Fix T43346: Window mapping is wrong in preview render

The issue was caused by the whole viewplane used for mapping calculation
which would for sure lead to differences between final camera render and
viewport render from the camera view.

This commit makes it so window texture mapping is the same as final render
when viewing from the camera in viewport render.

It's not totally clear what's the right thing to do when viewport is not
in the camera view mode and that part is left unchanged.

3 files changed, 69 insertions, 20 deletions

diff --git a/intern/cycles/blender/blender_camera.cpp b/intern/cycles/blender/blender_camera.cpp
index e5214fb5c30..16f555cb58c 100644
--- a/intern/cycles/blender/blender_camera.cpp
+++ b/intern/cycles/blender/blender_camera.cpp
@@ -67,6 +67,7 @@ struct BlenderCamera {
 
 	BoundBox2D border;
 	BoundBox2D pano_viewplane;
+	BoundBox2D viewport_camera_border;
 
 	Transform matrix;
 };
@@ -86,6 +87,8 @@ static void blender_camera_init(BlenderCamera *bcam, BL::RenderSettings b_render
 	bcam->border.top = 1.0f;
 	bcam->pano_viewplane.right = 1.0f;
 	bcam->pano_viewplane.top = 1.0f;
+	bcam->viewport_camera_border.right = 1.0f;
+	bcam->viewport_camera_border.top = 1.0f;
 
 	/* render resolution */
 	bcam->full_width = render_resolution_x(b_render);
@@ -365,6 +368,7 @@ static void blender_camera_sync(Camera *cam, BlenderCamera *bcam, int width, int
 
 	/* border */
 	cam->border = bcam->border;
+	cam->viewport_camera_border = bcam->viewport_camera_border;
 
 	/* set update flag */
 	if(cam->modified(prevcam))
@@ -516,6 +520,25 @@ static void blender_camera_view_subset(BL::RenderSettings b_render, BL::Scene b_
 	*cam_box = cam * (1.0f/cam_aspect);
 }
 
+static void blender_camera_border_subset(BL::RenderSettings b_render,
+                                         BL::Scene b_scene,
+                                         BL::SpaceView3D b_v3d,
+                                         BL::RegionView3D b_rv3d,
+                                         BL::Object b_ob,
+                                         int width, int height,
+                                         const BoundBox2D &border,
+                                         BoundBox2D *result)
+{
+	/* Determine camera viewport subset. */
+	BoundBox2D view_box, cam_box;
+	blender_camera_view_subset(b_render, b_scene, b_ob, b_v3d, b_rv3d, width, height,
+	                           &view_box, &cam_box);
+
+	/* Determine viewport subset matching given border. */
+	cam_box = cam_box.make_relative_to(view_box);
+	*result = cam_box.subset(border);
+}
+
 static void blender_camera_border(BlenderCamera *bcam, BL::RenderSettings b_render, BL::Scene b_scene, BL::SpaceView3D b_v3d,
 	BL::RegionView3D b_rv3d, int width, int height)
 {
@@ -534,32 +557,45 @@ static void blender_camera_border(BlenderCamera *bcam, BL::RenderSettings b_rend
 			bcam->border.right = b_v3d.render_border_max_x();
 			bcam->border.bottom = b_v3d.render_border_min_y();
 			bcam->border.top = b_v3d.render_border_max_y();
-
-			return;
 		}
-	}
-	else if(!b_render.use_border())
 		return;
+	}
 
 	BL::Object b_ob = (b_v3d.lock_camera_and_layers())? b_scene.camera(): b_v3d.camera();
 
 	if(!b_ob)
 		return;
 
+	/* Determine camera border inside the viewport. */
+	BoundBox2D full_border;
+	blender_camera_border_subset(b_render,
+	                             b_scene,
+	                             b_v3d,
+	                             b_rv3d,
+	                             b_ob,
+	                             width, height,
+	                             full_border,
+	                             &bcam->viewport_camera_border);
+
+	if(!b_render.use_border()) {
+		return;
+	}
+
 	bcam->border.left = b_render.border_min_x();
 	bcam->border.right = b_render.border_max_x();
 	bcam->border.bottom = b_render.border_min_y();
 	bcam->border.top = b_render.border_max_y();
 
-	/* determine camera viewport subset */
-	BoundBox2D view_box, cam_box;
-
-	blender_camera_view_subset(b_render, b_scene, b_ob, b_v3d, b_rv3d, width, height,
-		&view_box, &cam_box);
-
-	/* determine viewport subset matching camera border */
-	cam_box = cam_box.make_relative_to(view_box);
-	bcam->border = cam_box.subset(bcam->border).clamp();
+	/* Determine viewport subset matching camera border. */
+	blender_camera_border_subset(b_render,
+	                             b_scene,
+	                             b_v3d,
+	                             b_rv3d,
+	                             b_ob,
+	                             width, height,
+	                             bcam->border,
+	                             &bcam->border);
+	bcam->border.clamp();
 }
 
 void BlenderSync::sync_view(BL::SpaceView3D b_v3d, BL::RegionView3D b_rv3d, int width, int height)
diff --git a/intern/cycles/render/camera.cpp b/intern/cycles/render/camera.cpp
index 7be3949d138..9d03a9e360e 100644
--- a/intern/cycles/render/camera.cpp
+++ b/intern/cycles/render/camera.cpp
@@ -109,16 +109,17 @@ void Camera::update()
 {
 	if(!need_update)
 		return;
-	
+
+	/* Full viewport to camera border in the viewport. */
+	Transform fulltoborder = transform_from_viewplane(viewport_camera_border);
+	Transform bordertofull = transform_inverse(fulltoborder);
+
 	/* ndc to raster */
 	Transform screentocamera;
-	Transform ndctoraster = transform_scale(width, height, 1.0f);
+	Transform ndctoraster = transform_scale(width, height, 1.0f) * bordertofull;
 
 	/* raster to screen */
-	Transform screentondc = 
-		transform_scale(1.0f/(viewplane.right - viewplane.left),
-		                1.0f/(viewplane.top - viewplane.bottom), 1.0f) *
-		transform_translate(-viewplane.left, -viewplane.bottom, 0.0f);
+	Transform screentondc = fulltoborder * transform_from_viewplane(viewplane);
 
 	Transform screentoraster = ndctoraster * screentondc;
 	Transform rastertoscreen = transform_inverse(screentoraster);
@@ -398,5 +399,15 @@ BoundBox Camera::viewplane_bounds_get()
 	return bounds;
 }
 
-CCL_NAMESPACE_END
+Transform Camera::transform_from_viewplane(BoundBox2D &viewplane)
+{
+	return
+		transform_scale(1.0f / (viewplane.right - viewplane.left),
+		                1.0f / (viewplane.top - viewplane.bottom),
+		                1.0f) *
+		transform_translate(-viewplane.left,
+		                    -viewplane.bottom,
+		                    0.0f);
+}
 
+CCL_NAMESPACE_END
diff --git a/intern/cycles/render/camera.h b/intern/cycles/render/camera.h
index 9525cce8109..1b431e88ac4 100644
--- a/intern/cycles/render/camera.h
+++ b/intern/cycles/render/camera.h
@@ -76,6 +76,7 @@ public:
 
 	/* border */
 	BoundBox2D border;
+	BoundBox2D viewport_camera_border;
 
 	/* transformation */
 	Transform matrix;
@@ -123,6 +124,7 @@ public:
 
 	BoundBox viewplane_bounds_get();
 	float3 transform_raster_to_world(float raster_x, float raster_y);
+	Transform transform_from_viewplane(BoundBox2D &viewplane);
 };
 
 CCL_NAMESPACE_END