# Perspective Guide Generator

> Create a transparent one- or two-point perspective guide for drawing. Set a horizon, vanishing points and ray density to generate a transparent SVG guide for painting, illustration or animation.

Part of usefulweb.site (https://usefulweb.site/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://fliplineperspectiveguide.usefulweb.site/ (interactive tool at https://fliplineperspectiveguide.usefulweb.site/tool)
- JSON API: POST https://fliplineperspectiveguide.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://fliplineperspectiveguide.usefulweb.site/api/v1/tool)
- OpenAPI: https://fliplineperspectiveguide.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://fliplineperspectiveguide.usefulweb.site/mcp - tool `flipline_perspective_guide`

## Inputs
- width (integer): Canvas width (px)
- height (integer): Canvas height (px)
- mode (select): Perspective
- horizon (number): Horizon from top (%)
- first (number): First vanishing point from left (%)
- second (number): Second vanishing point from left (%)
- rays (integer): Target rays per point
- lineColor (text): Ray color (six-digit HEX)
- horizonColor (text): Horizon color (six-digit HEX)
- opacity (number): Guide opacity (%)

## Method
- The horizon is a percentage of canvas height from the top. Vanishing points are percentages of width from the left and lie on the horizon. Values from -200% to 300% allow points outside the canvas.
- For each point, target positions are spaced uniformly around the canvas perimeter. Infinite lines through the point and targets are clipped to the canvas; duplicate lines are removed. Actual line count may be lower than the target.
- The horizon is drawn only when it lies within the canvas. Colors must be six-digit HEX; opacity applies to both horizon and rays. The exported SVG is transparent and contains no external resources.