Projection Example - Downstage Curtains

This technique is sometimes used on downstage curtains or gauze surfaces where physical position tracking is unavailable during movement. The goal is to provide a workaround preventing visible “snapping” of scenery when the curtain is raised, instead creating a smooth blend between curtain and scenery content.

Stage setup

• Multiple projectors (proj1, proj2, …)
• Projection-mapped scenery (scenery)
• Downstage curtain projection surface (curtain) - can be raised and lowered manually. The position of the curtain is untracked.

Stage direction

To understand the physical show conditions, the following cues are given as stage direction:

1. Curtain down - curtain is lowered - it is visible to the audience and a set change / other event is happening behind curtain. curtain has a show logo mapped.
2. Enter scene - curtain is raised. Scenery must be projection mapped at all times. Curtain’s logo should fade out.
3. Exit scene - curtain is lowered. scenery must remain projection mapped until the curtain is fully dropped. Curtain’s logo should be visible.

The problem

Since curtain is untracked, and the stage direction is to have scenery projection mapped at all times, we can’t know when scenery becomes visible to the projector.

Further, it is impossible to apply a single blend to the projector because there are two very distinct “blend scenes” - the curtain down and the curtain up, which require different blends to ensure the projection surface looks good.

The solution

Therefore, we can map scenery while curtain is lowered. Then while the physical curtain is raised, fade the content on curtain out.

The idea in the real world would be to raise the physical curtain quickly and cross-fade the curtain and scenery content such that the audience does not notice the imprecise projection mapping during the transition while the physical curtain is raised and content is cross-fading.

Project setup

Stage setup

Ensuring the screens and projectors in the stage are correctly configured is required to ensure the effect is performed correctly.

1. Include both curtain and scenery in all projector surfaces.
2. Enable Projector View Blending on the curtain.
3. Enable Dynamic Blend on all projectors.
4. Calibrate projectors for good alignment on scenery, with acceptable alignment on the lowered curtain.
5. Minimize warps, as multi-depth projection is incompatible with 2D warping.
6. Prioritize focus on the most important scene element (typically on-stage scenery rather than the physical curtain).

Curtain down cue

When curtain content is visible (scenery not yet revealed), optimise the content’s appearance for the best possible rendition:

The following must be programmed to ensure the correct look in this cue:

1. Map one or more layers to the curtain with appropriate content (e.g., logo).
2. Set curtain Alpha to 1.0 (fully opaque.).
3. Minimise the visibility of any blend zones by spreading the content accordingly across the projection.

Note that the blend is targeting the scenery, not the curtain, so blend zones may be visible on the curtain. The screenshot below shows the worst case. To mitigate this, consider:

• Adding the curtain to only one projector — this removes blend areas but reduces brightness.
• Adjusting projector positions or content placement so that blend zones do not overlap the curtain content — this is more technical/creative but can produce the best result.

“Enter scene” cue

As the curtain is raised, both surfaces (scenery and curtain) should have content mapped. Consider using Universal Crossfade to cross-fade content appropriately during the transition. The goal is that as the audience focusses on the stage, the content projected onto the scenery should look as good as possible.

1. Map one or more layers to the curtain with the appropriate content (e.g. logo)
2. Map one or more layers to the scenery with the appropriate content.
3. Fade the curtain Alpha to 0.0 (fully transparent) at a defined point in the cue to progressively reveal the scenery during the transition. For instance, this can be achieved using an open layer mapped to the curtain’s alpha property.
4. Optionally, animate the curtain position to follow the physical curtain as it is raised — this is not required but can improve the visual result (the screenshots below show this approach).

“Exit scene” cue

This cue reverses the “Enter Scene” sequence: fade curtain alpha back to 1.0 to prioritize the curtain content as it descends.