render.py

            # Maybe change the above to a funtion copyInternalRenderer settings when
            # user pushes a button, then:
            #scene.pov.radio_enable = world.light_settings.use_indirect_light
            # and other such translations but maybe this would not be allowed either?

        ###############################################################

        mist = world.mist_settings

        if mist.use_mist:
            tabWrite("fog {\n")
            tabWrite("distance %.6f\n" % mist.depth)
            tabWrite("color rgbt<%.3g, %.3g, %.3g, %.3g>\n" % \
                     (*world.horizon_color, 1.0 - mist.intensity))
            #tabWrite("fog_offset %.6f\n" % mist.start)
            #tabWrite("fog_alt 5\n")
            #tabWrite("turbulence 0.2\n")
            #tabWrite("turb_depth 0.3\n")
            tabWrite("fog_type 1\n")
            tabWrite("}\n")
        if scene.pov.media_enable:
            tabWrite("media {\n")
            tabWrite("scattering { 1, rgb <%.4g, %.4g, %.4g>}\n" % scene.pov.media_color[:])
            tabWrite("samples %.d\n" % scene.pov.media_samples)
            tabWrite("}\n")

    def exportGlobalSettings(scene):

        tabWrite("global_settings {\n")
        tabWrite("assumed_gamma 1.0\n")
        tabWrite("max_trace_level %d\n" % scene.pov.max_trace_level)

        if scene.pov.radio_enable:
            tabWrite("radiosity {\n")
            tabWrite("adc_bailout %.4g\n" % scene.pov.radio_adc_bailout)
            tabWrite("always_sample %d\n" % scene.pov.radio_always_sample)
            tabWrite("brightness %.4g\n" % scene.pov.radio_brightness)
            tabWrite("count %d\n" % scene.pov.radio_count)
            tabWrite("error_bound %.4g\n" % scene.pov.radio_error_bound)
            tabWrite("gray_threshold %.4g\n" % scene.pov.radio_gray_threshold)
            tabWrite("low_error_factor %.4g\n" % scene.pov.radio_low_error_factor)
            tabWrite("media %d\n" % scene.pov.radio_media)
            tabWrite("minimum_reuse %.4g\n" % scene.pov.radio_minimum_reuse)
            tabWrite("nearest_count %d\n" % scene.pov.radio_nearest_count)
            tabWrite("normal %d\n" % scene.pov.radio_normal)
            tabWrite("pretrace_start %.3g\n" % scene.pov.radio_pretrace_start)
            tabWrite("pretrace_end %.3g\n" % scene.pov.radio_pretrace_end)
            tabWrite("recursion_limit %d\n" % scene.pov.radio_recursion_limit)
            tabWrite("}\n")
        onceSss = 1
        onceAmbient = 1
        oncePhotons = 1
        for material in bpy.data.materials:
            if material.subsurface_scattering.use and onceSss:
                # In pov, the scale has reversed influence compared to blender. these number
                # should correct that
                tabWrite("mm_per_unit %.6f\n" % \
                         (material.subsurface_scattering.scale * 1000.0))
                         # 1000 rather than scale * (-100.0) + 15.0))

                # In POV-Ray, the scale factor for all subsurface shaders needs to be the same
                
                # formerly sslt_samples were multiplied by 100 instead of 10
                sslt_samples = (11 - material.subsurface_scattering.error_threshold) * 10 

                tabWrite("subsurface { samples %d, %d }\n" % (sslt_samples, sslt_samples / 10))
                onceSss = 0

            if world and onceAmbient:
                tabWrite("ambient_light rgbt<%.3g, %.3g, %.3g,1>\n" % world.ambient_color[:])
                onceAmbient = 0

            if (oncePhotons and
                    (material.pov.refraction_type == "2" or
                    material.pov.photons_reflection == True)):
                tabWrite("photons {\n")
                tabWrite("spacing %.6f\n" % scene.pov.photon_spacing)
                tabWrite("max_trace_level %d\n" % scene.pov.photon_max_trace_level)
                tabWrite("adc_bailout %.3g\n" % scene.pov.photon_adc_bailout)
                tabWrite("gather %d, %d\n" % (scene.pov.photon_gather_min,
                    scene.pov.photon_gather_max))
                tabWrite("}\n")
                oncePhotons = 0

        tabWrite("}\n")

    def exportCustomCode():
        # Write CurrentAnimation Frame for use in Custom POV Code
        file.write("#declare CURFRAMENUM = %d;\n" % bpy.context.scene.frame_current)
        #Change path and uncomment to add an animated include file by hand:
        file.write("//#include \"/home/user/directory/animation_include_file.inc\"\n")
        for txt in bpy.data.texts:
            if txt.pov.custom_code:
                # Why are the newlines needed?
                file.write("\n")
                file.write(txt.as_string())
                file.write("\n")

    sel = renderable_objects()
    if comments:
        file.write("//----------------------------------------------\n" \
                   "//--Exported with POV-Ray exporter for Blender--\n" \
                   "//----------------------------------------------\n\n")
    file.write("#version 3.7;\n")

    if comments:
        file.write("\n//--Global settings--\n\n")

    exportGlobalSettings(scene)

    
    if comments:
        file.write("\n//--Custom Code--\n\n")
    exportCustomCode()

    if comments:
        file.write("\n//--Patterns Definitions--\n\n")
    LocalPatternNames = []
    for texture in bpy.data.textures: #ok?
        if texture.users > 0:
            currentPatName = string_strip_hyphen(bpy.path.clean_name(texture.name)) 
            #string_strip_hyphen(patternNames[texture.name]) #maybe instead of the above
            LocalPatternNames.append(currentPatName) 
            #use above list to prevent writing texture instances several times and assign in mats?
            file.write("\n #declare PAT_%s = \n" % currentPatName)
            file.write(exportPattern(texture))
            file.write("\n")                
    if comments:
        file.write("\n//--Background--\n\n")

    exportWorld(scene.world)

    if comments:
        file.write("\n//--Cameras--\n\n")

    exportCamera()

    if comments:
        file.write("\n//--Lamps--\n\n")

    exportLamps([L for L in sel if (L.type == 'LAMP' and L.pov.object_as != 'RAINBOW')])
    
    if comments:
        file.write("\n//--Rainbows--\n\n")
    exportRainbows([L for L in sel if (L.type == 'LAMP' and L.pov.object_as == 'RAINBOW')])


    if comments:
        file.write("\n//--Special Curves--\n\n")
    for c in sel:
        if c.type == 'CURVE' and (c.pov.curveshape in {'lathe','sphere_sweep','loft','birail'}):
            exportCurves(scene,c)    

            
    if comments:
        file.write("\n//--Material Definitions--\n\n")
    # write a default pigment for objects with no material (comment out to show black)
    file.write("#default{ pigment{ color rgb 0.8 }}\n")
    # Convert all materials to strings we can access directly per vertex.
    #exportMaterials()
    shading.writeMaterial(DEF_MAT_NAME, scene, tabWrite, safety, comments, uniqueName, materialNames, None)  # default material
    for material in bpy.data.materials:
        if material.users > 0:
            shading.writeMaterial(DEF_MAT_NAME, scene, tabWrite, safety, comments, uniqueName, materialNames, material)
    if comments:
        file.write("\n")

    exportMeta([m for m in sel if m.type == 'META'])

    if comments:
        file.write("//--Mesh objects--\n")

    exportMeshes(scene, sel)

    #What follow used to happen here:
    #exportCamera()
    #exportWorld(scene.world)
    #exportGlobalSettings(scene)
    # MR:..and the order was important for implementing pov 3.7 baking
    #      (mesh camera) comment for the record
    # CR: Baking should be a special case than. If "baking", than we could change the order.

    #print("pov file closed %s" % file.closed)
    file.close()
    #print("pov file closed %s" % file.closed)


def write_pov_ini(scene, filename_ini, filename_pov, filename_image):
    feature_set = bpy.context.user_preferences.addons[__package__].preferences.branch_feature_set_povray
    using_uberpov = (feature_set=='uberpov')
    #scene = bpy.data.scenes[0]
    render = scene.render

    x = int(render.resolution_x * render.resolution_percentage * 0.01)
    y = int(render.resolution_y * render.resolution_percentage * 0.01)

    file = open(filename_ini, "w")
    file.write("Version=3.7\n")
    file.write("Input_File_Name='%s'\n" % filename_pov)
    file.write("Output_File_Name='%s'\n" % filename_image)

    file.write("Width=%d\n" % x)
    file.write("Height=%d\n" % y)

    # Border render.
    if render.use_border:
        file.write("Start_Column=%4g\n" % render.border_min_x)
        file.write("End_Column=%4g\n" % (render.border_max_x))

        file.write("Start_Row=%4g\n" % (1.0 - render.border_max_y))
        file.write("End_Row=%4g\n" % (1.0 - render.border_min_y))

    file.write("Bounding_Method=2\n")  # The new automatic BSP is faster in most scenes

    # Activated (turn this back off when better live exchange is done between the two programs
    # (see next comment)
    file.write("Display=1\n")
    file.write("Pause_When_Done=0\n")
    # PNG, with POV-Ray 3.7, can show background color with alpha. In the long run using the
    # POV-Ray interactive preview like bishop 3D could solve the preview for all formats.
    file.write("Output_File_Type=N\n")
    #file.write("Output_File_Type=T\n") # TGA, best progressive loading
    file.write("Output_Alpha=1\n")

    if scene.pov.antialias_enable:
        # method 2 (recursive) with higher max subdiv forced because no mipmapping in POV-Ray
        # needs higher sampling.
        # aa_mapping = {"5": 2, "8": 3, "11": 4, "16": 5}
        if using_uberpov:
            method = {"0": 1, "1": 2, "2": 3}
        else:
            method = {"0": 1, "1": 2, "2": 2}
        file.write("Antialias=on\n")
        file.write("Antialias_Depth=%d\n" % scene.pov.antialias_depth)
        file.write("Antialias_Threshold=%.3g\n" % scene.pov.antialias_threshold)
        if using_uberpov and scene.pov.antialias_method == '2':
            file.write("Sampling_Method=%s\n" % method[scene.pov.antialias_method])
            file.write("Antialias_Confidence=%.3g\n" % scene.pov.antialias_confidence)
        else:
            file.write("Sampling_Method=%s\n" % method[scene.pov.antialias_method])
        file.write("Antialias_Gamma=%.3g\n" % scene.pov.antialias_gamma)
        if scene.pov.jitter_enable:
            file.write("Jitter=on\n")
            file.write("Jitter_Amount=%3g\n" % scene.pov.jitter_amount)
        else:
            file.write("Jitter=off\n")  # prevent animation flicker

    else:
        file.write("Antialias=off\n")
    #print("ini file closed %s" % file.closed)
    file.close()
    #print("ini file closed %s" % file.closed)


class PovrayRender(bpy.types.RenderEngine):
    bl_idname = 'POVRAY_RENDER'
    bl_label = "POV-Ray 3.7"
    DELAY = 0.5

    @staticmethod
    def _locate_binary():
        addon_prefs = bpy.context.user_preferences.addons[__package__].preferences

        # Use the system preference if its set.
        pov_binary = addon_prefs.filepath_povray
        if pov_binary:
            if os.path.exists(pov_binary):
                return pov_binary
            else:
                print("User Preferences path to povray %r NOT FOUND, checking $PATH" % pov_binary)

        # Windows Only
        # assume if there is a 64bit binary that the user has a 64bit capable OS
        if sys.platform[:3] == "win":
            import winreg
            win_reg_key = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
                "Software\\POV-Ray\\v3.7\\Windows")
            win_home = winreg.QueryValueEx(win_reg_key, "Home")[0]

            # First try 64bits UberPOV
            pov_binary = os.path.join(win_home, "bin", "uberpov64.exe")
            if os.path.exists(pov_binary):
                return pov_binary
                
            # Then try 64bits POV
            pov_binary = os.path.join(win_home, "bin", "pvengine64.exe")
            if os.path.exists(pov_binary):
                return pov_binary

            # Then try 32bits UberPOV
            pov_binary = os.path.join(win_home, "bin", "uberpov32.exe")
            if os.path.exists(pov_binary):
                return pov_binary 
                
            # Then try 32bits POV
            pov_binary = os.path.join(win_home, "bin", "pvengine.exe")
            if os.path.exists(pov_binary):
                return pov_binary

        # search the path all os's
        pov_binary_default = "povray"

        os_path_ls = os.getenv("PATH").split(':') + [""]

        for dir_name in os_path_ls:
            pov_binary = os.path.join(dir_name, pov_binary_default)
            if os.path.exists(pov_binary):
                return pov_binary
        return ""

    def _export(self, scene, povPath, renderImagePath):
        import tempfile

        if scene.pov.tempfiles_enable:
            self._temp_file_in = tempfile.NamedTemporaryFile(suffix=".pov", delete=False).name
            # PNG with POV 3.7, can show the background color with alpha. In the long run using the
            # POV-Ray interactive preview like bishop 3D could solve the preview for all formats.
            self._temp_file_out = tempfile.NamedTemporaryFile(suffix=".png", delete=False).name
            #self._temp_file_out = tempfile.NamedTemporaryFile(suffix=".tga", delete=False).name
            self._temp_file_ini = tempfile.NamedTemporaryFile(suffix=".ini", delete=False).name
        else:
            self._temp_file_in = povPath + ".pov"
            # PNG with POV 3.7, can show the background color with alpha. In the long run using the
            # POV-Ray interactive preview like bishop 3D could solve the preview for all formats.
            self._temp_file_out = renderImagePath + ".png"
            #self._temp_file_out = renderImagePath + ".tga"
            self._temp_file_ini = povPath + ".ini"
            '''
            self._temp_file_in = "/test.pov"
            # PNG with POV 3.7, can show the background color with alpha. In the long run using the
            # POV-Ray interactive preview like bishop 3D could solve the preview for all formats.
            self._temp_file_out = "/test.png"
            #self._temp_file_out = "/test.tga"
            self._temp_file_ini = "/test.ini"
            '''

        def info_callback(txt):
            self.update_stats("", "POV-Ray 3.7: " + txt)

        # os.makedirs(user_dir, exist_ok=True)  # handled with previews
        os.makedirs(preview_dir, exist_ok=True)

        write_pov(self._temp_file_in, scene, info_callback)

    def _render(self, scene):
        try:
            os.remove(self._temp_file_out)  # so as not to load the old file
        except OSError:
            pass

        pov_binary = PovrayRender._locate_binary()
        if not pov_binary:
            print("POV-Ray 3.7: could not execute povray, possibly POV-Ray isn't installed")
            return False

        write_pov_ini(scene, self._temp_file_ini, self._temp_file_in, self._temp_file_out)

        print ("***-STARTING-***")

        extra_args = []

        if scene.pov.command_line_switches != "":
            for newArg in scene.pov.command_line_switches.split(" "):
                extra_args.append(newArg)

        self._is_windows = False
        if sys.platform[:3] == "win":
            self._is_windows = True
            if"/EXIT" not in extra_args and not scene.pov.pov_editor:
                extra_args.append("/EXIT")
        else:
            # added -d option to prevent render window popup which leads to segfault on linux
            extra_args.append("-d")

        # Start Rendering!
        try:
            self._process = subprocess.Popen([pov_binary, self._temp_file_ini] + extra_args,
                                             stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
        except OSError:
            # TODO, report api
            print("POV-Ray 3.7: could not execute '%s'" % pov_binary)
            import traceback
            traceback.print_exc()
            print ("***-DONE-***")
            return False

        else:
            print("Engine ready!...")
            print("Command line arguments passed: " + str(extra_args))
            return True

        # Now that we have a valid process

    def _cleanup(self):
        for f in (self._temp_file_in, self._temp_file_ini, self._temp_file_out):
            for i in range(5):
                try:
                    os.unlink(f)
                    break
                except OSError:
                    # Wait a bit before retrying file might be still in use by Blender,
                    # and Windows does not know how to delete a file in use!
                    time.sleep(self.DELAY)
        for i in unpacked_images:
            for c in range(5):
                try:
                    os.unlink(i)
                    break
                except OSError:
                    # Wait a bit before retrying file might be still in use by Blender,
                    # and Windows does not know how to delete a file in use!
                    time.sleep(self.DELAY)
    def render(self, scene):
        import tempfile

        print("***INITIALIZING***")

##WIP output format
##        if r.image_settings.file_format == 'OPENEXR':
##            fformat = 'EXR'
##            render.image_settings.color_mode = 'RGBA'
##        else:
##            fformat = 'TGA'
##            r.image_settings.file_format = 'TARGA'
##            r.image_settings.color_mode = 'RGBA'

        blendSceneName = bpy.data.filepath.split(os.path.sep)[-1].split(".")[0]
        povSceneName = ""
        povPath = ""
        renderImagePath = ""

        # has to be called to update the frame on exporting animations
        scene.frame_set(scene.frame_current)

        if not scene.pov.tempfiles_enable:

            # check paths
            povPath = bpy.path.abspath(scene.pov.scene_path).replace('\\', '/')
            if povPath == "":
                if bpy.data.is_saved:
                    povPath = bpy.path.abspath("//")
                else:
                    povPath = tempfile.gettempdir()
            elif povPath.endswith("/"):
                if povPath == "/":
                    povPath = bpy.path.abspath("//")
                else:
                    povPath = bpy.path.abspath(scene.pov.scene_path)

            if not os.path.exists(povPath):
                try:
                    os.makedirs(povPath)
                except:
                    import traceback
                    traceback.print_exc()

                    print("POV-Ray 3.7: Cannot create scenes directory: %r" % povPath)
                    self.update_stats("", "POV-Ray 3.7: Cannot create scenes directory %r" % \
                                      povPath)
                    time.sleep(2.0)
                    return

            '''
            # Bug in POV-Ray RC3
            renderImagePath = bpy.path.abspath(scene.pov.renderimage_path).replace('\\','/')
            if renderImagePath == "":
                if bpy.data.is_saved:
                    renderImagePath = bpy.path.abspath("//")
                else:
                    renderImagePath = tempfile.gettempdir()
                #print("Path: " + renderImagePath)
            elif path.endswith("/"):
                if renderImagePath == "/":
                    renderImagePath = bpy.path.abspath("//")
                else:
                    renderImagePath = bpy.path.abspath(scene.pov.renderimage_path)
            if not os.path.exists(path):
                print("POV-Ray 3.7: Cannot find render image directory")
                self.update_stats("", "POV-Ray 3.7: Cannot find render image directory")
                time.sleep(2.0)
                return
            '''

            # check name
            if scene.pov.scene_name == "":
                if blendSceneName != "":
                    povSceneName = blendSceneName
                else:
                    povSceneName = "untitled"
            else:
                povSceneName = scene.pov.scene_name
                if os.path.isfile(povSceneName):
                    povSceneName = os.path.basename(povSceneName)
                povSceneName = povSceneName.split('/')[-1].split('\\')[-1]
                if not povSceneName:
                    print("POV-Ray 3.7: Invalid scene name")
                    self.update_stats("", "POV-Ray 3.7: Invalid scene name")
                    time.sleep(2.0)
                    return
                povSceneName = os.path.splitext(povSceneName)[0]

            print("Scene name: " + povSceneName)
            print("Export path: " + povPath)
            povPath = os.path.join(povPath, povSceneName)
            povPath = os.path.realpath(povPath)

            # for now this has to be the same like the pov output. Bug in POV-Ray RC3.
            # renderImagePath = renderImagePath + "\\" + povSceneName
            renderImagePath = povPath  # Bugfix for POV-Ray RC3 bug
            # renderImagePath = os.path.realpath(renderImagePath)  # Bugfix for POV-Ray RC3 bug

            #print("Export path: %s" % povPath)
            #print("Render Image path: %s" % renderImagePath)

        # start export
        self.update_stats("", "POV-Ray 3.7: Exporting data from Blender")
        self._export(scene, povPath, renderImagePath)
        self.update_stats("", "POV-Ray 3.7: Parsing File")

        if not self._render(scene):
            self.update_stats("", "POV-Ray 3.7: Not found")
            return

        r = scene.render
        # compute resolution
        x = int(r.resolution_x * r.resolution_percentage * 0.01)
        y = int(r.resolution_y * r.resolution_percentage * 0.01)

        # This makes some tests on the render, returning True if all goes good, and False if
        # it was finished one way or the other.
        # It also pauses the script (time.sleep())
        def _test_wait():
            time.sleep(self.DELAY)

            # User interrupts the rendering
            if self.test_break():
                try:
                    self._process.terminate()
                    print("***POV INTERRUPTED***")
                except OSError:
                    pass
                return False

            poll_result = self._process.poll()
            # POV process is finisehd, one way or the other
            if poll_result is not None:
                if poll_result < 0:
                    print("***POV PROCESS FAILED : %s ***" % poll_result)
                    self.update_stats("", "POV-Ray 3.7: Failed")
                return False

            return True

        # Wait for the file to be created
        # XXX This is no more valid, as 3.7 always creates output file once render is finished!
        parsing = re.compile(br"= \[Parsing\.\.\.\] =")
        rendering = re.compile(br"= \[Rendering\.\.\.\] =")
        percent = re.compile(r"\(([0-9]{1,3})%\)")
        # print("***POV WAITING FOR FILE***")

        data = b""
        last_line = ""
        while _test_wait():
            # POV in Windows does not output its stdout/stderr, it displays them in its GUI
            if self._is_windows:
                self.update_stats("", "POV-Ray 3.7: Rendering File")
            else:
                t_data = self._process.stdout.read(10000)
                if not t_data:
                    continue

                data += t_data
                # XXX This is working for UNIX, not sure whether it might need adjustments for
                #     other OSs
                # First replace is for windows
                t_data = str(t_data).replace('\\r\\n', '\\n').replace('\\r', '\r')
                lines = t_data.split('\\n')
                last_line += lines[0]
                lines[0] = last_line
                print('\n'.join(lines), end="")
                last_line = lines[-1]

                if rendering.search(data):
                    _pov_rendering = True
                    match = percent.findall(str(data))
                    if match:
                        self.update_stats("", "POV-Ray 3.7: Rendering File (%s%%)" % match[-1])
                    else:
                        self.update_stats("", "POV-Ray 3.7: Rendering File")

                elif parsing.search(data):
                    self.update_stats("", "POV-Ray 3.7: Parsing File")

        if os.path.exists(self._temp_file_out):
            # print("***POV FILE OK***")
            #self.update_stats("", "POV-Ray 3.7: Rendering")

            # prev_size = -1

            xmin = int(r.border_min_x * x)
            ymin = int(r.border_min_y * y)
            xmax = int(r.border_max_x * x)
            ymax = int(r.border_max_y * y)

            # print("***POV UPDATING IMAGE***")
            result = self.begin_result(0, 0, x, y)
            # XXX, tests for border render.
            #result = self.begin_result(xmin, ymin, xmax - xmin, ymax - ymin)
            #result = self.begin_result(0, 0, xmax - xmin, ymax - ymin)
            lay = result.layers[0]

            # This assumes the file has been fully written We wait a bit, just in case!
            time.sleep(self.DELAY)
            try:
                lay.load_from_file(self._temp_file_out)
                # XXX, tests for border render.
                #lay.load_from_file(self._temp_file_out, xmin, ymin)
            except RuntimeError:
                print("***POV ERROR WHILE READING OUTPUT FILE***")

            # Not needed right now, might only be useful if we find a way to use temp raw output of
            # pov 3.7 (in which case it might go under _test_wait()).
            '''
            def update_image():
                # possible the image wont load early on.
                try:
                    lay.load_from_file(self._temp_file_out)
                    # XXX, tests for border render.
                    #lay.load_from_file(self._temp_file_out, xmin, ymin)
                    #lay.load_from_file(self._temp_file_out, xmin, ymin)
                except RuntimeError:
                    pass

            # Update while POV-Ray renders
            while True:
                # print("***POV RENDER LOOP***")

                # test if POV-Ray exists
                if self._process.poll() is not None:
                    print("***POV PROCESS FINISHED***")
                    update_image()
                    break

                # user exit
                if self.test_break():
                    try:
                        self._process.terminate()
                        print("***POV PROCESS INTERRUPTED***")
                    except OSError:
                        pass

                    break

                # Would be nice to redirect the output
                # stdout_value, stderr_value = self._process.communicate() # locks

                # check if the file updated
                new_size = os.path.getsize(self._temp_file_out)

                if new_size != prev_size:
                    update_image()
                    prev_size = new_size

                time.sleep(self.DELAY)
            '''

            self.end_result(result)

        else:
            print("***POV FILE NOT FOUND***")

        print("***POV FINISHED***")

        self.update_stats("", "")

        if scene.pov.tempfiles_enable or scene.pov.deletefiles_enable:
            self._cleanup()


##################################################################################
#################################Operators########################################
##################################################################################
class RenderPovTexturePreview(Operator):
    bl_idname = "tex.preview_update"
    bl_label = "Update preview"
    def execute(self, context):
        tex=bpy.context.object.active_material.active_texture #context.texture
        texPrevName=string_strip_hyphen(bpy.path.clean_name(tex.name))+"_prev"

        ## Make sure Preview directory exists and is empty
        if not os.path.isdir(preview_dir):
            os.mkdir(preview_dir)

        iniPrevFile=os.path.join(preview_dir, "Preview.ini")
        inputPrevFile=os.path.join(preview_dir, "Preview.pov")
        outputPrevFile=os.path.join(preview_dir, texPrevName)
        ##################### ini ##########################################
        fileIni=open("%s"%iniPrevFile,"w")
        fileIni.write('Version=3.7\n')
        fileIni.write('Input_File_Name="%s"\n'%inputPrevFile)
        fileIni.write('Output_File_Name="%s.png"\n'%outputPrevFile)
        fileIni.write('Library_Path="%s"\n' % preview_dir)
        fileIni.write('Width=256\n')
        fileIni.write('Height=256\n')
        fileIni.write('Pause_When_Done=0\n')
        fileIni.write('Output_File_Type=N\n')
        fileIni.write('Output_Alpha=1\n')
        fileIni.write('Antialias=on\n')
        fileIni.write('Sampling_Method=2\n')
        fileIni.write('Antialias_Depth=3\n')
        fileIni.write('-d\n')
        fileIni.close()
        ##################### pov ##########################################
        filePov=open("%s"%inputPrevFile,"w")
        PATname = "PAT_"+string_strip_hyphen(bpy.path.clean_name(tex.name))
        filePov.write("#declare %s = \n"%PATname)
        filePov.write(exportPattern(tex))

        filePov.write("#declare Plane =\n")
        filePov.write("mesh {\n")
        filePov.write("    triangle {<-2.021,-1.744,2.021>,<-2.021,-1.744,-2.021>,<2.021,-1.744,2.021>}\n")
        filePov.write("    triangle {<-2.021,-1.744,-2.021>,<2.021,-1.744,-2.021>,<2.021,-1.744,2.021>}\n")
        filePov.write("    texture{%s}\n"%PATname)
        filePov.write("}\n")
        filePov.write("object {Plane}\n")
        filePov.write("light_source {\n")
        filePov.write("    <0,4.38,-1.92e-07>\n")
        filePov.write("    color rgb<4, 4, 4>\n")
        filePov.write("    parallel\n")
        filePov.write("    point_at  <0, 0, -1>\n")
        filePov.write("}\n")
        filePov.write("camera {\n")
        filePov.write("    location  <0, 0, 0>\n")
        filePov.write("    look_at  <0, 0, -1>\n")
        filePov.write("    right <-1.0, 0, 0>\n")
        filePov.write("    up <0, 1, 0>\n")
        filePov.write("    angle  96.805211\n")
        filePov.write("    rotate  <-90.000003, -0.000000, 0.000000>\n")
        filePov.write("    translate <0.000000, 0.000000, 0.000000>\n")
        filePov.write("}\n")
        filePov.close()
        ##################### end write ##########################################

        pov_binary = PovrayRender._locate_binary()
        
        if sys.platform[:3] == "win":
            p1=subprocess.Popen(["%s"%pov_binary,"/EXIT","%s"%iniPrevFile],
                stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
        else:
            p1=subprocess.Popen(["%s"%pov_binary,"-d","%s"%iniPrevFile],
                stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
        p1.wait()

        tex.use_nodes = True
        tree = tex.node_tree
        links = tree.links
        for n in tree.nodes:
            tree.nodes.remove(n)
        im = tree.nodes.new("TextureNodeImage")  
        pathPrev="%s.png"%outputPrevFile
        im.image = bpy.data.images.load(pathPrev)
        name=pathPrev
        name=name.split("/")
        name=name[len(name)-1]
        im.name = name  
        im.location = 200,200
        previewer = tree.nodes.new('TextureNodeOutput')    
        previewer.label = "Preview"
        previewer.location = 400,400
        links.new(im.outputs[0],previewer.inputs[0])
        #tex.type="IMAGE" # makes clip extend possible
        #tex.extension="CLIP"
        return {'FINISHED'}