如何创建大纲

Question

我有一组点，这是一条线的形状。

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我们如何创建新的点集，这将是在一个偏移的距离，目前的一组点，并使用GL_TRIANGLE_STRIP，我们将能够创建一个多边形形状。

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这是我当前的代码，但我无法从中得到任何有意义的结果。

// outlineVertices are existing set of points from which we would generate the offsetPoints

for (int i = 0; i < outlineVertices.size() - 3 ; i += 3) {
        finalVertices.push_back(outlineVertices[i]);
        finalVertices.push_back(outlineVertices[i + 1]);
        finalVertices.push_back(outlineVertices[i + 2]);        

        glm::vec3 point1 = glm::vec3(outlineVertices[i], outlineVertices[i + 1], outlineVertices[i + 2]);
        glm::vec3 point2 = glm::vec3(outlineVertices[i + 7], outlineVertices[i + 1 + 7], outlineVertices[i + 2 + 7]);
        glm::vec4 directionVector = GetPerpendicularVectorDirection(point1, point2);
    
        finalVertices.push_back(outlineVertices[i] - (directionVector.x * outlineWidth ));
        finalVertices.push_back(outlineVertices[i + 1] + (directionVector.y * outlineWidth));
        finalVertices.push_back(outlineVertices[i + 2]);
        finalVertices.push_back(outlineVertices[i + 3]);
        
    }
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

glm::vec4 RectangleOutline::GetPerpendicularVectorDirection(glm::vec3 point1, glm::vec3 point2) {

    glm::vec3 Direction = glm::normalize(point1 - point2);
    float x, y;
    x = Direction.x;
    Direction.x = -y;
    Direction.y = x;
    return glm::vec4(Direction, 0);
}

Answer 1

你必须计算两个线段之间的人字关节。为此，您需要计算要连接的线段上的向量。计算到线段的归一化法向量。沿人字形关节的矢量是法向量之和。(您甚至可以在顶点着色器：OpenGL线宽中完成此操作)

如果你有3分(p1，p2，p3)

p1       p2
  +-----+
         \
          \
           +
             p3

然后，在p2中，沿人头肌关节的法线矢量是：

// vectors along the line
glm::vec2 v12 = p2 - p1;
glm::vec2 v23 = p3 - p2;

// normalized normal vectors to the line segments
glm::vec2 vn12 = glm::normlalize(glm::vec2(-v12.y, v12.x));
glm::vec2 vn23 = glm::normlalize(glm::vec2(-v23.y, v23.x));

// normalized vector along miter joint
glm::vec2 vm2 = glm::normalize(vn12 + vn23);

接头上的点(pa，pb)是：

          pa
    -----+
     p2 / \
  -----+    \
      / \
-----+    \
  pb  \
        \

float d = thickness / glm::dot(vm2, vn12);

glm::vec2 pa = p2 + vm2 * d/2;
glm::vec2 pb = p2 - vm2 * d/2;