Data previews: add utils to generate/clear previews.

Not much to add, you can now clear previews from current .blend file, or a set of non-opened files.
Likewise, you can generate previews (for mat/tex, objects, groups, scenes, ...).

12 files changed, 1030 insertions, 6 deletions

diff --git a/release/scripts/modules/bl_previews_utils/bl_previews_render.py b/release/scripts/modules/bl_previews_utils/bl_previews_render.py
new file mode 100644
index 00000000000..0ef49601c43
--- /dev/null
+++ b/release/scripts/modules/bl_previews_utils/bl_previews_render.py
@@ -0,0 +1,489 @@
+# ***** BEGIN GPL LICENSE BLOCK *****
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ***** END GPL LICENSE BLOCK *****
+
+# <pep8 compliant>
+
+# Populate a template file (POT format currently) from Blender RNA/py/C data.
+# Note: This script is meant to be used from inside Blender!
+
+import collections
+import os
+import sys
+
+import bpy
+from mathutils import Vector, Euler
+
+
+INTERN_PREVIEW_TYPES = {'MATERIAL', 'LAMP', 'WORLD', 'TEXTURE', 'IMAGE'}
+OBJECT_TYPES_RENDER = {'MESH', 'CURVE', 'SURFACE', 'META', 'FONT'}
+
+
+def rna_backup_gen(data, include_props=None, exclude_props=None, root=()):
+    # only writable properties...
+    for p in data.bl_rna.properties:
+        pid = p.identifier
+        if pid in {'rna_type',}:
+            continue
+        path = root + (pid,)
+        if include_props is not None and path not in include_props:
+            continue
+        if exclude_props is not None and path in exclude_props:
+            continue
+        val = getattr(data, pid)
+        if val is not None and p.type == 'POINTER':
+            # recurse!
+            yield from rna_backup_gen(val, include_props, exclude_props, root=path)
+        elif data.is_property_readonly(pid):
+            continue
+        else:
+            yield path, val
+
+
+def rna_backup_restore(data, backup):
+    for path, val in backup:
+        dt = data
+        for pid in path[:-1]:
+            dt = getattr(dt, pid)
+        setattr(dt, path[-1], val)
+
+
+def do_previews(do_objects, do_groups, do_scenes, do_data_intern):
+    # Helpers.
+    RenderContext = collections.namedtuple("RenderContext", (
+        "scene", "world", "camera", "lamp", "camera_data", "lamp_data", "image",  # All those are names!
+        "backup_scene", "backup_world", "backup_camera", "backup_lamp", "backup_camera_data", "backup_lamp_data",
+    ))
+
+    RENDER_PREVIEW_SIZE = bpy.app.render_preview_size
+
+    def render_context_create(engine, objects_ignored):
+        if engine == '__SCENE':
+            backup_scene, backup_world, backup_camera, backup_lamp, backup_camera_data, backup_lamp_data = [()] * 6
+            scene = bpy.context.screen.scene
+            exclude_props = {('world',), ('camera',), ('tool_settings',), ('preview',)}
+            backup_scene = tuple(rna_backup_gen(scene, exclude_props=exclude_props))
+            world = scene.world
+            camera = scene.camera
+            if camera:
+                camera_data = camera.data
+            else:
+                backup_camera, backup_camera_data = [None] * 2
+                camera_data = bpy.data.cameras.new("TEMP_preview_render_camera")
+                camera = bpy.data.objects.new("TEMP_preview_render_camera", camera_data)
+                camera.rotation_euler = Euler((1.1635528802871704, 0.0, 0.7853981852531433), 'XYZ')  # (66.67, 0.0, 45.0)
+                scene.camera = camera
+                scene.objects.link(camera)
+            # TODO: add lamp if none found in scene?
+            lamp = None
+            lamp_data = None
+        else:
+            backup_scene, backup_world, backup_camera, backup_lamp, backup_camera_data, backup_lamp_data = [None] * 6
+
+            scene = bpy.data.scenes.new("TEMP_preview_render_scene")
+            world = bpy.data.worlds.new("TEMP_preview_render_world")
+            camera_data = bpy.data.cameras.new("TEMP_preview_render_camera")
+            camera = bpy.data.objects.new("TEMP_preview_render_camera", camera_data)
+            lamp_data = bpy.data.lamps.new("TEMP_preview_render_lamp", 'SPOT')
+            lamp = bpy.data.objects.new("TEMP_preview_render_lamp", lamp_data)
+
+            objects_ignored.add((camera.name, lamp.name))
+
+            scene.world = world
+
+            camera.rotation_euler = Euler((1.1635528802871704, 0.0, 0.7853981852531433), 'XYZ')  # (66.67, 0.0, 45.0)
+            scene.camera = camera
+            scene.objects.link(camera)
+
+            lamp.rotation_euler = Euler((0.7853981852531433, 0.0, 1.7453292608261108), 'XYZ')  # (45.0, 0.0, 100.0)
+            lamp_data.falloff_type = 'CONSTANT'
+            lamp_data.spot_size = 1.0471975803375244  # 60
+            scene.objects.link(lamp)
+
+            if engine == 'BLENDER_RENDER':
+                scene.render.engine = 'BLENDER_RENDER'
+                scene.render.alpha_mode = 'TRANSPARENT'
+
+                world.use_sky_blend = True
+                world.horizon_color = 0.9, 0.9, 0.9
+                world.zenith_color = 0.5, 0.5, 0.5
+                world.ambient_color = 0.1, 0.1, 0.1
+                world.light_settings.use_environment_light = True
+                world.light_settings.environment_energy = 1.0
+                world.light_settings.environment_color = 'SKY_COLOR'
+            elif engine == 'CYCLES':
+                scene.render.engine = 'CYCLES'
+                scene.cycles.film_transparent = True
+                # TODO: define Cycles world?
+
+        scene.render.image_settings.file_format = 'PNG'
+        scene.render.image_settings.color_depth = '8'
+        scene.render.image_settings.color_mode = 'RGBA'
+        scene.render.image_settings.compression = 25
+        scene.render.resolution_x = RENDER_PREVIEW_SIZE
+        scene.render.resolution_y = RENDER_PREVIEW_SIZE
+        scene.render.resolution_percentage = 100
+        scene.render.filepath = os.path.join(bpy.app.tempdir, 'TEMP_preview_render.png')
+        scene.render.use_overwrite = True
+        scene.render.use_stamp = False
+
+        image = bpy.data.images.new("TEMP_render_image", RENDER_PREVIEW_SIZE, RENDER_PREVIEW_SIZE, alpha=True)
+        image.source = 'FILE'
+        image.filepath = scene.render.filepath
+
+        return RenderContext(
+            scene.name, world.name if world else None, camera.name, lamp.name if lamp else None,
+            camera_data.name, lamp_data.name if lamp_data else None, image.name,
+            backup_scene, backup_world, backup_camera, backup_lamp, backup_camera_data, backup_lamp_data,
+        )
+
+    def render_context_delete(render_context):
+        # We use try/except blocks here to avoid crash, too much things can go wrong, and we want to leave the current
+        # .blend as clean as possible!
+        success = True
+
+        scene = bpy.data.scenes[render_context.scene]
+        try:
+            if render_context.backup_scene is None:
+                scene.world = None
+                scene.camera = None
+                if render_context.camera:
+                    scene.objects.unlink(bpy.data.objects[render_context.camera])
+                if render_context.lamp:
+                    scene.objects.unlink(bpy.data.objects[render_context.lamp])
+                bpy.data.scenes.remove(scene)
+                scene = None
+            else:
+                rna_backup_restore(scene, render_context.backup_scene)
+        except Exception as e:
+            print("ERROR:", e)
+            success = False
+
+        if render_context.world is not None:
+            try:
+                world = bpy.data.worlds[render_context.world]
+                if render_context.backup_world is None:
+                    if scene is not None:
+                        scene.world = None
+                    world.user_clear()
+                    bpy.data.worlds.remove(world)
+                else:
+                    rna_backup_restore(world, render_context.backup_world)
+            except Exception as e:
+                print("ERROR:", e)
+                success = False
+
+        if render_context.camera:
+            try:
+                camera = bpy.data.objects[render_context.camera]
+                if render_context.backup_camera is None:
+                    if scene is not None:
+                        scene.camera = None
+                        scene.objects.unlink(camera)
+                    camera.user_clear()
+                    bpy.data.objects.remove(camera)
+                    bpy.data.cameras.remove(bpy.data.cameras[render_context.camera_data])
+                else:
+                    rna_backup_restore(camera, render_context.backup_camera)
+                    rna_backup_restore(bpy.data.cameras[render_context.camera_data], render_context.backup_camera_data)
+            except Exception as e:
+                print("ERROR:", e)
+                success = False
+
+        if render_context.lamp:
+            try:
+                lamp = bpy.data.objects[render_context.lamp]
+                if render_context.backup_lamp is None:
+                    if scene is not None:
+                        scene.objects.unlink(lamp)
+                    lamp.user_clear()
+                    bpy.data.objects.remove(lamp)
+                    bpy.data.lamps.remove(bpy.data.lamps[render_context.lamp_data])
+                else:
+                    rna_backup_restore(lamp, render_context.backup_lamp)
+                    rna_backup_restore(bpy.data.lamps[render_context.lamp_data], render_context.backup_lamp_data)
+            except Exception as e:
+                print("ERROR:", e)
+                success = False
+
+        try:
+            image = bpy.data.images[render_context.image]
+            image.user_clear()
+            bpy.data.images.remove(image)
+        except Exception as e:
+            print("ERROR:", e)
+            success = False
+
+        return success
+
+    def objects_render_engine_guess(obs):
+        for obname in obs:
+            ob = bpy.data.objects[obname]
+            for matslot in ob.material_slots:
+                mat = matslot.material
+                if mat and mat.use_nodes and mat.node_tree:
+                    for nd in mat.node_tree.nodes:
+                        if nd.shading_compatibility == {'NEW_SHADING'}:
+                            return 'CYCLES'
+        return 'BLENDER_RENDER'
+
+    def object_bbox_merge(bbox, ob, ob_space):
+        if ob.bound_box:
+            ob_bbox = ob.bound_box
+        else:
+            ob_bbox = ((-ob.scale.x, -ob.scale.y, -ob.scale.z), (ob.scale.x, ob.scale.y, ob.scale.z))
+        for v in ob.bound_box:
+            v = ob_space.matrix_world.inverted() * ob.matrix_world * Vector(v)
+            if bbox[0].x > v.x:
+                bbox[0].x = v.x
+            if bbox[0].y > v.y:
+                bbox[0].y = v.y
+            if bbox[0].z > v.z:
+                bbox[0].z = v.z
+            if bbox[1].x < v.x:
+                bbox[1].x = v.x
+            if bbox[1].y < v.y:
+                bbox[1].y = v.y
+            if bbox[1].z < v.z:
+                bbox[1].z = v.z
+
+    def objects_bbox_calc(camera, objects):
+        bbox = (Vector((1e9, 1e9, 1e9)), Vector((-1e9, -1e9, -1e9)))
+        for obname in objects:
+            ob = bpy.data.objects[obname]
+            object_bbox_merge(bbox, ob, camera)
+        # Our bbox has been generated in camera local space, bring it back in world one
+        bbox[0][:] = camera.matrix_world * bbox[0]
+        bbox[1][:] = camera.matrix_world * bbox[1]
+        cos = (
+            bbox[0].x, bbox[0].y, bbox[0].z,
+            bbox[0].x, bbox[0].y, bbox[1].z,
+            bbox[0].x, bbox[1].y, bbox[0].z,
+            bbox[0].x, bbox[1].y, bbox[1].z,
+            bbox[1].x, bbox[0].y, bbox[0].z,
+            bbox[1].x, bbox[0].y, bbox[1].z,
+            bbox[1].x, bbox[1].y, bbox[0].z,
+            bbox[1].x, bbox[1].y, bbox[1].z,
+        )
+        return cos
+
+    def preview_render_do(render_context, item_container, item_name, objects):
+        scene = bpy.data.scenes[render_context.scene]
+        if objects is not None:
+            camera = bpy.data.objects[render_context.camera]
+            lamp = bpy.data.objects[render_context.lamp] if render_context.lamp is not None else None
+            cos = objects_bbox_calc(camera, objects)
+            loc, ortho_scale = camera.camera_fit_coords(scene, cos)
+            camera.location = loc
+            if lamp:
+                loc, ortho_scale = lamp.camera_fit_coords(scene, cos)
+                lamp.location = loc
+        scene.update()
+
+        bpy.ops.render.render(write_still=True)
+
+        image = bpy.data.images[render_context.image]
+        item = getattr(bpy.data, item_container)[item_name]
+        image.reload()
+        # Note: we could use struct module here, but not quite sure it'd give any advantage really...
+        pix = tuple((round(r * 255)) + (round(g * 255) << 8) + (round(b * 255) << 16) + (round(a * 255) << 24)
+                    for r, g, b, a in zip(*[iter(image.pixels)] * 4))
+        item.preview.image_size = (RENDER_PREVIEW_SIZE, RENDER_PREVIEW_SIZE)
+        item.preview.image_pixels = pix
+
+    # And now, main code!
+    do_save = True
+
+    if do_data_intern:
+        bpy.ops.wm.previews_clear(id_type=INTERN_PREVIEW_TYPES)
+        bpy.ops.wm.previews_ensure()
+
+    render_contexts = {}
+
+    objects_ignored = set()
+    groups_ignored = set()
+
+    prev_scenename = bpy.context.screen.scene.name
+
+    if do_objects:
+        prev_shown = tuple(ob.hide_render for ob in bpy.data.objects)
+        for ob in bpy.data.objects:
+            if ob in objects_ignored:
+                continue
+            ob.hide_render = True
+        for root in bpy.data.objects:
+            if root.name in objects_ignored:
+                continue
+            if root.type not in OBJECT_TYPES_RENDER:
+                continue
+            objects = (root.name,)
+
+            render_engine = objects_render_engine_guess(objects)
+            render_context = render_contexts.get(render_engine, None)
+            if render_context is None:
+                render_context = render_context_create(render_engine, objects_ignored)
+                render_contexts[render_engine] = render_context
+
+            scene = bpy.data.scenes[render_context.scene]
+            bpy.context.screen.scene = scene
+
+            for obname in objects:
+                ob = bpy.data.objects[obname]
+                if obname not in scene.objects:
+                    scene.objects.link(ob)
+                ob.hide_render = False
+            scene.update()
+
+            preview_render_do(render_context, 'objects', root.name, objects)
+
+            # XXX Hyper Super Uber Suspicious Hack!
+            #     Without this, on windows build, script excepts with following message:
+            #         Traceback (most recent call last):
+            #         File "<string>", line 1, in <module>
+            #         File "<string>", line 451, in <module>
+            #         File "<string>", line 443, in main
+            #         File "<string>", line 327, in do_previews
+            #         OverflowError: Python int too large to convert to C long
+            #    ... :(
+            import sys
+            scene = bpy.data.scenes[render_context.scene]
+            for obname in objects:
+                ob = bpy.data.objects[obname]
+                scene.objects.unlink(ob)
+                ob.hide_render = True
+
+        for ob, is_rendered in zip(bpy.data.objects, prev_shown):
+            ob.hide_render = is_rendered
+
+    if do_groups:
+        for grp in bpy.data.groups:
+            if grp.name in groups_ignored:
+                continue
+            objects = tuple(ob.name for ob in grp.objects)
+
+            render_engine = objects_render_engine_guess(objects)
+            render_context = render_contexts.get(render_engine, None)
+            if render_context is None:
+                render_context = render_context_create(render_engine, objects_ignored)
+                render_contexts[render_engine] = render_context
+
+            scene = bpy.data.scenes[render_context.scene]
+            bpy.context.screen.scene = scene
+
+            bpy.ops.object.group_instance_add(group=grp.name)
+            grp_ob = next((ob for ob in scene.objects if ob.dupli_group and ob.dupli_group.name == grp.name))
+            grp_obname = grp_ob.name
+            scene.update()
+
+            preview_render_do(render_context, 'groups', grp.name, objects)
+
+            scene = bpy.data.scenes[render_context.scene]
+            scene.objects.unlink(bpy.data.objects[grp_obname])
+
+    bpy.context.screen.scene = bpy.data.scenes[prev_scenename]
+    for render_context in render_contexts.values():
+        if not render_context_delete(render_context):
+            do_save = False  # Do not save file if something went wrong here, we could 'pollute' it with temp data...
+
+    if do_scenes:
+        for scene in bpy.data.scenes:
+            has_camera = scene.camera is not None
+            bpy.context.screen.scene = scene
+            render_context = render_context_create('__SCENE', objects_ignored)
+            scene.update()
+
+            objects = None
+            if not has_camera:
+                # We had to add a temp camera, now we need to place it to see interesting objects!
+                objects = tuple(ob.name for ob in scene.objects
+                                        if (not ob.hide_render) and (ob.type in OBJECT_TYPES_RENDER))
+
+            preview_render_do(render_context, 'scenes', scene.name, objects)
+
+            if not render_context_delete(render_context):
+                do_save = False
+
+    bpy.context.screen.scene = bpy.data.scenes[prev_scenename]
+    if do_save:
+        print("Saving %s..." % bpy.data.filepath)
+        try:
+            bpy.ops.wm.save_mainfile()
+        except Exception as e:
+            # Might fail in some odd cases, like e.g. in regression files we have glsl/ram_glsl.blend which
+            # references an inexistent texture... Better not break in this case, just spit error to console.
+            print("ERROR:", e)
+    else:
+        print("*NOT* Saving %s, because some error(s) happened while deleting temp render data..." % bpy.data.filepath)
+
+
+def do_clear_previews(do_objects, do_groups, do_scenes, do_data_intern):
+    if do_data_intern:
+        bpy.ops.wm.previews_clear(id_type=INTERN_PREVIEW_TYPES)
+
+    if do_objects:
+        for ob in bpy.data.objects:
+            ob.preview.image_size = (0, 0)
+
+    if do_groups:
+        for grp in bpy.data.groups:
+            grp.preview.image_size = (0, 0)
+
+    if do_scenes:
+        for scene in bpy.data.scenes:
+            scene.preview.image_size = (0, 0)
+
+    print("Saving %s..." % bpy.data.filepath)
+    bpy.ops.wm.save_mainfile()
+
+
+def main():
+    try:
+        import bpy
+    except ImportError:
+        print("This script must run from inside blender")
+        return
+
+    import sys
+    import argparse
+
+    # Get rid of Blender args!
+    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+
+    parser = argparse.ArgumentParser(description="Use Blender to generate previews for currently open Blender file's items.")
+    parser.add_argument('--clear', default=False, action="store_true", help="Clear previews instead of generating them.")
+    parser.add_argument('--no_scenes', default=True, action="store_false", help="Do not generate/clear previews for scene IDs.")
+    parser.add_argument('--no_groups', default=True, action="store_false", help="Do not generate/clear previews for group IDs.")
+    parser.add_argument('--no_objects', default=True, action="store_false", help="Do not generate/clear previews for object IDs.")
+    parser.add_argument('--no_data_intern', default=True, action="store_false",
+                        help="Do not generate/clear previews for mat/tex/image/etc. IDs (those handled by core Blender code).")
+    args = parser.parse_args(argv)
+
+    if args.clear:
+        print("clear!")
+        do_clear_previews(do_objects=args.no_objects, do_groups=args.no_groups, do_scenes=args.no_scenes,
+                          do_data_intern=args.no_data_intern)
+    else:
+        print("render!")
+        do_previews(do_objects=args.no_objects, do_groups=args.no_groups, do_scenes=args.no_scenes,
+                    do_data_intern=args.no_data_intern)
+
+
+if __name__ == "__main__":
+    print("\n\n *** Running {} *** \n".format(__file__))
+    print(" *** Blend file {} *** \n".format(bpy.data.filepath))
+    main()
+    bpy.ops.wm.quit_blender()
diff --git a/release/scripts/startup/bl_operators/__init__.py b/release/scripts/startup/bl_operators/__init__.py
index 4047505652f..35c7a55b6da 100644
--- a/release/scripts/startup/bl_operators/__init__.py
+++ b/release/scripts/startup/bl_operators/__init__.py
@@ -28,6 +28,7 @@ _modules = [
     "anim",
     "clip",
     "console",
+    "file",
     "image",
     "mask",
     "mesh",
diff --git a/release/scripts/startup/bl_operators/file.py b/release/scripts/startup/bl_operators/file.py
new file mode 100644
index 00000000000..a6a6982e746
--- /dev/null
+++ b/release/scripts/startup/bl_operators/file.py
@@ -0,0 +1,243 @@
+# ##### BEGIN GPL LICENSE BLOCK #####
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ##### END GPL LICENSE BLOCK #####
+
+# <pep8 compliant>
+
+import bpy
+from bpy.types import Operator
+from bpy.props import (
+        StringProperty,
+        BoolProperty,
+        CollectionProperty,
+        )
+
+# ########## Datablock previews... ##########
+
+class WM_OT_previews_batch_generate(Operator):
+    """Generate selected .blend file's previews"""
+    bl_idname = "wm.previews_batch_generate"
+    bl_label = "Batch-Generate Previews"
+    bl_options = {'REGISTER'}
+
+    # -----------
+    # File props.
+    files = CollectionProperty(
+            type=bpy.types.OperatorFileListElement,
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+
+    directory = StringProperty(
+            maxlen=1024,
+            subtype='FILE_PATH',
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+
+    # Show only images/videos, and directories!
+    filter_blender = BoolProperty(
+            default=True,
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+    filter_folder = BoolProperty(
+            default=True,
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+
+    # -----------
+    # Own props.
+    use_scenes = BoolProperty(
+            default=True,
+            name="Scenes",
+            description="Generate scenes' previews",
+            )
+    use_groups = BoolProperty(
+            default=True,
+            name="Groups",
+            description="Generate groups' previews",
+            )
+    use_objects = BoolProperty(
+            default=True,
+            name="Objects",
+            description="Generate objects' previews",
+            )
+    use_intern_data = BoolProperty(
+            default=True,
+            name="Mat/Tex/...",
+            description="Generate 'internal' previews (materials, textures, images, etc.)",
+            )
+
+    use_trusted = BoolProperty(
+            default=False,
+            name="Trusted Blend Files",
+            description="Enable python evaluation for selected files",
+            )
+
+    def invoke(self, context, event):
+        context.window_manager.fileselect_add(self)
+        return {'RUNNING_MODAL'}
+
+    def execute(self, context):
+        if "subprocess" in locals():
+            import imp
+            imp.reload(preview_render)
+        else:
+            import os
+            import subprocess
+            from bl_previews_utils import bl_previews_render as preview_render
+
+        context.window_manager.progress_begin(0, len(self.files))
+        context.window_manager.progress_update(0)
+        for i, fn in enumerate(self.files):
+            blen_path = os.path.join(self.directory, fn.name)
+            cmd = [
+                bpy.app.binary_path,
+                "--background",
+                "--factory-startup",
+                "-noaudio",
+            ]
+            if self.use_trusted:
+                cmd.append("--enable-autoexec")
+            cmd.extend([
+                blen_path,
+                "--python",
+                os.path.join(os.path.dirname(preview_render.__file__), "bl_previews_render.py"),
+                "--",
+            ])
+            if not self.use_scenes:
+                cmd.append('--no_scenes')
+            if not self.use_groups:
+                cmd.append('--no_groups')
+            if not self.use_objects:
+                cmd.append('--no_objects')
+            if not self.use_intern_data:
+                cmd.append('--no_data_intern')
+            if subprocess.call(cmd):
+                self.report({'ERROR'}, "Previews generation process failed for file '%s'!" % blen_path)
+                context.window_manager.progress_end()
+                return {'CANCELLED'}
+            context.window_manager.progress_update(i + 1)
+        context.window_manager.progress_end()
+
+        return {'FINISHED'}
+
+
+class WM_OT_previews_batch_clear(Operator):
+    """Clear selected .blend file's previews"""
+    bl_idname = "wm.previews_batch_clear"
+    bl_label = "Batch-Clear Previews"
+    bl_options = {'REGISTER'}
+
+    # -----------
+    # File props.
+    files = CollectionProperty(
+            type=bpy.types.OperatorFileListElement,
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+
+    directory = StringProperty(
+            maxlen=1024,
+            subtype='FILE_PATH',
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+
+    # Show only images/videos, and directories!
+    filter_blender = BoolProperty(
+            default=True,
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+    filter_folder = BoolProperty(
+            default=True,
+            options={'HIDDEN', 'SKIP_SAVE'},
+            )
+
+    # -----------
+    # Own props.
+    use_scenes = BoolProperty(
+            default=True,
+            name="Scenes",
+            description="Clear scenes' previews",
+            )
+    use_groups = BoolProperty(default=True,
+            name="Groups",
+            description="Clear groups' previews",
+            )
+    use_objects = BoolProperty(
+            default=True,
+            name="Objects",
+            description="Clear objects' previews",
+            )
+    use_intern_data = BoolProperty(
+            default=True,
+            name="Mat/Tex/...",
+            description="Clear 'internal' previews (materials, textures, images, etc.)",
+            )
+
+    use_trusted = BoolProperty(
+            default=False,
+            name="Trusted Blend Files",
+            description="Enable python evaluation for selected files",
+            )
+
+    def invoke(self, context, event):
+        context.window_manager.fileselect_add(self)
+        return {'RUNNING_MODAL'}
+
+    def execute(self, context):
+        if "subprocess" in locals():
+            import imp
+            imp.reload(preview_render)
+        else:
+            import os
+            import subprocess
+            from bl_previews_utils import bl_previews_render as preview_render
+
+        context.window_manager.progress_begin(0, len(self.files))
+        context.window_manager.progress_update(0)
+        for i, fn in enumerate(self.files):
+            blen_path = os.path.join(self.directory, fn.name)
+            cmd = [
+                bpy.app.binary_path,
+                "--background",
+                "--factory-startup",
+                "-noaudio",
+            ]
+            if self.use_trusted:
+                cmd.append("--enable-autoexec")
+            cmd.extend([
+                blen_path,
+                "--python",
+                os.path.join(os.path.dirname(preview_render.__file__), "bl_previews_render.py"),
+                "--",
+                "--clear",
+            ])
+            if not self.use_scenes:
+                cmd.append('--no_scenes')
+            if not self.use_groups:
+                cmd.append('--no_groups')
+            if not self.use_objects:
+                cmd.append('--no_objects')
+            if not self.use_intern_data:
+                cmd.append('--no_data_intern')
+            if subprocess.call(cmd):
+                self.report({'ERROR'}, "Previews clear process failed for file '%s'!" % blen_path)
+                context.window_manager.progress_end()
+                return {'CANCELLED'}
+            context.window_manager.progress_update(i + 1)
+        context.window_manager.progress_end()
+
+        return {'FINISHED'}
+
diff --git a/release/scripts/startup/bl_ui/space_info.py b/release/scripts/startup/bl_ui/space_info.py
index 48a1b28289e..d295cc19fb7 100644
--- a/release/scripts/startup/bl_ui/space_info.py
+++ b/release/scripts/startup/bl_ui/space_info.py
@@ -203,6 +203,12 @@ class INFO_MT_file_previews(Menu):
         layout = self.layout
 
         layout.operator("wm.previews_ensure")
+        layout.operator("wm.previews_batch_generate")
+
+        layout.separator()
+
+        layout.operator("wm.previews_clear")
+        layout.operator("wm.previews_batch_clear")
 
 
 class INFO_MT_game(Menu):
diff --git a/source/blender/blenkernel/BKE_idcode.h b/source/blender/blenkernel/BKE_idcode.h
index 420df77ff1e..ebad0d42232 100644
--- a/source/blender/blenkernel/BKE_idcode.h
+++ b/source/blender/blenkernel/BKE_idcode.h
@@ -39,6 +39,9 @@ int         BKE_idcode_from_name(const char *name);
 bool        BKE_idcode_is_linkable(int code);
 bool        BKE_idcode_is_valid(int code);
 
+int         BKE_idcode_to_idfilter(const int idcode);
+int         BKE_idcode_from_idfilter(const int idfilter);
+
 /**
  * Return an ID code and steps the index forward 1.
  *
diff --git a/source/blender/blenkernel/intern/idcode.c b/source/blender/blenkernel/intern/idcode.c
index 091d8a6ea17..3101d7874a6 100644
--- a/source/blender/blenkernel/intern/idcode.c
+++ b/source/blender/blenkernel/intern/idcode.c
@@ -166,6 +166,90 @@ int BKE_idcode_from_name(const char *name)
 }
 
 /**
+ * Convert an idcode into an idfilter (e.g. ID_OB -> FILTER_ID_OB).
+ */
+int BKE_idcode_to_idfilter(const int idcode)
+{
+#define CASE_IDFILTER(_id) case ID_##_id: return FILTER_ID_##_id
+
+	switch (idcode) {
+		CASE_IDFILTER(AC);
+		CASE_IDFILTER(AR);
+		CASE_IDFILTER(BR);
+		CASE_IDFILTER(CA);
+		CASE_IDFILTER(CU);
+		CASE_IDFILTER(GD);
+		CASE_IDFILTER(GR);
+		CASE_IDFILTER(IM);
+		CASE_IDFILTER(LA);
+		CASE_IDFILTER(LS);
+		CASE_IDFILTER(LT);
+		CASE_IDFILTER(MA);
+		CASE_IDFILTER(MB);
+		CASE_IDFILTER(MC);
+		CASE_IDFILTER(ME);
+		CASE_IDFILTER(MSK);
+		CASE_IDFILTER(NT);
+		CASE_IDFILTER(OB);
+		CASE_IDFILTER(PAL);
+		CASE_IDFILTER(PC);
+		CASE_IDFILTER(SCE);
+		CASE_IDFILTER(SPK);
+		CASE_IDFILTER(SO);
+		CASE_IDFILTER(TE);
+		CASE_IDFILTER(TXT);
+		CASE_IDFILTER(VF);
+		CASE_IDFILTER(WO);
+		default:
+			return 0;
+	}
+
+#undef CASE_IDFILTER
+}
+
+/**
+ * Convert an idfilter into an idcode (e.g. FILTER_ID_OB -> ID_OB).
+ */
+int BKE_idcode_from_idfilter(const int idfilter)
+{
+#define CASE_IDFILTER(_id) case FILTER_ID_##_id: return ID_##_id
+
+	switch (idfilter) {
+		CASE_IDFILTER(AC);
+		CASE_IDFILTER(AR);
+		CASE_IDFILTER(BR);
+		CASE_IDFILTER(CA);
+		CASE_IDFILTER(CU);
+		CASE_IDFILTER(GD);
+		CASE_IDFILTER(GR);
+		CASE_IDFILTER(IM);
+		CASE_IDFILTER(LA);
+		CASE_IDFILTER(LS);
+		CASE_IDFILTER(LT);
+		CASE_IDFILTER(MA);
+		CASE_IDFILTER(MB);
+		CASE_IDFILTER(MC);
+		CASE_IDFILTER(ME);
+		CASE_IDFILTER(MSK);
+		CASE_IDFILTER(NT);
+		CASE_IDFILTER(OB);
+		CASE_IDFILTER(PAL);
+		CASE_IDFILTER(PC);
+		CASE_IDFILTER(SCE);
+		CASE_IDFILTER(SPK);
+		CASE_IDFILTER(SO);
+		CASE_IDFILTER(TE);
+		CASE_IDFILTER(TXT);
+		CASE_IDFILTER(VF);
+		CASE_IDFILTER(WO);
+		default:
+			return 0;
+	}
+
+#undef CASE_IDFILTER
+}
+
+/**
  * Convert an idcode into a name (plural).
  *
  * \param code The code to convert.
diff --git a/source/blender/editors/include/UI_interface_icons.h b/source/blender/editors/include/UI_interface_icons.h
index 634dd3d5bbc..945ac1b6db9 100644
--- a/source/blender/editors/include/UI_interface_icons.h
+++ b/source/blender/editors/include/UI_interface_icons.h
@@ -34,9 +34,12 @@
 
 struct bContext;
 struct ID;
+struct Scene;
 struct PreviewImage;
 struct PointerRNA;
 
+enum eIconSizes;
+
 typedef struct IconFile {
 	struct IconFile *next, *prev;
 	char filename[256]; /* FILE_MAXFILE size */
@@ -60,6 +63,7 @@ int UI_icon_get_height(int icon_id);
 
 void UI_id_icon_render(
         const struct bContext *C, struct Scene *scene, struct ID *id, const bool big, const bool use_job);
+int UI_preview_render_size(enum eIconSizes size);
 
 void UI_icon_draw(float x, float y, int icon_id);
 void UI_icon_draw_preview(float x, float y, int icon_id);
@@ -78,5 +82,6 @@ int UI_iconfile_get_index(const char *filename);
 struct PreviewImage *UI_icon_to_preview(int icon_id);
 
 int UI_rnaptr_icon_get(struct bContext *C, struct PointerRNA *ptr, int rnaicon, const bool big);
+int UI_idcode_icon_get(const int idcode);
 
 #endif /*  __UI_INTERFACE_ICONS_H__ */
diff --git a/source/blender/editors/interface/interface_icons.c b/source/blender/editors/interface/interface_icons.c
index db1eacf57dc..95139c5656e 100644
--- a/source/blender/editors/interface/interface_icons.c
+++ b/source/blender/editors/interface/interface_icons.c
@@ -900,7 +900,7 @@ void UI_icons_init(int first_dyn_id)
 
 /* Render size for preview images and icons
  */
-static int preview_render_size(enum eIconSizes size)
+int UI_preview_render_size(enum eIconSizes size)
 {
 	switch (size) {
 		case ICON_SIZE_ICON:
@@ -916,7 +916,7 @@ static int preview_render_size(enum eIconSizes size)
  */
 static void icon_create_rect(struct PreviewImage *prv_img, enum eIconSizes size)
 {
-	unsigned int render_size = preview_render_size(size);
+	unsigned int render_size = UI_preview_render_size(size);
 
 	if (!prv_img) {
 		if (G.debug & G_DEBUG)
@@ -1399,6 +1399,68 @@ int UI_rnaptr_icon_get(bContext *C, PointerRNA *ptr, int rnaicon, const bool big
 	return rnaicon;
 }
 
+int UI_idcode_icon_get(const int idcode)
+{
+	switch (idcode) {
+		case ID_AC:
+			return ICON_ANIM_DATA;
+		case ID_AR:
+			return ICON_ARMATURE_DATA;
+		case ID_BR:
+			return ICON_BRUSH_DATA;
+		case ID_CA:
+			return ICON_CAMERA_DATA;
+		case ID_CU:
+			return ICON_CURVE_DATA;
+		case ID_GD:
+			return ICON_GREASEPENCIL;
+		case ID_GR:
+			return ICON_GROUP;
+		case ID_IM:
+			return ICON_IMAGE_DATA;
+		case ID_LA:
+			return ICON_LAMP_DATA;
+		case ID_LS:
+			return ICON_LINE_DATA;
+		case ID_LT:
+			return ICON_LATTICE_DATA;
+		case ID_MA:
+			return ICON_MATERIAL_DATA;
+		case ID_MB:
+			return ICON_META_DATA;
+		case ID_MC:
+			return ICON_CLIP;
+		case ID_ME:
+			return ICON_MESH_DATA;
+		case ID_MSK:
+			return ICON_MOD_MASK;  /* TODO! this would need its own icon! */
+		case ID_NT:
+			return ICON_NODETREE;
+		case ID_OB:
+			return ICON_OBJECT_DATA;
+		case ID_PAL:
+			return ICON_COLOR;  /* TODO! this would need its own icon! */
+		case ID_PC:
+			return ICON_CURVE_BEZCURVE;  /* TODO! this would need its own icon! */
+		case ID_SCE:
+			return ICON_SCENE_DATA;
+		case ID_SPK:
+			return ICON_SPEAKER;
+		case ID_SO:
+			return ICON_SOUND;
+		case ID_TE:
+			return ICON_TEXTURE_DATA;
+		case ID_TXT:
+			return ICON_TEXT;
+		case ID_VF:
+			return ICON_FONT_DATA;
+		case ID_WO:
+			return ICON_WORLD_DATA;
+		default:
+			return ICON_NONE;
+	}
+}
+
 static void icon_draw_at_size(
         float x, float y, int icon_id, float aspect, float alpha,
         enum eIconSizes size, const bool nocreate)
diff --git a/source/blender/makesdna/DNA_ID.h b/source/blender/makesdna/DNA_ID.h
index 6b9de26f0a4..88e728c0e37 100644
--- a/source/blender/makesdna/DNA_ID.h
+++ b/source/blender/makesdna/DNA_ID.h
@@ -290,6 +290,41 @@ enum {
 	LIB_ID_RECALC_ALL   = (LIB_ID_RECALC | LIB_ID_RECALC_DATA),
 };
 
+/* To filter ID types (filter_id) */
+/* XXX We cannot put all needed IDs inside an enum...
+ *     We'll have to see whether we can fit all needed ones inside 32 values,
+ *     or if we need to fallback to longlong defines :/
+ */
+enum {
+	FILTER_ID_AC        = (1 << 0),
+	FILTER_ID_AR        = (1 << 1),
+	FILTER_ID_BR        = (1 << 2),
+	FILTER_ID_CA        = (1 << 3),
+	FILTER_ID_CU        = (1 << 4),
+	FILTER_ID_GD        = (1 << 5),
+	FILTER_ID_GR        = (1 << 6),
+	FILTER_ID_IM        = (1 << 7),
+	FILTER_ID_LA        = (1 << 8),
+	FILTER_ID_LS        = (1 << 9),
+	FILTER_ID_LT        = (1 << 10),
+	FILTER_ID_MA        = (1 << 11),
+	FILTER_ID_MB        = (1 << 12),
+	FILTER_ID_MC        = (1 << 13),
+	FILTER_ID_ME        = (1 << 14),
+	FILTER_ID_MSK       = (1 << 15),
+	FILTER_ID_NT        = (1 << 16),
+	FILTER_ID_OB        = (1 << 17),
+	FILTER_ID_PAL       = (1 << 18),
+	FILTER_ID_PC        = (1 << 19),
+	FILTER_ID_SCE       = (1 << 20),
+	FILTER_ID_SPK       = (1 << 21),
+	FILTER_ID_SO        = (1 << 22),
+	FILTER_ID_TE        = (1 << 23),
+	FILTER_ID_TXT       = (1 << 24),
+	FILTER_ID_VF        = (1 << 25),
+	FILTER_ID_WO        = (1 << 26),
+};
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/blender/makesrna/intern/rna_ID.c b/source/blender/makesrna/intern/rna_ID.c
index 65db92ab9e6..19b5a1b8219 100644
--- a/source/blender/makesrna/intern/rna_ID.c
+++ b/source/blender/makesrna/intern/rna_ID.c
@@ -472,14 +472,14 @@ static void rna_ImagePreview_size_set(PointerRNA *ptr, const int *values, enum e
 		BLI_assert(prv_img == BKE_previewimg_id_ensure(id));
 	}
 
-	BKE_previewimg_ensure(prv_img, size);
+	BKE_previewimg_clear_single(prv_img, size);
 
 	if (values[0] && values[1]) {
 		prv_img->rect[size] = MEM_callocN(values[0] * values[1] * sizeof(unsigned int), "prv_rect");
-	}
 
-	prv_img->w[size] = values[0];
-	prv_img->h[size] = values[1];
+		prv_img->w[size] = values[0];
+		prv_img->h[size] = values[1];
+	}
 
 	prv_img->flag[size] |= (PRV_CHANGED | PRV_USER_EDITED);
 }
@@ -600,6 +600,14 @@ static void rna_ImagePreview_icon_reload(PreviewImage *prv)
 	}
 }
 
+static PointerRNA rna_IDPreview_get(PointerRNA *ptr)
+{
+	ID *id = (ID *)ptr->data;
+	PreviewImage *prv_img = BKE_previewimg_id_ensure(id);
+
+	return rna_pointer_inherit_refine(ptr, &RNA_ImagePreview, prv_img);
+}
+
 #else
 
 static void rna_def_ID_properties(BlenderRNA *brna)
@@ -840,6 +848,11 @@ static void rna_def_ID(BlenderRNA *brna)
 	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
 	RNA_def_property_ui_text(prop, "Library", "Library file the datablock is linked from");
 
+	prop = RNA_def_pointer(srna, "preview", "ImagePreview", "Preview",
+	                       "Preview image and icon of this datablock (None if not supported for this type of data)");
+	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+	RNA_def_property_pointer_funcs(prop, "rna_IDPreview_get", NULL, NULL, NULL);
+
 	/* functions */
 	func = RNA_def_function(srna, "copy", "rna_ID_copy");
 	RNA_def_function_ui_description(func, "Create a copy of this datablock (not supported for all datablocks)");
diff --git a/source/blender/python/intern/bpy_app.c b/source/blender/python/intern/bpy_app.c
index 1cf0c44fd87..90d97cad880 100644
--- a/source/blender/python/intern/bpy_app.c
+++ b/source/blender/python/intern/bpy_app.c
@@ -50,6 +50,10 @@
 #include "BKE_blender.h"
 #include "BKE_global.h"
 
+#include "DNA_ID.h"
+
+#include "UI_interface_icons.h"
+
 #include "../generic/py_capi_utils.h"
 #include "../generic/python_utildefines.h"
 
@@ -298,6 +302,14 @@ static PyObject *bpy_app_driver_dict_get(PyObject *UNUSED(self), void *UNUSED(cl
 	return Py_INCREF_RET(bpy_pydriver_Dict);
 }
 
+PyDoc_STRVAR(bpy_app_preview_render_size_doc,
+"Reference size for icon/preview renders (read-only)"
+);
+static PyObject *bpy_app_preview_render_size_get(PyObject *UNUSED(self), void *closure)
+{
+	return PyLong_FromLong((long)UI_preview_render_size(GET_INT_FROM_POINTER(closure)));
+}
+
 static PyObject *bpy_app_autoexec_fail_message_get(PyObject *UNUSED(self), void *UNUSED(closure))
 {
 	return PyC_UnicodeFromByte(G.autoexec_fail);
@@ -322,6 +334,9 @@ static PyGetSetDef bpy_app_getsets[] = {
 	{(char *)"tempdir", bpy_app_tempdir_get, NULL, (char *)bpy_app_tempdir_doc, NULL},
 	{(char *)"driver_namespace", bpy_app_driver_dict_get, NULL, (char *)bpy_app_driver_dict_doc, NULL},
 
+    {(char *)"render_icon_size", bpy_app_preview_render_size_get, NULL, (char *)bpy_app_preview_render_size_doc, (void *)ICON_SIZE_ICON},
+    {(char *)"render_preview_size", bpy_app_preview_render_size_get, NULL, (char *)bpy_app_preview_render_size_doc, (void *)ICON_SIZE_PREVIEW},
+
 	/* security */
 	{(char *)"autoexec_fail", bpy_app_global_flag_get, NULL, NULL, (void *)G_SCRIPT_AUTOEXEC_FAIL},
 	{(char *)"autoexec_fail_quiet", bpy_app_global_flag_get, NULL, NULL, (void *)G_SCRIPT_AUTOEXEC_FAIL_QUIET},
diff --git a/source/blender/windowmanager/intern/wm_operators.c b/source/blender/windowmanager/intern/wm_operators.c
index 37d434faa6e..1455b7000e9 100644
--- a/source/blender/windowmanager/intern/wm_operators.c
+++ b/source/blender/windowmanager/intern/wm_operators.c
@@ -74,6 +74,7 @@
 #include "BKE_brush.h"
 #include "BKE_context.h"
 #include "BKE_depsgraph.h"
+#include "BKE_icons.h"
 #include "BKE_idprop.h"
 #include "BKE_image.h"
 #include "BKE_library.h"
@@ -4897,6 +4898,72 @@ static void WM_OT_previews_ensure(wmOperatorType *ot)
 	ot->exec = previews_ensure_exec;
 }
 
+/* *************************** Datablocks previews clear ************* */
+
+/* Only types supporting previews currently. */
+static EnumPropertyItem preview_id_type_items[] = {
+    {FILTER_ID_SCE, "SCENE", 0, "Scenes", ""},
+    {FILTER_ID_GR, "GROUP", 0, "Groups", ""},
+	{FILTER_ID_OB, "OBJECT", 0, "Objects", ""},
+    {FILTER_ID_MA, "MATERIAL", 0, "Materials", ""},
+    {FILTER_ID_LA, "LAMP", 0, "Lamps", ""},
+    {FILTER_ID_WO, "WORLD", 0, "Worlds", ""},
+    {FILTER_ID_TE, "TEXTURE", 0, "Textures", ""},
+    {FILTER_ID_IM, "IMAGE", 0, "Images", ""},
+#if 0  /* XXX TODO */
+    {FILTER_ID_BR, "BRUSH", 0, "Brushes", ""},
+#endif
+    {0, NULL, 0, NULL, NULL}
+};
+
+static int previews_clear_exec(bContext *C, wmOperator *op)
+{
+	Main *bmain = CTX_data_main(C);
+	ListBase *lb[] = {&bmain->object, &bmain->group,
+	                  &bmain->mat, &bmain->world, &bmain->lamp, &bmain->tex, &bmain->image, NULL};
+	int i;
+
+	const int id_filters = RNA_enum_get(op->ptr, "id_type");
+
+	for (i = 0; lb[i]; i++) {
+		ID *id = lb[i]->first;
+
+		if (!id) continue;
+
+//		printf("%s: %d, %d, %d -> %d\n", id->name, GS(id->name), BKE_idcode_to_idfilter(GS(id->name)),
+//		                                 id_filters, BKE_idcode_to_idfilter(GS(id->name)) & id_filters);
+
+		if (!id || !(BKE_idcode_to_idfilter(GS(id->name)) & id_filters)) {
+			continue;
+		}
+
+		for (; id; id = id->next) {
+			PreviewImage *prv_img = BKE_previewimg_id_ensure(id);
+
+			BKE_previewimg_clear(prv_img);
+		}
+	}
+
+	return OPERATOR_FINISHED;
+}
+
+static void WM_OT_previews_clear(wmOperatorType *ot)
+{
+	ot->name = "Clear DataBlock Previews";
+	ot->idname = "WM_OT_previews_clear";
+	ot->description = "Clear datablock previews (only for some types like objects, materials, textures, etc.)";
+
+	ot->exec = previews_clear_exec;
+	ot->invoke = WM_menu_invoke;
+
+	ot->prop = RNA_def_enum_flag(ot->srna, "id_type", preview_id_type_items,
+	                             FILTER_ID_SCE | FILTER_ID_OB | FILTER_ID_GR |
+		                         FILTER_ID_MA | FILTER_ID_LA | FILTER_ID_WO | FILTER_ID_TE | FILTER_ID_IM,
+	                             "DataBlock Type", "Which datablock previews to clear");
+}
+
+/* *************************** Doc from UI ************* */
+
 static int doc_view_manual_ui_context_exec(bContext *C, wmOperator *UNUSED(op))
 {
 	PointerRNA ptr_props;
@@ -5025,6 +5092,7 @@ void wm_operatortype_init(void)
 	WM_operatortype_append(WM_OT_console_toggle);
 #endif
 	WM_operatortype_append(WM_OT_previews_ensure);
+	WM_operatortype_append(WM_OT_previews_clear);
 	WM_operatortype_append(WM_OT_doc_view_manual_ui_context);
 }