PerspectiveCamera.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / System / Windows / Media3D / PerspectiveCamera.cs / 1 / PerspectiveCamera.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;
 
namespace System.Windows.Media.Media3D 
{
    ///  
    ///     Encapsulates a perspective projection camera.
    /// 
    public partial class PerspectiveCamera : ProjectionCamera
    { 
        //-----------------------------------------------------
        // 
        //  Constructors 
        //
        //----------------------------------------------------- 

        #region Constructors

        /// 
        public PerspectiveCamera() {}
 
        /// 
        public PerspectiveCamera(Point3D position, Vector3D lookDirection, Vector3D upDirection, double fieldOfView)
        { 
            Position = position;
            LookDirection = lookDirection;
            UpDirection = upDirection;
            FieldOfView = fieldOfView; 
        }
 
        #endregion Constructors 

        //------------------------------------------------------ 
        //
        //  Public Methods
        //
        //----------------------------------------------------- 

        //------------------------------------------------------ 
        // 
        //  Public Properties
        // 
        //------------------------------------------------------

        //-----------------------------------------------------
        // 
        //  Public Events
        // 
        //------------------------------------------------------ 

        //----------------------------------------------------- 
        //
        //  Internal Methods
        //
        //----------------------------------------------------- 

        #region Internal Methods 
 
        internal Matrix3D GetProjectionMatrix(double aspectRatio, double zn, double zf)
        { 
            double fov = M3DUtil.DegreesToRadians(FieldOfView);

            // Note: h and w are 1/2 of the inverse of the width/height ratios:
            // 
            //  h = 1/(heightDepthRatio) * (1/2)
            //  w = 1/(widthDepthRatio) * (1/2) 
            // 
            // Computation for h is a bit different than what you will find in
            // D3DXMatrixPerspectiveFovRH because we have a horizontal rather 
            // than vertical FoV.

            double halfWidthDepthRatio = Math.Tan(fov/2);
            double h = aspectRatio/halfWidthDepthRatio; 
            double w = 1/halfWidthDepthRatio;
 
            double m22 = zf != Double.PositiveInfinity ? zf/(zn-zf) : -1; 
            double m32 = zn*m22;
 
            return new Matrix3D(
                w,  0,  0,     0,
                0,  h,  0,     0,
                0,  0,  m22,  -1, 
                0,  0,  m32,   0);
        } 
 
        internal override Matrix3D GetProjectionMatrix(double aspectRatio)
        { 
            return GetProjectionMatrix(aspectRatio, NearPlaneDistance, FarPlaneDistance);
        }

        internal override RayHitTestParameters RayFromViewportPoint(Point p, Size viewSize, Rect3D boundingRect, out double distanceAdjustment) 
        {
            // The camera may be animating.  Take a snapshot of the current value 
            // and get the property values we need. (Window OS #992662) 
            Point3D position = Position;
            Vector3D lookDirection = LookDirection; 
            Vector3D upDirection = UpDirection;
            Transform3D transform = Transform;
            double zn = NearPlaneDistance;
            double zf = FarPlaneDistance; 
            double fov = M3DUtil.DegreesToRadians(FieldOfView);
 
            // 
            //  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); 

            // Note: h and w are 1/2 of the inverse of the width/height ratios: 
            // 
            //  h = 1/(heightDepthRatio) * (1/2)
            //  w = 1/(widthDepthRatio) * (1/2) 
            //
            // Computation for h is a bit different than what you will find in
            // D3DXMatrixPerspectiveFovRH because we have a horizontal rather
            // than vertical FoV. 
            double aspectRatio = M3DUtil.GetAspectRatio(viewSize);
            double halfWidthDepthRatio = Math.Tan(fov/2); 
            double h = aspectRatio/halfWidthDepthRatio; 
            double w = 1/halfWidthDepthRatio;
 
            // To get from projective space to camera space we apply the
            // width/height ratios to find our normalized point at 1 unit
            // in front of the camera.  (1 is convenient, but has no other
            // special significance.) See note above about the construction 
            // of w and h.
            Vector3D rayDirection = new Vector3D(np.X/w, np.Y/h, -1); 
 
            // Apply the inverse of the view matrix to our rayDirection vector
            // to convert it from camera to world space. 
            //
            // NOTE: Because our construction of the ray assumes that the
            //       viewMatrix translates the position to the origin we pass
            //       null for the Camera.Transform below and account for it 
            //       later.
 
            Matrix3D viewMatrix = CreateViewMatrix(/* trasform = */ null, ref position, ref lookDirection, ref upDirection); 
            Matrix3D invView = viewMatrix;
            invView.Invert(); 
            invView.MultiplyVector(ref rayDirection);

            // The we have the ray direction, now we need the origin.  The camera's
            // position would work except that we would intersect geometry between 
            // the camera plane and the near plane so instead we must find the
            // point on the project plane where the ray (position, rayDirection) 
            // intersect (Windows OS #1005064): 
            //
            //                     | _.>       p = camera position 
            //                rd  _+"          ld = camera look direction
            //                 .-" |ro         pp = projection plane
            //             _.-"    |           rd = ray direction
            //         p +"--------+--->       ro = desired ray origin on pp 
            //                ld   |
            //                     pp 
            // 
            // Above we constructed the direction such that it's length projects to
            // 1 unit on the lookDirection vector. 
            //
            //
            //                rd  _.>
            //                 .-"        rd = unnormalized rayDirection 
            //             _.-"           ld = normalized lookDirection (length = 1)
            //           -"---------> 
            //                 ld 
            //
            // So to find the desired rayOrigin on the projection plane we simply do: 
            Point3D rayOrigin = position + zn*rayDirection;
            rayDirection.Normalize();

            // Account for the Camera.Transform we ignored during ray construction above. 
            if (transform != null && transform != Transform3D.Identity)
            { 
                Matrix3D m = transform.Value; 
                m.MultiplyPoint(ref rayOrigin);
                m.MultiplyVector(ref rayDirection); 

                PrependInverseTransform(m, ref viewMatrix);
            }
 
            RayHitTestParameters rayParameters = new RayHitTestParameters(rayOrigin, rayDirection);
 
            // 
            //  Compute HitTestProjectionMatrix
            // 

            Matrix3D projectionMatrix = GetProjectionMatrix(aspectRatio, zn, zf);

            // The projectionMatrix takes camera-space 3D points into normalized clip 
            // space.
 
            // The viewportMatrix will take normalized clip space into 
            // viewport coordinates, with an additional 2D translation
            // to put the ray at the rayOrigin. 
            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 = 
                viewMatrix *
                projectionMatrix * 
                viewportMatrix;

            //
            // Perspective camera doesn't allow negative NearPlanes, so there's 
            // not much point in adjusting the ray origin. Hence, 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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