难以理解 Vulkan 着色器

Question

#version 450
#extension GL_ARB_separate_shader_objects : enable

out gl_PerVertex {
    vec4 gl_Position;
};

vec2 positions[3] = vec2[](
    vec2(0.0, -0.5),
    vec2(0.5, 0.5),
    vec2(-0.5, 0.5)
);

void main() {
    gl_Position = vec4(positions[gl_VertexIndex], 0.0, 1.0);
}

问题 1：这是什么意思？

out gl_PerVertex {
    vec4 gl_Position;
};

问题 2： 什么解释了语法 vec2 positions[3] = vec2[](...)？要初始化数组，语法不应该是

vec2 positions[3] = {
    vec2(0.0, -0.5),
    vec2(0.5, 0.5),
    vec2(-0.5, 0.5)
};

这是特定于着色器的语法，还是 arrayType[](...) 也可以用作 C++ 中的构造函数？

Answer 1

Question 1: What does this designate?

这个

out gl_PerVertex {
    vec4 gl_Position;
};

是一个Output Interface Block. (See further GLSL Specification - 4.3.9 Interface Blocks)

Question 2: What explains the syntax vec2 positions3 = vec2? To initialize the array, shouldn't the syntax be ...

没有

参见 Array constructors

Arrays can be constructed using array constructor syntax. In this case, the type also contains the [] array notation:
const float array[3] = float[3](2.5, 7.0, 1.5);

见 GLSL Specification - 4.1.11 Initializers:

If an initializer is a list of initializers enclosed in curly braces, the variable being declared must be a vector, a matrix, an array, or a structure.
int i = { 1 }; // illegal, i is not a composite 
....

All of the following declarations result in a compile-time error.
float a[2] = { 3.4, 4.2, 5.0 }; // illegal
....

If an initializer (of either form) is provided for an unsized array, the size of the array is determined by the number of top-level (non-nested) initializers within the initializer. All of the following declarations create arrays explicitly sized with five elements:
float a[] = float[](3.4, 4.2, 5.0, 5.2, 1.1);
float b[] = { 3.4, 4.2, 5.0, 5.2, 1.1 };
float c[] = a; // c is explicitly size 5
float d[5] = b; // means the same thing

难以理解 Vulkan 着色器

Trouble Understanding Vulkan Shader

glsl

vulkan