shooter/engine/Camera.cpp

//
// Created by Иван Ильин on 14.01.2021.
//

#include "Camera.h"
#include "utils/Log.h"

std::vector<Triangle> &Camera::project(Mesh& mesh, Screen::ViewMode mode) {

    if(!ready) {
        Log::log("Camera::project(): cannot project tris without camera initialization ( Camera::init() ) ");
        return this->triangles;
    }

    if(!mesh.isVisible())
        return this->triangles;

    // Model transform matrix: translate tris in the origin of mesh.
    Matrix4x4 M = Matrix4x4::Translation(mesh.position());
    VM = V * M;

    // We don't want to waste time re-allocating memory every time
    std::vector<Triangle> clippedTriangles, tempBuffer;
    for(auto& t : mesh.triangles()) {

        double dot = t.norm().dot((mesh.position() + t[0] - p_position).normalize());

        if(dot > 0)
            continue;

        Triangle clipped[2];
        // It needs to be cleared because it's reused through iterations. Usually it doesn't free memory.
        clippedTriangles.clear();

        // In the beginning we need to to translate triangle from world coordinate to our camera system:
        // After that we apply clipping for all planes from clipPlanes
        clippedTriangles.emplace_back(t * VM);
        for(auto& plane : clipPlanes)
        {
            while(!clippedTriangles.empty())
            {
                clipped[0] = clippedTriangles.back();
                clipped[1] = clipped[0];
                clippedTriangles.pop_back();
                int additional = plane.clip(clipped[0], clipped[1]);

                for(int i = 0; i < additional; i++)
                    tempBuffer.emplace_back(clipped[i]);
            }
            clippedTriangles.swap(tempBuffer);
        }

        for(auto& clippedTriangle : clippedTriangles) {
            if(mode != Screen::ViewMode::Clipped) {
                clippedTriangle.color = sf::Color(clippedTriangle.color.r * (0.3 * std::abs(dot) + 0.7),
                                                  clippedTriangle.color.g * (0.3 * std::abs(dot) + 0.7),
                                                  clippedTriangle.color.b * (0.3 * std::abs(dot) + 0.7),
                                                  (mode == Screen::ViewMode::Transparency ||
                                                   mode == Screen::ViewMode::Normals) ? 100 : clippedTriangle.color.a);
            }

            // Finally its time to project our clipped colored triangle from 3D -> 2D
            // and transform it's coordinate to screen space (in pixels):
            clippedTriangle *= SP;

            clippedTriangle[0] /= clippedTriangle[0].w();
            clippedTriangle[1] /= clippedTriangle[1].w();
            clippedTriangle[2] /= clippedTriangle[2].w();

            triangles.emplace_back(clippedTriangle);
        }
    }

    return this->triangles;
}

void Camera::init(int width, int height, double fov, double ZNear, double ZFar) {
    // We need to init camera only after creation or changing width, height, fov, ZNear or ZFar.
    // Because here we calculate matrix that does not change during the motion of _objects or camera
    w = width; h = height;
    aspect = (double)width / (double)height;
    P = Matrix4x4::Projection(fov, aspect, ZNear, ZFar);
    S = Matrix4x4::ScreenSpace(width, height);

    SP = S * P; // screen-space-projections matrix

    // This is planes for clipping tris.
    // Motivation: we are not interest in tris that we cannot see.
    clipPlanes.emplace_back(Plane(Point4D{0, 0, 1}, Point4D{0, 0, ZNear})); // near plane
    clipPlanes.emplace_back(Plane(Point4D{0, 0, -1}, Point4D{0, 0, ZFar})); // far plane

    double thetta1 = M_PI*fov*0.5/180.0;
    double thetta2 = atan(aspect*tan(thetta1));
    clipPlanes.emplace_back(Plane(Point4D{-cos(thetta2), 0, sin(thetta2)}, Point4D{0, 0, 0})); // left plane
    clipPlanes.emplace_back(Plane(Point4D{cos(thetta2), 0, sin(thetta2)}, Point4D{0, 0, 0})); // right plane
    clipPlanes.emplace_back(Plane(Point4D{0, cos(thetta1), sin(thetta1)}, Point4D{0, 0, 0})); // down plane
    clipPlanes.emplace_back(Plane(Point4D{0, -cos(thetta1), sin(thetta1)},Point4D{0, 0, 0})); // up plane

    ready = true;
    Log::log("Camera::init(): camera successfully initialized.");
}

std::vector<Triangle> &Camera::sorted() {

    // Sort tris from back to front
    // This is some replacement for Z-buffer
    std::sort(triangles.begin(), triangles.end(), [](Triangle &t1, Triangle &t2)
    {
        std::vector<double> v_z1({t1[0].z(), t1[1].z(), t1[2].z()});
        std::vector<double> v_z2({t2[0].z(), t2[1].z(), t2[2].z()});

        std::sort(v_z1.begin(), v_z1.end());
        std::sort(v_z2.begin(), v_z2.end());

        double a = 1;
        double b = 1;
        double c = 1;

        double z1 = (a*v_z1[0] + b*v_z1[1] + c*v_z1[2]);
        double z2 = (a*v_z2[0] + b*v_z2[1] + c*v_z2[2]);

        return z1 > z2;
    });

    return triangles;
}

void Camera::record() {
    // Cleaning all tris and recalculation of View matrix
    // That is like preparation for new camera shot: we need to set
    // the position of camera and insert new cartridge for photo.
    triangles.clear();
    V = Matrix4x4::View(p_left, p_up, p_lookAt, p_position);
}

void Camera::rotateX(double rx) {
    p_angle = Point4D{p_angle.x() + rx, p_angle.y(), p_angle.z()};
    p_left = Matrix4x4::RotationX(rx) * p_left;
    p_up = Matrix4x4::RotationX(rx) * p_up;
    p_lookAt = Matrix4x4::RotationX(rx) * p_lookAt;
}

void Camera::rotateY(double ry) {
    p_angle = Point4D{p_angle.x(), p_angle.y() + ry, p_angle.z()};
    p_left = Matrix4x4::RotationY(ry) * p_left;
    p_up = Matrix4x4::RotationY(ry) * p_up;
    p_lookAt = Matrix4x4::RotationY(ry) * p_lookAt;
}

void Camera::rotateZ(double rz) {
    p_angle = Point4D{p_angle.x(), p_angle.y(), p_angle.z() + rz};
    p_left = Matrix4x4::RotationZ(rz) * p_left;
    p_up = Matrix4x4::RotationZ(rz) * p_up;
    p_lookAt = Matrix4x4::RotationZ(rz) * p_lookAt;
}

void Camera::rotate(double rx, double ry, double rz) {
    rotateX(rx);
    rotateY(ry);
    rotateZ(rz);

    if(v_attached.empty())
        return;
    for(auto& attached : v_attached)
        attached->rotateRelativePoint(position(), Point4D{rx, ry, rz});

}

void Camera::rotate(const Point4D& r) {
    rotate(r.x(), r.y(), r.z());
}


void Camera::rotate(const Point4D& v, double rv) {
    p_left = Matrix4x4::Rotation(v, rv) * p_left;
    p_up = Matrix4x4::Rotation(v, rv) * p_up;
    p_lookAt = Matrix4x4::Rotation(v, rv) * p_lookAt;

    if(v_attached.empty())
        return;
    for(auto& attached : v_attached)
        attached->rotateRelativePoint(position(), v, rv);
}

void Camera::rotateLeft(double rl) {
    p_angleLeftUpLookAt = Point4D{p_angleLeftUpLookAt.x() + rl, p_angleLeftUpLookAt.y(), p_angleLeftUpLookAt.z()};

    rotate(p_left, rl);

    if(v_attached.empty())
        return;
    for(auto& attached : v_attached)
        attached->rotateRelativePoint(position(), p_left, rl);
}

void Camera::rotateUp(double ru) {
    p_angleLeftUpLookAt = Point4D{p_angleLeftUpLookAt.x(), p_angleLeftUpLookAt.y() + ru, p_angleLeftUpLookAt.z()};
    rotate(p_up, ru);

    if(v_attached.empty())
        return;
    for(auto& attached : v_attached)
        attached->rotateRelativePoint(position(), p_up, ru);
}

void Camera::rotateLookAt(double rlAt) {
    p_angleLeftUpLookAt = Point4D{p_angleLeftUpLookAt.x(), p_angleLeftUpLookAt.y(), p_angleLeftUpLookAt.z() + rlAt};
    rotate(p_lookAt, rlAt);

    if(v_attached.empty())
        return;
    for(auto& attached : v_attached)
        attached->rotateRelativePoint(position(), p_lookAt, rlAt);
}

void Camera::rotateRelativePoint(const Point4D &s, double rx, double ry, double rz) {
    p_angle += Point4D{rx, ry, rz};

    // Translate XYZ by vector r1
    Point4D r1 = p_position - s;
    // In translated coordinate system we rotate camera and position
    Point4D r2 = Matrix4x4::Rotation(rx, ry, rz)*r1;
    rotate(rx, ry, rz);

    // After rotation we translate XYZ by vector -r2 and recalculate position
    p_position = s + r2;

    if(v_attached.empty())
        return;
    for(auto& attached : v_attached)
        attached->rotateRelativePoint(s, Point4D{rx, ry, rz});
}

void Camera::rotateRelativePoint(const Point4D &s, const Point4D &r) {
    rotateRelativePoint(s, r.x(), r.y(), r.z());
}

void Camera::rotateRelativePoint(const Point4D &s, const Point4D &v, double r) {
    // Translate XYZ by vector r1
    Point4D r1 = p_position - s;
    // In translated coordinate system we rotate camera and position
    Point4D r2 = Matrix4x4::Rotation(v, r)*r1;
    rotate(v, r);

    // After rotation we translate XYZ by vector -r2 and recalculate position
    p_position = s + r2;

    if(v_attached.empty())
        return;
    for(auto& attached : v_attached)
        attached->rotateRelativePoint(s, v, r);
}

void Camera::translateToPoint(const Point4D &point) {
    translate(point - p_position);
}