Cycles: Implement camera zoom motion blur

Works totally similar to camera motion blur and majority of the changes are
related on just passing extra arguments to sync() functions.

Couple of things still to look into:

- Motion pass will not include motion caused by the zoom.
- Only perspective cameras are supported currently.
- Motion is being interpolated on projected coordinates, which might give
  different results from constructing projection matrix from interpolated
  field of view.

  This could be good enough for us, but we need to consider improving this
  at some point.

Reviewers: juicyfruit, dingto

Reviewed By: dingto

Differential Revision: https://developer.blender.org/D1383

1 files changed, 76 insertions, 26 deletions

diff --git a/intern/cycles/blender/blender_camera.cpp b/intern/cycles/blender/blender_camera.cpp
index 90b42ea4ec2..18e9aa8bc17 100644
--- a/intern/cycles/blender/blender_camera.cpp
+++ b/intern/cycles/blender/blender_camera.cpp
@@ -244,8 +244,11 @@ static Transform blender_camera_matrix(const Transform& tfm,
 	return transform_clear_scale(result);
 }
 
-static void blender_camera_viewplane(BlenderCamera *bcam, int width, int height,
-	BoundBox2D *viewplane, float *aspectratio, float *sensor_size)
+static void blender_camera_viewplane(BlenderCamera *bcam,
+                                     int width, int height,
+                                     BoundBox2D *viewplane,
+                                     float *aspectratio,
+                                     float *sensor_size)
 {
 	/* dimensions */
 	float xratio = (float)width*bcam->pixelaspect.x;
@@ -258,24 +261,34 @@ static void blender_camera_viewplane(BlenderCamera *bcam, int width, int height,
 	/* sensor fitting */
 	if(bcam->sensor_fit == BlenderCamera::AUTO) {
 		horizontal_fit = (xratio > yratio);
-		*sensor_size = bcam->sensor_width;
+		if(sensor_size != NULL) {
+			*sensor_size = bcam->sensor_width;
+		}
 	}
 	else if(bcam->sensor_fit == BlenderCamera::HORIZONTAL) {
 		horizontal_fit = true;
-		*sensor_size = bcam->sensor_width;
+		if(sensor_size != NULL) {
+			*sensor_size = bcam->sensor_width;
+		}
 	}
 	else {
 		horizontal_fit = false;
-		*sensor_size = bcam->sensor_height;
+		if(sensor_size != NULL) {
+			*sensor_size = bcam->sensor_height;
+		}
 	}
 
 	if(horizontal_fit) {
-		*aspectratio = xratio/yratio;
+		if(aspectratio != NULL) {
+			*aspectratio = xratio/yratio;
+		}
 		xaspect = *aspectratio;
 		yaspect = 1.0f;
 	}
 	else {
-		*aspectratio = yratio/xratio;
+		if(aspectratio != NULL) {
+			*aspectratio = yratio/xratio;
+		}
 		xaspect = 1.0f;
 		yaspect = *aspectratio;
 	}
@@ -284,31 +297,37 @@ static void blender_camera_viewplane(BlenderCamera *bcam, int width, int height,
 	if(bcam->type == CAMERA_ORTHOGRAPHIC) {
 		xaspect = xaspect*bcam->ortho_scale/(*aspectratio*2.0f);
 		yaspect = yaspect*bcam->ortho_scale/(*aspectratio*2.0f);
-		*aspectratio = bcam->ortho_scale/2.0f;
+		if(aspectratio != NULL) {
+			*aspectratio = bcam->ortho_scale/2.0f;
+		}
 	}
 
 	if(bcam->type == CAMERA_PANORAMA) {
 		/* set viewplane */
-		*viewplane = bcam->pano_viewplane;
+		if(viewplane != NULL) {
+			*viewplane = bcam->pano_viewplane;
+		}
 	}
 	else {
 		/* set viewplane */
-		viewplane->left = -xaspect;
-		viewplane->right = xaspect;
-		viewplane->bottom = -yaspect;
-		viewplane->top = yaspect;
-
-		/* zoom for 3d camera view */
-		*viewplane = (*viewplane) * bcam->zoom;
-
-		/* modify viewplane with camera shift and 3d camera view offset */
-		float dx = 2.0f*(*aspectratio*bcam->shift.x + bcam->offset.x*xaspect*2.0f);
-		float dy = 2.0f*(*aspectratio*bcam->shift.y + bcam->offset.y*yaspect*2.0f);
-
-		viewplane->left += dx;
-		viewplane->right += dx;
-		viewplane->bottom += dy;
-		viewplane->top += dy;
+		if(viewplane != NULL) {
+			viewplane->left = -xaspect;
+			viewplane->right = xaspect;
+			viewplane->bottom = -yaspect;
+			viewplane->top = yaspect;
+
+			/* zoom for 3d camera view */
+			*viewplane = (*viewplane) * bcam->zoom;
+
+			/* modify viewplane with camera shift and 3d camera view offset */
+			float dx = 2.0f*(*aspectratio*bcam->shift.x + bcam->offset.x*xaspect*2.0f);
+			float dy = 2.0f*(*aspectratio*bcam->shift.y + bcam->offset.y*yaspect*2.0f);
+
+			viewplane->left += dx;
+			viewplane->right += dx;
+			viewplane->bottom += dy;
+			viewplane->top += dy;
+		}
 	}
 }
 
@@ -386,7 +405,10 @@ static void blender_camera_sync(Camera *cam, BlenderCamera *bcam, int width, int
 	cam->motion.pre = cam->matrix;
 	cam->motion.post = cam->matrix;
 	cam->use_motion = false;
+	cam->use_perspective_motion = false;
 	cam->shuttertime = bcam->shuttertime;
+	cam->fov_pre = cam->fov;
+	cam->fov_post = cam->fov;
 
 	/* border */
 	cam->border = bcam->border;
@@ -435,7 +457,10 @@ void BlenderSync::sync_camera(BL::RenderSettings b_render, BL::Object b_override
 	blender_camera_sync(cam, &bcam, width, height);
 }
 
-void BlenderSync::sync_camera_motion(BL::Object b_ob, float motion_time)
+void BlenderSync::sync_camera_motion(BL::RenderSettings b_render,
+                                     BL::Object b_ob,
+                                     int width, int height,
+                                     float motion_time)
 {
 	Camera *cam = scene->camera;
 	BL::Array<float, 16> b_ob_matrix;
@@ -454,6 +479,31 @@ void BlenderSync::sync_camera_motion(BL::Object b_ob, float motion_time)
 			cam->use_motion = true;
 		}
 	}
+
+	if(cam->type == CAMERA_PERSPECTIVE) {
+		BlenderCamera bcam;
+		float aspectratio, sensor_size;
+		blender_camera_init(&bcam, b_render);
+		blender_camera_from_object(&bcam, b_engine, b_ob);
+		blender_camera_viewplane(&bcam,
+		                         width, height,
+		                         NULL,
+		                         &aspectratio,
+		                         &sensor_size);
+		/* TODO(sergey): De-duplicate calculation with camera sync. */
+		float fov = 2.0f * atanf((0.5f * sensor_size) / bcam.lens / aspectratio);
+		if(fov != cam->fov) {
+			VLOG(1) << "Camera " << b_ob.name() << " FOV change detected.";
+			if(motion_time == -1.0f) {
+				cam->fov_pre = fov;
+				cam->use_perspective_motion = true;
+			}
+			else if(motion_time == 1.0f) {
+				cam->fov_post = fov;
+				cam->use_perspective_motion = true;
+			}
+		}
+	}
 }
 
 /* Sync 3D View Camera */