SLFrustum.cpp

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/**
 * \file      SLFrustum.cpp
 * \authors   Luc Girod, Marcus Hudritsch
 * \date      Summer 2021
 * \copyright http://opensource.org/licenses/GPL-3.0
 * \remarks   Please use clangformat to format the code. See more code style on
 *            https://github.com/cpvrlab/SLProject4/wiki/SLProject-Coding-Style
*/
 
#include <vector>
#include <SLPlane.h>
#include <SLMat4.h>
#include <SLFrustum.h>
 
//-----------------------------------------------------------------------------
/*!
 * Calculates the coefficients of the 6 frustum planes from the passed
 * projection and view matrices. See the paper from Gribb and Hartmann:
 * https://www.gamedevs.org/uploads/fast-extraction-viewing-frustum-planes-from-world-view-projection-matrix.pdf
 * \param planes Pointer to an array of 6 SLPlanes (L R T B N F)
 * \param projectionMat 4x4 projection matrix
 * \param viewMat 4x4 view matrix
 */
void SLFrustum::viewToFrustumPlanes(SLPlane*       planes,
                                    const SLMat4f& projectionMat,
                                    const SLMat4f& viewMat)
{
    // Combine view and projection matrix
    SLMat4f A = projectionMat * viewMat;
 
    // Order is L R T B N F
    viewToFrustumPlanes(planes, A);
}
//-----------------------------------------------------------------------------
/*!
 * Calculates the coefficients of the 6 frustum planes from the passed
 * matrix A. See the paper from Gribb and Hartmann:
 * https://www.gamedevs.org/uploads/fast-extraction-viewing-frustum-planes-from-world-view-projection-matrix.pdf
 * \param planes Pointer to an array of 6 SLPlanes (L R T B N F)
 * \param A The projection matrix
 */
void SLFrustum::viewToFrustumPlanes(SLPlane* planes, const SLMat4f& A)
{
    // set the A,B,C & D coefficient for each plane
    // Order is L R T B N F
    planes[0].setCoefficients(A.m(0) + A.m(3),
                              A.m(4) + A.m(7),
                              A.m(8) + A.m(11),
                              A.m(12) + A.m(15));
    planes[1].setCoefficients(-A.m(0) + A.m(3),
                              -A.m(4) + A.m(7),
                              -A.m(8) + A.m(11),
                              -A.m(12) + A.m(15));
    planes[2].setCoefficients(-A.m(1) + A.m(3),
                              -A.m(5) + A.m(7),
                              -A.m(9) + A.m(11),
                              -A.m(13) + A.m(15));
    planes[3].setCoefficients(A.m(1) + A.m(3),
                              A.m(5) + A.m(7),
                              A.m(9) + A.m(11),
                              A.m(13) + A.m(15));
    planes[4].setCoefficients(A.m(2) + A.m(3),
                              A.m(6) + A.m(7),
                              A.m(10) + A.m(11),
                              A.m(14) + A.m(15));
    planes[5].setCoefficients(-A.m(2) + A.m(3),
                              -A.m(6) + A.m(7),
                              -A.m(10) + A.m(11),
                              -A.m(14) + A.m(15));
}
//-----------------------------------------------------------------------------
//! Returns frustum points in view space
void SLFrustum::getPointsInViewSpace(SLVec3f* points,
                                     float    fovV,
                                     float    ratio,
                                     float    clipNear,
                                     float    clipFar)
{
    SLfloat tanFovV = tan(Utils::DEG2RAD * fovV * 0.5f);
 
    // Calculate the 4 points on the near plane
    SLfloat t = tanFovV * clipNear; // top
    SLfloat b = -t;                 // bottom
    SLfloat r = ratio * t;          // right
    SLfloat l = -r;                 // left
    points[0] = (SLVec3f(r, t, -clipNear));
    points[1] = (SLVec3f(r, b, -clipNear));
    points[2] = (SLVec3f(l, t, -clipNear));
    points[3] = (SLVec3f(l, b, -clipNear));
 
    // Calculate the 4 points on the far plane
    t = tanFovV * clipFar; // top
    b = -t;                // bottom
    r = ratio * t;         // right
    l = -r;                // left
 
    points[4] = (SLVec3f(r, t, -clipFar));
    points[5] = (SLVec3f(r, b, -clipFar));
    points[6] = (SLVec3f(l, t, -clipFar));
    points[7] = (SLVec3f(l, b, -clipFar));
}
//-----------------------------------------------------------------------------