Declare struct outside layout block to allow reuse in multiple shaders

Question

I'm using GLSL for shaders in my Vulkan application. I'm refactoring some shader code to declare a struct in a common GLSL file. The struct is used in multiple uniforms across different shaders.

Shader code to refactor:

layout (set = 0, binding = 0) uniform Camera
{
    mat4 projection;
    mat4 view;
    vec3 position;
} u_camera;

I would like to move the definition of what is a Camera to a common GLSL include file, but I don't want to move the whole layout statement because the descriptor set index might change from shader to shader. I'd like to only move the definition of Camera.

Here's what I tried:
In my common GLSL file:

struct Camera
{
    mat4 projection;
    mat4 view;
    vec3 position;
};

Then in my shader:

layout (set = 0, binding = 0) uniform Camera u_camera;

However, I get a shader compiler error on that line in my shader: error: '' : syntax error, unexpected IDENTIFIER, expecting LEFT_BRACE or COMMA or SEMICOLON

I'm using version 450 (I can upgrade if necessary). No extensions enabled.
Is it possible to do what I want? If yes, please guide me towards how to do it. If not, please try to explain why if it's in the spec.

Answer 1

What you're describing is a legacy GLSL uniform, which can't be used in Vulkan. In Vulkan you have to create a uniform block instead:

layout (set = 1, binding = 0) uniform CameraBlock {
    Camera u_camera;
};

While this looks like something nested, you can still access the members of your u_camera directly:

vec3 some_vec = u_camera.position;