autocad-hatch-pat

name

autocad-hatch-pat

description

Generate AutoCAD-compatible .pat hatch pattern files from images or descriptions of tile/brick/stone patterns. Use this skill whenever the user mentions: PAT file, hatch pattern, AutoCAD hatch, tile pattern, brick pattern, stone pattern, repeating pattern for CAD, Revit pattern, custom hatch, or any request to create a .pat file. Also trigger when the user uploads a screenshot or photo of a tile/material pattern and wants to use it in CAD. The skill visualizes the pattern interactively BEFORE generating the file so the user can adjust dimensions and confirm before output.

AutoCAD Hatch Pattern Generator

Converts images or descriptions of repeating tile/brick/stone patterns into production-ready AutoCAD .pat files. Always shows a live visual preview and gets user approval before generating the file.

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Workflow

Step 1 — Gather Input

Accept one of:

• Screenshot or photo of a tile/material pattern (preferred)
• Text description with tile names and dimensions

If an image is provided, analyze it carefully:

• Count tile types (e.g., one field tile + one accent tile)
• Estimate the aspect ratio and relative sizes of each tile
• Identify the offset pattern (none / 1/2 / 1/3 / custom)
• Note if tiles run horizontally or vertically

Ask for any missing critical information. The minimum needed is:

• Tile width(s) and height(s) in inches
• Grout joint width in inches
• Row offset amount (0, 1/2, 1/3, etc.)
• Orientation (tiles run horizontal = landscape, or vertical = portrait)
• Pattern name for the file (suggest one from context, ≤31 chars, no spaces/slashes)

Always ask about grout joint width — this is the most commonly forgotten dimension and makes a big difference to output quality. Common values: 1/16" (0.0625), 1/8" (0.125), 3/16" (0.1875), 1/4" (0.25).

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Step 2 — Visualize the Pattern

Before generating any file, build an interactive HTML visualization using the show_widget tool. If show_widget is unavailable, present a text table of the pattern dimensions (tile sizes, grout width, offset, repeat unit) and ask the user to confirm before proceeding to Step 3.

Read references/visualization.md (in this skill's directory) for full widget implementation details and the editable parameter panel spec.

The visualization must:

• Render the tile pattern to approximate scale in a canvas (600×400px minimum)
• Show grout joints as a contrasting color (light gray on white tiles, or vice versa)
• Display at least 3 full repeat cycles horizontally and 3 vertically
• For mixed-tile patterns (e.g., accent + field), shade each tile type differently
• Include an editable parameter panel alongside or below the canvas with fields for all key dimensions
• Update the pattern live when parameters change
• Show a "Generate .pat File" button that, when clicked, sends a message like "generate the pat file now" to proceed

Do not proceed to Step 3 until the user approves the visualization or clicks generate.

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Step 3 — Generate the .pat File

Use the proven formula from references/pat-math.md. For standard tile patterns the algorithm is:

row_height = tile_height + grout
horiz_period = sum of (tile_width + grout) for each tile in one horizontal unit
offset_per_row = horiz_period × offset_fraction
vert_repeat = num_offset_rows × row_height

# Line 1: horizontal grout joints (continuous, one family covers all rows)
"0, 0, 0, 0, {row_height}"

# Lines 2+: one vertical line family per joint per row
for each row in range(num_offset_rows):
    y0 = row × row_height
    x_shift = row × offset_per_row
    for each grout joint in this row's tile sequence:
        x_joint = x_shift + (accumulated tile widths + grouts up to this joint)
        dash = row_height
        gap = -(vert_repeat - row_height)
        "90, {x_joint}, {y0}, 0, {horiz_period}, {dash}, {gap}"

For full math details and edge cases (herringbone, diagonal, mixed tiles, non-standard offsets), read references/pat-math.md.

File format rules (all mandatory — violations break AutoCAD):

• Plain ASCII only — no em dashes, curly quotes, or any non-ASCII character
• Windows CRLF line endings (\r\n) throughout
• Pattern name ≤ 31 characters, no spaces, no punctuation except underscore/hyphen
• File must end with a blank line
• No comments or semicolons in the data lines

Always write the file using Python to guarantee encoding and line endings:

content = "*PATTERN_NAME, description\r\n"
content += "0, 0,0, 0,{row_height}\r\n"
# ... add all vertical line families ...
content += "\r\n"  # mandatory trailing blank line

assert all(ord(c) < 128 for c in content), "Non-ASCII found!"

with open('/path/to/output/PATTERN_NAME.pat', 'w', newline='') as f:
    f.write(content)

Verify with python3 -c "data=open('file.pat','rb').read(); print('ASCII:', all(b<128 for b in data)); print('CRLF:', b'\\r\\n' in data)" before presenting.

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Step 4 — Present and Install Instructions

Present the file using present_files. Then include AutoCAD installation steps:

1. Copy the .pat file to AutoCAD's Support folder (usually C:\Users\[name]\AppData\Roaming\Autodesk\AutoCAD 20xx\[version]\Support\)
2. Restart AutoCAD
3. Use HATCH command → select "Custom" pattern type → browse for the file
4. Set Scale = 1 for inch drawings, Scale = 12 for foot drawings
5. If the hatch looks too dense/sparse, adjust scale accordingly

For Revit users: Import via Manage → Additional Settings → Fill Patterns → New → Import. Choose "Model" pattern type for real-world dimensions.

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Common Pattern Types

Read references/pat-math.md for the specific formulas for each type.

Pattern	Rows	Offset	Vertical families needed
Stack bond	1	0	1 per grout joint
Running bond (1/2)	2	0.5	2 per grout joint
Running bond (1/3)	3	0.333	3 per grout joint
Mixed tiles (accent+field, 1/3)	3	0.333	6 (2 joints × 3 rows)
Herringbone	Complex	—	See pat-math.md

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Error Handling

If the user reports the pattern looks wrong in AutoCAD:

• Lines in wrong position: Check x_joint calculation — verify x_shift is applied correctly per row
• Pattern too dense / rejected: Tell user to increase HPMAXLINES via (setenv "MaxHatch" "10000000") in AutoCAD console, or simplify the pattern
• Pattern tiles but with gaps: The horiz_period or vert_repeat is incorrect — recalculate
• Lines run continuously instead of per-tile: The dash/gap values are wrong — gap must be large enough to skip non-active rows
• File not recognized: Check for non-ASCII characters, missing trailing blank line, or name > 31 chars