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// Miss Shader (.rmiss) - With Explicit Bindings
// Executed when a ray doesn't hit any geometry

// DATA TYPES
// Scalar types
// bool, int, uint, half, float, double

// Vectors
float3 skyColorHorizon;
float3 skyColorZenith;

// PARAMETERS WITH EXPLICIT BINDINGS
[[vk::binding(0, 1)]]
cbuffer MissParams {
    float4 horizonColor;
    float4 zenithColor;
    float  sunIntensity;
    float3 sunDirection;
};

// PAYLOAD
struct RayPayload {
    float4 color;
    float  hitT;
    float3 normal;
    float3 worldPos;
    uint   recursionDepth;
    bool   isShadowRay;
};

// VARIABLES
// Global
static const float PI = 3.14159265358979323846f;

// MISS SHADER ENTRY POINT
[shader("miss")]
void main(inout RayPayload payload) {
    // Local variables
    float3 rayDir = WorldRayDirection();
    
    // Simple sky model
    float t = 0.5 * (rayDir.y + 1.0);
    float3 skyColor = (1.0 - t) * horizonColor.xyz + t * zenithColor.xyz;
    
    // Add sun if looking in sun direction
    float sunDot = max(0.0, dot(rayDir, normalize(sunDirection)));
    float sunHighlight = pow(sunDot, 128.0) * sunIntensity;
    
    // For shadow rays, just set a flag that nothing was hit
    if (payload.isShadowRay) {
        payload.hitT = -1.0;
    } else {
        // Regular rays get the sky color
        payload.color = float4(skyColor + sunHighlight, 1.0);
        payload.hitT = -1.0;
        payload.normal = float3(0, 1, 0);
        payload.worldPos = float3(0, 0, 0);
    }
}