prism docs · Designing · Draw and Pen

Draw and Pen

When none of the ready-made shapes fits, make your own. Draw lets you sketch a shape in one stroke and tidies it into a clean surface. The Pen places points one by one, with smooth curves wherever you drag. Afterwards you can curve the edges of any shape.

WhereDesign ▸ Add ▸ Draw (D) or Pen (Shift + D)

Drawone stroke becomes a quad, triangle, circle, curved outline or line

Penclick for a corner, drag for a curve

ModeSimple Draw, curving points on the canvas
Advanced the Pen, the Curves section

1 · Draw a shape freehand 2 · What your stroke becomes 3 · The Pen: points and curves 4 · Curves on any shape 5 · Draw a mask 6 · Hints and tips 7 · When something looks wrong 8 · Mouse and keyboard

1Draw a shape freehand

Press Add ▸ Draw, or D. A lime Draw chip appears in the canvas tool bar, and the right panel shows how to draw.
Press and drag to draw the shape in one stroke. End near where you started to make an area; end somewhere else (or hold Alt) to make a line.
Let go. The stroke becomes a clean shape with few points, already selected, with the Test Grid on it. Drawing stops after one shape: press D again for the next.

A rectangle being drawn freehand on the canvas — Drawing a rectangle by hand. The **Draw** chip in the tool bar shows the job; the hint at the bottom says how it works; Done at the bottom right (or `Esc`) goes back to the canvas.

The Draw panel with its keys — The right panel while drawing: its “?” explains the rules, and the list shows the keys.

Where it lands. The shape appears exactly where you drew it. It joins the group of the surface you had selected, right above it in the list, and it is one undo step (“Draw Quad 2”).

2What your stroke becomes

prism recognises simple shapes, so a hand-drawn rectangle comes out as a true quad with straight sides and sharp corners.

Five drawn shapes: a quad, a circle, a curved blob, a wavy line and a triangle — Five strokes, five shapes: a quad, a circle, a curved outline (selected, with its smooth points and handles), a wavy line and a triangle.

You draw	You get
A rectangle, even a wobbly one	A quad. Its corners go where your sides meet, so rounded pen corners still give sharp ones.
A triangle	A triangle.
A round loop	A circle, or an ellipse when it's oval.
Any other closed shape	A polygon with smooth curves (up to 32 points). Nearly straight sides come out exactly straight.
An open stroke, or anything drawn with `Alt` held	A line: straight if you drew nearly straight, otherwise curved (up to 64 points). It starts plain white.

Draw at a comfortable size. Small wobbles are smoothed away, but a very small shape drawn at a low zoom can come out as a curved outline instead of a quad. Zoom in, or draw it bigger.

3The Pen: points and curves Advanced

The Pen is for outlines you want exactly: you place every point, and you decide where the curves go.

Press Add ▸ Pen, or Shift + D.
Click to place a corner.
Press and drag to place a smooth point: its two handles follow the pointer and set the curve. Hold Alt while you drag to move only the outgoing handle, for a sharp turn after a curve.
Go round the outline. Backspace takes the last point back.
Finish by clicking the first point, double-clicking, or pressing Enter (or Finish shape under the canvas). A shape needs at least three points.

The Pen drawing: two corners, a smooth point and a handle being dragged — While you work, the Pen shows the true curve so far, the rubber band to the pointer, the dashed closing edge and the handles you are dragging.

The finished Pen shape with its handles — The finished shape: a polygon with two smooth points. Four corners and no curves would have made a quad.

Esc cancels. The first Esc drops the unfinished shape and keeps the Pen; a second one leaves it. Finish with Enter first if you want to keep the shape.

4Curves on any shape

Quads, triangles, polygons and lines can all have curved edges, whether you drew them or added them. (Circles can't, and neither can a mesh-warped shape.)

To…	Do this
Make a corner smooth	Double-click the point. Its handles appear along its neighbours. Double-click again to make it a corner.
Bend the curve	Drag a handle (the small lime dot at the end of a line). The opposite handle turns with it, so the point stays smooth.
Bend one side only	`Alt` + drag a handle: it moves alone, for a sharp point between two curves.
Pull handles out of a corner	`Alt` + drag the point itself.
Curve or straighten one edge	Right-click the edge ▸ Curve this edge (it bows outwards) or Straighten edge.
Do the whole shape	Inspector ▸ Curves ▸ Smooth all corners or Straighten all edges.

A quad with its top-left corner made smooth and a handle pulled up — The top-left corner double-clicked to smooth, then its handle dragged: the edges on both sides bend.

The same shape with its bottom edge curved — Right-click ▸ Curve this edge on the bottom edge: an arch shape in three moves.

The edge's right-click menu — An edge's menu: Add point here, Curve this edge, Straighten edge (greyed: it is straight already).

The Curves section of the inspector — Inspector ▸ **Curves**. In Simple mode it is behind the inspector's More….

A curved quad keeps its perspective. A quad's picture is still placed by its four corners; its curves only change its outline. Handy for an arched doorway: the picture stays straight, the edge follows the arch.

5Draw a mask

Both tools can also draw masks, which cut away part of a surface instead of adding one: Add ▸ Mask ▸ Draw a mask (both modes) or Pen mask Advanced. The mask cuts the surface you had selected. See Masks.

6Hints and tips

Draw quickly and confidently. A slow, shaky stroke is smoothed away anyway; a confident one gives cleaner corners.
A rectangle you draw is a quad, with its picture in perspective. No need to switch to Add ▸ Quad.
Trace real objects with the Pen with the projector window open and the canvas zoomed in (Shift + 2): place each point where you see the real corner.
Straight into a curve: in the Pen, Alt-drag the point where the straight part starts, so only its outgoing handle bends.
Fewer points, smoother shapes. A curved edge between two points is smoother than many small straight ones.
Undo takes back a whole shape: Ctrl + Z after a stroke removes it in one go.

7When something looks wrong

You see	Why	Fix
My rectangle came out as a curved outline	It was very wobbly, or small on screen.	Zoom in or draw it bigger. Or Add ▸ Quad and drag its corners.
I wanted an area and got a line	The stroke ended too far from where it started.	End the stroke near its start; don't hold `Alt`.
“Press and drag to draw a shape…”	The stroke was too short to be a shape.	Press, drag round the outline, then let go.
A double-click doesn't curve the point	It is a circle's corner (circles don't take curves), or the end of a line (“An end of a line has one edge…”).	Use a polygon, or smooth a point in the middle of the line.
“The projector doesn't reach that spot…”	In the camera view, the Pen can't place a point outside the projector's picture.	Place points inside the lit area, or switch to the projector view.

8Mouse and keyboard

Action	How
Draw · Pen	`D` · `Shift` + `D`
Draw a line (Draw)	End away from the start, or hold `Alt`
Corner · smooth point (Pen)	Click · press and drag (`Alt`: one handle)
Finish (Pen)	Click the first point · double-click · `Enter`
Take a point back (Pen)	`Backspace`
Cancel the shape, then leave	`Esc`, `Esc` · Done
Smooth or corner a point	Double-click it
Move one handle alone	`Alt` + drag the handle
Pull handles out	`Alt` + drag the point

Draw and Pen

1Draw a shape freehand

2What your stroke becomes

3The Pen: points and curves Advanced

4Curves on any shape

5Draw a mask

6Hints and tips

7When something looks wrong

8Mouse and keyboard

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