/// <summary>
/// Transforms a box with a specified transform.
/// </summary>
/// <param name="inBox">The box to transform.</param>
/// <param name="transform">The transform.</param>
/// <returns>The transformed box.</returns>
public static Box3F Transform(ref Box3F inBox, ref Matrix transform)
{
Vector3 center = 0.5f * (inBox.Min + inBox.Max);
Vector3 extent = inBox.Max - center;
Vector3 newExtent = new Vector3(
extent.X * Math.Abs(transform.M11) + extent.Y * Math.Abs(transform.M21) + extent.Z * Math.Abs(transform.M31),
extent.X * Math.Abs(transform.M12) + extent.Y * Math.Abs(transform.M22) + extent.Z * Math.Abs(transform.M32),
extent.X * Math.Abs(transform.M13) + extent.Y * Math.Abs(transform.M23) + extent.Z * Math.Abs(transform.M33));
center = Vector3.Transform(center, transform);
Box3F outBox = new Box3F(center - newExtent, center + newExtent);
#if extra_strict_check
// extra strict check
{
// Cycle through all the corners of the box and transform them. Then
// extend test box by transformed corners. This box should match the
// one we computed above except for precision errors.
Box3F testBox= new Box3F(10E10f,10E10f,10E10f,-10E10f,-10E10f,-10E10f);
center = 0.5f * (inBox.Min + inBox.Max);
for (int i = 0; i < 8; i++)
{
Vector3 corner = center;
corner.X += ((i & 1) == 0) ? extent.X : -extent.X;
corner.Y += ((i & 2) == 0) ? extent.Y : -extent.Y;
corner.Z += ((i & 4) == 0) ? extent.Z : -extent.Z;
corner = Vector3.Transform(corner, transform);
testBox.Extend(corner);
}
Assert.Fatal(Math.Abs(testBox.Min.X - outBox.Min.X) < 0.001f && Math.Abs(testBox.Min.Y - outBox.Min.Y) < 0.001f && Math.Abs(testBox.Min.Z - outBox.Min.Z) < 0.001f, "doh");
Assert.Fatal(Math.Abs(testBox.Max.X - outBox.Max.X) < 0.001f && Math.Abs(testBox.Max.Y - outBox.Max.Y) < 0.001f && Math.Abs(testBox.Max.Z - outBox.Max.Z) < 0.001f, "doh");
}
#endif
return outBox;
}
/// <summary>
/// Generate the frustum.
/// </summary>
/// <param name="nearDist">The distance to the near plane.</param>
/// <param name="farDist">The distance to the far plane.</param>
/// <param name="fov">The field of view of the frustum.</param>
/// <param name="aspectRatio">The aspect ratio.</param>
/// <param name="camToWorld">The camera transform.</param>
public void SetFrustum(float nearDist, float farDist, float fov, float aspectRatio, Matrix camToWorld)
{
_nearDist = nearDist;
_farDist = farDist;
float left = -farDist * (float)Math.Tan(fov * 0.5f) * aspectRatio;
float right = -left;
float bottom = left / aspectRatio;
float top = -bottom;
Vector3 farPosLeftUp = new Vector3(left, farDist, top);
Vector3 farPosLeftDown = new Vector3(left, farDist, bottom);
Vector3 farPosRightUp = new Vector3(right, farDist, top);
Vector3 farPosRightDown = new Vector3(right, farDist, bottom);
_cameraPos = camToWorld.Translation;
_cameraY = MatrixUtil.MatrixGetRow(1, ref camToWorld);
farPosLeftUp = MatrixUtil.MatMulP(ref farPosLeftUp, ref camToWorld);
farPosLeftDown = MatrixUtil.MatMulP(ref farPosLeftDown, ref camToWorld);
farPosRightUp = MatrixUtil.MatMulP(ref farPosRightUp, ref camToWorld);
farPosRightDown = MatrixUtil.MatMulP(ref farPosRightDown, ref camToWorld);
_bounds = new Box3F(_cameraPos, _cameraPos);
_bounds.Extend(farPosLeftUp);
_bounds.Extend(farPosLeftDown);
_bounds.Extend(farPosRightUp);
_bounds.Extend(farPosRightDown);
_leftPlaneNormal = Vector3.Cross(farPosLeftUp - _cameraPos, farPosLeftDown - _cameraPos);
_rightPlaneNormal = Vector3.Cross(farPosRightDown - _cameraPos, farPosRightUp - _cameraPos);
_topPlaneNormal = Vector3.Cross(farPosRightUp - _cameraPos, farPosLeftUp - _cameraPos);
_bottomPlaneNormal = Vector3.Cross(farPosLeftDown - _cameraPos, farPosRightDown - _cameraPos);
_leftPlaneNormal.Normalize();
_rightPlaneNormal.Normalize();
_topPlaneNormal.Normalize();
_bottomPlaneNormal.Normalize();
_leftPlaneDist = Vector3.Dot(_leftPlaneNormal, _cameraPos);
_rightPlaneDist = Vector3.Dot(_rightPlaneNormal, _cameraPos);
_topPlaneDist = Vector3.Dot(_topPlaneNormal, _cameraPos);
_bottomPlaneDist = Vector3.Dot(_bottomPlaneNormal, _cameraPos);
_nearPlaneDist = -nearDist - Vector3.Dot(_cameraY, _cameraPos);
_farPlaneDist = farDist + Vector3.Dot(_cameraY, _cameraPos);
// precompute sin for quick object accept
float minr = Math.Min(right, top);
Assert.Fatal(minr > 0.0f, "doh!");
_acceptCos = _farDist / (float)Math.Sqrt(_farDist * _farDist + minr * minr);
_acceptInvSin = 1.0f / (float)Math.Sqrt(1.0f - _acceptCos * _acceptCos);
// precompute sin for object culling
float maxr = (float)Math.Sqrt(right * right + bottom * bottom); // anything outside this cone rejected
_rejectCos = _farDist / (float)Math.Sqrt(_farDist * _farDist + maxr * maxr);
_rejectInvSin = 1.0f / (float)Math.Sqrt(1.0f - _rejectCos * _rejectCos);
}
