Question

我遇到了一些与我进行截头剔除的问题有关的问题。目前的方法确实在剔除时解决，但有一个非常奇怪的效果。当我太靠近我的主要父对象时，我使用场景图来渲染所有东西，对象开始快速闪烁。当我离开时，这已经消失了。我已经尝试了很多东西，但已经没有想法了。你们有什么想法吗？非常感谢任何帮助。

我首先创建一个由我的模型周围的八个点组成的边界框。据我所知，经过大量测试后，这些都是正确的。

这是我计算平截头体平面点的方法。相机位置是世界空间中的位置，方向是它所看到的方向。此外，每次旋转相机时都会计算cameraUp和cameraRight。

    Vector3 pos = Camera.staticPosition;
    Vector3 view = Camera.staticOrientation;
    Vector3 upVector3 = Camera.cameraUp;
    Vector3 rightVector3 = Camera.cameraRight;
    float toRadians = (float)Math.PI / 180.0f;
    float nearDis = .1f;
    float farDistance = 1000f;
    float fov = Game.FOV;
    float aspectRatio = 1.3f;

    //Get with and height of near and far plane
    float tanDiv = 2 * (float) Math.Tan(fov*toRadians / 2);
    float heightNear = tanDiv * nearDis;
    float widthNear = heightNear * aspectRatio;

    float heightFar = tanDiv * farDistance;
    float widthFar = heightFar * aspectRatio;

    // get the centre points of the planes so they can be used to calculate the edge points
    Vector3 centreNear = pos + view * nearDis;
    Vector3 centreFar = pos + view * farDistance;

    // get the halfht values of the width and hegiht to make sure you can get the points
    float hNearHalf = heightNear / 2;
    float wNearHalf = widthNear / 2;
    float hFarHalf = heightFar / 2;
    float wFarHalf = widthFar / 2;

    Vector3 nearTopLeft = centreNear + (upVector3 * hNearHalf) - (rightVector3 * wNearHalf);
    Vector3 nearTopRight = centreNear + (upVector3 * hNearHalf) + (rightVector3 * wNearHalf);
    Vector3 nearBottomLeft = centreNear - (upVector3 * hNearHalf) - (rightVector3 * wNearHalf);
    Vector3 nearBottomRight = centreNear - (upVector3 * hNearHalf) + (rightVector3 * wNearHalf);

    Vector3 farTopLeft = centreFar + (upVector3 * hFarHalf) - (rightVector3 * wFarHalf);
    Vector3 farTopRight = centreFar + (upVector3 * hFarHalf) + (rightVector3 * wFarHalf);
    Vector3 farBotomLeft = centreFar - (upVector3 * hFarHalf) - (rightVector3 * wFarHalf);
    Vector3 farBottomRight = centreFar - (upVector3 * hFarHalf) + (rightVector3 * wFarHalf);

我将平截头体积存在一个数组中。首先是近平面点，然后是飞机，topplane，bottomplane，左翼，最后是右翼。然后我遍历所有六个平面和边界框的8个点，如果该点位于平面的右侧，则增加字典中该键的值。

    Vector3[] frustumPoints = new Vector3[18]
    {
        nearTopLeft, nearTopRight, nearBottomLeft, farTopLeft, farTopRight, farBotomLeft, nearTopLeft, farTopLeft,
        nearTopRight, nearBottomLeft, farBotomLeft, nearBottomRight, nearTopLeft, nearBottomLeft, farTopLeft,
        nearTopRight, nearBottomRight, farTopRight
    };
    Dictionary<Vector3, int> count = new Dictionary<Vector3, int>(8);
    for (int value = 0; value < 8; value++)
    {
        count.Add(cubePositions[value], 0);
    }

    for (int x = 0; x < 18; x += 3)
    {
        Vector3 normal = NormalPlane(frustumPoints[x], frustumPoints[x + 1], frustumPoints[x + 2]);

        for (int y = 0; y < 8; y++)
        {
            Vector3 pointPlane = frustumPoints[x] - cubePositions[y];
            float dot = Vector3.Dot(pointPlane, normal);


            if (dot <= 0 && x % 6 == 0)
            {
                count[cubePositions[y]]++;
            }
            else if (dot >= 0 && x % 3 == 0)
            {
                count[cubePositions[y]]++;
            }

        }
    }

这是我获取飞机法线的方法

   Vector3 NormalPlane(Vector3 pointOne, Vector3 pointTwo, Vector3 pointThree)
{
    Vector3 normal;
    Vector3 edgeOne = pointTwo - pointOne; // calculate vector from point one to point two
    Vector3 edgeTwo = pointThree - pointOne; // calculate vector from point one to point three

    normal = Vector3.Normalize(Vector3.Cross(edgeOne, edgeTwo)); // calculate the cross product of the two given vectors. Then normalize it so you have normal of plane

    return normal; // return the normal 
}

如果对于立方体上的这些点之一，计数为6，则点在所有平面内，因此截锥体和我绘制对象。如果这些点都不等于6，则不会绘制对象。

问题是我不知道我在哪里犯了错误所以你们有什么想法吗？

提前致谢，

Jeromer

Answer 1

如果对于立方体上的这些点之一，计数为6，则点在所有平面内，因此截锥体和我绘制对象。如果这些点都不等于6，则不会绘制对象。

这里的逻辑似乎是

＆＃34;如果立方体内没有立方体的顶点，则立方体不可见。＆＃34;

然而。这只是错误。即使立方体的所有8个顶点都位于平截头体之外，立方体仍然可以与平截头体相交，如2D草图中所示：

                  *----------*
                  |          |
+-----------------+--+       |
 \                | /        |
  \               |/         |
   \              /          |
    \            /|          |
     \          / *----------*
      \        /
       \      /
        +----+

因此，你剔除可能可见的东西。

截头剔除的通常逻辑是，只有当所有顶点被同一平面拒绝时才剔除该框。（这会导致一些奇怪的情况，即盒子完全在外面而不是剔除，但这些情况不太可能，通常也不用担心。）

目前的平截头体剔除效果导致openTk

1 个答案: