Rounded Polygon 节点

描述

以输入 Width 和 Height 指定的大小基于输入 UV 生成圆角多边形。输入 Sides 确定多边形的边数，输入 Roundness 定义每个角的圆度。

通过连接 Tiling And Offset 节点可以偏移或平铺该形状。为了保留在 UV 空间内偏移形状的能力，如果进行平铺，形状将不会自动重复。要实现重复圆角多边形效果，应首先通过 Fraction 节点连接 UV 输入。

Rounded Polygon 节点只能在片元着色器阶段使用。

端口

名称	方向	类型	绑定	描述
UV	输入	矢量 2	UV	输入 UV 值
Width	输入	Float	无	圆角多边形宽度
Height	输入	Float	无	圆角多边形高度
Sides	输入	Float	无	多边形的边数
Roundness	输入	Float	无	角的圆度
Out	输出	Float	无	输出值

生成的代码示例

以下示例代码表示此节点的一种可能结果。

void RoundedPolygon_Func_float(float2 UV, float Width, float Height, float Sides, float Roundness, out float Out)
{
    UV = UV * 2. + float2(-1.,-1.);
    float epsilon = 1e-6;
    UV.x = UV.x / ( Width + (Width==0)*epsilon);
    UV.y = UV.y / ( Height + (Height==0)*epsilon);
    Roundness = clamp(Roundness, 1e-6, 1.);
    float i_sides = floor( abs( Sides ) );
    float fullAngle = 2. * PI / i_sides;
    float halfAngle = fullAngle / 2.;
    float opositeAngle = HALF_PI - halfAngle;
    float diagonal = 1. / cos( halfAngle );
    // Chamfer values
    float chamferAngle = Roundness * halfAngle; // Angle taken by the chamfer
    float remainingAngle = halfAngle - chamferAngle; // Angle that remains
    float ratio = tan(remainingAngle) / tan(halfAngle); // This is the ratio between the length of the polygon's triangle and the distance of the chamfer center to the polygon center
    // Center of the chamfer arc
    float2 chamferCenter = float2(
        cos(halfAngle) ,
        sin(halfAngle)
    )* ratio * diagonal;
    // starting of the chamfer arc
    float2 chamferOrigin = float2(
        1.,
        tan(remainingAngle)
    );
    // Using Al Kashi algebra, we determine:
    // The distance distance of the center of the chamfer to the center of the polygon (side A)
    float distA = length(chamferCenter);
    // The radius of the chamfer (side B)
    float distB = 1. - chamferCenter.x;
    // The refence length of side C, which is the distance to the chamfer start
    float distCref = length(chamferOrigin);
    // This will rescale the chamfered polygon to fit the uv space
    // diagonal = length(chamferCenter) + distB;
    float uvScale = diagonal;
    UV *= uvScale;
    float2 polaruv = float2 (
        atan2( UV.y, UV.x ),
        length(UV)
    );
    polaruv.x += HALF_PI + 2*PI;
    polaruv.x = fmod( polaruv.x + halfAngle, fullAngle );
    polaruv.x = abs(polaruv.x - halfAngle);
    UV = float2( cos(polaruv.x), sin(polaruv.x) ) * polaruv.y;
    // Calculate the angle needed for the Al Kashi algebra
    float angleRatio = 1. - (polaruv.x-remainingAngle) / chamferAngle;
    // Calculate the distance of the polygon center to the chamfer extremity
    float distC = sqrt( distA*distA + distB*distB - 2.*distA*distB*cos( PI - halfAngle * angleRatio ) );
    Out = UV.x;
    float chamferZone = ( halfAngle - polaruv.x ) < chamferAngle;
    Out = lerp( UV.x, polaruv.y / distC, chamferZone );
    // Output this to have the shape mask instead of the distance field
    Out = saturate((1 - Out) / fwidth(Out));
}