Cycles: Nishita Sky: Fix sun disk imprecision for large elevation

The issue was introduced by rBad5e3d30a2d2 which made possible to use
unbounded elevation angle.

In order to not touch the shading code, we just remap the value to the
expected range the shading code expects. This means that elevation angles
above +/-PI/2 effectively flip the sun rotation angle.

1 files changed, 16 insertions, 2 deletions

diff --git a/intern/cycles/blender/shader.cpp b/intern/cycles/blender/shader.cpp
index 81a64457c88..4218a9a8a68 100644
--- a/intern/cycles/blender/shader.cpp
+++ b/intern/cycles/blender/shader.cpp
@@ -928,8 +928,22 @@ static ShaderNode *add_node(Scene *scene,
     sky->set_sun_disc(b_sky_node.sun_disc());
     sky->set_sun_size(b_sky_node.sun_size());
     sky->set_sun_intensity(b_sky_node.sun_intensity());
-    sky->set_sun_elevation(b_sky_node.sun_elevation());
-    sky->set_sun_rotation(b_sky_node.sun_rotation());
+    /* Patch sun position to be able to animate daylight cycle while keeping the shading code
+     * simple. */
+    float sun_rotation = b_sky_node.sun_rotation();
+    /* Wrap into [-2PI..2PI] range. */
+    float sun_elevation = fmodf(b_sky_node.sun_elevation(), M_2PI_F);
+    /* Wrap into [-PI..PI] range. */
+    if (fabsf(sun_elevation) >= M_PI_F) {
+      sun_elevation -= copysignf(2.0f, sun_elevation) * M_PI_F;
+    }
+    /* Wrap into [-PI/2..PI/2] range while keeping the same absolute position. */
+    if (sun_elevation >= M_PI_2_F || sun_elevation <= -M_PI_2_F) {
+      sun_elevation = copysignf(M_PI_F, sun_elevation) - sun_elevation;
+      sun_rotation += M_PI_F;
+    }
+    sky->set_sun_elevation(sun_elevation);
+    sky->set_sun_rotation(sun_rotation);
     sky->set_altitude(b_sky_node.altitude());
     sky->set_air_density(b_sky_node.air_density());
     sky->set_dust_density(b_sky_node.dust_density());