prism docs · Designing · Blend modes

Blend modes

A blend mode decides how a surface mixes with the surfaces below it. Normal covers them. Multiply darkens them like a coloured gel. Screen and Add brighten them, like light added to light. prism has 14 modes for surfaces, groups and layers, and they are there in Simple mode too.

WhereInspector ▸ Blend with surfaces below, or right-click ▸ Blend mode

14 modesNormal, four that lighten, four that darken, three for contrast, two differences

With itOpacity, 0 to 100 %

ModeSimple surface and group blends, opacity
Advanced Layer mix

1 · Set a surface's blend 2 · All 14 at a glance 3 · Each mode 4 · Opacity 5 · Groups 6 · Surface blend and Layer mix 7 · Hints and tips 8 · When something looks wrong 9 · Mouse and keyboard

1Set a surface's blend

Make sure the surface sits above the one it should mix with: higher in the Surfaces list, and overlapping it.
Select it. In the inspector, under Blend with surfaces below, choose a Blend mode. Or right-click it ▸ Blend mode.
Set its Opacity if you want less of the effect.

The Blend with surfaces below section with Multiply chosen — The inspector's Blend with surfaces below. The “?” beside Blend mode explains the chosen mode.

The Blend mode submenu with all 14 modes in their families — Right-click ▸ Blend mode: the 14 modes in five families, each with a few words. Hover one for a longer explanation.

No black base. A surface on Normal is opaque: where its look is empty, it shows black. On any other mode it is drawn without that black base, so where its look is transparent the surfaces below show through as they are.

Several at once: select several surfaces and the section sets them all (it says “2 surfaces”; the picker reads Mixed when they differ). Locked surfaces are left as they are.
Each change is one undo step, such as “Set the blend of Poster to multiply”.

2All 14 at a glance

The same two surfaces in every mode, straight from prism's renderer: a blue-to-orange gradient below, and a black-to-white gradient on top. The top one overlaps the left one on its dark end; on its right it hangs over the black background, where you see how each mode treats black.

A grid of 14 pictures, one per blend mode — Rows from the top: Normal, Add, Screen, Lighten · Colour dodge, Multiply, Darken, Colour burn · Subtract, Overlay, Soft light, Hard light · Difference, Exclusion.

On a projector, black is no light. That is why Add, Screen and Lighten make a surface's black parts vanish, while Multiply and Darken make them black out what is below.

3Each mode

Normal

Modes that lighten

**Add** adds its light to what's below; black adds nothing. For glows, beams and sparkles on top of another look.

**Screen** brightens softly: black shows what's below, white stays white. Like Add without blowing out; good for mist and smoke.

**Lighten** keeps whichever is brighter, colour by colour. For combining two bright looks without adding them up.

**Colour dodge** brightens what's below strongly; black leaves it as it is. For intense, burnt-out highlights.

Modes that darken

**Multiply** darkens: white shows what's below, black hides it. Like a gel over a light; for tints, shadows and the glass-box effect.

**Colour burn** darkens what's below strongly; white leaves it as it is. Deep, saturated shadows.

**Subtract** takes its light away from what's below; black takes nothing. For dark shapes cut into a lit picture.

Modes that add contrast

**Overlay** darkens the dark parts of what's below and brightens the bright ones; 50 % grey changes nothing. Adds texture while keeping the colours below.

**Soft light** gently darkens or brightens what's below; 50 % grey changes nothing. A light wash of colour or texture.

**Hard light** multiplies where it's dark and screens where it's bright; 50 % grey changes nothing. The top picture's contrast leads.

Differences

**Exclusion** is like Difference with less contrast: white inverts, black leaves it.

4Opacity

Opacity mixes the surface's result with what is below. With Normal it fades the surface; with another mode it weakens the effect: Multiply at 50 % darkens half as much.

Normal at 50 % opacity — Normal at 50 %: half the top gradient, half what is below.

Multiply at 50 % opacity — Multiply at 50 %: a lighter darkening. Compare with Multiply above.

Right-click ▸ Opacity offers 100, 75, 50, 25 and 0 %.

5Groups

A group has its own Opacity and Blend with what is below (the group's settings, or right-click its row ▸ Blend mode / Opacity). Its members are drawn together first; then the group's picture is blended with what is below it. So a box of three faces on Multiply darkens the wall behind it once, not three times. See A group's settings.

Blends inside a group mix with the other members first. A member on Multiply inside a Normal group still darkens the wall behind the group.

6Surface blend and Layer mix

There are two kinds of mixing, and they are easy to confuse.

Setting	Mixes with	Where
Blend with surfaces below	the other surfaces under this one	The surface's inspector, right under its look
Layer mix Advanced	the layers below it on the same surface	Under the layer stack, for the selected layer (Layers)

Multiply on a layer won't show the wall. A surface's bottom layer sits on the surface's own black base, so a layer mix can never reach the surfaces below. To let a surface darken or brighten what is under it, set the surface's blend. (Old projects that used the layer for this are moved over for you when they open.)

7Hints and tips

Blends need something below. Put the blended surface higher in the list, overlapping another surface.
Glows on top of looks: a surface with Edge Glow or Sparkle on Add or Screen lets its black background vanish.
Tint a whole wall: a Solid colour on Multiply over it, at an opacity that suits.
Judge on the real object. Modes look different on a lit wall than on a screen; keep the projector window open while you choose.
Copy a blend with the rest of the style: Ctrl + Alt + C copies a surface's layers, blend and opacity; Ctrl + Alt + V pastes them onto the selection.
A few blends are free; dozens of surfaces on the rarer modes cost a little more drawing time on a slow computer.

8When something looks wrong

You see	Why	Fix
The blend does nothing	Nothing is below it: it is the lowest surface there, or doesn't overlap another.	Move it above the surface it should mix with.
Multiply turned the surface black	Below it is only the black background: no light to darken.	Put a surface under it. On a 3D object, turn on Show the hidden sides.
Multiply on a layer turned it black	That is the layer's mix inside the surface.	Set the layer back to Normal and use Blend with surfaces below.
Some selected surfaces didn't change	They are locked (or in a locked group), or they are masks.	Unlock them and set the blend again.
The effect is weaker than expected	The surface's opacity is below 100 %, or its group's is.	Check Opacity on the surface and the group.

9Mouse and keyboard

Action	How
Blend mode	Inspector picker · right-click ▸ Blend mode
Opacity	Inspector slider · right-click ▸ Opacity
Copy · paste style	`Ctrl` + `Alt` + `C` · `Ctrl` + `Alt` + `V`
Undo a change	`Ctrl` + `Z`

Blend modes

1Set a surface's blend

2All 14 at a glance

3Each mode

Normal

Modes that lighten

Modes that darken

Modes that add contrast

Differences

4Opacity

5Groups

6Surface blend and Layer mix

7Hints and tips

8When something looks wrong

9Mouse and keyboard

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