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Fix handling of double_sided for normal maps (#10326)

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# Objective

Right now, we flip the `world_normal` in response to `double_sided &&
!is_front`, however when calculating `N` from tangents and the normal
map, we don't flip the normal read from the normal map, which produces
extremely weird results.

## Solution

- Pass `double_sided` and `is_front` flags to the
`apply_normal_mapping()` function and use them to conditionally flip
`Nt`

## Comparison

Note: These are from a custom scene running with the `transmission`
branch, (#8015) I noticed lighting got pretty weird for the back side of
translucent `double_sided` materials whenever I added a normal map.

### Before

<img width="1392" alt="Screenshot 2023-10-31 at 01 26 06"
src="https://github.com/bevyengine/bevy/assets/418473/d5f8c9c3-aca1-4c2f-854d-f0d0fd2fb19a">

### After

<img width="1392" alt="Screenshot 2023-10-31 at 01 25 42"
src="https://github.com/bevyengine/bevy/assets/418473/fa0e1aa2-19ad-4c27-bb08-37299d97971c">


---

## Changelog

- Fixed a bug where `StandardMaterial::double_sided` would interact
incorrectly with normal maps, producing broken results.
This commit is contained in:
Marco Buono 2023-10-31 06:44:40 -03:00 committed by GitHub
parent 3628e09045
commit dc1f76d9a2
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 9 additions and 0 deletions
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2
crates/bevy_pbr/src/render/pbr_fragment.wgsl
View File

@ -148,6 +148,8 @@ fn pbr_input_from_standard_material(
pbr_input.N = pbr_functions::apply_normal_mapping( pbr_input.N = pbr_functions::apply_normal_mapping(
pbr_bindings::material.flags, pbr_bindings::material.flags,
pbr_input.world_normal, pbr_input.world_normal,
double_sided,
is_front,
#ifdef VERTEX_TANGENTS #ifdef VERTEX_TANGENTS
#ifdef STANDARDMATERIAL_NORMAL_MAP #ifdef STANDARDMATERIAL_NORMAL_MAP
in.world_tangent, in.world_tangent,

7
crates/bevy_pbr/src/render/pbr_functions.wgsl
View File

@ -61,6 +61,8 @@ fn prepare_world_normal(
fn apply_normal_mapping( fn apply_normal_mapping(
standard_material_flags: u32, standard_material_flags: u32,
world_normal: vec3<f32>, world_normal: vec3<f32>,
double_sided: bool,
is_front: bool,
#ifdef VERTEX_TANGENTS #ifdef VERTEX_TANGENTS
#ifdef STANDARDMATERIAL_NORMAL_MAP #ifdef STANDARDMATERIAL_NORMAL_MAP
world_tangent: vec4<f32>, world_tangent: vec4<f32>,
@ -106,6 +108,11 @@ fn apply_normal_mapping(
if (standard_material_flags & pbr_types::STANDARD_MATERIAL_FLAGS_FLIP_NORMAL_MAP_Y) != 0u { if (standard_material_flags & pbr_types::STANDARD_MATERIAL_FLAGS_FLIP_NORMAL_MAP_Y) != 0u {
Nt.y = -Nt.y; Nt.y = -Nt.y;
} }
if double_sided && !is_front {
Nt = -Nt;
}
// NOTE: The mikktspace method of normal mapping applies maps the tangent-space normal from // NOTE: The mikktspace method of normal mapping applies maps the tangent-space normal from
// the normal map texture in this way to be an EXACT inverse of how the normal map baker // the normal map texture in this way to be an EXACT inverse of how the normal map baker
// calculates the normal maps so there is no error introduced. Do not change this code // calculates the normal maps so there is no error introduced. Do not change this code