Cycles: Pole merging for spherical stereo

The idea of pole merge is to fade interocular distance after a certain
altitude to zero when altitude goes closer to a pole. This should prevent
annoyances looking up in the sky or down to the bottom.

Works for both panorama and perspective cameras when Spherical Stereo
is enabled.

Reviewers: dfelinto, brecht

Reviewed By: brecht

Subscribers: sebastian_k

Differential Revision: https://developer.blender.org/D1998

1 files changed, 16 insertions, 1 deletions

diff --git a/intern/cycles/kernel/kernel_projection.h b/intern/cycles/kernel/kernel_projection.h
index c1a359e9269..8be6742699a 100644
--- a/intern/cycles/kernel/kernel_projection.h
+++ b/intern/cycles/kernel/kernel_projection.h
@@ -225,7 +225,7 @@ ccl_device float3 spherical_stereo_position(KernelGlobals *kg,
                                             float3 dir,
                                             float3 pos)
 {
-	const float interocular_offset = kernel_data.cam.interocular_offset;
+	float interocular_offset = kernel_data.cam.interocular_offset;
 
 	/* Interocular offset of zero means either non stereo, or stereo without
 	 * spherical stereo.
@@ -234,6 +234,21 @@ ccl_device float3 spherical_stereo_position(KernelGlobals *kg,
 		return pos;
 	}
 
+	if(kernel_data.cam.pole_merge_angle_to > 0.0f) {
+		float3 normalized_direction = normalize(dir);
+		const float pole_merge_angle_from = kernel_data.cam.pole_merge_angle_from,
+		            pole_merge_angle_to = kernel_data.cam.pole_merge_angle_to;
+		float altitude = fabsf(safe_asinf(normalized_direction.z));
+		if(altitude > pole_merge_angle_to) {
+			interocular_offset = 0.0f;
+		}
+		else if(altitude > pole_merge_angle_from) {
+			float fac = (altitude - pole_merge_angle_from) / (pole_merge_angle_to - pole_merge_angle_from);
+			float fade = cosf(fac * M_PI_2_F);
+			interocular_offset *= fade;
+		}
+	}
+
 	float3 up = make_float3(0.0f, 0.0f, 1.0f);
 	float3 side = normalize(cross(dir, up));