path: root/StarsEx/Projector.cpp

/*  Starshatter: The Open Source Project
    Copyright (c) 2021-2022, Starshatter: The Open Source Project Contributors
    Copyright (c) 2011-2012, Starshatter OpenSource Distribution Contributors
    Copyright (c) 1997-2006, Destroyer Studios LLC.

    AUTHOR:       John DiCamillo


    OVERVIEW
    ========
    3D Projection Camera class
*/

#ifndef NOMINMAX
#define NOMINMAX
#endif

#include <algorithm>

#include "Projector.h"
#include "Utils.h"

// +--------------------------------------------------------------------+

static const float   CLIP_PLANE_EPSILON   = 0.0001f;
static const double  Z_NEAR               = 1.0;

// +--------------------------------------------------------------------+

static Camera  emergency_cam;

// +--------------------------------------------------------------------+

Projector::Projector(Window* window, Camera* cam)
: camera(cam), infinite(0), depth_scale(1.0f), orthogonal(false), field_of_view(2)
{
    if (!camera)
    camera = &emergency_cam;

    UseWindow(window);
}

Projector::~Projector()
{ }

// +--------------------------------------------------------------------+

void
Projector::UseCamera(Camera* cam)
{
    if (cam)
    camera = cam;
    else
    camera = &emergency_cam;
}

void
Projector::UseWindow(Window* win)
{
    Rect r  = win->GetRect();
    width   = r.w;
    height  = r.h;

    xcenter = (width  / 2.0);
    ycenter = (height / 2.0);

    xclip0  = 0.0f;
    xclip1  = (float) width-0.5f;
    yclip0  = 0.0f;
    yclip1  = (float) height-0.5f;

    SetFieldOfView(field_of_view);
}

void
Projector::SetFieldOfView(double fov)
{
    field_of_view = fov;

    xscreenscale = width  / fov;
    yscreenscale = height / fov;

    maxscale     = std::max(xscreenscale, yscreenscale);

    xangle       = atan(2.0/fov * maxscale/xscreenscale);
    yangle       = atan(2.0/fov * maxscale/yscreenscale);
}

double
Projector::GetFieldOfView() const
{
    return field_of_view;
}

void
Projector::SetDepthScale(float scale)
{
    depth_scale = scale;
}

double
Projector::GetDepthScale() const
{
    return depth_scale;
}

int
Projector::SetInfinite(int i)
{
    int old = infinite;
    infinite = i;
    return old;
}

// +--------------------------------------------------------------------+

void
Projector::StartFrame()
{
    SetUpFrustum();
    SetWorldSpace();
}

// +--------------------------------------------------------------------+
// Transform a point from worldspace to viewspace.
// +--------------------------------------------------------------------+

void
Projector::Transform(Vec3& vec) const
{
    Vec3 tvert = vec;

    // Translate into a viewpoint-relative coordinate
    if (!infinite)
    tvert -= camera->Pos();

    // old method:
    vec.x = (tvert * camera->vrt());
    vec.y = (tvert * camera->vup());
    vec.z = (tvert * camera->vpn());

    // Rotate into the view orientation
    // vec = tvert * camera->Orientation();
}

// +--------------------------------------------------------------------+
// Transform a point from worldspace to viewspace.
// +--------------------------------------------------------------------+

void
Projector::Transform(Point& point) const
{
    Point tvert = point;

    // Translate into a viewpoint-relative coordinate
    if (!infinite)
    tvert -= camera->Pos();

    // old method:
    point.x = (tvert * camera->vrt());
    point.y = (tvert * camera->vup());
    point.z = (tvert * camera->vpn());

    // Rotate into the view orientation
    // point = tvert * camera->Orientation();
}

// +--------------------------------------------------------------------+
// APPARENT RADIUS OF PROJECTED OBJECT
// Project a viewspace point into screen coordinates.
// Use projected Z to determine apparent radius of object.
// +--------------------------------------------------------------------+

float
Projector::ProjectRadius(const Vec3& v, float radius) const
{
    return (float) fabs((radius * maxscale) / v.z);
}

// +--------------------------------------------------------------------+
// IN PLACE PROJECTION OF POINT
// Project a viewspace point into screen coordinates.
// Note that the y axis goes up in worldspace and viewspace, but
// goes down in screenspace.
// +--------------------------------------------------------------------+

void
Projector::Project(Vec3& v, bool clamp) const
{
    double  zrecip;

    if (orthogonal) {
        double scale = field_of_view/2;
        v.x  = (float)           (xcenter + scale * v.x);
        v.y  = (float) (height - (ycenter + scale * v.y));
        v.z  = (float) (0.0f);
    }

    else {
        //zrecip = 2 * (1.0e5 / (1.0e5-1)) / v.z;
        //zrecip = 2 * 0.97 / v.z; -- what the heck was this version used for?

        zrecip = 2 / v.z;
        v.x  = (float)           (xcenter + maxscale * v.x * zrecip);
        v.y  = (float) (height - (ycenter + maxscale * v.y * zrecip));
        v.z  = (float) (1 - zrecip);
    }

    // clamp the point to the viewport:
    if (clamp) {
        if (v.x < xclip0) v.x = xclip0;
        if (v.x > xclip1) v.x = xclip1;
        if (v.y < yclip0) v.y = yclip0;
        if (v.y > yclip1) v.y = yclip1;
    }
}

// +--------------------------------------------------------------------+
// IN PLACE PROJECTION OF POINT
// Project a viewspace point into screen coordinates.
// Note that the y axis goes up in worldspace and viewspace, but
// goes down in screenspace.
// +--------------------------------------------------------------------+

void
Projector::Project(Point& v, bool clamp) const
{
    double  zrecip;

    if (orthogonal) {
        double scale = field_of_view/2;
        v.x  =           (xcenter + scale * v.x);
        v.y  = (height - (ycenter + scale * v.y));
        v.z  = 0;
    }

    else {
        zrecip = 1 / v.z;
        v.x  =           (xcenter + 2 * maxscale * v.x * zrecip);
        v.y  = (height - (ycenter + 2 * maxscale * v.y * zrecip));
        v.z  = (1 - zrecip);
    }

    // clamp the point to the viewport:
    if (clamp) {
        if (v.x < xclip0) v.x = xclip0;
        if (v.x > xclip1) v.x = xclip1;
        if (v.y < yclip0) v.y = yclip0;
        if (v.y > yclip1) v.y = yclip1;
    }
}

// +--------------------------------------------------------------------+
// IN PLACE UN-PROJECTION OF POINT
// Convert a point in screen coordinates back to viewspace.
// Note that the y axis goes up in worldspace and viewspace, but
// goes down in screenspace.
// +--------------------------------------------------------------------+

void
Projector::Unproject(Point& v) const
{
    double  zrecip = 1 / v.z;

    /***
    * forward projection:
v.x  = (xcenter + maxscale * v.x * zrecip);
v.y  = (height - (ycenter + maxscale * v.y * zrecip));
v.z  = (1 - zrecip);
***/

    v.x  = (         v.x - xcenter) / (maxscale * zrecip);
    v.y  = (height - v.y - ycenter) / (maxscale * zrecip);
}

// +--------------------------------------------------------------------+
// IN PLACE PROJECTION OF RECTANGLE (FOR SPRITES)
// Project a viewspace point into screen coordinates.
// Note that the y axis goes up in worldspace and viewspace, but
// goes down in screenspace.
// +--------------------------------------------------------------------+

void
Projector::ProjectRect(Point& v, double& w, double& h) const
{
    double  zrecip;

    if (orthogonal) {
        double scale = field_of_view/2;
        v.x  =           (xcenter + scale * v.x);
        v.y  = (height - (ycenter + scale * v.y));
        v.z  = 0;
    }

    else {
        zrecip = 1 / v.z;
        v.x  =           (xcenter + 2 * maxscale * v.x * zrecip);
        v.y  = (height - (ycenter + 2 * maxscale * v.y * zrecip));
        v.z  = (1 - Z_NEAR*zrecip);

        w   *= maxscale * zrecip;
        h   *= maxscale * zrecip;
    }
}

// +--------------------------------------------------------------------+
// Set up a clip plane with the specified normal.
// +--------------------------------------------------------------------+

void
Projector::SetWorldspaceClipPlane(Vec3& normal, Plane& plane)
{
    // Rotate the plane normal into worldspace
    ViewToWorld(normal, plane.normal);
    plane.distance = (float) (camera->Pos() * plane.normal + CLIP_PLANE_EPSILON);
}

// +--------------------------------------------------------------------+
// Set up the planes of the frustum, in worldspace coordinates.
// +--------------------------------------------------------------------+

void
Projector::SetUpFrustum()
{
    double  angle, s, c;
    Vec3    normal;

    angle = XAngle();
    s = sin(angle);
    c = cos(angle);

    // Left clip plane
    normal.x = (float) s;
    normal.y = (float) 0;
    normal.z = (float) c;
    view_planes[0].normal   = normal;
    view_planes[0].distance = CLIP_PLANE_EPSILON;
    SetWorldspaceClipPlane(normal, world_planes[0]);

    // Right clip plane
    normal.x = (float) -s;
    view_planes[1].normal   = normal;
    view_planes[1].distance = CLIP_PLANE_EPSILON;
    SetWorldspaceClipPlane(normal, world_planes[1]);

    angle = YAngle();
    s = sin(angle);
    c = cos(angle);

    // Bottom clip plane
    normal.x = (float) 0;
    normal.y = (float) s;
    normal.z = (float) c;
    view_planes[2].normal   = normal;
    view_planes[2].distance = CLIP_PLANE_EPSILON;
    SetWorldspaceClipPlane(normal, world_planes[2]);

    // Top clip plane
    normal.y = (float) -s;
    view_planes[3].normal   = normal;
    view_planes[3].distance = CLIP_PLANE_EPSILON;
    SetWorldspaceClipPlane(normal, world_planes[3]);
}

// +--------------------------------------------------------------------+
// Clip the point against the frustum and return 1 if partially inside
// Return 2 if completely inside
// +--------------------------------------------------------------------+

int
Projector::IsVisible(const Vec3& v, float radius) const
{
    int visible = 1;
    int complete = 1;

    Plane* plane = (Plane*) frustum_planes;
    if (infinite) {
        complete = 0;

        for (int i = 0; visible && (i < NUM_FRUSTUM_PLANES); i++) {
            visible = ((v * plane->normal) >= CLIP_PLANE_EPSILON);
            plane++;
        }
    }
    else {
        for (int i = 0; visible && (i < NUM_FRUSTUM_PLANES); i++) {
            float dot = v * plane->normal;
            visible  = ((dot + radius) >= plane->distance);
            complete = complete && ((dot - radius) >= plane->distance);
            plane++;
        }
    }

    return visible + complete;
}

// +--------------------------------------------------------------------+
// Clip the bouding point against the frustum and return non zero
// if at least partially inside.  This version is not terribly
// efficient as it checks all eight box corners rather than just
// the minimum two.
// +--------------------------------------------------------------------+

int
Projector::IsBoxVisible(const Point* p) const
{
    int   i, j, outside = 0;

    // if all eight corners are outside of the same
    // frustrum plane, then the box is not visible
    Plane* plane = (Plane*) frustum_planes;

    if (infinite) {
        for (i = 0; !outside && (i < NUM_FRUSTUM_PLANES); i++) {
            for (j = 0; j < 8; j++)
            outside += (p[j] * plane->normal) < CLIP_PLANE_EPSILON;

            if (outside < 8)
            outside = 0;

            plane++;
        }
    }
    else {
        for (i = 0; !outside && (i < NUM_FRUSTUM_PLANES); i++) {
            for (j = 0; j < 8; j++)
            outside += (p[j] * plane->normal) < plane->distance;

            if (outside < 8)
            outside = 0;

            plane++;
        }
    }

    // if not outside, then the box is visible
    return !outside;
}

// +--------------------------------------------------------------------+

float
Projector::ApparentRadius(const Vec3& v, float radius) const
{
    Vec3 vloc = v;

    Transform(vloc);                  // transform in place
    return ProjectRadius(vloc, radius);
}


// +--------------------------------------------------------------------+
// Rotate a vector from viewspace to worldspace.
// +--------------------------------------------------------------------+

void
Projector::ViewToWorld(Point& pin, Point& pout)
{
    // Rotate into the world orientation
    pout.x = pin.x * camera->vrt().x + pin.y * camera->vup().x + pin.z * camera->vpn().x;
    pout.y = pin.x * camera->vrt().y + pin.y * camera->vup().y + pin.z * camera->vpn().y;
    pout.z = pin.x * camera->vrt().z + pin.y * camera->vup().z + pin.z * camera->vpn().z;
}

void
Projector::ViewToWorld(Vec3& vin, Vec3& vout)
{
    // Rotate into the world orientation
    vout.x = (float) (vin.x * camera->vrt().x + vin.y * camera->vup().x + vin.z * camera->vpn().x);
    vout.y = (float) (vin.x * camera->vrt().y + vin.y * camera->vup().y + vin.z * camera->vpn().y);
    vout.z = (float) (vin.x * camera->vrt().z + vin.y * camera->vup().z + vin.z * camera->vpn().z);
}