Set the new naga capabilities

[teoxoy]

Checklist

• Run cargo clippy.
• Run RUSTFLAGS=--cfg=web_sys_unstable_apis cargo clippy --target wasm32-unknown-unknown if applicable.
• Add change to CHANGELOG.md. See simple instructions inside file.

Connections

Description

• set the right naga capabilities
• add Features::SHADER_EARLY_DEPTH_TEST
• set the MULTISAMPLED_SHADING downlevel flag for gles and dx11

Testing

[maaku]

I'm going through the process of upgrading to wgpu 0.16, and this PR has broken my application. The following excerpt of my fragment shader for imposter-based drawing of atoms (spheres) has worked in all previous version of wgpu, on all platforms I have access to test (Metal on macOS, Vulkan on Linux, DX12 on Windows, WebGL2 for web):

    const float dist = length(uv);
    if (dist > element.radius) {
        discard;
    }

    const float z = sqrt(element.radius * element.radius - dist * dist);
    const vec4 in_pos_clipspace = position_clip_space + camera.projection[2] * z;

    gl_FragDepth = in_pos_clipspace.z / in_pos_clipspace.w;

Why is this feature gated for GLES 3.1+ only? As noted in the code review above, it works perfectly fine on other platforms.

[Wumpf]

@maaku what error are you getting? The snippet seems unrelated to both multisampled shading and early depth test

[maaku]

[2023-06-29T10:32:00Z ERROR wgpu::backend::direct] Handling wgpu errors as fatal by default
thread 'main' panicked at 'wgpu error: Validation Error

Caused by:
    In Device::create_shader_module
      note: label = `/Users/mark/Development/atomCAD/target/debug/build/atomcad-render-30b7e31c716879fe/out/shaders/billboard.frag`
    
Shader validation error: 


    Entry point main at Fragment is invalid
    Capability EARLY_DEPTH_TEST is not supported

Here is the whole fragment shader:

#version 450

struct Element {
    vec3 color;
    float radius;
};

layout(set = 0, binding = 0) uniform Camera {
    vec4 projection[4];
    vec4 view[4];
    vec4 projection_view[4];
} camera;

layout(location = 0) in vec2 uv;
layout(location = 1) in vec4 position_clip_space;
layout(location = 2) flat in vec4 element_vec;
layout(location = 4) flat in vec4 center_view_space;
layout(location = 5) in vec4 position_view_space;

layout(depth_greater) out float gl_FragDepth;
layout(location = 0) out vec4 color;
layout(location = 1) out vec4 normal;

float map(float value, float low1, float high1, float low2, float high2) {
    return low2 + (value - low1) * (high2 - low2) / (high1 - low1);
}

vec4 linear_to_srgb(vec4 input_color) {
    bvec3 cutoff = lessThan(input_color.rgb, vec3(0.0031308));
    vec3 higher = vec3(1.005) * pow(input_color.rgb, vec3(1.0 / 2.4)) - vec3(0.055);
    vec3 lower = input_color.rgb * vec3(12.92);

    return vec4(mix(higher, lower, cutoff), input_color.a);
}

void main(void) {
    Element element;
    element.color = element_vec.xyz;
    element.radius = element_vec.w;
    const float dist = length(uv);
    if (dist > element.radius) {
        discard;
    }

    const float z = sqrt(element.radius * element.radius - dist * dist);
    const vec4 in_pos_clipspace = position_clip_space + camera.projection[2] * z;

    gl_FragDepth = in_pos_clipspace.z / in_pos_clipspace.w;

    color = vec4(
        element.color * map(z, 0.0, element.radius, 0.25, 1.0),
        1.0
    );
    normal = vec4(normalize(position_view_space.xyz - center_view_space.xyz), 0.0);

#ifdef TARGET_WASM
    // Currently, firefox webgpu doesn't automatically convert linear rgb outputs to srgb
    // so we do it manually.
    color = linear_to_srgb(color);
#endif
}

[teoxoy]

That shader doesn't seem to contain the early_fragment_tests qualifier, so I don't see how the validation would get triggered in this case.

Also, trying to validate the shader via naga cli, I'm getting:

error: Unexpected qualifier
   ┌─ test.frag:20:8
   │
20 │ layout(depth_greater) out float gl_FragDepth;
   │        ^^^^^^^^^^^^^

Which sounds right since we don't have conservative depth implemented in the GLSL frontend.

[maaku]

Thank you. I think I misunderstood how early fragment tests worked. I thought that setting was required for what I was doing. Removing it fixes the problem and I was able to upgrade to 0.16 without any other major issues. Thank you.