Optional alpha compositing for lighting

[kwvanderlinde]

Identify the Bug or Feature request

Refines #3817

Description of the Change

Based on testing feedback, there were several improvements that could be made to the new environmental lighting and lumens overlay.

1. Lights weren't showing by default, leading to confusion as users were required to find a new menu option just to be able to see them again. This has now been inverted so that lights are shown by default.
2. The help text for sights and lights in the Campaign Properties dialog was out-of-date. This has been updated to match the new syntax, and has been reformatted into a description list to make it more legible.
3. Lights easily brighten too much. In the future, a radial falloff with help more with this, but for now the adjustable boosting parameter has been reduced to give a little more headroom for lights to overlap.
4. Darkness was not being rendered in colour for GMs. This has been fixed
5. Sometimes the zone vision is refered to as "Vision" (e.g., in the Map menu) and sometimes as "Lights" (e.g., in the Map Properties dialog). This is not new, but it annoyed me and could cause some confusion going forward, so it has been fixed to consistently use the term "Vision".
6. Some maps are not full-colour artwork and would not benefit from environmental lighting. In fact, the classic style of a white background with black pen strokes had no ability to dispaly light colours as white is already considered fully illuminated, and black is black no matter how much light shines on it. A new option has been added to use alpha compositing for such maps.

Possible Drawbacks

Point-by-point:

1. Lighting performance is still not fantastic, so users may have a degraded experience upon upgrading, especially with many lights.
2. None
3. Someone will disagree over exactly how much lights should brighten the map. This is always going to be a matter of taste.
4. None
5. None (at least no more than already exists 🙂)
6. The Preferences dialog continues to be bloated, and the new lighting style option is just one more thing to check when creating a map.

Documentation Notes

Maps have a lighting style that can be configured when creating or editing a map.

The "Overlay" lighting style is useful for black & white or other simplified maps, as the lights will be drawn overtop of the map.

If we had instead used "Environmental" for this map, none of the light colours would show, because white is already completely illuminated:

The purpose of "Environmental" lighting style is for full-colour artwork maps, as it renders lights as though they are illuminating the map:

If we had instead used "Overlay", the map would look more washed out as the map is obscured by the lights instead of illuminated by them:

Release Notes

• Renamed "Lights" to "Vision" in the Map Properties dialog, to match the Map menu. Likewise renamed "New Map Lights" to "New Map Vision" in the Preferences dialog.
• Added a "Lighting style" option to the Map Properties dialog so lights can be environmental (useful for colour maps) or alpha-composited (useful for black & white maps).

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