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 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2017                                                               *
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#include <modules/globebrowsing/chunk/culling/frustumculler.h>

#include <modules/globebrowsing/chunk/chunk.h>
#include <modules/globebrowsing/globes/renderableglobe.h>
#include <openspace/util/updatestructures.h>

namespace openspace::globebrowsing::culling {

FrustumCuller::FrustumCuller(AABB3 viewFrustum)
    : _viewFrustum(std::move(viewFrustum))
{}

bool FrustumCuller::isCullable(const Chunk& chunk, const RenderData& data) {
    // Calculate the MVP matrix
    glm::dmat4 modelTransform = chunk.owner().modelTransform();
    glm::dmat4 viewTransform = glm::dmat4(data.camera.combinedViewMatrix());
    glm::dmat4 modelViewProjectionTransform = glm::dmat4(data.camera.sgctInternal.projectionMatrix())
        * viewTransform * modelTransform;

    const std::vector<glm::dvec4>& corners = chunk.getBoundingPolyhedronCorners();
        
    // Create a bounding box that fits the patch corners
    AABB3 bounds; // in screen space
    std::vector<glm::vec4> clippingSpaceCorners(8);
    for (size_t i = 0; i < 8; ++i) {
        glm::dvec4 cornerClippingSpace = modelViewProjectionTransform * corners[i];
        clippingSpaceCorners[i] = cornerClippingSpace;

        glm::dvec3 ndc = glm::dvec3((1.0f / glm::abs(cornerClippingSpace.w)) * cornerClippingSpace);
        bounds.expand(ndc);
    }
        
    return !(_viewFrustum.intersects(bounds));
}

} // namespace openspace::globebrowsing::culling