Frustum.cpp

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#include "Engine/Camera/Frustum.hpp"
#include "Engine/Camera/Camera.hpp"

namespace Engine
{
    Frustum::Frustum(Camera& camera, glm::vec3 right, glm::vec3 up)
    {
        float fov = camera.GetFoV();
        float aspectRatio = camera.GetAspectRatio();
        glm::vec3 cameraPosition = camera.GetPosition();
        glm::vec3 cameraDirection = camera.GetRotation();
        glm::vec2 clippingPlanes = camera.GetClippingPlanes();

        float nearPlaneHeight = 2 * tan(fov / 2) * clippingPlanes.x;
        float nearPlaneWidth = nearPlaneHeight * aspectRatio;

        float farPlaneHeight = 2 * tan(fov / 2) * clippingPlanes.y;
        float farPlaneWidth = farPlaneHeight * aspectRatio;

        glm::vec3 farCenter = cameraPosition + cameraDirection * clippingPlanes.y;

        glm::vec3 ftl = farCenter + (up * farPlaneHeight / 2.0f) - (right * farPlaneWidth / 2.0f); // far top left
        glm::vec3 ftr = farCenter + (up * farPlaneHeight / 2.0f) + (right * farPlaneWidth / 2.0f); // far top right
        glm::vec3 fbl = farCenter - (up * farPlaneHeight / 2.0f) - (right * farPlaneWidth / 2.0f); // far bottom left
        glm::vec3 fbr = farCenter - (up * farPlaneHeight / 2.0f) + (right * farPlaneWidth / 2.0f); // far bottom right

        glm::vec3 nearCenter = cameraPosition + cameraDirection * clippingPlanes.x;

        glm::vec3 ntl = nearCenter + (up * nearPlaneHeight / 2.0f) - (right * nearPlaneWidth / 2.0f); // near top left
        glm::vec3 ntr = nearCenter + (up * nearPlaneHeight / 2.0f) + (right * nearPlaneWidth / 2.0f); // near top right
        glm::vec3 nbl = nearCenter - (up * nearPlaneHeight / 2.0f) - (right * nearPlaneWidth / 2.0f); // near bottom left
        glm::vec3 nbr = nearCenter - (up * nearPlaneHeight / 2.0f) + (right * nearPlaneWidth / 2.0f); // near bottom right

        topFace = Face(ntr, ntl, ftl);
        bottomFace = Face(nbl, nbr, fbl);
        leftFace = Face(ntl, nbl, fbl);
        rightFace = Face(nbr, ntr, fbr);
        frontFace = Face(ntl, ntr, nbr);
        backFace = Face(ftr, ftl, fbl);
    }

    Frustum::Face::Face(glm::vec3 p0, glm::vec3 p1, glm::vec3 p2)
    {
        position0 = p0;
        position1 = p1;
        position2 = p2;

        v = p1 - p0;
        u = p2 - p0;
        normal = v * u;
        glm::normalize(normal);

        d = glm::dot(-normal, p0);
    }

    Frustum::Face Frustum::GetFrontFace() const
    {
        return frontFace;
    }

    Frustum::Face Frustum::GetBackFace() const
    {
        return backFace;
    }

    Frustum::Face Frustum::GetTopFace() const
    {
        return topFace;
    }

    Frustum::Face Frustum::GetRightFace() const
    {
        return rightFace;
    }

    Frustum::Face Frustum::GetBottomFace() const
    {
        return bottomFace;
    }

    Frustum::Face Frustum::GetLeftFace() const
    {
        return leftFace;
    }
} // namespace Engine