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[Merged by Bors] - use blendstate blend for alphamode::blend #7899

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[Merged by Bors] - use blendstate blend for alphamode::blend #7899

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23 changes: 14 additions & 9 deletions crates/bevy_pbr/src/material.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -445,14 +445,19 @@ pub fn queue_material_meshes<M: Material>(
let mut mesh_key =
MeshPipelineKey::from_primitive_topology(mesh.primitive_topology)
| view_key;
let alpha_mode = material.properties.alpha_mode;
if let AlphaMode::Blend | AlphaMode::Premultiplied | AlphaMode::Add = alpha_mode
{
// Blend, Premultiplied and Add all share the same pipeline key
// They're made distinct in the PBR shader, via `premultiply_alpha()`
mesh_key |= MeshPipelineKey::BLEND_PREMULTIPLIED_ALPHA;
} else if let AlphaMode::Multiply = alpha_mode {
mesh_key |= MeshPipelineKey::BLEND_MULTIPLY;
match material.properties.alpha_mode {
AlphaMode::Blend => {
mesh_key |= MeshPipelineKey::BLEND_ALPHA;
}
AlphaMode::Premultiplied | AlphaMode::Add => {
// Premultiplied and Add share the same pipeline key
// They're made distinct in the PBR shader, via `premultiply_alpha()`
mesh_key |= MeshPipelineKey::BLEND_PREMULTIPLIED_ALPHA;
}
AlphaMode::Multiply => {
mesh_key |= MeshPipelineKey::BLEND_MULTIPLY;
}
_ => (),
}

let pipeline_id = pipelines.specialize(
Expand All @@ -474,7 +479,7 @@ pub fn queue_material_meshes<M: Material>(

let distance = rangefinder.distance(&mesh_uniform.transform)
+ material.properties.depth_bias;
match alpha_mode {
match material.properties.alpha_mode {
AlphaMode::Opaque => {
opaque_phase.add(Opaque3d {
entity: *visible_entity,
Expand Down
6 changes: 5 additions & 1 deletion crates/bevy_pbr/src/prepass/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -235,6 +235,9 @@ where
if blend_key == MeshPipelineKey::BLEND_PREMULTIPLIED_ALPHA {
shader_defs.push("BLEND_PREMULTIPLIED_ALPHA".into());
}
if blend_key == MeshPipelineKey::BLEND_ALPHA {
shader_defs.push("BLEND_ALPHA".into());
}

if layout.contains(Mesh::ATTRIBUTE_POSITION) {
shader_defs.push("VERTEX_POSITIONS".into());
Expand Down Expand Up @@ -285,7 +288,8 @@ where
// or the material uses alpha cutoff values and doesn't rely on the standard prepass shader
let fragment = if key.mesh_key.contains(MeshPipelineKey::NORMAL_PREPASS)
|| ((key.mesh_key.contains(MeshPipelineKey::ALPHA_MASK)
|| blend_key == MeshPipelineKey::BLEND_PREMULTIPLIED_ALPHA)
|| blend_key == MeshPipelineKey::BLEND_PREMULTIPLIED_ALPHA
|| blend_key == MeshPipelineKey::BLEND_ALPHA)
&& self.material_fragment_shader.is_some())
{
// Use the fragment shader from the material if present
Expand Down
9 changes: 8 additions & 1 deletion crates/bevy_pbr/src/render/mesh.rs
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Expand Up @@ -574,6 +574,7 @@ bitflags::bitflags! {
const BLEND_OPAQUE = (0 << Self::BLEND_SHIFT_BITS); // ← Values are just sequential within the mask, and can range from 0 to 3
const BLEND_PREMULTIPLIED_ALPHA = (1 << Self::BLEND_SHIFT_BITS); //
const BLEND_MULTIPLY = (2 << Self::BLEND_SHIFT_BITS); // ← We still have room for one more value without adding more bits
const BLEND_ALPHA = (3 << Self::BLEND_SHIFT_BITS);
const MSAA_RESERVED_BITS = Self::MSAA_MASK_BITS << Self::MSAA_SHIFT_BITS;
const PRIMITIVE_TOPOLOGY_RESERVED_BITS = Self::PRIMITIVE_TOPOLOGY_MASK_BITS << Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
const TONEMAP_METHOD_RESERVED_BITS = Self::TONEMAP_METHOD_MASK_BITS << Self::TONEMAP_METHOD_SHIFT_BITS;
Expand Down Expand Up @@ -708,7 +709,13 @@ impl SpecializedMeshPipeline for MeshPipeline {

let (label, blend, depth_write_enabled);
let pass = key.intersection(MeshPipelineKey::BLEND_RESERVED_BITS);
if pass == MeshPipelineKey::BLEND_PREMULTIPLIED_ALPHA {
if pass == MeshPipelineKey::BLEND_ALPHA {
label = "alpha_blend_mesh_pipeline".into();
blend = Some(BlendState::ALPHA_BLENDING);
// For the transparent pass, fragments that are closer will be alpha blended
// but their depth is not written to the depth buffer
depth_write_enabled = false;
} else if pass == MeshPipelineKey::BLEND_PREMULTIPLIED_ALPHA {
label = "premultiplied_alpha_mesh_pipeline".into();
blend = Some(BlendState::PREMULTIPLIED_ALPHA_BLENDING);
shader_defs.push("PREMULTIPLY_ALPHA".into());
Expand Down
14 changes: 1 addition & 13 deletions crates/bevy_pbr/src/render/pbr_functions.wgsl
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Original file line number Diff line number Diff line change
Expand Up @@ -327,19 +327,7 @@ fn premultiply_alpha(standard_material_flags: u32, color: vec4<f32>) -> vec4<f32
//
// result = 1 * src_color + (1 - src_alpha) * dst_color
let alpha_mode = standard_material_flags & STANDARD_MATERIAL_FLAGS_ALPHA_MODE_RESERVED_BITS;
if alpha_mode == STANDARD_MATERIAL_FLAGS_ALPHA_MODE_BLEND {
// Here, we premultiply `src_color` by `src_alpha` (ahead of time, here in the shader)
//
// src_color *= src_alpha
//
// We end up with:
//
// result = 1 * (src_alpha * src_color) + (1 - src_alpha) * dst_color
// result = src_alpha * src_color + (1 - src_alpha) * dst_color
//
// Which is the blend operation for regular alpha blending `BlendState::ALPHA_BLENDING`
return vec4<f32>(color.rgb * color.a, color.a);
} else if alpha_mode == STANDARD_MATERIAL_FLAGS_ALPHA_MODE_ADD {
if alpha_mode == STANDARD_MATERIAL_FLAGS_ALPHA_MODE_ADD {
// Here, we premultiply `src_color` by `src_alpha`, and replace `src_alpha` with 0.0:
//
// src_color *= src_alpha
Expand Down
8 changes: 4 additions & 4 deletions crates/bevy_pbr/src/render/pbr_prepass.wgsl
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Expand Up @@ -28,9 +28,11 @@ fn prepass_alpha_discard(in: FragmentInput) {
// #if defined(ALPHA_MASK) || defined(BLEND_PREMULTIPLIED_ALPHA)
#ifndef ALPHA_MASK
#ifndef BLEND_PREMULTIPLIED_ALPHA
#ifndef BLEND_ALPHA

#define EMPTY_PREPASS_ALPHA_DISCARD

#endif // BLEND_ALPHA
#endif // BLEND_PREMULTIPLIED_ALPHA not defined
#endif // ALPHA_MASK not defined

Expand All @@ -47,9 +49,7 @@ fn prepass_alpha_discard(in: FragmentInput) {
if ((material.flags & STANDARD_MATERIAL_FLAGS_ALPHA_MODE_MASK) != 0u) && output_color.a < material.alpha_cutoff {
discard;
}
#endif // ALPHA_MASK

#ifdef BLEND_PREMULTIPLIED_ALPHA
#else // BLEND_PREMULTIPLIED_ALPHA || BLEND_ALPHA
let alpha_mode = material.flags & STANDARD_MATERIAL_FLAGS_ALPHA_MODE_RESERVED_BITS;
if (alpha_mode == STANDARD_MATERIAL_FLAGS_ALPHA_MODE_BLEND || alpha_mode == STANDARD_MATERIAL_FLAGS_ALPHA_MODE_ADD)
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Hmm I think this will needleslly run in BLEND_MULTIPLY, maybe we can guard it with a #ifndef BLEND_MULTIPLY?

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i think it's ok as is, since if we have BLEND_MULTIPLY, which implies we have !BLEND_PREMULTIPLIED_ALPHA && !BLEND_ALPHA && !ALPHA_MASK, then EMPTY_PREPASS_ALPHA_DISCARD gets defined and this whole containing block is skipped.

i think this set of defs could use a bit of a rationalization at some point though, it seems complex for what it's actually doing.

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Yeah. Probably better to do that after 0.10 is out to avoid subtly breaking anything.

I wanna try adding a dither-based alpha mode that renders “transparency” in the opaque pass (would go well with TAA) so maybe that could be a good time to do that

&& output_color.a < PREMULTIPLIED_ALPHA_CUTOFF {
Expand All @@ -58,7 +58,7 @@ fn prepass_alpha_discard(in: FragmentInput) {
&& all(output_color < vec4(PREMULTIPLIED_ALPHA_CUTOFF)) {
discard;
}
#endif // BLEND_PREMULTIPLIED_ALPHA
#endif // !ALPHA_MASK

#endif // EMPTY_PREPASS_ALPHA_DISCARD not defined
}
Expand Down