我有一个正在与其他人一起制作的程序，但遇到了问题。我正在努力在 XNA 窗口中将多边形模型添加到我们的场景中。我已经完成了那部分。我也有围绕每个多边形绘制的边界球体（我知道我标记为边界框，但没有边界球体标记）。我的问题是，当我在 3D 空间中移动多边形时，边界球的移动量是多边形的两倍。我想象它在我的多边形矩阵中的一些东西，我用它来创建边界球，使它移动两倍，但这只是推测。所以为了澄清，我会给你一个我的问题的例子。如果我按住 D 沿 X 轴移动多边形。(model.position.X--;) 多边形按预期移动，但多边形周围的边界球移动两倍。谢谢你们的帮助！
这是我绘制模型和边界球体的方法：
public void Draw(Matrix view, Matrix projection, bool drawBoundingSphere)
{
Matrix translateMatrix = Matrix.CreateTranslation(position);
Matrix worldMatrix = translateMatrix * Matrix.CreateScale(scaleRatio);
foreach (ModelMesh mesh in model.Meshes)
{
foreach (BasicEffect effect in mesh.Effects)
{
effect.World = worldMatrix * modelAbsoluteBoneTransforms[mesh.ParentBone.Index];
effect.View = view;
effect.Projection = projection;
effect.EnableDefaultLighting();
effect.PreferPerPixelLighting = true;
}
mesh.Draw();
if (drawBoundingSphere)
{
// the mesh's BoundingSphere is stored relative to the mesh itself.
// (Mesh space). We want to get this BoundingSphere in terms of world
// coordinates. To do this, we calculate a matrix that will transform
// from coordinates from mesh space into world space....
Matrix world = modelAbsoluteBoneTransforms[mesh.ParentBone.Index] * worldMatrix;
// ... and then transform the BoundingSphere using that matrix.
BoundingSphere sphere = BoundingSphereRenderer.TransformBoundingSphere(mesh.BoundingSphere, world);
// now draw the sphere with our renderer
BoundingSphereRenderer.Draw(sphere, view, projection);
}
}
这是 BoundingSphereRenderer 代码：
private static VertexBuffer vertexBuffer;
private static BasicEffect effect;
private static int lineCount;
public static void Initialize(GraphicsDevice graphicsDevice, int sphereResolution)
{
// create our effect
effect = new BasicEffect(graphicsDevice);
effect.LightingEnabled = false;
effect.VertexColorEnabled = true;
// calculate the number of lines to draw for all circles
lineCount = (sphereResolution + 1) * 3;
// we need two vertices per line, so we can allocate our vertices
VertexPositionColor[] vertices = new VertexPositionColor[lineCount * 2];
// compute our step around each circle
float step = MathHelper.TwoPi / sphereResolution;
// used to track the index into our vertex array
int index = 0;
//create the loop on the XY plane first
for (float angle = 0f; angle < MathHelper.TwoPi; angle += step)
{
vertices[index++] = new VertexPositionColor(new Vector3((float)Math.Cos(angle), (float)Math.Sin(angle), 0f), Color.Blue);
vertices[index++] = new VertexPositionColor(new Vector3((float)Math.Cos(angle + step), (float)Math.Sin(angle + step), 0f), Color.Blue);
}
//next on the XZ plane
for (float angle = 0f; angle < MathHelper.TwoPi; angle += step)
{
vertices[index++] = new VertexPositionColor(new Vector3((float)Math.Cos(angle), 0f, (float)Math.Sin(angle)), Color.Red);
vertices[index++] = new VertexPositionColor(new Vector3((float)Math.Cos(angle + step), 0f, (float)Math.Sin(angle + step)), Color.Red);
}
//finally on the YZ plane
for (float angle = 0f; angle < MathHelper.TwoPi; angle += step)
{
vertices[index++] = new VertexPositionColor(new Vector3(0f, (float)Math.Cos(angle), (float)Math.Sin(angle)), Color.Green);
vertices[index++] = new VertexPositionColor(new Vector3(0f, (float)Math.Cos(angle + step), (float)Math.Sin(angle + step)), Color.Green);
}
// now we create the vertex buffer and put the vertices in it
vertexBuffer = new VertexBuffer(graphicsDevice, typeof(VertexPositionColor), vertices.Length, BufferUsage.WriteOnly);
vertexBuffer.SetData(vertices);
}
public static void Draw(this BoundingSphere sphere, Matrix view, Matrix projection)
{
if (effect == null)
throw new InvalidOperationException("You must call Initialize before you can render any spheres.");
// set the vertex buffer
effect.GraphicsDevice.SetVertexBuffer(vertexBuffer);
// update our effect matrices
effect.World = Matrix.CreateScale(sphere.Radius) * Matrix.CreateTranslation(sphere.Center);
effect.View = view;
effect.Projection = projection;
// draw the primitives with our effect
effect.CurrentTechnique.Passes[0].Apply();
effect.GraphicsDevice.DrawPrimitives(PrimitiveType.LineList, 0, lineCount);
}
public static BoundingSphere TransformBoundingSphere(BoundingSphere sphere, Matrix transform)
{
BoundingSphere transformedSphere;
// the transform can contain different scales on the x, y, and z components.
// this has the effect of stretching and squishing our bounding sphere along
// different axes. Obviously, this is no good: a bounding sphere has to be a
// SPHERE. so, the transformed sphere's radius must be the maximum of the
// scaled x, y, and z radii.
// to calculate how the transform matrix will affect the x, y, and z
// components of the sphere, we'll create a vector3 with x y and z equal
// to the sphere's radius...
Vector3 scale3 = new Vector3(sphere.Radius, sphere.Radius, sphere.Radius);
// then transform that vector using the transform matrix. we use
// TransformNormal because we don't want to take translation into account.
scale3 = Vector3.TransformNormal(scale3, transform);
// scale3 contains the x, y, and z radii of a squished and stretched sphere.
// we'll set the finished sphere's radius to the maximum of the x y and z
// radii, creating a sphere that is large enough to contain the original
// squished sphere.
transformedSphere.Radius = Math.Max(scale3.X, Math.Max(scale3.Y, scale3.Z));
// transforming the center of the sphere is much easier. we can just use
// Vector3.Transform to transform the center vector. notice that we're using
// Transform instead of TransformNormal because in this case we DO want to
// take translation into account.
transformedSphere.Center = Vector3.Transform(sphere.Center, transform);
return transformedSphere;
}