/*
 * Copyright 2011, Blender Foundation.
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

CCL_NAMESPACE_BEGIN

/* Perspective Camera */

__device void camera_sample_perspective(KernelGlobals *kg, float raster_x, float raster_y, float lens_u, float lens_v, Ray *ray)
{
	/* create ray form raster position */
	Transform rastertocamera = kernel_data.cam.rastertocamera;
	float3 Pcamera = transform(&rastertocamera, make_float3(raster_x, raster_y, 0.0f));

	ray->P = make_float3(0.0f, 0.0f, 0.0f);
	ray->D = Pcamera;

	/* modify ray for depth of field */
	float lensradius = kernel_data.cam.lensradius;

	if(lensradius > 0.0f) {
		/* sample point on lens */
		float2 lensuv;

		lensuv = concentric_sample_disk(lens_u, lens_v);
		lensuv *= lensradius;

		/* compute point on plane of focus */
		float ft = kernel_data.cam.focaldistance/ray->D.z;
		float3 Pfocus = ray->P + ray->D*ft;

		/* update ray for effect of lens */
		ray->P = make_float3(lensuv.x, lensuv.y, 0.0f);
		ray->D = normalize(Pfocus - ray->P);
	}

	/* transform ray from camera to world */
	Transform cameratoworld = kernel_data.cam.cameratoworld;

	ray->P = transform(&cameratoworld, ray->P);
	ray->D = transform_direction(&cameratoworld, ray->D);
	ray->D = normalize(ray->D);

#ifdef __RAY_DIFFERENTIALS__
	/* ray differential */
	float3 Ddiff = transform_direction(&cameratoworld, Pcamera);

	ray->dP.dx = make_float3(0.0f, 0.0f, 0.0f);
	ray->dP.dy = make_float3(0.0f, 0.0f, 0.0f);

	ray->dD.dx = normalize(Ddiff + kernel_data.cam.dx) - normalize(Ddiff);
	ray->dD.dy = normalize(Ddiff + kernel_data.cam.dy) - normalize(Ddiff);
#endif

#ifdef __CAMERA_CLIPPING__
	/* clipping */
	ray->P += kernel_data.cam.nearclip*ray->D;
	ray->t = kernel_data.cam.cliplength;
#else
	ray->t = FLT_MAX;
#endif
}

/* Orthographic Camera */

__device void camera_sample_orthographic(KernelGlobals *kg, float raster_x, float raster_y, Ray *ray)
{
	/* create ray form raster position */
	Transform rastertocamera = kernel_data.cam.rastertocamera;
	float3 Pcamera = transform(&rastertocamera, make_float3(raster_x, raster_y, 0.0f));

	ray->P = Pcamera;
	ray->D = make_float3(0.0f, 0.0f, 1.0f);

	/* transform ray from camera to world */
	Transform cameratoworld = kernel_data.cam.cameratoworld;

	ray->P = transform(&cameratoworld, ray->P);
	ray->D = transform_direction(&cameratoworld, ray->D);
	ray->D = normalize(ray->D);

#ifdef __RAY_DIFFERENTIALS__
	/* ray differential */
	ray->dP.dx = kernel_data.cam.dx;
	ray->dP.dy = kernel_data.cam.dy;

	ray->dD.dx = make_float3(0.0f, 0.0f, 0.0f);
	ray->dD.dy = make_float3(0.0f, 0.0f, 0.0f);
#endif

#ifdef __CAMERA_CLIPPING__
	/* clipping */
	ray->t = kernel_data.cam.cliplength;
#else
	ray->t = FLT_MAX;
#endif
}

/* Common */

__device void camera_sample(KernelGlobals *kg, int x, int y, float filter_u, float filter_v, float lens_u, float lens_v, Ray *ray)
{
	/* pixel filter */
	float raster_x = x + kernel_tex_interp(__filter_table, filter_u);
	float raster_y = y + kernel_tex_interp(__filter_table, filter_v);

	/* motion blur */
	//ray->time = lerp(time_t, kernel_data.cam.shutter_open, kernel_data.cam.shutter_close);

	/* sample */
	if(kernel_data.cam.ortho)
		camera_sample_orthographic(kg, raster_x, raster_y, ray);
	else
		camera_sample_perspective(kg, raster_x, raster_y, lens_u, lens_v, ray);
}

CCL_NAMESPACE_END