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Improve refraction math by propagating refracted ray through world space, then projecting to view

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This commit is contained in:
Marco Buono 2023-03-27 00:45:22 -03:00
parent 4c408d0b21
commit bb6913825f
2 changed files with 9 additions and 7 deletions
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2
crates/bevy_pbr/src/render/pbr_functions.wgsl
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@ -257,7 +257,7 @@ fn pbr(
// Transmitted Light
var transmitted_light: vec3<f32> = vec3<f32>(0.0);
if transmission > 0.0 {
transmitted_light = transmissive_light(in.frag_coord.xyz, in.N, in.V, ior, thickness, perceptual_roughness, transmissive_color).rgb;
transmitted_light = transmissive_light(in.world_position, in.frag_coord.xyz, in.N, in.V, ior, thickness, perceptual_roughness, transmissive_color).rgb;
}
// Total light

14
crates/bevy_pbr/src/render/pbr_lighting.wgsl
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@ -281,7 +281,7 @@ fn directional_light(light_id: u32, roughness: f32, NdotV: f32, normal: vec3<f32
return (specular_light + diffuse) * (*light).color.rgb * NoL;
}
fn transmissive_light(frag_coord: vec3<f32>, N: vec3<f32>, V: vec3<f32>, ior: f32, thickness: f32, perceptual_roughness: f32, transmissive_color: vec3<f32>) -> vec3<f32> {
fn transmissive_light(world_position: vec4<f32>, frag_coord: vec3<f32>, N: vec3<f32>, V: vec3<f32>, ior: f32, thickness: f32, perceptual_roughness: f32, transmissive_color: vec3<f32>) -> vec3<f32> {
// Calculate view aspect ratio, used later to scale offset so that it's proportionate
let aspect = view.viewport.z / view.viewport.w;
@ -296,12 +296,14 @@ fn transmissive_light(frag_coord: vec3<f32>, N: vec3<f32>, V: vec3<f32>, ior: f3
let k = 1.0 - eta * eta * (1.0 - NdotI * NdotI);
let T = eta * I - (eta * NdotI + sqrt(k)) * N;
// Transform refracted direction into view space
let view_T = (view.inverse_view * vec4<f32>(T.xyz, 0.0)).xyz;
// Calculate the exit position of the refracted ray, by propagating refacted direction through thickness
let exit_position = world_position.xyz + T * thickness;
// Calculate an offset position, by multiplying the refracted direction by the thickness and adding it to
// the fragment position scaled by viewport size. Use the aspect ratio calculated earlier stay proportionate
let offset_position = frag_coord.xy / view.viewport.zw + view_T.xy * thickness * vec2<f32>(1.0, -aspect) ;
// Transform exit_position into clip space
let clip_exit_position = view.view_proj * vec4<f32>(exit_position, 1.0);
// Scale / offset position so that coordinate is in right space for sampling transmissive background texture
let offset_position = (clip_exit_position.xy / clip_exit_position.w) * vec2<f32>(0.5, -0.5) + 0.5;
// Fetch background color
let background_color = fetch_transmissive_background(offset_position, frag_coord, aspect, perceptual_roughness);