# Illustrating a Shoutengai Using Isometric Projection

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## Introduction

Isometric projection is a method of representing a 3D object in a 2D plane where the object sides are equally foreshortened on the three coordinate axes (x, y, z). Objects are drawn at 30° from the horizontal plane and three sides of them are always present to the viewer. The equal foreshortening effect is caused by the same scaling on the axes. The axes also have equal angle between them which is 120°.

The term isometric comes from the Greek “isometria” which means “having equal measurement”.

Isometric projection, along with dimetric and trimetric projection, are categorized under axonometric projection. Axonometric projection is a type of parallel projection, where the projection lines are parallel to each other. These parallel lines extend forever in parallel projection because of non-existent vanishing point unlike in perspective projection in which parallel lines converge into a single, vanishing point.

For comparison between the three axonometric projections, take a look at illustration below.

Axis lines with the same color indicate same scaling. Also, sides with the same color indicate same foreshortening. In isometric projection, as described in the beginning, all sides are equally foreshortened because of the same scaling on the three coordinate axes. In dimetric projection, two sides are foreshortened equally than the other side (two of the axes have same scaling; one axis have different scaling) whereas in trimetric projection, all sides are foreshortened differently from each other (the axes have different scaling).

Because of the non-existent vanishing point, objects in parallel projection don’t appear larger or smaller relative to the viewer. This can result in distortion and create an optical illusion. This limitation is apparent especially in isometric projection. Take a look at this optical illusion drawn using isometric projection below. Did you notice something weird with it?

## Before Beginning

What is “shoutengai”? Shoutengai (商店街, literally “shopping district”) is a style of shopping/commercial district in Japan.

Shoutengai have a diverse variety of storefronts on them, ranging from basic needs like groceries to specific stuffs like hobby shop. They are mostly located near train stations. However, there are ones that located near tourist spots and have specialized stores. Shoutengai that have roofs on them (arcade shoutengai) are usually pedestrian only but unroofed ones, like the ones on the side of a main road, allow traffic indefinitely or only on certain hours.

In this tutorial, I am going to draw a stylized isometric illustration of a shoutengai environment. The method I am going to use is a mix of isometric transformation and direct isometric drawing using isometric ruler. Let’s begin!

## Isometric Ruler

Start by creating a new document. I use a fairly huge canvas size (3000 px x 2000 px in 72 dpi) for this tutorial.

Before drawing, let’s make an isometric ruler first. Isometric ruler will help assisting us when drawing directly in isometric projection. To make an isometric ruler, we will use [Perspective ruler].

Create a new raster layer. Set [Process] to [Add vanishing point] and uncheck [Change perspective drawing method] in the [Tool Property] palette.

Hold Shift to make the vanishing point snap at a fixed angle, that is 0°, 45°, or 90° (and their mirrors). Even though the angles are fixed, there is a trick to make it snap at any angle we want, and in this case it’s 30°. Here is how to do it.

Create a new layer for the ruler. In [Navigator palette], rotate the canvas by 60°. While pressing Shift, draw the ruler vertically twice with some distance between them. Don’t let the vanishing points converge into a single point otherwise it would just be a normal perspective ruler.

Rotate the canvas again, but this time by -60°. Press Shift and draw the ruler again vertically twice with some distance between them.

After that, reset the canvas rotation. The isometric ruler is basically ready to use at this point.

This trick works because the fixed angles don’t move with the rotation of the canvas. So if we rotate the canvas by 60° then drawing the ruler in 90° direction (vertical direction), we get 90° - 60° = 30° as the result.

Use [Object] sub tool on [Operation] tool category to make it looks neat. After that, move the ruler layer to the bottom and set it to [Show in All Layers].

## Isometric Transformation

When transforming a multi view plan (the front-side-top view) into an isometric projection, we need to consider the isometric scale.

The multi view plan is usually drawn using true lengths, but in isometric projection, an object is foreshortened approximately 82% (81.6% to be precise) of its true lengths in all axes. It is because in isometric projection, the object is rotated on its all axes and that makes it shows its three views at the same time unlike in multi view plan which only shows one view of the object at a time. The rotation causes the foreshortening effect on the object.

The scaling between foreshortened length and true length is called isometric scale.

You can also use true lengths in an isometric projection but when converting back into multi view plan, you need to scale them accordingly.

I will demonstrate this by transforming a multi view of a cube into an isometric projection of a cube. I add a little arrow symbol for the top view so that we know we are transforming it in the right direction.

To begin isometric transformation, select the view you want to transform then press Ctrl+T.

Uncheck [Keep Aspect Ratio] and [Change vector width] on [Tool property] palette.

Still on [Tool property] palette, set Width to 71, Height to 82 for front and side.

Skew by 30° vertically for the front view. To do that, change [Process] to [Skew] and drag either the right or left handle of the transformation boundary.

Drag it vertically to make it transforming along vertical plane. Pay attention to [Rotation angle] on [Tool property] palette to assist the process.

For the side view, repeat the process but skew by -30° vertically.

For the top view, reverse the Width to 82 and Height to 71.

Because skew transformation only shows the angle when skewing an object vertically, we need to rotate the top view by 90°. This is also why we need to reverse the value in the previous step.

After that, skew by 30° vertically.

Then rotate by -60°.

After that, assemble them into a cube. The transformation process is finished.

As of why setting the width to 71, let's take a look at the explanation below.

We can use 82% as is in the z axis as it is the scaled height of the object because skew transformation doesn’t change the length of the lines in the skew direction. Skew transformation only changes the length of the lines that are not in the skew direction. We want the lengths to be changed exactly 82% of the original length. To get that, we need to use simple trigonometry.

If we arrange it like this, we get a triangle with its hypotenuse (h) as the 82% of the true length and b as the scaled width to transform. Since isometric projection is angled 30° from the horizontal plane, we can use cosine 30° to get the length of b.

cos 30° = b/h

b = cos 30° * h

b = 0.866 * 82

b = 71.014

We get the value for the scaled width that is approximately 71%.

## Drawing the Individual Buildings/Shops

In this tutorial, I am going to draw six shops for the main focus. They are florist shop, bookshop, ramen shop, udon shop, hobby shop, and bakery and coffee shop (both share the same building). I choose those shops because I think they will fit for the theme of the illustration.

To make it not too overwhelming, rather than drawing all the buildings at the same time, I draw one at a time. I also find that it’s relatively easier (at least for this tutorial) to draw the buildings one by one rather than directly drawing them as a single line art.

1. Florist Shop

I mostly use grid to assist drawing the front view only. To use grid, click [View] → [Grid] and check [Snap to Grid] to enable line snapping. Set [Gap] at 30 px and [Number of divisions] at 1, 2, 4, and 8 at [Grid/Ruler settings…]. The 30 px value is used as a base unit for the thickness of the wall and the height of the building. The [Number of divisions] increases according to level of detail. For example, I draw the main walls with [Number of divisions] at “1” and the windows at “8”. I don’t go for [Number of divisions] larger than 8 because it’s not really needed in the illustration.

First, I only draw the front view of the shop. The front view will be used as a base for the isometric transformation and also works as a sketch. I mostly use [Straight Line] and [Rectangle] sub tool from [Figure] tools with 4 brush size on vector layers to draw it. Hide the isometric ruler before drawing.

To manage layers effectively, I separate a building into its parts, each on their own vector layers. Those primary parts are “main building” or the general shape of the building, “window(s)”, “door(s)”, “billboard”, “shade”, and “roof” if it uses roof. Some parts that are exclusive to certain buildings are also drawn in its own vector layer. The parts are then colored differently using [Layer color] in [Layer property] and grouped into a folder.

I draw reusable parts only once, such as windows and the side billboard.

Finished front view.

After that, transform the front view using isometric transformation method above.

Turn on the isometric ruler. Complete the building structure by drawing them using [Straight line] sub tool with 4 brush size.

The lines of the windows and the doors look too crowded, so erase some of them just enough to suggest a 3D look for the parts. Use [Vector] eraser for this.

Erase the parts that are hidden behind the other parts.

Move the layer into a new layer folder. Then add a new layer above it and fill it with black and set it to [Clip to layer below]. This will make the entire line art have black color. You can merge the line art and its color after this by selecting them then press Shift+Alt+E ([Layer]→[Merge selected layers]) or you can just leave as is.

Create a new raster layer below the line art for the building colors. To color, use [Refer other layers] sub tool in [Fill] tool category. Enable [Area scaling] and set it to 2. Make the colors of the shop unique so that it stands apart from the other building. I use aqua green as the image color of this shop.

After that add the store name and the side billboard text.

I draw an air conditioning fan for another details. This drawing can also be reused at another building later.

Since this is a florist shop, I draw flowers and the flowerpots at the front of the shop as an added details. To draw a round flowerpot, use the same method as above.

Use built-in flower brush to draw the flowers and the plants each on its own raster layer. Set the layer to have black outline at 1 px and antialiasing turned off using [Layer property] palette. After drawing them, rasterize the layer and smooth it using [Filter]→[Blur]→[Smoothing].

For variations, I draw a cube flowerpot. To draw a cube flowerpot, you can use [Polygon] tool set to hexagon. This works because regular hexagon has the outline of an isometric cube. Regular hexagon lines are angled at 120° which is exact angle between the axes in isometric drawing.

Draw more flowerpots for added details.

The shop is finished.

All the drawings here are drawn using the same method as this shop.

2. Bookshop

I decided to redraw my previous bookshop on my old tutorial but in isometric projection. Though it’s not exactly the same (because of a few omitted details) since this shop is going to be a part of a larger illustration rather than a stand-alone drawing.

I reuse the windows and the side billboard from the florist shop at this drawing.

After that, add color to the drawing. I use blue theme as the image color for this shop.

Finished drawing.

3. Ramen Shop

Usually, you will see a noren (暖簾) hung at the front of many ramen shops so I add it to the drawing as a detail of this shop.

I also reuse the doors, the windows, and the side billboard from the florist shop at this drawing.

I use yellow theme as the image color for this shop. For the noren, it’s usually red for a ramen shop so I use that color too.

Finished drawing.

4. Udon Shop

Udon shop usually has a noren hung at the front too. To make variations, I use a short noren and add two vending machines in the front of the shop. I also use two-panel doors and two-panel windows here to make it different from the previous shops.

I also use yellow theme as the image color like the ramen shop but this time I use white color for the noren.

Finished drawing.

5. Hobby Shop

To make variations, I make this shop to have three floors instead of two. I also use a huge single window for the entrance.

I reuse the windows and the side billboard from the florist shop and the udon shop here.

I use light blue and gray theme for the image color to differentiate it from the bookshop. For the billboard on the rooftop, I add a simple advertisement mock-up design using the same isometric transformation method.

Finished drawing.

6. Bakery and Coffee Shop

These two shops share the same building. The building has three floors and only the first two floors are used for the shops. The bakery is located on the first floor and the coffee shop is on the second floor.

I duplicate the front view and mirror it using  → [Transform] → [Flip Horizontal...]. After that, I roughly draw the building structure.

I think it's too empty on the rooftop so I add a service floor on it. It's not part of the original front view but we can draw it using isometric ruler easily.

I reuse the windows from the florist shop and the udon shop too here. The rest of the parts are from the original front view of this shop.

For the windows facing the viewer, you only need to scale their height to 82. It is because the width is not located on any axis therefore it’s not foreshortened.

I use brown theme as the image color. For the bakery, I use brown and for the coffee shop, I use a darker brown. Both kind of represent the color of their products.

Finished drawing.

## Drawing the Shoutengai Gate

In real life, most shoutengai have gates that are unique to them so I decided to add one for the illustration.

I make the gate at least the width of a one lane road and the height of a three-floor building. Because most of the gate designs are symmetrical, I use [Symmetrical ruler] with [Number of lines] set to 2 when drawing.

Try to make the gate design as unique as possible.

After that, add the text to the title sign. The result looks like a sci-fi looking gate.

To complete the gate, use the same method as above but this time skew it by -30°.

After that, add the color of the gate. I use blue for the title sign above and gray-black for the rest.

## Drawing Miscellaneous Props (Streetlights and Traffic Lights)

To make it easier to manage, I draw streetlights and traffic lights separately rather than directly drawing them later.

Here is the drawing process of front-facing and back-facing streetlights.

Here is the drawing process of traffic lights.

Usually you will see utility poles in a lot of roof-less shoutengai, but I decided to not add them here because I think it would obstruct the main shops from focus.

## Arranging the Buildings

First, merge the layers of the shoutengai gate, each of the buildings, and props flat into their own layers.

After that, arrange them to make it look like a shoutengai. These buildings will be the focus of illustration so make sure they are arranged to catch the eye of the viewer.

Then, draw the main street and the pedestrian pavement.

After that, draw road drainage to the pavement outline.

I draw more details and add two pedestrian crossing to the main intersection.

After that, color the street using [Refer other layers] sub tool. I choose a light salmon-orange color for the pavement and yellowish light-gray for the street

I draw bike lanes to make the street less plain.

After that, arrange the props so that they won’t obstruct the shops too much.

Add the background buildings. You can reuse the other buildings or if you like it, you can draw them. I choose to reuse other buildings and redraw them to fit as the background buildings.

Color the background buildings so that they won’t distract the viewer from the main shoutengai buildings.

Lastly, add gate drawing to the illustration.

Finished arrangement with isometric ruler turned off.

## Finishing

For this illustration, I assume the light rays coming towards the buildings and the objects are parallel, which means the projected shadows are parallel too.

For visualization, take a look at the image below. The light rays (red line) coming towards the objects are set at 30° and the shadow edge (black line) parallel to the y axis.

Create a layer folder above the main illustration. Set it to 90% opacity and mode to [Multiply]. Create a new raster layer inside that layer folder. This layer will be our main shadow layer.

Draw the shadows by tracing the light rays blocked by the objects. You can use any opaque round brush or even Straight line sub tool to draw them. Use gray-blue for the shadow color.

For the gate, I avoid drawing the shadow on the title sign to make it kind of stand out.

To add a bit realism, draw the shadow for the horizontal part on the bakery and coffee shops on another raster layer but with lighter opacity. This is done because the horizontal part is not entirely lit by the light source and is not entirely in the main shadow either.

Here is the arrangement of the shadow layers.

After that, let’s create a light effect for the environment.

Duplicate the shadow layer folder and set the opacity back to 100% and the mode to [Normal]. Flatten the duplicated layer folder by right-clicking the layer folder and selecting [Merge selected layers].

Blur the resulting layer using [Filter] → [Blur] → [Gaussian blur...] by 20.

Select the merged layer. Then Ctrl+Click the folder icon on the shadow layer folder. This will create a selection based on it. After that, press Delete.

Deselect the selection. Change the layer color to orange by selecting the color then using →[Convert to drawing color(H)]. Set the light effect opacity to 20%.

The illustration is finished.

Hope this tutorial is useful. Thanks for reading!