Method GetProjectionMatrix

GTE/Graphics/PlanarShadowEffect.cpp:280–335

}

bool PlanarShadowEffect::GetProjectionMatrix(size_t i, Matrix4x4<float>& projection)
{
    // Compute the equation for the planeVisual in world coordinates.
    auto const& wMatrix = mPlaneVisuals[i]->worldTransform.GetHMatrix();
    auto const& msTriangle = mModelSpaceTriangles[i];
    std::array<Vector4<float>, 3> wsTriangle{};
    for (size_t j = 0; j < 3; ++j)
    {
        wsTriangle[j] = DoTransform(wMatrix, msTriangle[j]);
    }
    CullingPlane<float> wPlane(wsTriangle[0], wsTriangle[1], wsTriangle[2]);
    wPlane.Normalize();

    // This is a conservative test to see whether a shadow should be cast.
    // This can cause incorrect results if the caster is large and intersects
    // the plane, but ordinarily we are not trying to cast shadows in such
    // situations.
    if (mShadowCaster->worldBound.WhichSide(wPlane) < 0)
    {
        // The shadow caster is on the far side of plane, so it cannot cast
        // a shadow.
        projection = Matrix4x4<float>::Identity();
        return false;
    }

    // Compute the projection matrix for the light source.
    auto normal = wPlane.GetNormal();
    if (mLightProjector->isPointLight)
    {
        float NdE = Dot(normal, mLightProjector->position);
        if (NdE <= 0.0f)
        {
            // The projection must be onto the positive side of the plane.
            projection = Matrix4x4<float>::Identity();
            return false;
        }

        projection = MakePerspectiveProjection(wsTriangle[0], normal,
            mLightProjector->position);
    }
    else
    {
        float NdD = Dot(normal, mLightProjector->direction);
        if (NdD >= 0.0f)
        {
            // The projection must be onto the positive side of the plane.
            projection = Matrix4x4<float>::Identity();
            return false;
        }

        projection = MakeObliqueProjection(wsTriangle[0], normal,
            mLightProjector->direction);
    }

    return true;
}