<?php
/*  _____________________
   |                     |
   |  The PHP Raytracer  |
   |                     |
    ~~~~~~~~~~~~~~~~~~~~~
  	This script was intended as a proof of concept.   I don't expect this to be developed 
   any further, much more efficient renderers are out there already.

	This main raytracing functions in this code were based off of a subset of the Povray 
   online documentation which describes how to write a raytracer in the Povray scene 
   descriptive language, SDL.   The povray site is located at:  http://www.povray.org/
	The various other functions came from my mathematics background or the depths of my
   imagination.

	You're free to use this code in any non-commercial way you please, as long as you make
   a point to give me credit for it.
	Output is either as a greyscale jpeg image or as a table.


	author:	Darren Abbey
	date:	07/31/2002
*/

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//=== output controls =========================================================================
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	if ($Output_type =="") {$Output_type = "Table";}		// "Table"/"Jpeg"

	$image_Width		= 80;		// Width/Height = 4/3
	$image_Height		= 60;		//
	
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//=== raytracer control options ===============================================================
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	$max_RecLev 		= 3;
	$bg_Color 		= array( 0,0,0 );
	$max_Dist		= 1000;

	$Font_name		= "render";
		// This name names the css font defined when the table is made.
		//	the option is here to avoid conflict with your other css fonts.
		// This is so the 'pixel' size of the table can be kept small, placing a couple 
		// of "&nbsp;"s to make sure the 'pixels' are relatively square.


	//--- form control --------------------------------------------------------------------
		$Specular_test 	= $_POST['spec'];
		$Diffuse_test 	= $_POST['diff'];
		$Reflection_test 	= $_POST['refl'];
		$s1 			= $_POST['s1'];
		$s2 			= $_POST['s2'];
		$s3 			= $_POST['s3'];
		$s4 			= $_POST['s4'];
		$s5 			= $_POST['s5'];
		$formused		= $_POST['formused'];
	//--- first load control --------------------------------------------------------------
		if ($formused != "true") {
			$Specular_test		= 1;
			$Diffuse_test		= 1;
			$Reflection_test		= 1;
			$s1				= 1;
			$s2				= 1;
			$s3				= 1;
			$s4				= 1;
			$s5				= 1;
		}


//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//=== scene definitions and setup =============================================================
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	// lights:      (X,Y,Z), (dX,dY,dZ), (R,G,B):	location, direction, and color.
	// spheres:	(X,Y,Z), (Radius, Reflection), (R,G,B), (phong_size, phong_amount)
	// ambient:	(R,G,B):	ambient light level/color.
	// camera:	(X,Y,Z):	location. (pointed in +z direction)

$lights_test = array( "lights" => array(
		array( array(-1, 0,-0.5), array(0.8,0.4,0.1) ),
		array( array( 1,-1,-0.5), array(  1,  1,  1) ),
		array( array( 0,-1,   0), array(0.1,0.2,0.5) )
	)
);
//sphere data: <x,y,z>, <radius, reflection>, <r,g,b>, <phong_size, amount>
$spheres = array ();
	if ($s1 == 1) {
		$sphere = array( array( array(-1.05, 0  ,4), array(1  ,0.5), array(1   , 0.5,0.25), array(40,0.8) ) );
		$spheres = $sphere;
	}
	if ($s2 == 1) {
		$sphere = array( array( array( 1.05, 0  ,4), array(1  ,0.5), array(0.5 , 1  ,0.5 ), array(40,0.8) ) );
		$spheres = array_merge($spheres,$sphere);
	}
	if ($s3 == 1) {
		$sphere = array( array( array( 0   , 3  ,5), array(2  ,0.5), array(0.25, 0.5,1   ), array(30,0.4) ) );
		$spheres = array_merge($spheres,$sphere);
	}
	if ($s4 == 1) {
		$sphere = array( array( array(-1   ,-2.3,9), array(2  ,0.5), array(0.5 , 0.3,0.1 ), array(30,0.4) ) );
		$spheres = array_merge($spheres,$sphere);
	}
	if ($s5 == 1) {
		$sphere = array( array( array( 1.3 ,-2.6,9), array(1.8,0.5), array(0.1 , 0.3,0.5 ), array(30,0.4) ) );
		$spheres = array_merge($spheres,$sphere);
	}	
$spheres_test = array ( "spheres" => $spheres );

$ambient_test = array( "ambient" => array( 0.2,0.2,0.2 ) );
$camera_test = array( "camera" => array( 0,0,-3 ) );
$test_scene = array_merge($lights_test, $spheres_test, $ambient_test, $camera_test);

$new_scene = array (
	"lights" => array(
		array( array(-1,0,-0.5), array(0.8,0.4,0.1) ),
		array( array( 1,1,-0.5), array(1  ,1  ,1  ) ),
		array( array( 0,1, 0  ), array(0.1,0.2,0.5) )
	),
	"spheres" => array (
		array( array( 1, 0,4), array(0.5,0), array(1,0,0), array(40,0.8) ),
		array( array(-1, 0,4), array(0.5,0), array(0,1,0), array(40,0.8) ),
		array( array( 0, 1,3), array(0.5,0), array(0,0,1), array(40,0.8) ),
		array( array( 0,-1,3), array(0.5,0), array(1,1,1), array(40,0.8) )
	),
	"ambient" => array( 0.2,0.2,0.2 ),
	"camera" => array( 0,0,-3 )
);

	$scene = $test_scene;
	$obj_Amnt = count( $scene[spheres] );
	$light_Amnt = count( $scene[lights] );
        $ind = 0;
	while( $ind < $light_Amnt ) {	//normalize included light vector directions.
		$nv_val = v_norm( $scene[lights][$ind][0]);
		$scene[lights][$ind][0] = $nv_val;
		$ind += 1;
	}
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//=== vector operations - (vectors are represented by three element arrays) ===================
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   //--- vector addition ---
	function v_add( $inp1, $inp2 ){	//input is two three element arrays, output is one three element array.
		return $output = array( ($inp1[0]+$inp2[0]), ($inp1[1]+$inp2[1]), ($inp1[2]+$inp2[2]) );
	}
   //--- vector subtraction ---
	function v_sub( $inp1, $inp2 ){  //input is two three element arrays, output is one three element array.
		return $output = array( ($inp1[0]-$inp2[0]), ($inp1[1]-$inp2[1]), ($inp1[2]-$inp2[2]) );
	}
   //--- vector multiplication --- //used in diffuse section, seems to do what it's supposed to do.
	function v_mult( $inp1, $inp2 ){
		return $output = array( ($inp1[0]*$inp2[0]), ($inp1[1]*$inp2[1]), ($inp1[2]*$inp2[2]) );
	}
   //--- scalar multiplication ---
	function v_scalarMult( $inp1, $inp2 ){	//input is a three element array and a scaler, output is one three element array.
		return $output = array( ($inp1[0]*$inp2), ($inp1[1]*$inp2), ($inp1[2]*$inp2) );	
	}
   //--- scalar division ---
	function v_scalarDiv( $inp1, $inp2 ){  //input is a three element array and a scaler, output is one three element array.
		return $output = array( ($inp1[0]/$inp2), ($inp1[1]/$inp2), ($inp1[2]/$inp2) );
	}
   //--- cross product ---
	function v_cross( $inp1, $inp2 ){  //input is two three element arrays, output is one three element array.
		return $output = array( ($inp1[1]*$inp2[2] - $inp2[1]*$inp1[2]), ($inp1[2]*$inp2[0] - $inp2[2]*$inp1[0]), ($inp1[0]*$inp2[1] - $inp2[0]*$inp1[1]) );
	}
   //--- dot product ---
	function v_dot( $inp1, $inp2 ){  //input is two three element arrays, scaler output.
		return $output = ($inp1[0]*$inp2[0] + $inp1[1]*$inp2[1] + $inp1[2]*$inp2[2]);
	}
   //--- length of vector ---
	function v_length( $inp ){		//input is a three element array, scaler output.
		return $output = sqrt( pow( $inp[0],2) + pow($inp[1],2) + pow($inp[2],2) );
	}
   //--- normalize vector ---
	function v_norm( $inp ){		//input is a three element array, output is one three element array.
		$v_dist = v_length( $inp );
		return $output = array( ($inp[0]/$v_dist), ($inp[1]/$v_dist), ($inp[2]/$v_dist) );
	}

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//=== ray-sphere intersection =================================================================
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	//sphere data: <x,y,z>, <radius, reflection>, <r,g,b>, <phong_size, amount>
	function calcRaySphereIntersection( $P, $D, $sphereInd ){	//starting point, ray direction, sphere index
		global $scene;
		$C = $scene[spheres][$sphereInd][0];	//--- sphere center.
		$V = v_sub( $P, $C );				
		$R = $scene[spheres][$sphereInd][1][0];	//--- radius of sphere.

		$DV = v_dot( $D, $V );
		$D2 = v_dot( $D, $D );
		$SQ = $DV*$DV - $D2*(v_dot($V,$V)-$R*$R);
		if ($SQ <= 0){
			$output = -1;
		}
		else {
			$SQ		= sqrt($SQ);
			$T1		= (-$DV+$SQ)/$D2;
			$T2		= (-$DV-$SQ)/$D2;
			$output	= min( $T1, $T2 );  
		}
		return $output;
	}
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//=== ray-tracing function ====================================================================
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	function Trace( $P, $D, $reclev ){		// starting point, ray direction, and recursion level.
		global $max_Dist, $obj_Amnt, $light_Amnt, $max_RecLev, $scene, 
			$Specular_test, $Diffuse_test, $Reflection_test;

		$minT = $max_Dist;
		$closest = $obj_Amnt;

		// Find closest intersection:
		$ind = 0;
		while( $ind < $obj_Amnt)
		{	$T = calcRaySphereIntersection( $P, $D, $ind );
			if (($T > 0) and ($T < $minT)) {
				$minT = $T;
				$closest = $ind;
			}
			$ind += 1;
		}
		$ind = 0;

		// If not found, return background color:
		if ($closest == $obj_Amnt)
		{	$Pixel = $bg_Color;
			//$Pixel = array(dechex(rand(0,127)+rand(0,127)), dechex(rand(0,127)+rand(0,127)), dechex(rand(0,127)+rand(0,127)));
		}
		else	// Else calculate the color of the intersection point:
		{	$IP = v_add( $P, v_scalarMult($D,$minT) );
			$R = $scene[spheres][$closest][1][0];
			$Normal = v_scalarDiv( v_sub($IP,$scene[spheres][$closest][0]),$R );

			$V = v_sub( $P, $IP );
			$Refl = v_sub( v_scalarMult($Normal,2*v_dot($Normal,$V)), $V );

			// Lighting:
			$Pixel = $scene[ambient];
			$ind = 0;
			while ($ind < $light_Amnt)
			{	$Light = $scene[lights][$ind][0];

				// Shadowtest:
				$Shadowed = false;
				$ind2 = 0;
				while ($ind2 < $obj_Amnt)
				{	if (($ind2 != $closest) and (calcRaySphereIntersection($IP,$Light,$ind2) > 0))
					{	$Shadowed = true;
						$ind2 = $obj_Amnt;
					}
					$ind2 += 1;
				}
			
				if ($Shadowed == false)
				{	if ($Diffuse_test == 1)		// Diffuse lighting:
					{	$Factor = v_dot($Normal, $Light);
						if ($Factor > 0)
						{	$Pixel = v_add( $Pixel, v_scalarMult( v_mult($scene[lights][$ind][1],$scene[spheres][$closest][2]),$Factor ) );
						}
					}
					if ($Specular_test == 1)	// Specular highlights:
					{	$Factor = v_dot( v_norm($Refl), $Light );
						if ($Factor > 0)
						{	$Pixel = v_add( $Pixel, v_scalarMult( $scene[lights][$ind][1],(pow($Factor,$scene[spheres][$closest][3][0])*$scene[spheres][$closest][3][1])));
						}
					}
				} //if(!Shadowed)
				$ind += 1;
			} //while($ind < $light_Amnt)

			if ($Reflection_test == 1)	// Reflections:
			{	if (($recLev < $max_RecLev) and ($scene[spheres][$closest][1][1] > 0))
				{	$Pixel = v_add( $Pixel,v_scalarMult( Trace($IP, $Refl, $recLev+1), $scene[spheres][$closest][1][1] ) );
				}
			}
		} //else
		return $Pixel;
	}

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//=== calculating the image --- also display image ============================================
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	
	if ($Output_type == "Table")
	{	print("<table><tr><td>\n");
		print("<STYLE TYPE=\"text/css\">\n<!--\nFONT.$Font_name { font-family: Verdana, Arial; font-size: 3px; }\n-->\n</STYLE>");
		print("<table align=middle width=".($image_Width*2)." height=".($image_Height*2)." border=0 cellpadding=0 cellspacing=0>\n");
	}
	elseif ($Output_type == "Jpeg")
	{	Header("Content-Type: image/jpeg");
		$renderR = imagecreate ( $image_Width,$image_Height )
			or die ("Cannot Initialize new GD image stream");
		//greyscale image...
		$ind = 0;
		while ($ind < 256)
		{	imagecolorallocate ($renderR, $ind,$ind,$ind );
			$ind += 1;
		}
	}
	$image_data = array();  
	$indY = 0;
	while ($indY < $image_Height)
	{	$coordY = $indY/($image_Height-1)*2-1;
		$indX = 0;
		while ($indX < $image_Width)
		{	$coordX = ($indX/($image_Width-1)-0.5)*2*$image_Width/$image_Height;
			$Pf = Trace( $scene[camera], array( $coordX,$coordY, 3), 1);
			array_push( $image_data, $Pf_rgb );

			if ($Output_type == "Table")
			{	print("<td bgcolor=#".(dechex( min( round($Pf[0]*256),255 ) ).dechex( min( round($Pf[1]*256),255 ) ).dechex( min( round($Pf[2]*256),255 ) )).">");
				print("<font class=\"".$Font_name."\">&nbsp;&nbsp;&nbsp;&nbsp;</font></td>");
			}
			elseif ($Output_type == "Jpeg")
			{	$color = (int)((min( round($Pf[0]*256),255 ) + min( round($Pf[1]*256),255 ) + min( round($Pf[2]*256),255 ))/3);
				imagesetpixel ( $renderR,$indX,$indY, $color );
			}
			$indX += 1;
		}
		if ($Output_type == "Table")
		{	print("</tr>");
		}
		$indY += 1;
	}
	if ($Output_type == "Table")
	{	print("</table>\n");
		print("</td><td>\n");
		?>
		<table>
		<tr><td align="top"><font class="text">
		<form method="post" action="">
		<input type="checkbox" name="s1" value="1" <?php if($s1==1){echo"checked";}?>>middle left sphere<br>
		<input type="checkbox" name="s2" value="1" <?php if($s2==1){echo"checked";}?>>middle right sphere<br>
		<input type="checkbox" name="s3" value="1" <?php if($s3==1){echo"checked";}?>>bottom sphere<br>
		<input type="checkbox" name="s4" value="1" <?php if($s4==1){echo"checked";}?>>top left sphere<br>
		<input type="checkbox" name="s5" value="1" <?php if($s5==1){echo"checked";}?>>top right sphere<br><br>
		<input type="checkbox" name="spec" value="1" <?php if($Specular_test==1){echo"checked";}?>>specular highlights<br>
		<input type="checkbox" name="diff" value="1" <?php if($Diffuse_test==1){echo"checked";}?>>diffuse lighting<br>
		<input type="checkbox" name="refl" value="1" <?php if($Reflection_test==1){echo"checked";}?>>reflections<br>
		<input type="hidden" name="formused" value="true"><br>
		<input type="submit" name="submit" value="Render">
		</form></font>
		</td></tr>
		</table>
		</td></tr>
		</table>
		<?php
	}
	elseif ($Output_type == "Jpeg")
	{	ImageJpeg($renderR);
		ImageDestroy($renderR);
	}
?>