#version 450

layout(location = 0) in vec3 fragColor;
layout(location = 1) in vec3 fragSegmentStart;
layout(location = 2) in vec3 fragSegmentEnd;
layout(location = 3) in vec3 fragWorldPos;

layout(location = 0) out vec4 outColor;

layout(binding = 0) uniform UniformBufferObject {
    mat4 proj;
    mat4 model;
    mat4 view;
} ubo;

layout(binding = 1) uniform DashParameters {
    float dashSize;
    float gapSize;
    float dashOffset;
    float uAASize;
    int useWorldSpace;
} dashParams;

void main() {
    // 转换为NDC坐标
    vec3 ndcStart = fragSegmentStart / fragSegmentStart.z;
    vec3 ndcEnd = fragSegmentEnd / fragSegmentEnd.z;
    vec3 fragNDC = gl_FragCoord.xyz / gl_FragCoord.z;
    fragNDC = (fragNDC * 2.0) - 1.0;

    // 计算当前片元在线段上的投影
    vec2 lineDir = normalize(ndcEnd.xy - ndcStart.xy);
    vec2 startToFrag = fragNDC.xy - ndcStart.xy;
    float projection = dot(startToFrag, lineDir);
    
    // 计算线段在屏幕空间的长度（用于抗锯齿）
    float segmentLength = length(ndcEnd.xy - ndcStart.xy);
    
    // 应用虚线模式
    float dashPeriod = dashParams.dashSize + dashParams.gapSize;
    float currentPos = mod(projection + dashParams.dashOffset, dashPeriod);
    
    // 抗锯齿处理
    float alpha = 1.0;
    
    // 线段开始处的抗锯齿（避免线段起始处出现半截虚线）
    alpha *= smoothstep(0.0, dashParams.uAASize / segmentLength, projection);
    
    // 线段结束处的抗锯齿  
    alpha *= 1.0 - smoothstep(segmentLength - dashParams.uAASize / segmentLength, 
                             segmentLength, projection);
    
    // 虚线模式抗锯齿
    alpha *= 1.0 - smoothstep(dashParams.dashSize, 
                             dashParams.dashSize + dashParams.uAASize / dashPeriod, 
                             currentPos);
    
    // 如果alpha接近0，直接丢弃片元
    if (alpha < 0.01) {
        discard;
    }
    
    outColor = vec4(fragColor, alpha);
}