Proposed RFC Feature =Shadow for QuadLight=

[Zeang]

O3DE RFC Feature (fake) Shadow for QuadLight

Summary:

The shadow feature for the quad light. In many projects, we use quad light for smoothing the light effect. However, O3DE doesn't support the shadow of quad light. It causes it useless in a real project. Now we add a projected shadow which same as the point shadow for it. What's more, it was used the same as UE4. Now, we can have a shadow feature of quad light for the project, and open this RFC feature request here to contribute to the O3DE community.

What is the relevance of this feature?

Offering at least an option for quad light to have (fake) shadow in real projects.

Feature design description:

It is just the same with the point shadow.

Technical design description:

• Explain the technical portion of the work in enough detail that members can implement the feature.
  The technology of the quad light shadow is the same as the point light shadow. It has six projected shadow maps and samples those maps to simulate the fake shadow of quad light. Here is the photo:
  

What are the advantages of the feature?

We can have the option to have a shadow of the quad light.

What are the disadvantages of the feature?

If we enable the shadow of quad light, It will generate six projected shadow maps per quad light which cost so much.

How will this be implemented or integrated into the O3DE environment?

The quad light shadow was integrated into Atom and AtomLyIntegration gems.

How will users learn this feature?

Just use it the same as point light shadow.

[invertednormal]

I'm all for adding shadows for a quad light, but I don't think that using six shadow maps like a point light is a good idea. Generally only one would be needed, especially if the quad light had barn doors / shutters on it (support for that would need to be added). This is how the disk light is handled. In the case where the full quad light needs to be shadowed, you still should never need more than 3 or 4 shadow maps, however it would require a little additional work to set up the correct shadow maps and blend the seams appropriately in the shader.

[invertednormal]

Something else to keep in mind - if barn doors / shutters were added to the quad light, then the location of the shadow view should update depending on the angle of the shutters, and the near plane of the shadow view would be the surface of the quad light. Something like this:

[Zeang]

I don't suppose to use the quad light shadow as the same as the disk light. But you are right, I can use fewer shadow maps for quad light and achieve the same shadow effect.