#include <math.h>
#include <jman/ri.h>
#include <jman/camset.h>

#define min(a,b) ((a)<(b)?(a):(b))
#define PI		3.1415926535897932384626433832795


/* PlaceCamera(): establish a viewpoint, viewing direction and orientation
 *    for a scene. This routine must be called before RiWorldBegin().
 *    position: a point giving the camera position
 *    direction: a point giving the camera direction relative to position
 *    roll: an optional rotation of the camera about its direction axis
 */
void PlaceCamera(RtPoint position, RtPoint direction, float roll)
{
	RiIdentity();                 /* Initialize the camera transformation */
	if (roll != 0.0)
		RiRotate(-roll, 0.0, 0.0, 1.0);
	AimZ(direction);
	RiTranslate(-position[0], -position[1], -position[2]);
}

void AimZ(RtPoint direction)
{
	double xzlen, yzlen, yrot, xrot;

	if (direction[0]==0 && direction[1]==0 && direction[2]==0)
		return;
	/*
	* The initial rotation about the y axis is given by the projection of
	* the direction vector onto the x,z plane: the x and z components
	* of the direction.
	*/

	xzlen = sqrt(direction[0]*direction[0]+direction[2]*direction[2]);
	if (xzlen == 0)
		yrot = (direction[1] < 0) ? 180 : 0;
	else
		yrot = 180*acos(direction[2]/xzlen)/PI;

	/*
	* The second rotation, about the x axis, is given by the projection on
	* the y,z plane of the y-rotated direction vector: the original y
	* component, and the rotated x,z vector from above.
	*/

	yzlen = sqrt(direction[1]*direction[1]+xzlen*xzlen);
	xrot = 180*acos(xzlen/yzlen)/PI;       /* yzlen should never be 0 */

	if (xrot != 0.0)
	{
		if (direction[1] > 0)
			RiRotate(xrot, 1.0, 0.0, 0.0);
		else
			RiRotate(-xrot, 1.0, 0.0, 0.0);
	}

	/* The last rotation declared gets performed first */
	if (yrot != 0.0)
	{
		if (direction[0] > 0)
			RiRotate(-yrot, 0.0, 1.0, 0.0);
		else
			RiRotate(yrot, 0.0, 1.0, 0.0);
	}
}

/* FrameCamera(): give physical parameters for a camera.
   Parameters:
    focallength: the "camera's" focal length.
    framewidth:  the width of the film frame
    frameheight: the height of the film frame
*/
void FrameCamera(float focallength, float framewidth, float frameheight)
{
	RtFloat normwidth, normheight;

	/* Focal length of 0 is taken to be an orthographic projection */
	if (focallength != 0.0)
	{
		RiProjection("perspective", RI_NULL);
		normwidth = (framewidth*.5)/focallength;
		normheight = (frameheight*.5)/focallength;
	}
	else
	{
		RiProjection("orthographic", RI_NULL);
		normwidth = framewidth*.5;
		normheight = frameheight*.5;
	}

	RiScreenWindow(-normwidth, normwidth, -normheight, normheight);
}

/* FrameCamera2(): give physical parameters for a camera.
 * Parameters:
 *    focallength: controls the width of the camera's field of view.
 *    framewidth: the width of the film image
 *    frameheight: the height of the film image*/
void FrameCamera2(float focallength, float framewidth, float frameheight)
{
	RtFloat fov;

	/* A nonzero focal length is taken to be a "normal" lens */
	if(focallength != 0.0)
	{
		fov = 2 * atan((min(framewidth,frameheight)*.5)/focallength) * 180.0/3.14159;
		RiProjection("perspective", RI_FOV, (RtPointer)&fov, RI_NULL);
	}
	else
	{
		RiProjection("orthographic", RI_NULL);
	}

	RiFrameAspectRatio((RtFloat)(framewidth/frameheight));
}