commit fb82549566225f9cb229afaea2fbf577b808e9de
parent ff511972d059f0fc13dc6890b6c185f264cd1309
Author: Vincent Forest <vincent.forest@meso-star.com>
Date: Wed, 21 Sep 2016 16:49:53 +0200
Implement the Beckmann microfacet distribution
Diffstat:
3 files changed, 151 insertions(+), 0 deletions(-)
diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
@@ -52,6 +52,7 @@ set(SSF_FILES_INC
ssf_fresnel_c.h
ssf_microfacet_distribution_c.h)
set(SSF_FILES_SRC
+ ssf_beckmann_distribution.c
ssf_bsdf.c
ssf_bsdf_view.c
ssf_bxdf.c
diff --git a/src/ssf.h b/src/ssf.h
@@ -145,6 +145,9 @@ SSF_API const struct ssf_fresnel_type ssf_fresnel_dielectric_dielectric;
/* Fresnel term between a dielectric and a conductor */
SSF_API const struct ssf_fresnel_type ssf_fresnel_dielectric_conductor;
+/* Beckmann microfacet distribution */
+SSF_API const struct ssf_microfacet_distribution_type ssf_beckmann_distribution;
+
/*******************************************************************************
* BSDF API - Bidirectionnal Scattering Distribution Function. Describes the
* way the light is scattered by a surface with a combination of BxDFs.
@@ -369,6 +372,11 @@ ssf_microfacet_distribution_get_data
(struct ssf_microfacet_distribution* distrib,
void** data);
+SSF_API res_T
+ssf_beckmann_distribution_setup
+ (struct ssf_microfacet_distribution* distrib,
+ const double roughness); /* Must be > 0 */
+
END_DECLS
#endif /* SSF_H */
diff --git a/src/ssf_beckmann_distribution.c b/src/ssf_beckmann_distribution.c
@@ -0,0 +1,142 @@
+/* Copyright (C) |Meso|Star> 2016 (contact@meso-star.com)
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>. */
+
+#include "ssf.h"
+#include "ssf_microfacet_distribution_c.h"
+
+#include <rsys/double3.h>
+#include <rsys/double33.h>
+
+struct beckmann_distribution {
+ double roughness;
+};
+
+/*******************************************************************************
+ * Private functions
+ ******************************************************************************/
+static res_T
+beckmann_distribution_init(struct mem_allocator* allocator, void* distrib)
+{
+ ASSERT(distrib);
+ (void)allocator;
+ ((struct beckmann_distribution*)distrib)->roughness = 1.0;
+ return RES_OK;
+}
+
+static void
+beckmann_distribution_release(void* distrib)
+{ (void)distrib; }
+
+static double
+beckmann_distribution_eval
+ (void* distrib, const double wo[3], const double N[3], const double wh[3])
+{
+ struct beckmann_distribution* beckmann = distrib;
+ double cos_wh_N, cos2_wh_N, sin2_wh_N, cos4_wh_N;
+ double m2;
+ ASSERT(distrib && wo && N && wh);
+ ASSERT(d3_is_normalized(wo) && d3_is_normalized(N) && d3_is_normalized(wh));
+ ASSERT(beckmann->roughness > 0);
+ (void)wo;
+ m2 = beckmann->roughness * beckmann->roughness;
+ cos_wh_N = d3_dot(wh, N);
+ cos2_wh_N = cos_wh_N * cos_wh_N;
+ sin2_wh_N = 1.0 - cos2_wh_N;
+ cos4_wh_N = cos2_wh_N * cos2_wh_N;
+ return exp(-sin2_wh_N / (cos2_wh_N * m2)) / (PI*m2*cos4_wh_N);
+}
+
+static void
+beckmann_distribution_sample
+ (void* distrib,
+ const double u,
+ const double v,
+ const double wo[3],
+ const double N[3],
+ double wh[3],
+ double* pdf)
+{
+ struct beckmann_distribution* beckmann = distrib;
+ double basis[9];
+ double dir[3];
+ double m2;
+ double phi;
+ double rcp_T;
+ double cos_theta_T, sin_theta_T;
+ double cos_theta, sin_theta;
+ double cos2_theta, sin2_theta;
+ ASSERT(u >= 0 && u < 1 && v >= 0 && v < 1 && wh && N && wo);
+ ASSERT(d3_is_normalized(wo) && d3_is_normalized(N));
+ (void)wo;
+
+ m2 = beckmann->roughness * beckmann->roughness;
+ phi = 2.0*PI*u;
+ sin_theta_T = sqrt(-log(v));
+ cos_theta_T = sqrt(1.0/m2);
+ rcp_T = 1.0 / sqrt(cos_theta_T*cos_theta_T + sin_theta_T*sin_theta_T);
+ cos_theta = cos_theta_T * rcp_T;
+ sin_theta = sin_theta_T * rcp_T;
+ cos2_theta = cos_theta * cos_theta;
+ sin2_theta = sin_theta * sin_theta;
+ dir[0] = cos(phi) * sin_theta;
+ dir[1] = sin(phi) * sin_theta;
+ dir[2] = cos_theta;
+ d33_muld3(wh, d33_basis(basis, N), dir);
+ *pdf = exp(-sin2_theta/(cos2_theta*m2)) / (PI*m2*cos_theta*cos2_theta);
+}
+
+static double
+beckmann_distribution_pdf
+ (void* distrib, const double wo[3], const double N[3], const double wh[3])
+{
+ struct beckmann_distribution* beckmann = distrib;
+ double cos_wh_N, cos2_wh_N, sin2_wh_N;
+ double m2;
+ ASSERT(distrib && wo && N && wh);
+ ASSERT(d3_is_normalized(wh) && d3_is_normalized(N));
+ (void)wo;
+ cos_wh_N = d3_dot(wh, N);
+ if(cos_wh_N < 0.0) return 0.0;
+ m2 = beckmann->roughness * beckmann->roughness;
+ cos2_wh_N = cos_wh_N * cos_wh_N;
+ sin2_wh_N = 1.0 - cos2_wh_N;
+ return exp(-sin2_wh_N/(cos2_wh_N*m2)) / (PI * m2 * cos_wh_N * cos2_wh_N);
+}
+
+/*******************************************************************************
+ * Exported symbols
+ ******************************************************************************/
+const struct ssf_microfacet_distribution_type ssf_beckmann_distribution = {
+ beckmann_distribution_init,
+ beckmann_distribution_release,
+ beckmann_distribution_sample,
+ beckmann_distribution_eval,
+ beckmann_distribution_pdf,
+ sizeof(struct beckmann_distribution),
+ ALIGNOF(struct beckmann_distribution)
+};
+
+res_T
+ssf_beckmann_distribution_setup
+ (struct ssf_microfacet_distribution* distrib,
+ const double roughness)
+{
+ if(!distrib || roughness <= 0) return RES_BAD_ARG;
+ if(!MICROFACET_DISTRIBUTION_TYPE_EQ(&distrib->type, &ssf_beckmann_distribution))
+ return RES_BAD_ARG;
+ ((struct beckmann_distribution*)distrib)->roughness = roughness;
+ return RES_OK;
+}
+
