctrl: that only selects.
Insert Method left on Edge or Vertex, so faces never appear.

Time target: novice 15 min, competent 5 min, fluent 2 min.

Good enough when

The patched corner follows its neighbours' flow.
There are no overlapping or doubled vertices. (Mesh Cleanup, in the Curve handles and helper ops step, checks this.)

Contours: tubes

Goal: Wrap loops around cylindrical forms: limbs, tails, necks, horns, poles.

A bent tube. A stroke drawn at an angle makes a twisted ring and is rejected. Four strokes drawn square across the tube each make a six-vertex ring, joined by sections with one cut loop between each pair.

Concept

You draw strokes across the form, perpendicular to its length. Each stroke becomes a ring [6].
Spans is how many vertices a new ring has. Cuts is how many loops sit between two rings.
Method: Walk (the best, but slower on dense meshes), SDF or Fast. Start with the default.
Tweak Loops is on by default: dragging an edge slides a whole loop.

Clicks and keys

Pick Contours. Deselect all.
Ctrl + left-drag across the tube near one end. A ring appears.
Straight away, Ctrl Scroll changes the number of vertices in the ring.
With the ring selected, drag a second stroke across the tube further along. It connects with a tube section.
Ctrl Scroll changes the loops in between. Shift Scroll or Alt T twists a ring.
Click and drag an edge to slide a loop along the form.

Exercise: add a Cylinder with a few cuts, bend it with Simple Deform or by moving vertices, and apply it so it's a plain mesh. Use it as a source. Draw 4 rings along it. Try 6 and 8 spans and count the faces.

Common mistakes

Drawing strokes at an angle, which twists the ring.
Too many spans.

Time target: novice 30 min, competent 10 min, fluent 4 min.

Good enough when

The rings are perpendicular to the form and evenly spaced.
Every ring has the same span count, as low as the silhouette allows (6 to 8 is a fair start for a toon tail).

Mirror: half a creature

Goal: Model one half and get the other half for free.

A quad mesh drawn on the left of a dashed symmetry plane. A dashed wire copy unfolds on the right; an ear added on the left appears on the right too. Apply turns the copy into real geometry, with a single row of vertices along the centre.

Concept

Retopoflow 4 uses Blender's real Mirror modifier; there's no separate symmetry mode [7].
A Mirror section in the tool settings toggles axes, changes the modifier's properties, or applies it.
Display modes: None, Applied (shows the mirrored side as real-looking geometry, which is confusing), Wire, Solid.
Blender's own Edit Mode symmetry isn't supported [7].

Clicks and keys

Put the target's origin on the symmetry plane (standard Blender practice).
Open the Mirror section in the tool settings and turn on the axis, usually X.
Pick a display mode. Wire is the least confusing.
Draw across the symmetry line. It works in PolyPen, Contours and PolyStrips.
If you can't see the mirrored half in Edit Mode, turn on the modifier's On Cage button (the triangle icon) [1] [7].
When the half is done, apply the mirror from the same section.

Exercise: mirror a half-cylinder and draw a strip across the centre line.

Common mistakes

Working on the "fake" side with Applied display: edits appear backwards [7].
Forgetting to apply.

Time target: novice 15 min, competent 5 min, fluent 2 min.

Good enough when

The centre seam has no gap and no doubled vertices.
The mirror is applied before export.

Reference

Next: curve handles, the whole flow, the capstone and a cheat sheet.

Sources

Retopoflow 4 manual, FAQ. docs.retopoflow.com/v4/faq.html
Retopoflow source code, v4 branch: the Add > Mesh labels in rfoperators/newtarget.py, and the legacy Patches switch, USE_NEW_PATCHES = False, in rftool_patches/patches.py. github.com/CGCookie/retopoflow/tree/v4
Retopoflow 4 manual, Retopoflow Mode (general use, settings, snapping, selection). docs.retopoflow.com/v4/general.html
Retopoflow 4 manual, Patches. docs.retopoflow.com/v4/patches.html
Retopoflow 4 manual, Helper Ops. docs.retopoflow.com/v4/operators.html
Retopoflow 4 manual, Contours. docs.retopoflow.com/v4/contours.html
Retopoflow 4 manual, Symmetry. docs.retopoflow.com/v4/symmetry.html
Retopoflow 4 manual, Relax Brush. docs.retopoflow.com/v4/relax.html
Retopoflow 4 manual, Tweak Brush. docs.retopoflow.com/v4/tweak.html
Retopoflow 4 manual, Change List (auto-save in 4.1.5, hotkeys added in 4.x). docs.retopoflow.com/v4/changelist.html
Retopoflow 4 manual, PolyPen. docs.retopoflow.com/v4/polypen.html