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This commit, a revamp of #12959, implements screen-space reflections (SSR), which approximate real-time reflections based on raymarching through the depth buffer and copying samples from the final rendered frame. This patch is a relatively minimal implementation of SSR, so as to provide a flexible base on which to customize and build in the future. However, it's based on the production-quality [raymarching code by Tomasz Stachowiak](https://gist.github.com/h3r2tic/9c8356bdaefbe80b1a22ae0aaee192db). For a general basic overview of screen-space reflections, see [1](https://lettier.github.io/3d-game-shaders-for-beginners/screen-space-reflection.html). The raymarching shader uses the basic algorithm of tracing forward in large steps, refining that trace in smaller increments via binary search, and then using the secant method. No temporal filtering or roughness blurring, is performed at all; for this reason, SSR currently only operates on very shiny surfaces. No acceleration via the hierarchical Z-buffer is implemented (though note that https://github.com/bevyengine/bevy/pull/12899 will add the infrastructure for this). Reflections are traced at full resolution, which is often considered slow. All of these improvements and more can be follow-ups. SSR is built on top of the deferred renderer and is currently only supported in that mode. Forward screen-space reflections are possible albeit uncommon (though e.g. *Doom Eternal* uses them); however, they require tracing from the previous frame, which would add complexity. This patch leaves the door open to implementing SSR in the forward rendering path but doesn't itself have such an implementation. Screen-space reflections aren't supported in WebGL 2, because they require sampling from the depth buffer, which Naga can't do because of a bug (`sampler2DShadow` is incorrectly generated instead of `sampler2D`; this is the same reason why depth of field is disabled on that platform). To add screen-space reflections to a camera, use the `ScreenSpaceReflectionsBundle` bundle or the `ScreenSpaceReflectionsSettings` component. In addition to `ScreenSpaceReflectionsSettings`, `DepthPrepass` and `DeferredPrepass` must also be present for the reflections to show up. The `ScreenSpaceReflectionsSettings` component contains several settings that artists can tweak, and also comes with sensible defaults. A new example, `ssr`, has been added. It's loosely based on the [three.js ocean sample](https://threejs.org/examples/webgl_shaders_ocean.html), but all the assets are original. Note that the three.js demo has no screen-space reflections and instead renders a mirror world. In contrast to #12959, this demo tests not only a cube but also a more complex model (the flight helmet). ## Changelog ### Added * Screen-space reflections can be enabled for very smooth surfaces by adding the `ScreenSpaceReflections` component to a camera. Deferred rendering must be enabled for the reflections to appear.  
59 lines
2.5 KiB
WebGPU Shading Language
59 lines
2.5 KiB
WebGPU Shading Language
// A shader that creates water ripples by overlaying 4 normal maps on top of one
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// another.
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//
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// This is used in the `ssr` example. It only supports deferred rendering.
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#import bevy_pbr::{
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pbr_deferred_functions::deferred_output,
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pbr_fragment::pbr_input_from_standard_material,
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prepass_io::{VertexOutput, FragmentOutput},
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}
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#import bevy_render::globals::Globals
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// Parameters to the water shader.
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struct WaterSettings {
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// How much to displace each octave each frame, in the u and v directions.
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// Two octaves are packed into each `vec4`.
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octave_vectors: array<vec4<f32>, 2>,
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// How wide the waves are in each octave.
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octave_scales: vec4<f32>,
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// How high the waves are in each octave.
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octave_strengths: vec4<f32>,
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}
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@group(0) @binding(1) var<uniform> globals: Globals;
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@group(2) @binding(100) var water_normals_texture: texture_2d<f32>;
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@group(2) @binding(101) var water_normals_sampler: sampler;
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@group(2) @binding(102) var<uniform> water_settings: WaterSettings;
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// Samples a single octave of noise and returns the resulting normal.
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fn sample_noise_octave(uv: vec2<f32>, strength: f32) -> vec3<f32> {
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let N = textureSample(water_normals_texture, water_normals_sampler, uv).rbg * 2.0 - 1.0;
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// This isn't slerp, but it's good enough.
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return normalize(mix(vec3(0.0, 1.0, 0.0), N, strength));
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}
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// Samples all four octaves of noise and returns the resulting normal.
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fn sample_noise(uv: vec2<f32>, time: f32) -> vec3<f32> {
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let uv0 = uv * water_settings.octave_scales[0] + water_settings.octave_vectors[0].xy * time;
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let uv1 = uv * water_settings.octave_scales[1] + water_settings.octave_vectors[0].zw * time;
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let uv2 = uv * water_settings.octave_scales[2] + water_settings.octave_vectors[1].xy * time;
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let uv3 = uv * water_settings.octave_scales[3] + water_settings.octave_vectors[1].zw * time;
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return normalize(
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sample_noise_octave(uv0, water_settings.octave_strengths[0]) +
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sample_noise_octave(uv1, water_settings.octave_strengths[1]) +
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sample_noise_octave(uv2, water_settings.octave_strengths[2]) +
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sample_noise_octave(uv3, water_settings.octave_strengths[3])
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);
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}
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@fragment
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fn fragment(in: VertexOutput, @builtin(front_facing) is_front: bool) -> FragmentOutput {
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// Create the PBR input.
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var pbr_input = pbr_input_from_standard_material(in, is_front);
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// Bump the normal.
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pbr_input.N = sample_noise(in.uv, globals.time);
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// Send the rest to the deferred shader.
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return deferred_output(in, pbr_input);
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}
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