C# XNA 缩放边界框？答案

【问题标题】：C# XNA scale BoundingBox?C# XNA 缩放边界框？
【发布时间】：2015-06-04 04:55:50
【问题描述】：

所以我找到了这些方法/函数来为我的缩小模型创建一个边界框，显然我必须将边界框缩放到相同的比例。我不太熟悉顶点的使用，但我知道如何使用矩阵进行缩放。在这种情况下，我如何缩放 BoundingBox？我已经在网上搜索了一段时间，但我还没有找到解决方案。

public Vector3[] GetVertexElement(ModelMeshPart meshPart, VertexElementUsage usage)
{
    VertexDeclaration vd = meshPart.VertexBuffer.VertexDeclaration;
    VertexElement[] elements = vd.GetVertexElements();

    Func<VertexElement, bool> elementPredicate = ve => ve.VertexElementUsage == usage && ve.VertexElementFormat == VertexElementFormat.Vector3;
    if (!elements.Any(elementPredicate))
        return null;

    VertexElement element = elements.First(elementPredicate);

    Vector3[] vertexData = new Vector3[meshPart.NumVertices];
    meshPart.VertexBuffer.GetData((meshPart.VertexOffset * vd.VertexStride) + element.Offset, vertexData, 0, vertexData.Length, vd.VertexStride);

    return vertexData;
}

public BoundingBox? GetBoundingBox(ModelMeshPart meshPart, Matrix transform)
{
    if (meshPart.VertexBuffer == null)
        return null;

    Vector3[] positions = GetVertexElement(meshPart, VertexElementUsage.Position);
    if (positions == null)
        return null;

    Vector3[] transformedPositions = new Vector3[positions.Length];
    Vector3.Transform(positions, ref transform, transformedPositions);

    return BoundingBox.CreateFromPoints(transformedPositions);
}

public BoundingBox CreateBoundingBox(Model model)
{
    Matrix[] boneTransforms = new Matrix[model.Bones.Count];
    model.CopyAbsoluteBoneTransformsTo(boneTransforms);

    BoundingBox result = new BoundingBox();
    foreach (ModelMesh mesh in model.Meshes)
    {
        foreach (ModelMeshPart meshPart in mesh.MeshParts)
        {
            BoundingBox? meshPartBoundingBox = GetBoundingBox(meshPart, boneTransforms[mesh.ParentBone.Index]);
            if (meshPartBoundingBox != null)
            result = BoundingBox.CreateMerged(result, meshPartBoundingBox.Value);
        }
    }
    return result;
}

【问题讨论】：

标签： c# xna bounding-box

【解决方案1】：

我不确定，但我认为你必须自己创建一个新的最大值和最小值。也不确定它是否有效，但我认为这会做到。

private Vector3 Scale(float scale, BoundingBox b)
{
    //Get delta values
    float dx = Math.Abs(b.Max.X - b.Min.X);
    float dy = Math.Abs(b.Max.Y - b.Min.Y);
    float dz = Math.Abs(b.Max.Z - b.Min.Z);

    //get new delta values
    float newdx = dx * scale;
    float newdy = dy * scale;
    float newdz = dz * scale;

    //new max vector
    //oldvalue - removed delta, of course divided by 2(half for max and half for min).
    Vecotr3 newMax = new Vecotr3(b.Max.X - ((dx-newdx)/2),
                                 b.Max.Y - ((dy-newdy)/2),
                                 b.Max.Z - ((dz-newdz)/2));

    //new min vector
    //oldvalue + removed delta, of course divided by 2(half for max and half for min).
    Vecotr3 newMin = new Vecotr3(b.Min.X + ((dx-newdx)/2),
                                 b.Min.Y + ((dy-newdy)/2),
                                 b.Min.Z + ((dz-newdz)/2));

    return new BoundingBox(newMin, mewMax);
{

【讨论】：