public static void InitializedRenderTriangle(Vertex v1, Vertex v2, Vertex v3, out List <RenderTriangle> list)
{
//Y轴，v3 v2 v1，所以当v1=v2的时候，只有一个三角形，底边在下方。v2=v3时，底边在上.
list = new List <RenderTriangle>(2);
if (v1.point.y > v2.point.y)
{
MyStaticMethod.SwapVertex(ref v1, ref v2);
}
if (v1.point.y > v3.point.y)
{
MyStaticMethod.SwapVertex(ref v1, ref v3);
}
if (v2.point.y > v3.point.y)
{
MyStaticMethod.SwapVertex(ref v2, ref v3);
}
if (v1.point.y == v2.point.y && v1.point.y == v3.point.y)
{
return;
}
if (v1.point.x == v2.point.x && v1.point.x == v3.point.x)
{
return;
}
//三角形尖角向下
if (v1.point.y == v2.point.y)
{
if (v1.point.x > v2.point.x)
{
MyStaticMethod.SwapVertex(ref v1, ref v2);
}
RenderTriangle n1 = new RenderTriangle(v1, v3, v2, v3, v1.point.y, v3.point.y);
list.Add(n1);
return;
}
//三角形尖角向上
if (v2.point.y == v3.point.y)
{
if (v2.point.x > v3.point.x)
{
MyStaticMethod.SwapVertex(ref v2, ref v3);
}
list.Add(new RenderTriangle(v1, v2, v1, v3, v1.point.y, v2.point.y));
return;
}
//剩下的情况必定是在Y轴上 v3 > v2 > v1 注意d3d的规则，图像上面的y轴比较小,从上向下排列是v1 2 3
double k = (v3.point.y - v1.point.y) / (v2.point.y - v1.point.y);
double x = v1.point.x + (v2.point.x - v1.point.x) * k;
if (x <= v3.point.x) //计算其延长线，如果顶点v3在延长线左边，则v1 连上v3为最长边，如果在右边。。。
{
list.Add(new RenderTriangle(v1, v2, v1, v3, v1.point.y, v2.point.y));
list.Add(new RenderTriangle(v2, v3, v1, v3, v2.point.y, v3.point.y));
}
else
{
list.Add(new RenderTriangle(v1, v3, v1, v2, v1.point.y, v2.point.y));
list.Add(new RenderTriangle(v1, v3, v2, v3, v2.point.y, v3.point.y));
}
}