Light Calibration

Flares OFX internally uses a 3D light source to drive the lens system. While this is physically intuitive, directly positioning lights in 3D space is often impractical for artists working in 2D compositing workflows.

To solve this, Flares OFX introduces an artist-friendly light input system that bridges 2D screen-space control with the underlying 3D light model.

Light calibration is the process of aligning these two representations so that the light behaves predictably and lands exactly where you expect on screen.

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Screen-Space Light Input

Instead of requiring direct 3D positioning, Flares OFX allows you to define the light position in normalized screen space:

• X and Y values range from 0 to 1
• The coordinate system spans the full screen
• This makes light placement intuitive and resolution-independent

You can think of this as placing a virtual light directly on the image plane rather than in world space.

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Light Distance

The Light Distance parameter defines how far the light source is from the camera in 3D space.

• At very close distances, light distance can noticeably affect flare behavior
• Once the light is more than a few meters in front of the camera, its influence becomes negligible
• In most practical setups, light distance is used primarily for calibration rather than artistic control

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Bridging 2D and 3D Space

After defining a desired light position in screen space, the system must translate that 2D position into a correct 3D light direction so that the light enters the lens at the expected angle.

This translation is controlled using Cursor Scale X and Cursor Scale Y.

• These parameters multiply the light’s X and Y positions
• They effectively control how screen-space coordinates map into 3D space
• Proper values ensure that the light ray passes through the lens correctly

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Direct Light Only Mode

To assist with calibration, Flares OFX provides a Direct Light Only mode.

When enabled:

• Only the direct incoming light ray is rendered
• Lens artifacts such as ghosts and diffraction are temporarily hidden
• The direct ray can be visually aligned with the on-screen cursor

Using this mode, you can adjust Cursor Scale X and Cursor Scale Y until the direct ray matches the intended screen-space position of the light.

This makes it easy to confirm that the 2D and 3D representations are correctly aligned.

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Why Calibration Matters

Lens geometry directly affects how light is transformed as it passes through the system. Any change to:

• Lens surfaces
• Curvature
• Spacing
• Optical properties
• Sensor size

can alter how a given light direction maps onto the image.

For this reason, light calibration should be repeated whenever lens geometry is modified. Without recalibration, the light may no longer land at the correct screen position, leading to inconsistent or unintuitive results.

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Practical Workflow

A typical calibration workflow looks like this:

1. Modify or finalize the lens geometry
2. Set the desired light position in screen space (0–1 range)
3. Enable Direct Light Only mode
4. Adjust Cursor Scale X and Cursor Scale Y until alignment is correct
5. Disable Direct Light Only mode and continue look development

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Summary

• Flares OFX uses a 3D light model internally
• Artists control light position using intuitive screen-space coordinates
• Cursor Scale parameters bridge 2D input with 3D behavior
• Direct Light Only mode simplifies calibration
• Recalibration is required after changing lens geometry

This system ensures predictable, repeatable lighting behavior while remaining comfortable for artist-driven workflows.