1 files changed, 263 insertions, 0 deletions
diff --git a/intern/cycles/kernel/kernel_path.h b/intern/cycles/kernel/kernel_path.h
new file mode 100644
index 00000000000..15c7e67f101
--- /dev/null
+++ b/intern/cycles/kernel/kernel_path.h
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+/*
+ * 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.
+ */
+
+#include "kernel_differential.h"
+#include "kernel_montecarlo.h"
+#include "kernel_triangle.h"
+#include "kernel_object.h"
+#ifdef __QBVH__
+#include "kernel_qbvh.h"
+#else
+#include "kernel_bvh.h"
+#endif
+#include "kernel_camera.h"
+#include "kernel_shader.h"
+#include "kernel_light.h"
+#include "kernel_emission.h"
+#include "kernel_random.h"
+
+CCL_NAMESPACE_BEGIN
+
+#ifdef __MODIFY_TP__
+__device float3 path_terminate_modified_throughput(KernelGlobals *kg, __global float3 *buffer, int x, int y, int pass)
+{
+	/* modify throughput to influence path termination probability, to avoid
+	   darker regions receiving fewer samples than lighter regions. also RGB
+	   are weighted differently. proper validation still remains to be done. */
+	const float3 weights = make_float3(1.0f, 1.33f, 0.66f);
+	const float3 one = make_float3(1.0f, 1.0f, 1.0f);
+	const int minpass = 5;
+	const float minL = 0.1f;
+
+	if(pass >= minpass) {
+		float3 L = buffer[x + y*kernel_data.cam.width];
+		float3 Lmin = make_float3(minL, minL, minL);
+		float correct = (float)(pass+1)/(float)pass;
+
+		L = film_map(L*correct, pass);
+
+		return weights/clamp(L, Lmin, one);
+	}
+
+	return weights;
+}
+#endif
+
+__device float path_terminate_probability(KernelGlobals *kg, int bounce, const float3 throughput)
+{
+	if(bounce >= kernel_data.integrator.maxbounce)
+		return 0.0f;
+	else if(bounce <= kernel_data.integrator.minbounce)
+		return 1.0f;
+
+	return average(throughput);
+}
+
+__device int path_flag_from_label(int path_flag, int label)
+{
+	/* reflect/transmit */
+	if(label & LABEL_REFLECT) {
+		path_flag |= PATH_RAY_REFLECT;
+		path_flag &= ~PATH_RAY_TRANSMIT;
+	}
+	else {
+		kernel_assert(label & LABEL_TRANSMIT);
+
+		path_flag |= PATH_RAY_TRANSMIT;
+		path_flag &= ~PATH_RAY_REFLECT;
+	}
+
+	/* diffuse/glossy/singular */
+	if(label & LABEL_DIFFUSE) {
+		path_flag |= PATH_RAY_DIFFUSE;
+		path_flag &= ~(PATH_RAY_GLOSSY|PATH_RAY_SINGULAR);
+	}
+	else if(label & LABEL_GLOSSY) {
+		path_flag |= PATH_RAY_GLOSSY;
+		path_flag &= ~(PATH_RAY_DIFFUSE|PATH_RAY_SINGULAR);
+	}
+	else {
+		kernel_assert(label & (LABEL_SINGULAR|LABEL_STRAIGHT));
+
+		path_flag |= PATH_RAY_SINGULAR;
+		path_flag &= ~(PATH_RAY_DIFFUSE|PATH_RAY_GLOSSY);
+	}
+	
+	/* ray through transparent is still camera ray */
+	if(!(label & LABEL_STRAIGHT))
+		path_flag &= ~PATH_RAY_CAMERA;
+	
+	return path_flag;
+}
+
+__device float3 kernel_path_integrate(KernelGlobals *kg, RNG *rng, int pass, Ray ray, float3 throughput)
+{
+	/* initialize */
+	float3 L = make_float3(0.0f, 0.0f, 0.0f);
+
+#ifdef __EMISSION__
+	float ray_pdf = 0.0f;
+#endif
+	int path_flag = PATH_RAY_CAMERA|PATH_RAY_SINGULAR;
+	int rng_offset = PRNG_BASE_NUM;
+
+	/* path iteration */
+	for(int bounce = 0; ; bounce++, rng_offset += PRNG_BOUNCE_NUM) {
+		/* intersect scene */
+		Intersection isect;
+
+		if(!scene_intersect(kg, &ray, false, &isect)) {
+			/* eval background shader if nothing hit */
+#ifdef __BACKGROUND__
+			ShaderData sd;
+			shader_setup_from_background(kg, &sd, &ray);
+			L += throughput*shader_eval_background(kg, &sd, path_flag);
+			shader_release(kg, &sd);
+#else
+			L += throughputmake_float3(0.8f, 0.8f, 0.8f);
+#endif
+			break;
+		}
+
+		/* setup shading */
+		ShaderData sd;
+		shader_setup_from_ray(kg, &sd, &isect, &ray);
+		float rbsdf = path_rng(kg, rng, pass, rng_offset + PRNG_BSDF);
+		shader_eval_surface(kg, &sd, rbsdf, path_flag);
+
+#ifdef __EMISSION__
+		/* emission */
+		if(kernel_data.integrator.use_emission) {
+			if(sd.flag & SD_EMISSION)
+				L += throughput*indirect_emission(kg, &sd, isect.t, path_flag, ray_pdf);
+
+			/* sample illumination from lights to find path contribution */
+			if((sd.flag & SD_BSDF_HAS_EVAL) &&
+				bounce != kernel_data.integrator.maxbounce) {
+				float light_t = path_rng(kg, rng, pass, rng_offset + PRNG_LIGHT);
+				float light_o = path_rng(kg, rng, pass, rng_offset + PRNG_LIGHT_F);
+				float light_u = path_rng(kg, rng, pass, rng_offset + PRNG_LIGHT_U);
+				float light_v = path_rng(kg, rng, pass, rng_offset + PRNG_LIGHT_V);
+
+				Ray light_ray;
+				float3 light_L;
+
+				if(direct_emission(kg, &sd, light_t, light_o, light_u, light_v, &light_ray, &light_L)) {
+					/* trace shadow ray */
+					if(!scene_intersect(kg, &light_ray, true, &isect))
+						L += throughput*light_L;
+				}
+			}
+		}
+#endif
+
+		/* sample BSDF */
+		float bsdf_pdf;
+		float3 bsdf_eval;
+		float3 bsdf_omega_in;
+		differential3 bsdf_domega_in;
+		float bsdf_u = path_rng(kg, rng, pass, rng_offset + PRNG_BSDF_U);
+		float bsdf_v = path_rng(kg, rng, pass, rng_offset + PRNG_BSDF_V);
+		int label;
+
+		label = shader_bsdf_sample(kg, &sd, bsdf_u, bsdf_v, &bsdf_eval,
+			&bsdf_omega_in, &bsdf_domega_in, &bsdf_pdf);
+
+		shader_release(kg, &sd);
+
+		if(bsdf_pdf == 0.0f || is_zero(bsdf_eval))
+			break;
+
+		/* modify throughput */
+		throughput *= bsdf_eval/bsdf_pdf;
+
+		/* set labels */
+#ifdef __EMISSION__
+		ray_pdf = bsdf_pdf;
+#endif
+
+		path_flag = path_flag_from_label(path_flag, label);
+
+		/* path termination */
+		float probability = path_terminate_probability(kg, bounce, throughput);
+		float terminate = path_rng(kg, rng, pass, rng_offset + PRNG_TERMINATE);
+
+		if(terminate >= probability)
+			break;
+
+		throughput /= probability;
+
+		/* setup ray */
+		ray.P = ray_offset(sd.P, (label & LABEL_TRANSMIT)? -sd.Ng: sd.Ng);
+		ray.D = bsdf_omega_in;
+		ray.t = FLT_MAX;
+#ifdef __RAY_DIFFERENTIALS__
+		ray.dP = sd.dP;
+		ray.dD = bsdf_domega_in;
+#endif
+	}
+
+	return L;
+}
+
+__device void kernel_path_trace(KernelGlobals *kg, __global float4 *buffer, __global uint *rng_state, int pass, int x, int y)
+{
+	/* initialize random numbers */
+	RNG rng;
+
+	float filter_u;
+	float filter_v;
+
+	path_rng_init(kg, rng_state, pass, &rng, x, y, &filter_u, &filter_v);
+
+	/* sample camera ray */
+	Ray ray;
+
+	float lens_u = path_rng(kg, &rng, pass, PRNG_LENS_U);
+	float lens_v = path_rng(kg, &rng, pass, PRNG_LENS_V);
+
+	camera_sample(kg, x, y, filter_u, filter_v, lens_u, lens_v, &ray);
+
+	/* integrate */
+#ifdef __MODIFY_TP__
+	float3 throughput = path_terminate_modified_throughput(kg, buffer, x, y, pass);
+	float3 L = kernel_path_integrate(kg, &rng, pass, ray, throughput)/throughput;
+#else
+	float3 throughput = make_float3(1.0f, 1.0f, 1.0f);
+	float3 L = kernel_path_integrate(kg, &rng, pass, ray, throughput);
+#endif
+
+	/* accumulate result in output buffer */
+	int index = x + y*kernel_data.cam.width;
+
+	float4 result;
+	result.x = L.x;
+	result.y = L.y;
+	result.z = L.z;
+	result.w = 1.0f;
+
+	if(pass == 0)
+		buffer[index] = result;
+	else
+		buffer[index] += result;
+
+	path_rng_end(kg, rng_state, rng, x, y);
+}
+
+CCL_NAMESPACE_END
+