Camera.cpp

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/* Copyright (C) 2010 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * CCamera holds a view and a projection matrix. It also has a frustum
 * which can be used to cull objects for rendering.
 */

#include "precompiled.h"

#include "Camera.h"

#include "graphics/HFTracer.h"
#include "graphics/Terrain.h"
#include "lib/ogl.h"
#include "maths/MathUtil.h"
#include "maths/Vector4D.h"
#include "ps/Game.h"
#include "ps/World.h"
#include "renderer/Renderer.h"
#include "renderer/WaterManager.h"

CCamera::CCamera()
{
    // set viewport to something anything should handle, but should be initialised
    // to window size before use
    m_ViewPort.m_X = 0;
    m_ViewPort.m_Y = 0;
    m_ViewPort.m_Width = 800;
    m_ViewPort.m_Height = 600;
}

CCamera::~CCamera()
{
}

void CCamera::SetProjection(float nearp, float farp, float fov)
{
    m_NearPlane = nearp;
    m_FarPlane = farp;
    m_FOV = fov;

    float aspect = (float)m_ViewPort.m_Width/(float)m_ViewPort.m_Height;
    float f = 1.0f/tanf(m_FOV/2);

    m_ProjMat.SetZero ();
    m_ProjMat._11 = f/aspect;
    m_ProjMat._22 = f;
    m_ProjMat._33 = -(m_FarPlane+m_NearPlane)/(m_NearPlane-m_FarPlane);
    m_ProjMat._34 = 2*m_FarPlane*m_NearPlane/(m_NearPlane-m_FarPlane);
    m_ProjMat._43 = 1.0f;
}

void CCamera::SetProjectionTile(int tiles, int tile_x, int tile_y)
{

    float aspect = (float)m_ViewPort.m_Width/(float)m_ViewPort.m_Height;
    float f = 1.0f/tanf(m_FOV/2);

    m_ProjMat._11 = tiles*f/aspect;
    m_ProjMat._22 = tiles*f;
    m_ProjMat._13 = -(1-tiles + 2*tile_x);
    m_ProjMat._23 = -(1-tiles + 2*tile_y);
}

//Updates the frustum planes. Should be called
//everytime the view or projection matrices are
//altered.
void CCamera::UpdateFrustum(const CBoundingBoxAligned& scissor)
{
    CMatrix3D MatFinal;
    CMatrix3D MatView;

    m_Orientation.GetInverse(MatView);

    MatFinal = m_ProjMat * MatView;

    // get the RIGHT plane
    m_ViewFrustum.SetNumPlanes(6);

    m_ViewFrustum.m_aPlanes[0].m_Norm.X = scissor[1].X*MatFinal._41 - MatFinal._11;
    m_ViewFrustum.m_aPlanes[0].m_Norm.Y = scissor[1].X*MatFinal._42 - MatFinal._12;
    m_ViewFrustum.m_aPlanes[0].m_Norm.Z = scissor[1].X*MatFinal._43 - MatFinal._13;
    m_ViewFrustum.m_aPlanes[0].m_Dist   = scissor[1].X*MatFinal._44 - MatFinal._14;

    // get the LEFT plane
    m_ViewFrustum.m_aPlanes[1].m_Norm.X = -scissor[0].X*MatFinal._41 + MatFinal._11;
    m_ViewFrustum.m_aPlanes[1].m_Norm.Y = -scissor[0].X*MatFinal._42 + MatFinal._12;
    m_ViewFrustum.m_aPlanes[1].m_Norm.Z = -scissor[0].X*MatFinal._43 + MatFinal._13;
    m_ViewFrustum.m_aPlanes[1].m_Dist   = -scissor[0].X*MatFinal._44 + MatFinal._14;

    // get the BOTTOM plane
    m_ViewFrustum.m_aPlanes[2].m_Norm.X = -scissor[0].Y*MatFinal._41 + MatFinal._21;
    m_ViewFrustum.m_aPlanes[2].m_Norm.Y = -scissor[0].Y*MatFinal._42 + MatFinal._22;
    m_ViewFrustum.m_aPlanes[2].m_Norm.Z = -scissor[0].Y*MatFinal._43 + MatFinal._23;
    m_ViewFrustum.m_aPlanes[2].m_Dist   = -scissor[0].Y*MatFinal._44 + MatFinal._24;

    // get the TOP plane
    m_ViewFrustum.m_aPlanes[3].m_Norm.X = scissor[1].Y*MatFinal._41 - MatFinal._21;
    m_ViewFrustum.m_aPlanes[3].m_Norm.Y = scissor[1].Y*MatFinal._42 - MatFinal._22;
    m_ViewFrustum.m_aPlanes[3].m_Norm.Z = scissor[1].Y*MatFinal._43 - MatFinal._23;
    m_ViewFrustum.m_aPlanes[3].m_Dist   = scissor[1].Y*MatFinal._44 - MatFinal._24;

    // get the FAR plane
    m_ViewFrustum.m_aPlanes[4].m_Norm.X = scissor[1].Z*MatFinal._41 - MatFinal._31;
    m_ViewFrustum.m_aPlanes[4].m_Norm.Y = scissor[1].Z*MatFinal._42 - MatFinal._32;
    m_ViewFrustum.m_aPlanes[4].m_Norm.Z = scissor[1].Z*MatFinal._43 - MatFinal._33;
    m_ViewFrustum.m_aPlanes[4].m_Dist   = scissor[1].Z*MatFinal._44 - MatFinal._34;

    // get the NEAR plane
    m_ViewFrustum.m_aPlanes[5].m_Norm.X = -scissor[0].Z*MatFinal._41 + MatFinal._31;
    m_ViewFrustum.m_aPlanes[5].m_Norm.Y = -scissor[0].Z*MatFinal._42 + MatFinal._32;
    m_ViewFrustum.m_aPlanes[5].m_Norm.Z = -scissor[0].Z*MatFinal._43 + MatFinal._33;
    m_ViewFrustum.m_aPlanes[5].m_Dist   = -scissor[0].Z*MatFinal._44 + MatFinal._34;
}

void CCamera::ClipFrustum(const CPlane& clipPlane)
{
    m_ViewFrustum.AddPlane(clipPlane);
}

void CCamera::SetViewPort(const SViewPort& viewport)
{
    m_ViewPort.m_X = viewport.m_X;
    m_ViewPort.m_Y = viewport.m_Y;
    m_ViewPort.m_Width = viewport.m_Width;
    m_ViewPort.m_Height = viewport.m_Height;
}


///////////////////////////////////////////////////////////////////////////////////////////////////////////////
// GetCameraPlanePoints: return four points in camera space at given distance from camera
void CCamera::GetCameraPlanePoints(float dist, CVector3D pts[4]) const
{
    float aspect = float(m_ViewPort.m_Width)/float(m_ViewPort.m_Height);
    float x = dist*aspect*tanf(m_FOV*0.5f);
    float y = dist*tanf(m_FOV*0.5f);

    pts[0].X = -x;
    pts[0].Y = -y;
    pts[0].Z = dist;
    pts[1].X = x;
    pts[1].Y = -y;
    pts[1].Z = dist;
    pts[2].X = x;
    pts[2].Y = y;
    pts[2].Z = dist;
    pts[3].X = -x;
    pts[3].Y = y;
    pts[3].Z = dist;
}

void CCamera::BuildCameraRay(int px, int py, CVector3D& origin, CVector3D& dir) const
{
    CVector3D cPts[4];
    GetCameraPlanePoints(m_FarPlane, cPts);

    // transform to world space
    CVector3D wPts[4];
    for (int i = 0; i < 4; i++)
        wPts[i] = m_Orientation.Transform(cPts[i]);

    // get world space position of mouse point
    float dx = (float)px / (float)g_Renderer.GetWidth();
    float dz = 1 - (float)py / (float)g_Renderer.GetHeight();

    CVector3D vdx = wPts[1] - wPts[0];
    CVector3D vdz = wPts[3] - wPts[0];
    CVector3D pt = wPts[0] + (vdx * dx) + (vdz * dz);

    // copy origin
    origin = m_Orientation.GetTranslation();
    // build direction
    dir = pt - origin;
    dir.Normalize();
}

void CCamera::GetScreenCoordinates(const CVector3D& world, float& x, float& y) const
{
    CMatrix3D transform = m_ProjMat * m_Orientation.GetInverse();

    CVector4D screenspace = transform.Transform(CVector4D(world.X, world.Y, world.Z, 1.0f));

    x = screenspace.X / screenspace.W;
    y = screenspace.Y / screenspace.W;
    x = (x + 1) * 0.5f * g_Renderer.GetWidth();
    y = (1 - y) * 0.5f * g_Renderer.GetHeight();
}

CVector3D CCamera::GetWorldCoordinates(int px, int py, bool aboveWater) const
{
    CHFTracer tracer(g_Game->GetWorld()->GetTerrain());
    int x, z;
    CVector3D origin, dir, delta, terrainPoint, waterPoint;

    BuildCameraRay(px, py, origin, dir);


    bool gotTerrain = tracer.RayIntersect(origin, dir, x, z, terrainPoint);

    if (!aboveWater)
    {
        if (gotTerrain)
            return terrainPoint;

        // Off the edge of the world?
        // Work out where it /would/ hit, if the map were extended out to infinity with average height.
        return GetWorldCoordinates(px, py, 50.0f);
    }

    CPlane plane;
    plane.Set(CVector3D(0.f, 1.f, 0.f),                                     // upwards normal
        CVector3D(0.f, g_Renderer.GetWaterManager()->m_WaterHeight, 0.f));  // passes through water plane

    bool gotWater = plane.FindRayIntersection( origin, dir, &waterPoint );

    // Clamp the water intersection to within the map's bounds, so that
    // we'll always return a valid position on the map
    ssize_t mapSize = g_Game->GetWorld()->GetTerrain()->GetVerticesPerSide();
    if (gotWater)
    {
        waterPoint.X = clamp(waterPoint.X, 0.f, (float)((mapSize-1)*TERRAIN_TILE_SIZE));
        waterPoint.Z = clamp(waterPoint.Z, 0.f, (float)((mapSize-1)*TERRAIN_TILE_SIZE));
    }

    if (gotTerrain)
    {
        if (gotWater)
        {
            // Intersecting both heightmap and water plane; choose the closest of those
            if ((origin - terrainPoint).LengthSquared() < (origin - waterPoint).LengthSquared())
                return terrainPoint;
            else
                return waterPoint;
        }
        else
        {
            // Intersecting heightmap but parallel to water plane
            return terrainPoint;
        }
    }
    else
    {
        if (gotWater)
        {
            // Only intersecting water plane
            return waterPoint;
        }
        else
        {
            // Not intersecting terrain or water; just return 0,0,0.
            return CVector3D(0.f, 0.f, 0.f);
        }
    }

}

CVector3D CCamera::GetWorldCoordinates(int px, int py, float h) const
{
    CPlane plane;
    plane.Set(CVector3D(0.f, 1.f, 0.f), CVector3D(0.f, h, 0.f)); // upwards normal, passes through h

    CVector3D origin, dir, delta, currentTarget;

    BuildCameraRay(px, py, origin, dir);

    if (plane.FindRayIntersection(origin, dir, &currentTarget))
        return currentTarget;

    // No intersection with the infinite plane - nothing sensible can be returned,
    // so just choose an arbitrary point on the plane
    return CVector3D(0.f, h, 0.f);
}

CVector3D CCamera::GetFocus() const
{
    // Basically the same as GetWorldCoordinates

    CHFTracer tracer(g_Game->GetWorld()->GetTerrain());
    int x, z;

    CVector3D origin, dir, delta, terrainPoint, waterPoint;

    origin = m_Orientation.GetTranslation();
    dir = m_Orientation.GetIn();

    bool gotTerrain = tracer.RayIntersect(origin, dir, x, z, terrainPoint);

    CPlane plane;
    plane.Set(CVector3D(0.f, 1.f, 0.f),                                     // upwards normal
        CVector3D(0.f, g_Renderer.GetWaterManager()->m_WaterHeight, 0.f));  // passes through water plane

    bool gotWater = plane.FindRayIntersection( origin, dir, &waterPoint );

    // Clamp the water intersection to within the map's bounds, so that
    // we'll always return a valid position on the map
    ssize_t mapSize = g_Game->GetWorld()->GetTerrain()->GetVerticesPerSide();
    if (gotWater)
    {
        waterPoint.X = clamp(waterPoint.X, 0.f, (float)((mapSize-1)*TERRAIN_TILE_SIZE));
        waterPoint.Z = clamp(waterPoint.Z, 0.f, (float)((mapSize-1)*TERRAIN_TILE_SIZE));
    }

    if (gotTerrain)
    {
        if (gotWater)
        {
            // Intersecting both heightmap and water plane; choose the closest of those
            if ((origin - terrainPoint).LengthSquared() < (origin - waterPoint).LengthSquared())
                return terrainPoint;
            else
                return waterPoint;
        }
        else
        {
            // Intersecting heightmap but parallel to water plane
            return terrainPoint;
        }
    }
    else
    {
        if (gotWater)
        {
            // Only intersecting water plane
            return waterPoint;
        }
        else
        {
            // Not intersecting terrain or water; just return 0,0,0.
            return CVector3D(0.f, 0.f, 0.f);
        }
    }
}

void CCamera::LookAt(const CVector3D& camera, const CVector3D& target, const CVector3D& up)
{
    CVector3D delta = target - camera;
    LookAlong(camera, delta, up);
}

void CCamera::LookAlong(CVector3D camera, CVector3D orientation, CVector3D up)
{
    orientation.Normalize();
    up.Normalize();
    CVector3D s = orientation.Cross(up);

    m_Orientation._11 = -s.X;   m_Orientation._12 = up.X;   m_Orientation._13 = orientation.X;  m_Orientation._14 = camera.X;
    m_Orientation._21 = -s.Y;   m_Orientation._22 = up.Y;   m_Orientation._23 = orientation.Y;  m_Orientation._24 = camera.Y;
    m_Orientation._31 = -s.Z;   m_Orientation._32 = up.Z;   m_Orientation._33 = orientation.Z;  m_Orientation._34 = camera.Z;
    m_Orientation._41 = 0.0f;   m_Orientation._42 = 0.0f;   m_Orientation._43 = 0.0f;           m_Orientation._44 = 1.0f;
}


///////////////////////////////////////////////////////////////////////////////////
// Render the camera's frustum
void CCamera::Render(int intermediates) const
{
#if CONFIG2_GLES
#warning TODO: implement camera frustum for GLES
#else
    CVector3D nearPoints[4];
    CVector3D farPoints[4];

    GetCameraPlanePoints(m_NearPlane, nearPoints);
    GetCameraPlanePoints(m_FarPlane, farPoints);
    for(int i = 0; i < 4; i++)
    {
        nearPoints[i] = m_Orientation.Transform(nearPoints[i]);
        farPoints[i] = m_Orientation.Transform(farPoints[i]);
    }

    // near plane
    glBegin(GL_POLYGON);
        glVertex3fv(&nearPoints[0].X);
        glVertex3fv(&nearPoints[1].X);
        glVertex3fv(&nearPoints[2].X);
        glVertex3fv(&nearPoints[3].X);
    glEnd();

    // far plane
    glBegin(GL_POLYGON);
        glVertex3fv(&farPoints[0].X);
        glVertex3fv(&farPoints[1].X);
        glVertex3fv(&farPoints[2].X);
        glVertex3fv(&farPoints[3].X);
    glEnd();

    // connection lines
    glBegin(GL_QUAD_STRIP);
        glVertex3fv(&nearPoints[0].X);
        glVertex3fv(&farPoints[0].X);
        glVertex3fv(&nearPoints[1].X);
        glVertex3fv(&farPoints[1].X);
        glVertex3fv(&nearPoints[2].X);
        glVertex3fv(&farPoints[2].X);
        glVertex3fv(&nearPoints[3].X);
        glVertex3fv(&farPoints[3].X);
        glVertex3fv(&nearPoints[0].X);
        glVertex3fv(&farPoints[0].X);
    glEnd();

    // intermediate planes
    CVector3D intermediatePoints[4];
    for(int i = 0; i < intermediates; ++i)
    {
        float t = (i+1.0)/(intermediates+1.0);

        for(int j = 0; j < 4; ++j)
            intermediatePoints[j] = nearPoints[j]*t + farPoints[j]*(1.0-t);

        glBegin(GL_POLYGON);
            glVertex3fv(&intermediatePoints[0].X);
            glVertex3fv(&intermediatePoints[1].X);
            glVertex3fv(&intermediatePoints[2].X);
            glVertex3fv(&intermediatePoints[3].X);
        glEnd();
    }
#endif
}