nuclear@1: /************************************************************************************
nuclear@1: 
nuclear@1: Filename    :   Util_Render_Stereo.cpp
nuclear@1: Content     :   Stereo rendering configuration implementation
nuclear@1: Created     :   October 22, 2012
nuclear@1: Authors     :   Michael Antonov, Andrew Reisse
nuclear@1: 
nuclear@1: Copyright   :   Copyright 2012 Oculus, Inc. All Rights reserved.
nuclear@1: 
nuclear@1: Use of this software is subject to the terms of the Oculus Inc license
nuclear@1: agreement provided at the time of installation or download, or which
nuclear@1: otherwise accompanies this software in either electronic or hard copy form.
nuclear@1: 
nuclear@1: *************************************************************************************/
nuclear@1: 
nuclear@1: #include "Util_Render_Stereo.h"
nuclear@1: 
nuclear@1: namespace OVR { namespace Util { namespace Render {
nuclear@1: 
nuclear@1: 
nuclear@1: //-----------------------------------------------------------------------------------
nuclear@1: 
nuclear@1: // DistortionFnInverse computes the inverse of the distortion function on an argument.
nuclear@1: float DistortionConfig::DistortionFnInverse(float r)
nuclear@1: {    
nuclear@1:     OVR_ASSERT((r <= 10.0f));
nuclear@1: 
nuclear@1:     float s, d;
nuclear@1:     float delta = r * 0.25f;
nuclear@1: 
nuclear@1:     s = r * 0.5f;
nuclear@1:     d = fabs(r - DistortionFn(s));
nuclear@1: 
nuclear@1:     for (int i = 0; i < 20; i++)
nuclear@1:     {
nuclear@1:         float sUp   = s + delta;
nuclear@1:         float sDown = s - delta;
nuclear@1:         float dUp   = fabs(r - DistortionFn(sUp));
nuclear@1:         float dDown = fabs(r - DistortionFn(sDown));
nuclear@1: 
nuclear@1:         if (dUp < d)
nuclear@1:         {
nuclear@1:             s = sUp;
nuclear@1:             d = dUp;
nuclear@1:         }
nuclear@1:         else if (dDown < d)
nuclear@1:         {
nuclear@1:             s = sDown;
nuclear@1:             d = dDown;
nuclear@1:         }
nuclear@1:         else
nuclear@1:         {
nuclear@1:             delta *= 0.5f;
nuclear@1:         }
nuclear@1:     }
nuclear@1: 
nuclear@1:     return s;
nuclear@1: }
nuclear@1: 
nuclear@1: 
nuclear@1: //-----------------------------------------------------------------------------------
nuclear@1: // **** StereoConfig Implementation
nuclear@1: 
nuclear@1: StereoConfig::StereoConfig(StereoMode mode, const Viewport& vp)
nuclear@1:     : Mode(mode),
nuclear@1:       InterpupillaryDistance(0.064f), AspectMultiplier(1.0f),
nuclear@1:       FullView(vp), DirtyFlag(true), IPDOverride(false),
nuclear@1:       YFov(0), Aspect(vp.w / float(vp.h)), ProjectionCenterOffset(0),
nuclear@1:       OrthoPixelOffset(0)
nuclear@1: {
nuclear@1:     // And default distortion for it.
nuclear@1:     Distortion.SetCoefficients(1.0f, 0.22f, 0.24f);
nuclear@1:     Distortion.Scale = 1.0f; // Will be computed later.
nuclear@1: 
nuclear@1:     // Fit left of the image.
nuclear@1:     DistortionFitX = -1.0f;
nuclear@1:     DistortionFitY = 0.0f;
nuclear@1: 
nuclear@1:     // Initialize "fake" default HMD values for testing without HMD plugged in.
nuclear@1:     // These default values match those returned by the HMD.
nuclear@1:     HMD.HResolution            = 1280;
nuclear@1:     HMD.VResolution            = 800;
nuclear@1:     HMD.HScreenSize            = 0.14976f;
nuclear@1:     HMD.VScreenSize            = HMD.HScreenSize / (1280.0f / 800.0f);
nuclear@1:     HMD.InterpupillaryDistance = InterpupillaryDistance;
nuclear@1:     HMD.LensSeparationDistance = 0.0635f;
nuclear@1:     HMD.EyeToScreenDistance    = 0.041f;
nuclear@1:     HMD.DistortionK[0]         = Distortion.K[0];
nuclear@1:     HMD.DistortionK[1]         = Distortion.K[1];
nuclear@1:     HMD.DistortionK[2]         = Distortion.K[2];
nuclear@1:     HMD.DistortionK[3]         = 0;
nuclear@1: 
nuclear@1:     Set2DAreaFov(DegreeToRad(85.0f));
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::SetFullViewport(const Viewport& vp)
nuclear@1: {
nuclear@1:     if (vp != FullView)
nuclear@1:     { 
nuclear@1:         FullView = vp;
nuclear@1:         DirtyFlag = true;
nuclear@1:     }
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::SetHMDInfo(const HMDInfo& hmd)
nuclear@1: {
nuclear@1:     HMD = hmd;
nuclear@1:     Distortion.K[0] = hmd.DistortionK[0];
nuclear@1:     Distortion.K[1] = hmd.DistortionK[1];
nuclear@1:     Distortion.K[2] = hmd.DistortionK[2];
nuclear@1:     Distortion.K[3] = hmd.DistortionK[3];
nuclear@1: 
nuclear@1:     Distortion.SetChromaticAberration(hmd.ChromaAbCorrection[0], hmd.ChromaAbCorrection[1],
nuclear@1:                                       hmd.ChromaAbCorrection[2], hmd.ChromaAbCorrection[3]);
nuclear@1: 
nuclear@1:     if (!IPDOverride)
nuclear@1:         InterpupillaryDistance = HMD.InterpupillaryDistance;
nuclear@1: 
nuclear@1:     DirtyFlag = true;
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::SetDistortionFitPointVP(float x, float y)
nuclear@1: {
nuclear@1:     DistortionFitX = x;
nuclear@1:     DistortionFitY = y;
nuclear@1:     DirtyFlag = true;
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::SetDistortionFitPointPixels(float x, float y)
nuclear@1: {
nuclear@1:     DistortionFitX = (4 * x / float(FullView.w)) - 1.0f;
nuclear@1:     DistortionFitY = (2 * y / float(FullView.h)) - 1.0f;
nuclear@1:     DirtyFlag = true;
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::Set2DAreaFov(float fovRadians)
nuclear@1: {
nuclear@1:     Area2DFov = fovRadians;
nuclear@1:     DirtyFlag = true;
nuclear@1: }
nuclear@1: 
nuclear@1: 
nuclear@1: const StereoEyeParams& StereoConfig::GetEyeRenderParams(StereoEye eye)
nuclear@1: {
nuclear@1:     static const UByte eyeParamIndices[3] = { 0, 0, 1 };
nuclear@1: 
nuclear@1:     updateIfDirty();
nuclear@1:     OVR_ASSERT(eye < sizeof(eyeParamIndices));
nuclear@1:     return EyeRenderParams[eyeParamIndices[eye]];
nuclear@1: }
nuclear@1: 
nuclear@1: 
nuclear@1: void StereoConfig::updateComputedState()
nuclear@1: {
nuclear@1:     // Need to compute all of the following:
nuclear@1:     //   - Aspect Ratio
nuclear@1:     //   - FOV
nuclear@1:     //   - Projection offsets for 3D
nuclear@1:     //   - Distortion XCenterOffset
nuclear@1:     //   - Update 2D
nuclear@1:     //   - Initialize EyeRenderParams
nuclear@1: 
nuclear@1:     // Compute aspect ratio. Stereo mode cuts width in half.
nuclear@1:     Aspect = float(FullView.w) / float(FullView.h);
nuclear@1:     Aspect *= (Mode == Stereo_None) ? 1.0f : 0.5f;
nuclear@1:     Aspect *= AspectMultiplier; 
nuclear@1: 
nuclear@1:     updateDistortionOffsetAndScale();
nuclear@1: 
nuclear@1:     // Compute Vertical FOV based on distance, distortion, etc.
nuclear@1:     // Distance from vertical center to render vertical edge perceived through the lens.
nuclear@1:     // This will be larger then normal screen size due to magnification & distortion.
nuclear@1:     //
nuclear@1:     // This percievedHalfRTDistance equation should hold as long as the render target
nuclear@1:     // and display have the same aspect ratios. What we'd like to know is where the edge
nuclear@1:     // of the render target will on the perceived screen surface. With NO LENS,
nuclear@1:     // the answer would be:
nuclear@1:     //
nuclear@1:     //  halfRTDistance = (VScreenSize / 2) * aspect *
nuclear@1:     //                   DistortionFn_Inverse( DistortionScale / aspect )
nuclear@1:     //
nuclear@1:     // To model the optical lens we eliminates DistortionFn_Inverse. Aspect ratios
nuclear@1:     // cancel out, so we get:
nuclear@1:     //
nuclear@1:     //  halfRTDistance = (VScreenSize / 2) * DistortionScale
nuclear@1:     //
nuclear@1:     if (Mode == Stereo_None)
nuclear@1:     {
nuclear@1:         YFov = DegreeToRad(80.0f);
nuclear@1:     }
nuclear@1:     else
nuclear@1:     {
nuclear@1:         float percievedHalfRTDistance = (HMD.VScreenSize / 2) * Distortion.Scale;    
nuclear@1:         YFov = 2.0f * atan(percievedHalfRTDistance/HMD.EyeToScreenDistance);
nuclear@1:     }
nuclear@1:     
nuclear@1:     updateProjectionOffset();
nuclear@1:     update2D();
nuclear@1:     updateEyeParams();
nuclear@1: 
nuclear@1:     DirtyFlag = false;
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::updateDistortionOffsetAndScale()
nuclear@1: {
nuclear@1:     // Distortion center shift is stored separately, since it isn't affected
nuclear@1:     // by the eye distance.
nuclear@1:     float lensOffset        = HMD.LensSeparationDistance * 0.5f;
nuclear@1:     float lensShift         = HMD.HScreenSize * 0.25f - lensOffset;
nuclear@1:     float lensViewportShift = 4.0f * lensShift / HMD.HScreenSize;
nuclear@1:     Distortion.XCenterOffset= lensViewportShift;
nuclear@1: 
nuclear@1:     // Compute distortion scale from DistortionFitX & DistortionFitY.
nuclear@1:     // Fit value of 0.0 means "no fit".
nuclear@1:     if ((fabs(DistortionFitX) < 0.0001f) &&  (fabs(DistortionFitY) < 0.0001f))
nuclear@1:     {
nuclear@1:         Distortion.Scale = 1.0f;
nuclear@1:     }
nuclear@1:     else
nuclear@1:     {
nuclear@1:         // Convert fit value to distortion-centered coordinates before fit radius
nuclear@1:         // calculation.
nuclear@1:         float stereoAspect = 0.5f * float(FullView.w) / float(FullView.h);
nuclear@1:         float dx           = DistortionFitX - Distortion.XCenterOffset;
nuclear@1:         float dy           = DistortionFitY / stereoAspect;
nuclear@1:         float fitRadius    = sqrt(dx * dx + dy * dy);
nuclear@1:         Distortion.Scale   = Distortion.DistortionFn(fitRadius)/fitRadius;
nuclear@1:     }
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::updateProjectionOffset()
nuclear@1: {
nuclear@1:     // Post-projection viewport coordinates range from (-1.0, 1.0), with the
nuclear@1:     // center of the left viewport falling at (1/4) of horizontal screen size.
nuclear@1:     // We need to shift this projection center to match with the lens center;
nuclear@1:     // note that we don't use the IPD here due to collimated light property of the lens.
nuclear@1:     // We compute this shift in physical units (meters) to
nuclear@1:     // correct for different screen sizes and then rescale to viewport coordinates.    
nuclear@1:     float viewCenter         = HMD.HScreenSize * 0.25f;
nuclear@1:     float eyeProjectionShift = viewCenter - HMD.LensSeparationDistance*0.5f;
nuclear@1:     ProjectionCenterOffset   = 4.0f * eyeProjectionShift / HMD.HScreenSize;
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::update2D()
nuclear@1: {
nuclear@1:     // Orthographic projection fakes a screen at a distance of 0.8m from the
nuclear@1:     // eye, where hmd screen projection surface is at 0.05m distance.
nuclear@1:     // This introduces an extra off-center pixel projection shift based on eye distance.
nuclear@1:     // This offCenterShift is the pixel offset of the other camera's center
nuclear@1:     // in your reference camera based on surface distance.    
nuclear@1:     float metersToPixels          = (HMD.HResolution / HMD.HScreenSize);
nuclear@1:     float lensDistanceScreenPixels= metersToPixels * HMD.LensSeparationDistance;
nuclear@1:     float eyeDistanceScreenPixels = metersToPixels * InterpupillaryDistance;
nuclear@1:     float offCenterShiftPixels    = (HMD.EyeToScreenDistance / 0.8f) * eyeDistanceScreenPixels;
nuclear@1:     float leftPixelCenter         = (HMD.HResolution / 2) - lensDistanceScreenPixels * 0.5f;
nuclear@1:     float rightPixelCenter        = lensDistanceScreenPixels * 0.5f;
nuclear@1:     float pixelDifference         = leftPixelCenter - rightPixelCenter;
nuclear@1:     
nuclear@1:     // This computes the number of pixels that fit within specified 2D FOV (assuming
nuclear@1:     // distortion scaling will be done).
nuclear@1:     float percievedHalfScreenDistance = tan(Area2DFov * 0.5f) * HMD.EyeToScreenDistance;
nuclear@1:     float vfovSize = 2.0f * percievedHalfScreenDistance / Distortion.Scale;
nuclear@1:     FovPixels = HMD.VResolution * vfovSize / HMD.VScreenSize;
nuclear@1:     
nuclear@1:     // Create orthographic matrix.   
nuclear@1:     Matrix4f& m      = OrthoCenter;
nuclear@1:     m.SetIdentity();
nuclear@1:     m.M[0][0] = FovPixels / (FullView.w * 0.5f);
nuclear@1:     m.M[1][1] = -FovPixels / FullView.h;
nuclear@1:     m.M[0][3] = 0;
nuclear@1:     m.M[1][3] = 0;
nuclear@1:     m.M[2][2] = 0;
nuclear@1: 
nuclear@1:     float orthoPixelOffset = (pixelDifference + offCenterShiftPixels/Distortion.Scale) * 0.5f;
nuclear@1:     OrthoPixelOffset = orthoPixelOffset * 2.0f / FovPixels;
nuclear@1: }
nuclear@1: 
nuclear@1: void StereoConfig::updateEyeParams()
nuclear@1: {
nuclear@1:     // Projection matrix for the center eye, which the left/right matrices are based on.
nuclear@1:     Matrix4f projCenter = Matrix4f::PerspectiveRH(YFov, Aspect, 0.01f, 2000.0f);
nuclear@1:    
nuclear@1:     switch(Mode)
nuclear@1:     {
nuclear@1:     case Stereo_None:
nuclear@1:         {
nuclear@1:             EyeRenderParams[0].Init(StereoEye_Center, FullView, 0, projCenter, OrthoCenter);
nuclear@1:         }
nuclear@1:         break;
nuclear@1: 
nuclear@1:     case Stereo_LeftRight_Multipass:
nuclear@1:         {
nuclear@1:             Matrix4f projLeft  = Matrix4f::Translation(ProjectionCenterOffset, 0, 0) * projCenter,
nuclear@1:                      projRight = Matrix4f::Translation(-ProjectionCenterOffset, 0, 0) * projCenter;
nuclear@1: 
nuclear@1:             EyeRenderParams[0].Init(StereoEye_Left,
nuclear@1:                 Viewport(FullView.x, FullView.y, FullView.w/2, FullView.h),
nuclear@1:                          +InterpupillaryDistance * 0.5f,  // World view shift.                       
nuclear@1:                          projLeft, OrthoCenter * Matrix4f::Translation(OrthoPixelOffset, 0, 0),
nuclear@1:                          &Distortion);
nuclear@1:             EyeRenderParams[1].Init(StereoEye_Right,
nuclear@1:                 Viewport(FullView.x + FullView.w/2, FullView.y, FullView.w/2, FullView.h),
nuclear@1:                          -InterpupillaryDistance * 0.5f,                         
nuclear@1:                          projRight, OrthoCenter * Matrix4f::Translation(-OrthoPixelOffset, 0, 0),
nuclear@1:                          &Distortion);
nuclear@1:         }
nuclear@1:         break;
nuclear@1:     }
nuclear@1: 
nuclear@1: }
nuclear@1: 
nuclear@1: 
nuclear@1: }}}  // OVR::Util::Render
nuclear@1: