2 commits

Author	SHA1	Message	Date
Marco Buono	44928e0df4	StandardMaterial Light Transmission (#8015) ... # Objective <img width="1920" alt="Screenshot 2023-04-26 at 01 07 34" src="https://user-images.githubusercontent.com/418473/234467578-0f34187b-5863-4ea1-88e9-7a6bb8ce8da3.png"> This PR adds both diffuse and specular light transmission capabilities to the `StandardMaterial`, with support for screen space refractions. This enables realistically representing a wide range of real-world materials, such as: - Glass; (Including frosted glass) - Transparent and translucent plastics; - Various liquids and gels; - Gemstones; - Marble; - Wax; - Paper; - Leaves; - Porcelain. Unlike existing support for transparency, light transmission does not rely on fixed function alpha blending, and therefore works with both `AlphaMode::Opaque` and `AlphaMode::Mask` materials. ## Solution - Introduces a number of transmission related fields in the `StandardMaterial`; - For specular transmission: - Adds logic to take a view main texture snapshot after the opaque phase; (in order to perform screen space refractions) - Introduces a new `Transmissive3d` phase to the renderer, to which all meshes with `transmission > 0.0` materials are sent. - Calculates a light exit point (of the approximate mesh volume) using `ior` and `thickness` properties - Samples the snapshot texture with an adaptive number of taps across a `roughness`-controlled radius enabling “blurry” refractions - For diffuse transmission: - Approximates transmitted diffuse light by using a second, flipped + displaced, diffuse-only Lambertian lobe for each light source. ## To Do - [x] Figure out where `fresnel_mix()` is taking place, if at all, and where `dielectric_specular` is being calculated, if at all, and update them to use the `ior` value (Not a blocker, just a nice-to-have for more correct BSDF) - To the _best of my knowledge, this is now taking place, after 964340cdd. The fresnel mix is actually "split" into two parts in our implementation, one `(1 - fresnel(...))` in the transmission, and `fresnel()` in the light implementations. A surface with more reflectance now will produce slightly dimmer transmission towards the grazing angle, as more of the light gets reflected. - [x] Add `transmission_texture` - [x] Add `diffuse_transmission_texture` - [x] Add `thickness_texture` - [x] Add `attenuation_distance` and `attenuation_color` - [x] Connect values to glTF loader - [x] `transmission` and `transmission_texture` - [x] `thickness` and `thickness_texture` - [x] `ior` - [ ] `diffuse_transmission` and `diffuse_transmission_texture` (needs upstream support in `gltf` crate, not a blocker) - [x] Add support for multiple screen space refraction “steps” - [x] Conditionally create no transmission snapshot texture at all if `steps == 0` - [x] Conditionally enable/disable screen space refraction transmission snapshots - [x] Read from depth pre-pass to prevent refracting pixels in front of the light exit point - [x] Use `interleaved_gradient_noise()` function for sampling blur in a way that benefits from TAA - [x] Drill down a TAA `#define`, tweak some aspects of the effect conditionally based on it - [x] Remove const array that's crashing under HLSL (unless a new `naga` release with https://github.com/gfx-rs/naga/pull/2496 comes out before we merge this) - [ ] Look into alternatives to the `switch` hack for dynamically indexing the const array (might not be needed, compilers seem to be decent at expanding it) - [ ] Add pipeline keys for gating transmission (do we really want/need this?) - [x] Tweak some material field/function names? ## A Note on Texture Packing _This was originally added as a comment to the `specular_transmission_texture`, `thickness_texture` and `diffuse_transmission_texture` documentation, I removed it since it was more confusing than helpful, and will likely be made redundant/will need to be updated once we have a better infrastructure for preprocessing assets_ Due to how channels are mapped, you can more efficiently use a single shared texture image for configuring the following: - R - `specular_transmission_texture` - G - `thickness_texture` - B - _unused_ - A - `diffuse_transmission_texture` The `KHR_materials_diffuse_transmission` glTF extension also defines a `diffuseTransmissionColorTexture`, that _we don't currently support_. One might choose to pack the intensity and color textures together, using RGB for the color and A for the intensity, in which case this packing advice doesn't really apply. --- ## Changelog - Added a new `Transmissive3d` render phase for rendering specular transmissive materials with screen space refractions - Added rendering support for transmitted environment map light on the `StandardMaterial` as a fallback for screen space refractions - Added `diffuse_transmission`, `specular_transmission`, `thickness`, `ior`, `attenuation_distance` and `attenuation_color` to the `StandardMaterial` - Added `diffuse_transmission_texture`, `specular_transmission_texture`, `thickness_texture` to the `StandardMaterial`, gated behind a new `pbr_transmission_textures` cargo feature (off by default, for maximum hardware compatibility) - Added `Camera3d::screen_space_specular_transmission_steps` for controlling the number of “layers of transparency” rendered for transmissive objects - Added a `TransmittedShadowReceiver` component for enabling shadows in (diffusely) transmitted light. (disabled by default, as it requires carefully setting up the `thickness` to avoid self-shadow artifacts) - Added support for the `KHR_materials_transmission`, `KHR_materials_ior` and `KHR_materials_volume` glTF extensions - Renamed items related to temporal jitter for greater consistency ## Migration Guide - `SsaoPipelineKey::temporal_noise` has been renamed to `SsaoPipelineKey::temporal_jitter` - The `TAA` shader def (controlled by the presence of the `TemporalAntiAliasSettings` component in the camera) has been replaced with the `TEMPORAL_JITTER` shader def (controlled by the presence of the `TemporalJitter` component in the camera) - `MeshPipelineKey::TAA` has been replaced by `MeshPipelineKey::TEMPORAL_JITTER` - The `TEMPORAL_NOISE` shader def has been consolidated with `TEMPORAL_JITTER`	2023-10-31 20:59:02 +00:00
robtfm	c99351f7c2	allow extensions to StandardMaterial (#7820) ... # Objective allow extending `Material`s (including the built in `StandardMaterial`) with custom vertex/fragment shaders and additional data, to easily get pbr lighting with custom modifications, or otherwise extend a base material. # Solution - added `ExtendedMaterial<B: Material, E: MaterialExtension>` which contains a base material and a user-defined extension. - added example `extended_material` showing how to use it - modified AsBindGroup to have "unprepared" functions that return raw resources / layout entries so that the extended material can combine them note: doesn't currently work with array resources, as i can't figure out how to make the OwnedBindingResource::get_binding() work, as wgpu requires a `&'a[&'a TextureView]` and i have a `Vec<TextureView>`. # Migration Guide manual implementations of `AsBindGroup` will need to be adjusted, the changes are pretty straightforward and can be seen in the diff for e.g. the `texture_binding_array` example. --------- Co-authored-by: Robert Swain <robert.swain@gmail.com>	2023-10-17 21:28:08 +00:00