1 files changed, 92 insertions, 0 deletions
diff --git a/intern/cycles/kernel/svm/svm_sky.h b/intern/cycles/kernel/svm/svm_sky.h
new file mode 100644
index 00000000000..dd02cb64cd7
--- /dev/null
+++ b/intern/cycles/kernel/svm/svm_sky.h
@@ -0,0 +1,92 @@
+/*
+ * 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
+
+__device float3 xyY_to_xyz(float x, float y, float Y)
+{
+	float X, Z;
+
+	if(y != 0.0f) X = (x / y) * Y;
+	else X = 0.0f;
+
+	if(y != 0.0f && Y != 0.0f) Z = (1.0f - x - y) / y * Y;
+	else Z = 0.0f;
+
+	return make_float3(X, Y, Z);
+}
+
+__device float3 xyz_to_rgb(float x, float y, float z)
+{
+	return make_float3(3.240479f * x + -1.537150f * y + -0.498535f * z,
+					  -0.969256f * x +  1.875991f * y +  0.041556f * z,
+					   0.055648f * x + -0.204043f * y +  1.057311f * z);
+}
+
+/*
+ * "A Practical Analytic Model for Daylight"
+ * A. J. Preetham, Peter Shirley, Brian Smits
+ */
+
+__device float sky_angle_between(float thetav, float phiv, float theta, float phi)
+{
+	float cospsi = sinf(thetav)*sinf(theta)*cosf(phi - phiv) + cosf(thetav)*cosf(theta);
+	return safe_acosf(cospsi);
+}
+
+__device float sky_perez_function(float lam[5], float theta, float gamma)
+{
+	float ctheta = cosf(theta);
+	float cgamma = cosf(gamma);
+
+	return (1.0f + lam[0]*expf(lam[1]/ctheta)) * (1.0f + lam[2]*expf(lam[3]*gamma)  + lam[4]*cgamma*cgamma);
+}
+
+__device float3 sky_radiance(KernelGlobals *kg, float3 dir)
+{
+	/* convert vector to spherical coordinates */
+	float2 spherical = direction_to_spherical(dir);
+	float theta = spherical.x;
+	float phi = spherical.y;
+
+	/* angle between sun direction and dir */
+	float gamma = sky_angle_between(theta, phi, kernel_data.sunsky.theta, kernel_data.sunsky.phi);
+
+	/* clamp theta to horizon */
+	theta = min(theta, M_PI_2_F - 0.001f);
+
+	/* compute xyY color space values */
+	float x = kernel_data.sunsky.zenith_x * sky_perez_function(kernel_data.sunsky.perez_x, theta, gamma);
+	float y = kernel_data.sunsky.zenith_y * sky_perez_function(kernel_data.sunsky.perez_y, theta, gamma);
+	float Y = kernel_data.sunsky.zenith_Y * sky_perez_function(kernel_data.sunsky.perez_Y, theta, gamma);
+
+	/* convert to RGB */
+	float3 xyz = xyY_to_xyz(x, y, Y);
+	return xyz_to_rgb(xyz.x, xyz.y, xyz.z);
+}
+
+__device void svm_node_tex_sky(KernelGlobals *kg, ShaderData *sd, float *stack, uint dir_offset, uint out_offset)
+{
+	float3 dir = stack_load_float3(stack, dir_offset);
+	float3 f = sky_radiance(kg, dir);
+
+	stack_store_float3(stack, out_offset, f);
+}
+
+CCL_NAMESPACE_END
+