metal - 在金属中画圆/半圆

Question

我是金属新手。我想画一个半圆。绘制半圆的任何想法或建议。我尝试使用镶嵌

float u = patch_coord.x;
float v = patch_coord.y;
float w = patch_coord.z;




   float x = u * patchIn.control_points[0].position.x + v * patchIn.control_points[1].position.x + w * patchIn.control_points[2].position.x;
    float y = u * patchIn.control_points[0].position.y + v * patchIn.control_points[1].position.y + w * patchIn.control_points[2].position.y;

    float2 tangent = normalize(float2(x, y)) / 25;

当我正常化时，它总是在屏幕中间。我想用手指画圈。