Hatch Pattern Generator ▦

What This Hatch Pattern Generator Does

AutoCAD and Revit hatch patterns are stored in .pat files: plain text where every repeating set of parallel lines is one line of numbers. Writing those numbers by hand is slow and error-prone, especially for sloping lines or offsets like brick bonds. This generator lets you draw the pattern on a repeating tile instead and writes the PAT code for you. The preview is drawn from the generated PAT data itself, so what you see is what AutoCAD or Revit will draw.

Looking for ready-made patterns instead? See our AutoCAD hatch patterns free download.

How to Use It

1. Pick a preset such as running bond brick, square tiles or basket weave, or choose "Blank grid".
2. Set the tile: the number of grid cells across and up, and the size of one cell in drawing units. A 2 × 2 tile with 112.5 × 75 cells gives a 225 × 75 mm brick module.
3. Draw: click two grid points for a line, use the dot tool for points, the eraser to remove items, and Undo to step back. The tile repeats in every direction.
4. Export: enter a name, choose AutoCAD or Revit, and download the .pat file.

Understanding the PAT Format

Each pattern starts with a header line, *NAME, description, followed by one line per family of parallel lines:

• angle: direction of the lines in degrees.
• x-origin, y-origin: a point the first line passes through.
• delta-x: how far each next line is shifted along the line direction (this creates offsets such as brick bonds).
• delta-y: the spacing between the parallel lines.
• dashes: positive values draw, negative values are gaps, and 0 is a dot. No dashes means a continuous line.

The running bond brick preset, for example, produces:

The two horizontal families draw the bed joints every 75 units; the two vertical families draw the head joints, 75 long with 75 gaps, the second one shifted half a brick for the bond.

How to Load the PAT File in AutoCAD

1. Give the pattern a name without spaces. The file name must be exactly the pattern name, for example MB_BRICK.pat; the generator names the download this way.
2. Copy the file into a folder on AutoCAD's support search path. Find or add one under OPTIONS → Files → Support File Search Path.
3. Run HATCH, open the pattern list and choose the Custom pattern, or type its name.
4. Set the hatch scale to 1 if you drew the cells in real drawing units, for example millimetres in a millimetre drawing.

How to Import It in Revit

1. Export with "Revit model pattern" for real-size surfaces such as brick, tiles and cladding, or "Revit drafting pattern" for symbols that stay the same size on paper.
2. In Revit go to Manage → Additional Settings → Fill Patterns, choose Model or Drafting, click New, select Custom and Import, and pick the file.
3. Check the import scale; with the units set correctly it should be 1.

Tips for Clean Patterns

• Draw only one of two matching tile edges. A line on the right edge repeats the left edge, and the generator removes the duplicate automatically.
• Keep sloping lines to simple grid steps such as 1:1, 2:1 or 3:1. Steep, odd slopes create very long repeat lengths.
• Very dense patterns at a small hatch scale slow AutoCAD down and can trigger the "hatch spacing too dense" message. Increase the cell size or the hatch scale.
• Use non-square cells (different X and Y sizes) for rectangular modules such as bricks, planks and tiles.

More CAD resources: AutoCAD advanced commands and tips for MEP and the AutoCAD blocks library for MEP systems.

FAQ

How do I create a custom hatch pattern in AutoCAD?

Write the pattern as a .pat file, with a header line *NAME followed by one line per family of parallel lines, save it with the same name as the pattern in a folder on AutoCAD's support path, and select it as a Custom pattern in the HATCH command. A generator like this one writes the PAT lines for you from a drawing.

Why does AutoCAD not show my custom hatch pattern?

Usually the file name does not match the pattern name, or the file is not in a folder on the support file search path. A custom .pat file must contain one pattern whose name matches the file name.

Can I use the same PAT file in Revit?

Revit reads PAT files but needs a ;%TYPE=MODEL or ;%TYPE=DRAFTING line and a units line. Choose a Revit format before downloading and the generator adds them.

What do delta-x and delta-y mean in a PAT file?

Delta-y is the spacing between the parallel lines of one family. Delta-x is the shift of each next line along its own direction, which is how offset patterns such as running bond brick are made.

What hatch scale should I use?

If you set the cell sizes in real drawing units, for example millimetres for a millimetre drawing, use a hatch scale of 1. Otherwise scale the hatch until the module matches the real size.

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