Add blender sdf export tutorial

examples/scripts/blender/sdf_exporter.py

@@ -0,0 +1,207 @@
+import bpy
+import os.path
+from bpy_extras.io_utils import ImportHelper
+from bpy.props import StringProperty, BoolProperty
+from bpy.types import Operator
+
+import xml.etree.ElementTree as ET
+from xml.dom import minidom
+
+# Target blender version: 2.82
+
+########################################################################################################################
+### Exports model.dae of the scene with textures, its corresponding model.sdf file, and a default model.config file ####
+########################################################################################################################
+def export_sdf(prefix_path):
+
+    dae_filename = 'meshes/model.dae'
+    sdf_filename = 'model.sdf'
+    model_config_filename = 'model.config'
+    lightmap_filename = 'LightmapBaked.png'
+    model_name = 'my_model'
+
+    # Exports the dae file and its associated textures
+    bpy.ops.wm.collada_export(filepath=prefix_path+dae_filename, check_existing=False, filter_blender=False, filter_image=False, filter_movie=False, filter_python=False, filter_font=False, filter_sound=False, filter_text=False, filter_btx=False, filter_collada=True, filter_folder=True, filemode=8)
+
+    # objects = bpy.context.selected_objects
+    objects = bpy.context.selectable_objects
+    mesh_objects = [ o for o in objects if o.type == 'MESH' ]
+    light_objects = [ o for o in objects if o.type == 'LIGHT' ]
+
+    #############################################
+    #### export sdf xml based off the scene #####
+    #############################################
+    sdf = ET.Element('sdf', attrib={'version':'1.8'})
+
+    # 1 model and 1 link
+    model = ET.SubElement(sdf, "model", attrib={"name":"test"})
+    static = ET.SubElement(sdf, "static")
+    static.text = "true"
+    link = ET.SubElement(model, "link", attrib={"name":"testlink"})
+    # for each geometry in geometry library add a <visual> tag
+    for o in mesh_objects:
+        visual = ET.SubElement(link, "visual", attrib={"name":o.name})
+
+        geometry = ET.SubElement(visual, "geometry")
+        mesh = ET.SubElement(geometry, "mesh")
+        uri = ET.SubElement(mesh, "uri")
+        uri.text = dae_filename
+        submesh = ET.SubElement(mesh, "submesh")
+        submesh_name = ET.SubElement(submesh, "name")
+        submesh_name.text = o.name
+
+        # grab diffuse/albedo map
+        diffuse_map = ""    
+        nodes = o.active_material.node_tree.nodes
+        principled = next(n for n in nodes if n.type == 'BSDF_PRINCIPLED')
+        if principled is not None:
+            base_color = principled.inputs['Base Color'] #Or principled.inputs[0]
+            value = base_color.default_value
+            if len(base_color.links):
+                link_node = base_color.links[0].from_node
+                diffuse_map = link_node.image.name
+
+        # setup diffuse/specular color
+        material = ET.SubElement(visual, "material")
+        diffuse = ET.SubElement(material, "diffuse")
+        diffuse.text = "1.0 1.0 1.0 1.0"
+        specular = ET.SubElement(material, "specular")
+        specular.text = "0.0 0.0 0.0 1.0"
+        pbr = ET.SubElement(material, "pbr")
+        metal = ET.SubElement(pbr, "metal")
+        if diffuse_map != "":
+            albedo_map = ET.SubElement(metal, "albedo_map")
+            albedo_map.text = diffuse_map
+
+        # for lightmapping, add the UV and turn off casting of shadows
+        if os.path.isfile(lightmap_filename):
+            light_map = ET.SubElement(metal, "light_map", attrib={"uv_set":"1"})
+            light_map.text = lightmap_filename
+
+            cast_shadows = ET.SubElement(visual, "cast_shadows")
+            cast_shadows.text = "0"
+
+    def add_attenuation_tags(light_tag, blender_light):
+        attenuation = ET.SubElement(light, "attenuation")
+        range = ET.SubElement(attenuation, "range")
+        range.text = str(blender_light.cutoff_distance)
+        linear_attenuation = ET.SubElement(attenuation, "linear")
+        linear_attenuation.text = str(blender_pointlight.linear_attenuation)
+        quad_attenuation = ET.SubElement(attenuation, "quadratic")
+        quad_attenuation.text = str(blender_pointlight.quadratic_coefficient)
+        const_attenuation = ET.SubElement(attenuation, "constant")
+        const_attenuation.text = str(blender_pointlight.constant_coefficient)
+
+    # export lights
+    for l in light_objects:
+        blender_light = l.data
+
+        if blender_light.type == "POINT":
+            light = ET.SubElement(link, "light", attrib={"name":l.name, "type":"point"})
+            diffuse = ET.SubElement(light, "diffuse")
+            diffuse.text = str(blender_light.color.r) + " " + str(blender_light.color.g) + " " + str(blender_light.color.b) + " 1.0"
+            blender_pointlight = bpy.types.PointLight(blender_light)
+
+            add_attenuation_tags(light, blender_pointlight)
+
+        if blender_light.type == "SPOT":
+            light = ET.SubElement(link, "light", attrib={"name":l.name, "type":"spot"})
+            diffuse = ET.SubElement(light, "diffuse")
+            diffuse.text = str(blender_light.color.r) + " " + str(blender_light.color.g) + " " + str(blender_light.color.b) + " 1.0"
+            blender_spotlight = bpy.types.SpotLight(blender_light)
+
+            add_attenuation_tags(light, blender_spotlight)
+            # note: unsupported <spot> tags in blender
+
+        if blender_light.type == "SUN":
+            light = ET.SubElement(link, "light", attrib={"name":l.name, "type":"directional"})
+            diffuse = ET.SubElement(light, "diffuse")
+            diffuse.text = str(blender_light.color.r) + " " + str(blender_light.color.g) + " " + str(blender_light.color.b) + " 1.0"
+            blender_pointlight = bpy.types.SunLight(blender_light)
+
+        if blender_light.type == "SUN" or blender_light.type == "SPOT":
+            direction = ET.SubElement(light, "direction")
+            direction.text = str(l.matrix_world[0][2]) + " " + str(l.matrix_world[1][2]) + " " + str(l.matrix_world[2][2])
+
+        # unsupported: AREA lights
+
+        cast_shadows = ET.SubElement(light, "cast_shadows")
+        cast_shadows.text = "true"
+
+        # todo : bpy.types.light script api lacks an intensity value, possible candidate is energy/power(Watts)?
+        intensity = ET.SubElement(light, "intensity")
+        intensity.text = "1.0"
+
+    ## sdf collision tags
+    collision = ET.SubElement(link, "collision", attrib={"name":"collision"})
+
+    geometry = ET.SubElement(collision, "geometry")
+    mesh = ET.SubElement(geometry, "mesh")
+    uri = ET.SubElement(mesh, "uri")
+    uri.text = dae_filename
+
+    surface = ET.SubElement(collision, "surface")
+    contact = ET.SubElement(collision, "contact")
+    collide_bitmask = ET.SubElement(collision, "collide_bitmask")
+    collide_bitmask.text = "0x01"
+
+    ## sdf write to file
+    xml_string = ET.tostring(sdf, encoding='unicode')
+    reparsed = minidom.parseString(xml_string)
+
+    sdf_file = open(prefix_path+sdf_filename, "w")
+    sdf_file.write(reparsed.toprettyxml(indent="  "))
+    sdf_file.close()
+
+    ##############################
+    ### generate model.config ####
+    ##############################
+    model = ET.Element('model')
+    name = ET.SubElement(model, 'name')
+    name.text = model_name
+    version = ET.SubElement(model, 'version')
+    version.text = "1.0"
+    sdf_tag = ET.SubElement(model, "sdf", attrib={"sdf":"1.8"})
+    sdf_tag.text = sdf_filename
+
+    author = ET.SubElement(model, 'author')
+    name = ET.SubElement(author, 'name')
+    name.text = "Generated by blender SDF tools"
+
+    xml_string = ET.tostring(model, encoding='unicode')
+    reparsed = minidom.parseString(xml_string)
+
+    config_file = open(prefix_path+model_config_filename, "w")
+    config_file.write(reparsed.toprettyxml(indent="  "))
+    config_file.close()
+
+
+#### UI Handling ####
+class OT_TestOpenFilebrowser(Operator, ImportHelper):
+  bl_idname = "test.open_filebrowser"
+  bl_label = "Save"
+
+  directory : bpy.props.StringProperty(name="Outdir Path")
+
+  def execute(self, context):
+    """Do the export with the selected file."""
+
+    if not os.path.isdir(self.directory):
+        print(self.directory + " is not a directory!")
+    else:
+        print("exporting to directory: " + self.directory)
+        export_sdf(self.directory)
+    return {'FINISHED'}
+
+def register(): 
+    bpy.utils.register_class(OT_TestOpenFilebrowser) 
+def unregister(): 
+    bpy.utils.unregister_class(OT_TestOpenFilebrowser)
+
+if __name__ == "__main__":
+    register() 
+    bpy.ops.test.open_filebrowser('INVOKE_DEFAULT')
+
+# alternatively comment the main code block and do a function call without going through all the ui
+# prefix_path = '/home/ddeng/blender_lightmap/final_office/office/'
+# export_sdf(prefix_path)

tutorials.md.in

@@ -30,6 +30,7 @@ Ignition @IGN_DESIGNATION_CAP@ library and how to use the library effectively.
 * \subpage collada_world_exporter "Collada World Exporter": Export an entire world to a single Collada mesh.
 * \subpage underwater_vehicles "Underwater Vehicles": Understand how to simulate underwater vehicles.
 * \subpage particle_mitter "Particle emitter": Using particle emitters in simulation
+* \subpage blender_sdf_exporter "Blender SDF Exporter": Use a blender script to export a model to the SDF format.
 
 **Migration from Gazebo classic**
 

tutorials/blender_sdf_exporter.md

@@ -0,0 +1,21 @@
+\page blender_sdf_exporter Blender SDF Exporter
+
+Blender is a Digital Content Creation (DCC) tool for working with 3d models.
+In some cases you may be using it to bake lighting and environment maps.
+
+The Blender SDF exporter is a blender script in which you can run within Blender to
+export your meshes, their associated textures and lights to a dae file, its 
+corresponding SDF file and config file.
+
+Please note that the SDF format does not have 1 to 1 parity of features with Blender's
+mesh/materials/lights feature set. As such feel free to customize the script as needed.
+
+## Using the Blender SDF Exporter
+
+1. Download the blender script in [sdf_exporter.py](https://github.com/ignitionrobotics/ign-gazebo/tree/ign-gazebo5/examples/scripts/blender/sdf_exporter.py). 
+
+2. Open the script under Blender's Scripting tab and run it.
+
+3. You will see a file dialog requesting for a location to save the files to. Hit 'Save' when you are done.
+
+4. The files `meshes/model.dae`, `model.config` and `model.sdf` will be created at the location you specified.