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

intern/cycles/blender/blender_camera.cpp

@@ -65,6 +65,9 @@ struct BlenderCamera {
 	bool use_spherical_stereo;
 	float interocular_distance;
 	float convergence_distance;
+	bool use_pole_merge;
+	float pole_merge_angle_from;
+	float pole_merge_angle_to;
 
 	enum { AUTO, HORIZONTAL, VERTICAL } sensor_fit;
 	float sensor_width;
@@ -183,6 +186,10 @@ static void blender_camera_from_object(BlenderCamera *bcam,
 		}
 		bcam->use_spherical_stereo = b_engine.use_spherical_stereo(b_ob);
 
+		bcam->use_pole_merge = b_camera.stereo().use_pole_merge();
+		bcam->pole_merge_angle_from = b_camera.stereo().pole_merge_angle_from();
+		bcam->pole_merge_angle_to = b_camera.stereo().pole_merge_angle_to();
+
 		bcam->ortho_scale = b_camera.ortho_scale();
 
 		bcam->lens = b_camera.lens();
@@ -427,6 +434,10 @@ static void blender_camera_sync(Camera *cam, BlenderCamera *bcam, int width, int
 			cam->stereo_eye = Camera::STEREO_NONE;
 	}
 
+	cam->use_pole_merge = bcam->use_pole_merge;
+	cam->pole_merge_angle_from = bcam->pole_merge_angle_from;
+	cam->pole_merge_angle_to = bcam->pole_merge_angle_to;
+
 	/* anamorphic lens bokeh */
 	cam->aperture_ratio = bcam->aperture_ratio;
 

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));
 

intern/cycles/kernel/kernel_types.h

@@ -909,9 +909,10 @@ typedef struct KernelCamera {
 	float4 equirectangular_range;
 
 	/* stereo */
-	int pad1, pad2;
 	float interocular_offset;
 	float convergence_distance;
+	float pole_merge_angle_from;
+	float pole_merge_angle_to;
 
 	/* matrices */
 	Transform cameratoworld;

intern/cycles/render/camera.cpp

@@ -76,6 +76,9 @@ Camera::Camera()
 	stereo_eye = STEREO_NONE;
 	interocular_distance = 0.065f;
 	convergence_distance = 30.0f * 0.065f;
+	use_pole_merge = false;
+	pole_merge_angle_from = 60.0f * M_PI_F / 180.0f;
+	pole_merge_angle_to = 75.0f * M_PI_F / 180.0f;
 
 	sensorwidth = 0.036f;
 	sensorheight = 0.024f;
@@ -367,6 +370,14 @@ void Camera::device_update(Device *device, DeviceScene *dscene, Scene *scene)
 	}
 
 	kcam->convergence_distance = convergence_distance;
+	if(use_pole_merge) {
+		kcam->pole_merge_angle_from = pole_merge_angle_from;
+		kcam->pole_merge_angle_to = pole_merge_angle_to;
+	}
+	else {
+		kcam->pole_merge_angle_from = -1.0f;
+		kcam->pole_merge_angle_to = -1.0f;
+	}
 
 	/* sensor size */
 	kcam->sensorwidth = sensorwidth;

intern/cycles/render/camera.h

@@ -104,6 +104,9 @@ public:
 	bool use_spherical_stereo;
 	float interocular_distance;
 	float convergence_distance;
+	bool use_pole_merge;
+	float pole_merge_angle_from;
+	float pole_merge_angle_to;
 
 	/* anamorphic lens bokeh */
 	float aperture_ratio;

release/scripts/startup/bl_ui/properties_data_camera.py

@@ -165,7 +165,15 @@ class DATA_PT_camera_stereoscopy(CameraButtonsPanel, Panel):
 
         if is_spherical_stereo:
             col.separator()
-            col.prop(st, "use_spherical_stereo")
+            row = col.row()
+            row.prop(st, "use_spherical_stereo")
+            sub = row.row()
+            sub.active = st.use_spherical_stereo
+            sub.prop(st, "use_pole_merge")
+            row = col.row(align=True)
+            row.active = st.use_pole_merge
+            row.prop(st, "pole_merge_angle_from")
+            row.prop(st, "pole_merge_angle_to")
 
         col.label(text="Pivot:")
         row = col.row()

source/blender/blenkernel/intern/camera.c

@@ -76,6 +76,8 @@ void BKE_camera_init(Camera *cam)
 	/* stereoscopy 3d */
 	cam->stereo.interocular_distance = 0.065f;
 	cam->stereo.convergence_distance = 30.f * 0.065f;
+	cam->stereo.pole_merge_angle_from = DEG2RAD(60.0f);
+	cam->stereo.pole_merge_angle_to = DEG2RAD(75.0f);
 }
 
 void *BKE_camera_add(Main *bmain, const char *name)

source/blender/blenloader/intern/versioning_270.c

@@ -1190,4 +1190,15 @@ void blo_do_versions_270(FileData *fd, Library *UNUSED(lib), Main *main)
 			}
 		}
 	}
+
+	{
+		for (Camera *camera = main->camera.first; camera != NULL; camera = camera->id.next) {
+			if (camera->stereo.pole_merge_angle_from == 0.0f &&
+			    camera->stereo.pole_merge_angle_to == 0.0f)
+			{
+				camera->stereo.pole_merge_angle_from = DEG2RAD(60.0f);
+				camera->stereo.pole_merge_angle_to = DEG2RAD(75.0f);
+			}
+		}
+	}
 }

source/blender/makesdna/DNA_camera_types.h

@@ -53,6 +53,10 @@ typedef struct CameraStereoSettings {
 	short pivot;
 	short flag;
 	short pad;
+	/* Cut-off angle at which interocular distance start to fade down. */
+	float pole_merge_angle_from;
+	/* Cut-off angle at which interocular distance stops to fade down. */
+	float pole_merge_angle_to;
 } CameraStereoSettings;
 
 typedef struct Camera {
@@ -152,6 +156,7 @@ enum {
 /* stereo->flag */
 enum {
 	CAM_S3D_SPHERICAL       = (1 << 0),
+	CAM_S3D_POLE_MERGE      = (1 << 1),
 };
 
 #ifdef __cplusplus

source/blender/makesrna/intern/rna_camera.c

@@ -151,6 +151,24 @@ static void rna_def_camera_stereo_data(BlenderRNA *brna)
 	                         "Render every pixel rotating the camera around the "
 	                         "middle of the interocular distance");
 	RNA_def_property_update(prop, NC_OBJECT | ND_DRAW, NULL);
+
+	prop = RNA_def_property(srna, "use_pole_merge", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", CAM_S3D_POLE_MERGE);
+	RNA_def_property_ui_text(prop, "Use Pole Merge",
+	                         "Fade interocular distance to 0 after the given cutoff angle");
+	RNA_def_property_update(prop, NC_OBJECT | ND_DRAW, NULL);
+
+	prop = RNA_def_property(srna, "pole_merge_angle_from", PROP_FLOAT, PROP_ANGLE);
+	RNA_def_property_range(prop, 0.0f, M_PI / 2.0f);
+	RNA_def_property_ui_text(prop, "Pole Merge Start Angle",
+	                         "Angle at which interocular distance starts to fade to 0");
+	RNA_def_property_update(prop, NC_OBJECT | ND_DRAW, NULL);
+
+	prop = RNA_def_property(srna, "pole_merge_angle_to", PROP_FLOAT, PROP_ANGLE);
+	RNA_def_property_range(prop, 0.0f, M_PI / 2.0f);
+	RNA_def_property_ui_text(prop, "Pole Merge End Angle",
+	                         "Angle at which interocular distance is 0");
+	RNA_def_property_update(prop, NC_OBJECT | ND_DRAW, NULL);
 }
 
 void RNA_def_camera(BlenderRNA *brna)