#CreativeFriday – Using Photoshop blending options to ‘Knock Out’, and cut out 2D shapes for 3D composites

Working with Tony Harmer this week, we encountered a Photoshop challenge which took us a while to bottom out. However, we haphazardly stumbled on another way to cut 2D shapes out from other layers and keep control of shape measurements.

There are currently many ways to cut out shapes in Photoshop, either using Layer Masks, Vector Masks, Clipping Masks, or using the subtract/exclude commands etc. The objective of this particular solution is another way to control specific measurements, especially with 3D printed objects.

For an example let us take something really simple. We want to take a 12cm by 12cm square and cut out a square hole in the middle which is 10cm by 10cm. The measurements are quite specific in the printing process, but maybe required in a 2D design also.

In the example, the new canvas is created, which has a transparent background (This means that later on we will only see the shape, regardless of what we do with it).

Screen Shot 2015-02-16 at 19.14.16The next step is to create a rectangle (marked red below) with the rectangle tool. Notice that the width and height of the rectangle are specified as 12cm by 12cm (marked in yellow) as this is a live shape which will give us flexibility and control of the shape.

Now to cut out the 10cm by 10cm square from the middle. Another rectangle is needed which in this case will be 10cm by 10cm width and height (marked in yellow below). The colour of the rectangle isn’t signifiant, it’s just to show it’s presence.

We will use the yellow square to knock the 10cm by 10cm hole in the 12cm square. To do this, we can put a blending option on the Yellow square layer and change the Knock out option. This can be achieved by adding an effect (marked in green) or by double clicking on the layer.

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Photoshop will bring up the Layer Style dialog box and should park on the Blending Options by default (for a new effect), as shown below. On this dialog under Blending options there is an option to use Advanced Blending (marked in orange). For this technique to work, the Fill opacity value will be set to 0.

Screen Shot 2015-02-16 at 19.29.52v10 copy

If the Knock out is kept at the default setting, ‘None’ and the Fill Opacity is reduced to zero, it will just remove the yellow rectangle and revel what was below it in the layer stack. If the knockout is changed to shallow when the Fill Opacity set to zero, the effect will be to remove the yellow rectangle, as well as removing the shape from the shape below it. In this case, the yellow rectangle will be removed from the blue larger shape and the background will be shown. (The shallow knock out will be one level deep in the layer stack, which essentially means that if it’s part of a group nothing will be knocked out).

Screen Shot 2015-02-16 at 19.54.23

The effect can be seen above (notice that the layers are all directly above and at one layer deep).

Below shows another layer that is added to the top of the stack, which is also one layer deep. When it’s Blending option is changed to shallow, the effect is the same and its shape is knocked out.












There is another option on the knock out, called ‘Deep’.

In the example below, there is a lot going on.

At the base there is a blue rectangle, immediately followed by square that cuts out the rectangle, by using a zero fill shallow knockout (as seen below).

Above this there is a group called ‘Octagons’, contained in this group there is another group called circles. Both of these, regardless of the groups and nesting of groups are controlled by a shallow knock out on the blue rectangle. This shallow knockout is at the top group level, so it’s still at one level deep. Therefore everything under a shallow knock out regardless of the nesting will inherit the Blending option from the one level deep Knockout configuration.

The Halfmoon group at the top of the layer stack does not knock out any part of the blue rectangle (notice there is no Blending option on the Half moon group to allow this to knock out at this level). Inside of the Half moon group, there is a small blue circle called ‘Elipse 3’, this shape is not cutting out the blur rectangle, but it is cutting into the pink circle, because ‘Elipse 3’ has a zero Fill knock out layer set to ‘shallow’. In this case the shallow only goes one level deep.

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To allow ‘Elipse 3’ (marked in red below) to cut into the blue rectangle (marked yellow), it needs to go past the first level ‘shallow’ and to the ‘Deep’ level. This can be controlled by changing the blending option to zero fill and knock out ‘Deep’ (marked in orange).

Screen Shot 2015-02-16 at 20.52.21

Ultimately, there are many options for this and many different combinations. i.e. You can have a photoshop layer cut into Photoshop layers, Photoshop layers cut into Illustrator placed layers, or even a combination of the above. This does mean that we are able to keep measurements and dimensions in tact, especially when 3D Printing.

Converting the 2D shape to a 3D object.

The first step is to group all layers together using Smart Objects, which will result in a single layer. The 3D conversion is executed by choosing the 3D menu 3D / New 3D Extrusion from Layer command. This option should create the 3D geometry for you.

Screen Shot 2015-02-16 at 21.27.16

To go a little further, attributes about the 3D object can be modifed. By clicking on the 3D object once will bring up the navigation widget. Pressing the V key whilst the navigation widget is shown, will cycle through the 3D modifiers. Things like bevel, inflate, taper, twist etc can be applied to the object. In the following example the front face of the object (blue painted face above) has had a bevel applied to it.

Screen Shot 2015-02-16 at 21.34.28The 2D shapes have now been converted into a 3D object, all of which are completely editable if desired. Re-editing the object can be achieved by double clicking into the Smart Object layer (Half Moon layer above).

I used this opportunity to make something out of this technique and made a fully rendered scene, the creation (not including rendering) took about an 1hr.

monster layout v4


The basis of the monsters were created using a Live shape rectangle with rounded corners, with 4 circles to cut away the bottom. In the example below there is a group called tentacles, which contains 4 circle shapes. The group level is then set to have a fill opacity of zero and a knock out of shallow. This will essentially cut the circles out of the rectangle leaving the tentacles.

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All of these layers are then converted into a single Smart Object by selecting them all and choosing Filter /  Convert to Smart Object (I find that labeling the layers is very useful to keep track of what’s going on).

Screen Shot 2015-02-20 at 13.38.11

Once the option 3D / New 3D Extrusion from selected layer command is issued, Photoshop will move into the 3D mode and show the new extrusion. To alter the final extrusion, the tools marked in red can be used and will appear as a widget on the 3D bounding box or cage (the V key can be used to cycle through the tools). At which point elements of the 3D geometry can be changed. i.e. the extrusion, bevel, tapering, inflation etc can all be modified to give the final required look.

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After configuring the extrusion, altering the taper and bevel, here’s what the modifications look like

Screen Shot 2015-02-20 at 15.27.06

For the render and final piece, there are two elements that i’ll add. One is a background, by just creating a layer underneath the 3D layer  (marked in Red), and pulling a gradient across the layer. The gradient tool is marked in yellow, and uses the foreground / background (marked in green) to construct an initial gradient (marked in blue). This layer isn’t locked, so can be transformed and scaled to make sure that it fits the scene.

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To render the scene and get a more realistic look, Image based lights can be used (IBL). The Photoshop team have created some IBL’s for you and are available here. From here you can download the creative and basic IBL’s just to get you started. An IBL will allow the renderer to give a more realistic look and feel.

The basic IBL’s ones are just black to white gradients, which hold back light in specific regions. However, the creative one’s are more complex and have the feel of a real studio with soft boxes etc.

To add an IBL to the scene, open the 3D panel using Window / 3D, and select the environment (marked in blue below). This will open the properties panel for this object, from here the IBL check box should be ticked on. Assuming it is on, the IBL that is currently being used is show in the small thumb nail next to it (marked in red). To replace the default IBL, click on the folder icon (marked in green) and replace it’s contents with the IBL (marked in red). The file dialog box is shown, and the one i’ve selected for this exercise is shown in pink (the IBL graphic is shown in yellow). Once this is added the scene lights can be moved around (as well as other lights that are having an impact on the scene.

Screen Shot 2015-02-20 at 15.43.35

A reflection can be added if required, by using the reflection option and opacity on the environment properties (marked red below).

The final activity is to render the scene. This can be performed by clicking on the render option, which can be found in numerous places inside the 3D environment in Photoshop (marked in red below).

Screen Shot 2015-02-20 at 15.57.06


I hope this blog post has given you some ideas of how to use 2D shapes and cut outs within 3D composites in Photoshop. The Final Behance page is here.


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