public function render() {
 
        // find which map block the camera is in
 
        $cameraBlockX = $this->camX >> 6;
        $cameraBlockY = $this->camY >> 6;
 
        $offset = 0;
 
        // clamp angle for lookup tables
 
        if ($this->camAngle < 0)        $this->camAngle += pi() * 2;
        if ($this->camAngle > pi() * 2) $this->camAngle -= pi() * 2;
 
        $angle = $this->camAngle + $this->camFov * 0.5;
        if ($angle > pi() * 2) $angle -= pi() * 2;
 
        $width = $this->width;
 
        $this->camPCentre = $this->height / 2 - $this->camRoll;
 
        $ang = ($this->camAngle * $this->divisor) | 0;
 
        $invertZ = 64 - $this->camZ;
 
        // loop through each vertical strip
 
        while ($width-- > 0) {
 
            // set nearest face to practical infinity
 
            $nearestFace = 4294967296;
 
            $angleLookup = ($angle * $this->divisor);
 
            // find oriented face aligned to X axis of map
 
            $x = $cameraBlockX;
            $y = $cameraBlockY;
 
            if ($this->sin[$angleLookup] < 0) {
 
                while ($y > -1 && $x > -1 && $x < $this->mapWidth) {
                    $absY = $y << 6;
                    $absX = $this->camX + ($absY - $this->camY) / $this->tan[$angleLookup];
                    $x    = $absX >> 6;
 
                    // check if there is a block here
 
                    if ($this->map[$x][--$y]) {
                        $nearestFace = pow($absX - $this->camX, 2) + pow($absY - $this->camY, 2);
                        $offset = $absX & 63;
                        break;
                    }
                }
 
            } else {
 
                while ($y++ < $this->mapHeight && $x > -1 && $x < $this->mapWidth) {
                    $absY = $y << 6;
                    $absX = $this->camX + ($absY - $this->camY) / $this->tan[$angleLookup];
                    $x    = $absX >> 6;
 
                    // check if there is a block here
 
                    if ($this->map[$x][$y]) {
                        $nearestFace = pow($absX - $this->camX, 2) + pow($absY - $this->camY, 2);
                        $offset = 64 - $absX & 63;
                        break;
                    }
                }
 
            }
 
            // find closest face oriented to Y axis of map
 
            $x = $cameraBlockX;
            $y = $cameraBlockY;
 
            if ($this->cos[$angleLookup] < 0) {
 
                while ($x > -1 && $y > -1 && $y < $this->mapHeight) {
                    $absX = $x << 6;
                    $absY = $this->camY + ($absX - $this->camX) * $this->tan[$angleLookup];
                    $y    = $absY >> 6;
 
                    // check if there is a block here
 
                    if ($this->map[--$x][$y]) {
                        $distance = pow($absX - $this->camX, 2) + pow($absY - $this->camY, 2);
 
                        if ($distance < $nearestFace) {
                            $nearestFace = $distance;
                            $offset = 64 - $absY & 63;
                        }
                        break;
                    }
                }
 
            } else {
 
                while ($x++ < $this->mapWidth && $y > -1 && $y < $this->mapHeight) {
                    $absX = $x << 6;
                    $absY = $this->camY + ($absX - $this->camX) * $this->tan[$angleLookup];
                    $y    = $absY >> 6;
 
                    // check if there is a block here
 
                    if ($this->map[$x][$y]) {
                        $distance = pow($absX - $this->camX, 2) + pow($absY - $this->camY, 2);
 
                        if ($distance < $nearestFace) {
                            $nearestFace = $distance;
                            $offset = $absY & 63;
                        }
                        break;
                    }
                }
 
            }
 
            // check whether the current strip is looking left or right of centre angle
 
            if ($angleLookup < $ang)    {
                $distort = $this->camDistance / $this->cos[7200 + $angleLookup - $ang];
            } else {
                $distort = $this->camDistance / $this->cos[$angleLookup - $ang];
            }
 
            $wallHeight = $distort / sqrt($nearestFace);
 
            $distanceFloor   = $invertZ * $distort;
            $distanceCeiling = $this->camZ * $distort;
 
            $floorLevel = (int) ($this->camPCentre + $wallHeight * $this->camZ + 0.5);
            $wallLevel  = (int) ($this->camPCentre - $wallHeight * $invertZ);
 
            $height = $this->height;
 
            // draw floor
 
            while (--$height > $floorLevel && $height >= 0) {
                $distance = $distanceFloor / ($height - $this->camPCentre);
                imagesetpixel($this->canvas, $width, $height, imagecolorat($this->texFloor, ($this->camX + $this->cos[$angleLookup] * $distance) & 63, ($this->camY + $this->sin[$angleLookup] * $distance) & 63));
            }
 
            // draw wall
 
            while (--$height > $wallLevel && $height >= 0) {
                imagesetpixel($this->canvas, $width, $height, imagecolorat($this->texWall, $offset, ($height - $wallLevel) / $wallHeight));
            }
 
            // draw ceiling
 
            while (--$height > -1) {
                $distance = $distanceCeiling / ($this->camPCentre - $height);
                imagesetpixel($this->canvas, $width, $height, imagecolorat($this->texCeil, ($this->camX + $this->cos[$angleLookup] * $distance) & 63, ($this->camY + $this->sin[$angleLookup] * $distance) & 63));
            }
 
            $angle -= $this->camPerRayAngle;
 
            if ($angle < 0) $angle += pi() * 2;
        }
    }