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Perspective Plotter

CAMERA MATCHING
📖5 min read
Overview Part 1: Overview and Quick Start
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Introduction​

Perspective Plotter is an interactive Blender add-on for modelers, architects, and artists that allows you to match a camera to an image directly in the viewport. It is useful for creating 3D models from 2D sketches, matching a 3D scene to a 2D photo, or animating a camera dynamically.

Inspired by the standalone application fSpy, Perspective Plotter brings similar functionality directly inside Blender, allowing for real-time adjustments and animation.

Real-time Matching

Dynamically match the camera in real time using perspective guides directly in the viewport.

Perspective Modes

Choose from 1, 2, or 3 point perspective modes to suit different types of images.

Documentation & DL

What is Perspective Plotter?​

Perspective Plotter is a Blender add-on that lets you match a 3D camera to a 2D image or video in real-time. It's similar to the standalone fSpy application but works directly inside Blender. This is essential for:

  • Creating 3D models from 2D images
  • Matching 3D scenes to 2D reference images
  • Matching 2D images to 3D scenes
  • Camera tracking and animation
Understanding Perspective

Before using this tool, it is highly recommended to understand the fundamentals of 1, 2, and 3-point perspective. Check out the Camera & Perspective page for a detailed overview.

Quick Start Guide​

Installation​

  1. Go to Edit > Preferences > Add-ons
  2. Click Install from File
  3. Select the downloaded .zip file
  4. Enable the add-on by checking the box next to "Perspective Plotter"

Basic Setup Workflow​

1. Enter Camera View​

  • Press 0 (numpad) or go to View > Cameras > Active Camera
  • Press N to open side panel
  • Look for the P Plotter tab (only visible in camera view)

2. Add Background Image​

  • In Outliner, select your camera
  • In Properties Panel, go to Camera tab
  • Enable Background Images
  • Click Add Image > Image or Movie Clip
  • Load your reference image/video
  • Adjust opacity if needed

3. Match Resolution​

  • If a red "Background Unmatched" button appears, click it
  • This automatically adjusts scene resolution to match your background image

4. Start Plotting​

  • Click Plot Perspective in the P Plotter panel
  • The button changes to "Plotting" and perspective lines appear
  • Camera adjusts to default position with control points ready

Working with Perspective Lines​

Understanding the System​

  • Perspective lines create vanishing points that automatically set camera focal length, location, and rotation
  • All controls are relative to the camera's frame border
  • Lines should be aligned with parallel edges in your reference image
  • Best practice: Choose edges that are far apart for accurate vanishing points

Manipulating Lines​

  • Left-click and drag the endpoints to position lines
  • Align lines with significant parallel edges in your image
  • If "Invalid Configuration" warning appears, keep adjusting until lines are valid
  • Each vanishing point has a pair of lines

The White Dot (Target Location)​

  • Represents the center of your 3D world that the camera looks at
  • Left-click and drag to reposition from viewport
  • Can also set manually in the side panel

Perspective Modes​

Two-Point Perspective (Default)​

  • Traditional mode for most sketches and architectural scenes
  • Uses two pairs of perspective lines
  • Principal point assumed at image center (can be set to manual)

One-Point Perspective​

  • Single vanishing point with horizon line
  • Requires manual focal length input
  • Vanishing point always converges at horizon line

Three-Point Perspective​

  • Best for extreme angles (looking up/down at tall objects)
  • Three pairs of lines for three vanishing points
  • Principal point automatically calculated
  • Provides greatest accuracy

Setting Camera Distance and Scale​

Why This Matters​

Vanishing points determine camera orientation and focal length, but cannot determine scene scale. You need to set camera distance manually.

Basic Method​

Use the Camera Distance parameter in the panel to move camera away from target location

Advanced Method: Reference Distance​

When you know the real-world length of something in your image:

  1. Switch Reference Distance to "Along X/Y/Z Axis" (choose axis parallel to your known edge)
  2. A blue reference line appears from scene center to vanishing point
  3. Adjust the line endpoints to match your known edge in the image
  4. Click the measuring icon next to Reference Length to manually control endpoints
  5. Set Reference Length to the actual measurement (e.g., 0.7 for a 0.7m table edge)
  6. The blue line now represents that exact length, correctly scaling your entire scene

Practical Example​

  • Find a clear edge parallel to a perspective line (e.g., table corner along Z-axis)
  • Know or estimate its real length (e.g., standard table height = 0.7m)
  • Position blue reference line along that edge
  • Set Reference Length to 0.7
  • Camera distance now creates correct scene scale

Multiple Cameras and Views​

Quad View Setup​

  • Ctrl+Alt+Q or View > Area > Toggle Quad View
  • Press N > View tab > Uncheck Lock Rotation to customize individual viewports

Multiple Cameras​

  1. Click and drag top-right corner of 3D viewport to duplicate it
  2. Add new camera to scene
  3. In new viewport: N > View tab > Enable Local Camera
  4. Select camera from dropdown
  5. Each viewport's P Plotter panel corresponds to its active camera
Resolution

All cameras share the scene's render resolution. When matching reference images with different aspect ratios, this affects all cameras. Recommended: Use reference images with the same aspect ratio when working with multiple cameras.

Additional Features​

  • Principal Point: Controls where the middle ray hits the camera lens (manual mode available in 1-point and 2-point perspective)
  • Flatten Horizon: Button to automatically level horizon line
  • Color Customization: Change control point colors in add-on preferences
  • Animation Support: Can be used for dynamic camera animation (see documentation)

Move Along View Tool​

This bundled mini-tool moves vertices along the camera's line of sight—crucial for modeling from 2D references.

Setup​

  1. Match camera to reference image first
  2. Press Ctrl+Alt+Q for Quad View (see top/side views)
  3. Add single vertex (enable Extra Objects add-on: Add > Single Vert > Add Single Vert)
  4. Add Mirror Modifier if modeling symmetrical objects

Using the Tool​

  1. Select a vertex
  2. Hover mouse in perspective viewport (important!)
  3. Press Alt+Y (default shortcut, customizable in preferences)
  4. Move mouse - vertex travels along camera's view line
  5. Watch other viewports to see depth movement
  6. Vertex stays fixed from camera's perspective but moves in 3D space
  7. Left-click to confirm, Right-click to cancel

Workflow​

  • Press G to position vertex in camera view
  • Press E to extrude and position next vertex
  • Use Move Along View to set correct depth by watching mirrored vertices
  • Repeat to build wireframe structure matching your reference

Tips and Best Practices​

  • Choose perspective line endpoints that are far apart for accuracy
  • Use edges with known measurements for proper scale
  • In Quad View, watch all viewports when using Move Along View
  • Match all reference images to same aspect ratio for multi-camera setups
  • Keep moving guides if "Invalid Configuration" appears—it will resolve

Summary​

Perspective Plotter is a powerful tool for anyone who needs to match 3D geometry to 2D images. By working directly inside Blender, it offers a smooth workflow for modeling from references and camera tracking tasks without needing external software.

Resources​