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[Merged by Bors] - bevy_pbr2: Add support for not casting/receiving shadows #2726

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superdump
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Objective

Allow marking meshes as not casting / receiving shadows.

Solution

  • Added NotShadowCaster and NotShadowReceiver zero-sized type components.
  • Extract these components into bools in ExtractedMesh
  • Only generate DrawShadowMesh Drawables for meshes without NotShadowCaster
  • Add a u32 bit flags member to MeshUniform with one flag indicating whether the mesh is a shadow receiver
  • If a mesh does not have the NotShadowReceiver component, then it is a shadow receiver, and so the bit in the MeshUniform is set, otherwise it is not set.
  • Added an example illustrating the functionality.

NOTE: I wanted to have the default state of a mesh as being a shadow caster and shadow receiver, hence the Not* components. However, I am on the fence about this. I don't want to have a negative performance impact, nor have people wondering why their custom meshes don't have shadows because they forgot to add ShadowCaster and ShadowReceiver components, but I also really don't like the double negatives the Not* approach incurs. What do you think?

@superdump superdump force-pushed the pipelined-dont-cast-dont-receive branch from 4f8292d to a1a5b01 Compare August 25, 2021 11:40
Having to add a zero-sized type component to every entity to mark it as a
shadow caster or shadow receiver by default feels quite unnecessary. As such, I
have added NotShadowCaster and NotShadowReceiver components. This introduces
double-negatives like Without<NotShadowReceiver>, etc but it means that only
the exceptions have to be specified in user code.

I also added an example to illustrate the effect.
@cart
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cart commented Aug 25, 2021

This looks good to me / I think its worth merging as-is for now. My biggest questions are around "ideal user facing apis". There are lots of options here. Some engines make "shadow receiving" a material property, which might make sense here. I also want to consider something like:

struct ShadowCaster {
  enabled: bool,
}

To avoid the need for adding removing components / make the settings more discoverable.

But yeah this impl looks solid and I'd rather integrate it sooner than later. I removed the camera controls from the new example because they make it bigger / more complicated and I dont think the example benefits from freedom of movement.

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cart commented Aug 25, 2021

bors r+

bors bot pushed a commit that referenced this pull request Aug 25, 2021
# Objective

Allow marking meshes as not casting / receiving shadows.

## Solution

- Added `NotShadowCaster` and `NotShadowReceiver` zero-sized type components.
- Extract these components into `bool`s in `ExtractedMesh`
- Only generate `DrawShadowMesh` `Drawable`s for meshes _without_ `NotShadowCaster`
- Add a `u32` bit `flags` member to `MeshUniform` with one flag indicating whether the mesh is a shadow receiver
- If a mesh does _not_ have the `NotShadowReceiver` component, then it is a shadow receiver, and so the bit in the `MeshUniform` is set, otherwise it is not set.
- Added an example illustrating the functionality.

NOTE: I wanted to have the default state of a mesh as being a shadow caster and shadow receiver, hence the `Not*` components. However, I am on the fence about this. I don't want to have a negative performance impact, nor have people wondering why their custom meshes don't have shadows because they forgot to add `ShadowCaster` and `ShadowReceiver` components, but I also really don't like the double negatives the `Not*` approach incurs. What do you think?

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
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bors bot commented Aug 25, 2021

@bors bors bot changed the title bevy_pbr2: Add support for not casting/receiving shadows [Merged by Bors] - bevy_pbr2: Add support for not casting/receiving shadows Aug 25, 2021
@bors bors bot closed this Aug 25, 2021
@cart cart added the A-Rendering Drawing game state to the screen label Aug 25, 2021
@cart cart added this to the Bevy 0.6 milestone Aug 25, 2021
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2 participants