SCR_TerrainHelper.c

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class SCR_TerrainHelper
{
    protected static const float MAX_TRACE_LENGTH = 100; //--- How far to search for geometry below given position
 
    //------------------------------------------------------------------------------------------------
    static float GetTerrainY(vector pos, BaseWorld world = null, bool noUnderwater = false, TraceParam trace = null)
    {
        if (!world)
            world = GetGame().GetWorld();
        if (!world)
            return 0;
 
        float surfaceY;
        if (trace)
        {
            trace.Start = pos;
            trace.End = Vector(pos[0], pos[1] - MAX_TRACE_LENGTH, pos[2]);
            
            if (trace.Flags == 0)
                trace.Flags = TraceFlags.WORLD | TraceFlags.ENTS;
            
            float traceCoef = world.TraceMove(trace, null);
            if (traceCoef < 1)
                surfaceY = trace.Start[1] - (trace.Start[1] - trace.End[1]) * traceCoef;
        }
        
        if (surfaceY == 0)
            surfaceY = world.GetSurfaceY(pos[0], pos[2]);
        
        if (noUnderwater)
            surfaceY = Math.Max(surfaceY, 0);
        
        return surfaceY;
    }
 
    //------------------------------------------------------------------------------------------------
    static float GetHeightAboveTerrain(vector pos, BaseWorld world = null, bool noUnderwater = false, TraceParam trace = null)
    {
        return pos[1] - GetTerrainY(pos, world, noUnderwater, trace);
    }
 
    //------------------------------------------------------------------------------------------------
    static vector GetTerrainNormal(inout vector pos, BaseWorld world = null, bool noUnderwater = false, TraceParam trace = null)
    {
        //--- Get world
        if (!world)
            world = GetGame().GetWorld();
 
        if (!world)
            return vector.Zero;
        
        //--- Trace defined, use it to calculate intersection
        if (trace)
        {
            //--- Make sure that trace does not start underground
            pos[1] = Math.Max(pos[1], world.GetSurfaceY(pos[0], pos[2]) + 0.01);
            
            trace.Start = pos;
            trace.End = Vector(pos[0], pos[1] - MAX_TRACE_LENGTH, pos[2]);
            
            if (trace.Flags == 0)
                trace.Flags = TraceFlags.WORLD | TraceFlags.ENTS;
            
            float traceCoef = world.TraceMove(trace, null);
            if (traceCoef < 1)
            {
                pos[1] = trace.Start[1] - (trace.Start[1] - trace.End[1]) * traceCoef;
                if (noUnderwater && pos[1] < world.GetOceanBaseHeight())
                {
                    //--- Underwater, use ocean surface normal (always up)
                    pos[1] = Math.Max(pos[1], world.GetOceanBaseHeight());
                    return vector.Up;
                }
                return trace.TraceNorm;
            }
            return vector.Up; //--- Default is up, not zero, as that could break calculations like vector.Dot
        }
        
        //--- Simplified calculation without custom trace
        float surfaceY = world.GetSurfaceY(pos[0], pos[2]);
        if (noUnderwater && surfaceY < world.GetOceanBaseHeight())
        {
            pos[1] = Math.Max(surfaceY, world.GetOceanBaseHeight());
            return vector.Up;
        }
        
        //--- Get surface normal
        pos[1] = surfaceY;
        TraceParam traceRef = new TraceParam();
        traceRef.Start = pos + vector.Up;
        traceRef.End = pos - vector.Up;
        traceRef.Flags = TraceFlags.WORLD;
        world.TraceMove(traceRef, null);
 
        return traceRef.TraceNorm;
    }
 
    //------------------------------------------------------------------------------------------------
    static bool GetTerrainBasis(vector pos, out vector result[4], BaseWorld world = null, bool noUnderwater = false, TraceParam trace = null)
    {
        vector normal = GetTerrainNormal(pos, world, noUnderwater, trace);
        if (normal == vector.Zero)
            return false;
 
        //--- Get basis matrix
        vector perpend = normal.Perpend();
        Math3D.DirectionAndUpMatrix(perpend, normal, result);
 
        //--- Rotate the matrix to always point North
        vector basis[4];
        Math3D.AnglesToMatrix(Vector(-perpend.VectorToAngles()[0], 0, 0), basis);
        Math3D.MatrixMultiply3(result, basis, result);
 
        //--- Set terrain position
        result[3] = pos;
 
        return true;
    }
 
    //------------------------------------------------------------------------------------------------
    static bool SnapToTerrain(out vector transform[4], BaseWorld world = null, bool noUnderwater = false, TraceParam trace = null)
    {
        //--- Get world
        if (!world)
            world = GetGame().GetWorld();
 
        if (!world)
            return false;
 
        //--- Get surface basis
        vector surfaceBasis[4];
        if (!GetTerrainBasis(transform[3], surfaceBasis, world, noUnderwater, trace))
            return false;
 
        //--- Set position to surface
        transform[3] = surfaceBasis[3];
        return true;
    }
 
    //------------------------------------------------------------------------------------------------
    static bool OrientToTerrain(out vector transform[4], BaseWorld world = null, bool noUnderwater = false, TraceParam trace = null)
    {
        //--- Get world
        if (!world)
            world = GetGame().GetWorld();
 
        if (!world)
            return false;
 
        //--- Get surface basis
        vector surfaceBasis[4];
        if (!GetTerrainBasis(transform[3], surfaceBasis, world, noUnderwater, trace))
            return false;
 
        //--- Reset pitch and roll, but preserve yaw
        //vector angles = Math3D.MatrixToAngles(transform);
        //Math3D.AnglesToMatrix(Vector(angles[0], 0, 0), transform);
 
        //--- Combine surface and entity transformations
        Math3D.MatrixMultiply3(surfaceBasis, transform, transform);
 
        return true;
    }
 
    //------------------------------------------------------------------------------------------------
    static bool SnapAndOrientToTerrain(out vector transform[4], BaseWorld world = null, bool noUnderwater = false, TraceParam trace = null)
    {
        //--- Get world
        if (!world)
            world = GetGame().GetWorld();
 
        if (!world)
            return false;
 
        //--- Get surface basis
        vector surfaceBasis[4];
        if (!GetTerrainBasis(transform[3], surfaceBasis, world, noUnderwater, trace))
            return false;
 
        //--- Set position to surface
        transform[3] = surfaceBasis[3];
 
        //--- Reset pitch and roll, but preserve yaw
        //vector angles = Math3D.MatrixToAngles(transform);
        //Math3D.AnglesToMatrix(Vector(angles[0], 0, 0), transform);
 
        //--- Combine surface and entity transformations
        Math3D.MatrixMultiply3(surfaceBasis, transform, transform);
 
        return true;
    }
};