In this tutorial I’m going to talk about scaling masonry bitmaps to get correct sizing. In particular scaling of elements like bricks, blocks, pavers, CMU’s, and similar items.
Many times we get hold of a great photo of some material but have no idea about how it was photographed. How far away was the camera? How big are those suckers in the real world? You need to know this to be able to get correct scaling of the photographed material onto your CAD based objects. Frequently people just guess the scaling but most times there is a better and more accurate way to get it right.
First off we’ll look at masonry patterns. Once you understand the basic patterns in common use and the modular sizes used in various countries, you will know how to treat your bitmap.
Secondly I’ll discuss what’s required to fix up the errors and shortcomings that commonly appear in photographed materials – even those that are professionally prepared. Lastly we’ll look at how to crop your bitmap and create a new AccuRender material so you’ll get a near perfect result when you use it.
While there dozens of ways to lay bricks, they are generally laid in a few standardized patterns, known as bonds. There are 4 main bonds used in face brickwork.
English bond – each alternate course shows brick faces only, the other courses show brick ends only. See diagram.
Flemish bond – each course consists of alternating faces and ends,
with each successive course offset by 50%. See diagram.
Stretcher bond – also known as running bond. Each course is laid one half brick along from the previous course. Only brick faces are seen. See diagram.
Soldier bond – bricks are laid in a grid pattern with no offsets, so that all joints line up in straight lines. Can be laid horizontally or vertically, either faces only or ends only may be seen.
Generally speaking, older or period buildings will be laid in English or Flemish bond (which was suitable for solid walls), while modern buildings employ Stretcher bond, or occasionally Soldier bond for feature panels. These are suited to cavity walls.
Although brick setouts have varied greatly over time and between cultures, we can nonetheless establish standards that comply with modern usage.
The standard U.S. modular setout is based on a module of 8 inches. This means 1 brick length plus mortar joint is 8 inches, and 3 courses in height including mortar joints totals 8 inches.
A standard brick is 7 5/8” long x 2 ¼” high x 3 ¾” wide.
The current U.K. metric standard varies a little from the traditional Imperial setout, and the module is now 225mm in length including mortar joint per brick, and 75 mm in height including mortar per course. The Imperial module was 9 inches in length and 3 inches in height.
A standard brick is 215 mm long x 102 mm high x 65 mm wide.
Australian & New Zealand Standards
This metric standard is based on a repeating module of 2400 mm x 600 mm. 10 bricks in length including mortar total 2400 mm and 7 courses of bricks including mortar total 600 mm in height. One course including mortar is therefore 85.7143 mm high and one brick including mortar is 240 mm long.
A standard brick is 230 mm long x 75 mm high x 110 mm wide.
Like bricks, concrete blocks have been made in many forms over the centuries, but are now made in standardized sizes and are laid in predictable patterns. Also known as CMU (for concrete masonry unit) in some countries, they may have a smooth face, a grooved face, or a rough face created by mechanical splitting of the manufactured units.
These units are usually laid in stretcher bond and occasionally in stack (vertical joints) bond.
Standard U.S. module is 8” long including mortar x 8” high including mortar x 8” wide.
The current U.K. metric standard is 450 mm in length (equal to 2 bricks) including mortar joint per unit, and 225 mm in height (equal to 3 bricks) including mortar joint per course.
Australian and New Zealand Standards
This metric standard is based on a repeating module of 400mm x 200mm. 1 block length including mortar totals 400mm and 1 block course including mortar totals 200mm in height. Sizes and thicknesses vary, but are generally multiples of 200 mm.
A common block size is 390 mm long x 190 mm high x 190 mm wide. Thus 6 block lengths equal 10 brick lengths, and 3 block heights equal 7 brick courses.
Paving Bricks and Tiles
Modern paving bricks and tiles are made in predictable sizes. While patterns are many, but if we know the unit size we can calculate the layout dimensions.
Common sizes are 8” long including mortar x 4” wide including mortar. Also 6” x 6” and 12” x 12” are common.
Common sizes are 200 mm long including mortar x 100 mm wide including mortar. Also 300 mm x 300 mm and 400 mm x 400 mm are common.
Australian and New Zealand Standard
Common sizes are 200 mm long including mortar x 100 mm wide including mortar. Also 300 mm x 300 mm and 400 mm x 400 mm are common.
Pavers and bricks are sometimes laid in diagonal, herringbone, or basketweave patterns. By knowing which shape has been used it’s possible to work out the correct usage for the bitmap. Two situations are common – square modules laid diagonally or rectangular modules laid diagonally. Knowing all this, bitmaps can be corrected to suit various CAD systems and national standards.
Most bitmaps, including those professionally prepared, require some fixing before they can be used. In this tutorial I am using Photoshop for corrections but most paint programs operate in a similar way, although they may not have all the bells and whistles of Photoshop.
The usual problems with bitmaps are rotation errors, lens distortion, angled shooting effects and exposure correction. Once these problems are fixed the bitmap can be cropped to suit our purposes and made into a seamless material.
When first opening an image I find it often pays dividends to use Photoshop’s Image/Adjustments “Auto Levels” and/or “Auto Contrast” tools. Although not perfect they can often remedy an imperfect image very quickly. If they don’t help much you can always adjust manually where needed.
You need to check that the image has not been rotated, or indeed that the camera was not out of alignment with original object being photographed. You could try turning on the grid to check the image’s alignment. It’s useful to zoom the image up to full screen to see more detail. Hit the Tab key to turn off all dialog boxes so just the image is visible. If it’s out of level here’s what to do.
Photoshop has a natty little item called the “Measure Tool” which you’ll find on the eyedropper flyout. Use it this way – pick a point on the image and then pick a second point that should be either directly horizontally opposite or directly vertical above/below the first point. In other words pick two points on the image that should be either horizontal or vertical to each other if the image was not distorted or rotated.
Now go to Image/ Rotate Canvas/Arbitrary. You’ll find that Photoshop has recorded the rotational error for you. Hit O.K. and magically the image is automatically corrected and made level.
If the image is still out of whack or distorted in some way – say for example the brick or tile joints don’t line up as they should, try using the Edit/Transform tools to correct any stretching or perspective errors. Now we come to cropping the image. I suggest you make a copy of the original before cropping.
The aim of this cropping is to create an image that tiles seamlessly when it’s applied over a large area. Ideally, what we want is an image that starts in the CENTER of a mortar line on the left edge and finishes in the CENTER of another mortar line at the right edge. If the image is for walling, we also want a FULL mortar line at the base edge and NO mortar line at the top edge. If the image is for paving, we want to crop in the CENTER of a mortar line at the base edge and in the CENTER of a mortar line at the top edge. It’s best to crop your image to the maximum size you can, and also remember to zoom up to full screen to have the best possible view of exactly where you’re cropping, as you cannot zoom after selecting the cropping tool.
NOTE – always crop your image so you have a FULL number of bricks/tiles on one row. Count them up and make sure there is a row of full ones. It’s O.K. if there are two half bricks/tiles, one at each end, because that still totals up to a row of full ones. It doesn’t matter how many there are in the total, however.
NOTE – always crop your image so there are a FULL number of brick/tile courses. It doesn’t matter how many so long as they are full courses.
Now let’s work a real example. The image below is a download from the BeldenBrick site at http://www.beldenbrick.com/. Note that it has a mortar line along the top, but almost none along the base. That’s fine for paving but not for walling. Why not? Because you don’t want a line of mortar running along the top of a wall – that’s why.
By having a full mortar edge along the bottom and none at the top of each tiled patch you create the impression of consistently repeating mortar lines till you get to the top, where it finishes neatly as brick without mortar. The left and right edges are a compromise. By cropping an image in the center of vertical mortar lines you achieve correctly tiled patches running left to right. This is a minor problem on exposed vertical corners such as pillars, where you’ll see a narrow line of vertical mortar where there should be none, but there’s no easy workaround for that.
Here’s the original bitmap. Note there are several problems with it. It’s too dark; it has no mortar line along the base; it doesn’t contain a full number of bricks left to right; and it has a half line of mortar along the top. Often times, just rotating or flipping the bitmap to get the mortar to the bottom, is a good starting point.
Now here’s our new bitmap, with all those problems fixed. Save it on an AR3 path.
NOTE – keep a written record of the number of full bricks across and the number of courses vertically – you’ll need that later.
Now the next issue is to create an AccuRender material from our new bitmap.
Let’s say we want to use this image for a metric sized brick wall and piers for a project in the U.K. We know from our previous work that brick modules in the U.K. are 225 mm long x 75 mm high. We also noted that our new bitmap is 8 bricks long x 14 courses high, so we want it to render at 1800 mm wide (225 x8) and 1050 mm high (75 x 14). Open AccuRender, create a new material, and select our new bitmap as the map.
Click on the Main tab and unlock the fixed ratio by picking on the padlock symbol and set the map size to X=1800 and Y=1050 (assuming you have your units set to millimeters). You may need to adjust the size of the preview cube/sphere to see the map clearly. Now save your new material. Refer to image below.
Below is a test rendering showing U.K. sized piers and wall with this material applied. Everything fits as it should and all brick joints are correctly located.
Another example. Let’s say we have a brick bitmap that is 12 bricks wide and 28 courses high for use on U.S. walls. We know from our previous work that the U.S. standard brick module is 8” long (1 brick) x 8” high (3 courses). Therefore we make our bitmap 96” wide (8 x 12) and 74.6666” high (8 x 9.3333). Note that you could also crop the bitmap to be 27 courses high for simplicity’s sake. Then your calculation would be 72” high (8 x 9). Note that you should also remake the material after cropping the bitmap, if you do that step.
Another example. For a brick bitmap having 7 full bricks width and 14 courses height, for use in Australia or New Zealand, the AccuRender material settings would be X = 1680 (240 x 7) and Y = 1200 (85.7142 x 14).
Concrete Block (CMU) Calculations
The issues here are exactly the same as for bricks. A CMU bitmap should be cropped in the same way as described for bricks. Create a new material in the same way.
Worked examples. A CMU bitmap having rectangular blocks twice as long as they are wide could fairly be presumed to be a 16” x 8” unit in the U.S.A. If it has 9 full block lengths and 7 full block widths showing, then the AccuRender material settings would be X = 144 (16 x 9) and Y = 56 (8 x 7) - assuming inches is set as the AccuRender unit.
As an example in the U.K., let’s say you have a bitmap that you want to use for block walling. The bitmap shows 11 full blocks in length and 9 full blocks in width after straightening and cropping. The U.K. module is 450 mm long and 225 mm high (refer above). Therefore the AccuRender map settings would be X = 4950 (450 x 11) and Y = 2025 (225 x 9) – again assuming the AccuRender units setting is millimeters.
Paving Bricks and Tiles
Where paving bricks or tiles are square or rectangular, and are laid horizontally or vertically, the settings are just the same as for wall bricks and blocks.
Where the units are laid out in a diagonal, herringbone or basketweave pattern things are a little more complicated, however. Standard formulas can be applied to these cases to solve most situations. It’s useful to understand that all these setouts are formulated around multiples of √2 (1.4142) where the tile size is either 1 x 1 units or 1 x 2 units in dimension, and this fact forms the basis of all calculations.
For diamond shaped setouts where the units are square, each repeating module of 4 tiles is 2 x √2 (2.8284) units long and 2 x √2 (2.8284) units wide, where each tile is 1 unit x 1 unit. Each tile measures √2 (1.4142) units corner to corner. Refer to diagram below. Bitmaps should be cropped to contain only full multiples of these units.
As a worked example, let’s say you have a bitmap composed of square paving bricks. You want this material to render as 300 mm bricks on a metric based project in the U.K. The bitmap when corrected and cropped shows 8 full bricks horizontally (4 full units) and 6 full bricks vertically (3 full units). Using the formula, the calculations for the AccuRender material are: X = 4 x 2.2824 x 300 = 2738.8800 and Y = 3 x 2.2824 x 300 = 2054.1600.
For a U.S. project where the pavers are to render at 12” x 12” and the AccuRender units are set to inches, the calculations would be X = 4 x 2.2824 x 12 = 109.5552 and Y = 3 x 2.2824 x 12 = 82.1664.
In the case of rectangular materials, the same principles apply, but with a slight twist. For basketweave setouts, each repeating module of 8 tiles is 4 x √2 (5.6568) units long and 4 x √2 (5.6568) units wide, where each tile measures 2 units x 1 unit. Refer to diagram below. Bitmaps should be cropped to the corners of full multiples of these units.
As a worked example in the U.S. where the tiles must render at say 8” x 4” each, and the corrected bitmap is 5 full modules long and 3 full modules wide, the AccuRender material settings would be X = 5 x 5.6568 x 4 = 113.1360 and Y = 3 x 5.6568 x 4 = 67.8816. This assumes the AccuRender units are set to inches.
For a metric example using the bitmap above, and where the tiles must render at say 300 mm x 150 mm, X = 5 x 5.6568 x 300 = 8485.2000 and Y = 3 x 5.6568 x 150 = 2545.56, where the AccuRender units are set to millimeters.
For herringbone setouts where the units are rectangular, each repeating module of 2 tiles is 2 x √2 (2.8284) units long and 2 x √2 (2.8284) units wide, where each tile measures 2 units x 1 unit. Similarly, each tile measures √2 (1.4142) units corner to corner. Refer to diagram below. Bitmaps should be cropped to contain only full multiples of these units.
The calculations for a bitmap of this type are similar to the other patterns. As an example, for a metric project in the U.K. where each brick/tile has to render at 200 mm x 100 mm, and the bitmap shows 11 full modules horizontally by 8 full modules vertically, the AccuRender material settings would be X = 11 x 2.8284 x 100 = 3111.2400 and Y = 8 x 2.8284 x 100 = 2262.7200.
As a practical example, consider the bitmap below. Apart from the usual problems, it has one more – the pattern does not repeat systematically. In the right hand portion there is either a laying error or a deliberate doubling up of some components, which upsets the symmetrical patterning.
To rectify this problem we must first identify where the module repeats fall within the image and so decide where to crop it. The white lines show where we will crop.
After cropping and adjustment, we must also do some further editing. For this bitmap to work successfully the various brick colors must repeat both horizontally and vertically at the seams. All “A” areas must be the same, as must all “B” areas and so on. Some selection with the lasso tool and some mirroring, cutting and pasting will fix this problem. The final bitmap is shown below.
In the image below the new bitmap has been applied as a paving material. Although a little repetitive due to the small sampling area that was available, it repeats seamlessly and all edges appear as they should.
The methods shown here can be extended to many other types of materials that have been photographed. In fact anything that is composed of identifiable units can be used to create a new material that is correctly scaled. Examples such as parquet flooring; glass bricks, roof tiles, shingles, sheet roofing, floorboards and similar items would be suitable for this purpose.
Note – a special thanks to Daniel Hargreaves of MPI Architects for valuable help with U.S. standards.