Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / System / Windows / Media3D / MatrixCamera.cs / 1305600 / MatrixCamera.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // //--------------------------------------------------------------------------- using System; using System.Diagnostics; using System.Windows; using MS.Internal.Media3D; using System.ComponentModel.Design.Serialization; using System.Windows.Markup; using CultureInfo = System.Globalization.CultureInfo; using SR=MS.Internal.PresentationCore.SR; using SRID=MS.Internal.PresentationCore.SRID; namespace System.Windows.Media.Media3D { ////// The MatrixCamera subclass of Camera provides a means for directly /// specifying a Matrix as the projection transformation. This is /// useful for apps that have their own projection matrix calculation /// mechanisms. /// public partial class MatrixCamera : Camera { //----------------------------------------------------- // // Constructors // //----------------------------------------------------- #region Constructors ////// Default constructor /// public MatrixCamera() {} ////// Construct a MatrixCamera from view and projection matrices /// public MatrixCamera(Matrix3D viewMatrix, Matrix3D projectionMatrix) { ViewMatrix = viewMatrix; ProjectionMatrix = projectionMatrix; } #endregion Constructors //------------------------------------------------------ // // Public Methods // //----------------------------------------------------- //------------------------------------------------------ // // Public Properties // //------------------------------------------------------ //----------------------------------------------------- // // Internal Methods // //------------------------------------------------------ #region Internal Methods // NOTE: We consider Camera.Transform to be part of the view matrix // here, where as the read/write ViewMatrix property does not // include the camera's Transform. internal override Matrix3D GetViewMatrix() { Matrix3D viewMatrix = ViewMatrix; PrependInverseTransform(Transform, ref viewMatrix); return viewMatrix; } internal override Matrix3D GetProjectionMatrix(double aspectRatio) { return ProjectionMatrix; } internal override RayHitTestParameters RayFromViewportPoint(Point p, Size viewSize, Rect3D boundingRect, out double distanceAdjustment) { // // Compute rayParameters // // Find the point on the projection plane in post-projective space where // the viewport maps to a 2x2 square from (-1,1)-(1,-1). Point np = M3DUtil.GetNormalizedPoint(p, viewSize); // // So (conceptually) the user clicked on the point (np.X, // np.Y, 0) in post-projection clipping space and the ray // extends in the direction (0, 0, 1) because our ray // after projection looks down the positive z axis. We // need to convert this ray and direction back to world // space. Matrix3D worldToCamera = GetViewMatrix() * ProjectionMatrix; Matrix3D cameraToWorld = worldToCamera; if (!cameraToWorld.HasInverse) { // // NTRAID#Longhorn-1180933-2004/07/30-danwo - Need to handle singular matrix cameras throw new NotSupportedException(SR.Get(SRID.HitTest_Singular)); } cameraToWorld.Invert(); Point4D origin4D = new Point4D(np.X,np.Y,0,1) * cameraToWorld; Point3D origin = new Point3D( origin4D.X/origin4D.W, origin4D.Y/origin4D.W, origin4D.Z/origin4D.W ); // To transform the direction we use the Jacobian of // cameraToWorld at the point np.X,np.Y,0 that we just // transformed. // // The Jacobian of the homogeneous matrix M is a 3x3 matrix. // // Let x be the point we are computing the Jacobian at, and y be the // result of transforming x by M, i.e. // (wy w) = (x 1) M // Where (wy w) is the homogeneous point representing y with w as its homogeneous coordinate // And (x 1) is the homogeneous point representing x with 1 as its homogeneous coordinate // // Then the i,j component of the Jacobian (at x) is // (M_ij - M_i4 y_j) / w // // Since we're only concerned with the direction of the // transformed vector and not its magnitude, we can scale // this matrix by a POSITIVE factor. The computation // below computes the Jacobian scaled by 1/w and then // after we normalize the final vector we flip it around // if w is negative. // // To transform a vector we just right multiply it by this Jacobian matrix. // // Compute the Jacobian at np.X,np.Y,0 ignoring the constant factor of w. // Here's the pattern // // double Jij = cameraToWorld.Mij - cameraToWorld.Mi4 * origin.j // // but we only need J31,J32,&J33 because we're only // transforming the vector 0,0,1 double J31 = cameraToWorld.M31 - cameraToWorld.M34 * origin.X; double J32 = cameraToWorld.M32 - cameraToWorld.M34 * origin.Y; double J33 = cameraToWorld.M33 - cameraToWorld.M34 * origin.Z; // Then multiply that matrix by (0, 0, 1) which is // the direction of the ray in post-projection space. Vector3D direction = new Vector3D( J31, J32, J33 ); direction.Normalize(); // We multiplied by the Jacobian times W, so we need to // account for whether that flipped our result or not. if (origin4D.W < 0) { direction = -direction; } RayHitTestParameters rayParameters = new RayHitTestParameters(origin, direction); // // Compute HitTestProjectionMatrix // // The viewportMatrix will take normalized clip space into // viewport coordinates, with an additional 2D translation // to put the ray at the origin. Matrix3D viewportMatrix = new Matrix3D(); viewportMatrix.TranslatePrepend(new Vector3D(-p.X,viewSize.Height-p.Y,0)); viewportMatrix.ScalePrepend(new Vector3D(viewSize.Width/2,-viewSize.Height/2,1)); viewportMatrix.TranslatePrepend(new Vector3D(1,1,0)); // `First world-to-camera, then camera's projection, then normalized clip space to viewport. rayParameters.HitTestProjectionMatrix = worldToCamera * viewportMatrix; // // MatrixCamera does not allow for Near/Far plane adjustment, so // the distanceAdjustment remains 0. // distanceAdjustment = 0.0; return rayParameters; } #endregion Internal Methods //----------------------------------------------------- // // Private Fields // //----------------------------------------------------- } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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