The Field Concept and Dependency Graphs. Tim Weißker

Transcription

1 The Field Concept and Dependency Graphs Tim Weißker

2 Recap: Scene Graphs hierarchical representation of the elements of a scene (and their properties) to be rendered simplified scene graph for a motorcycle 2 The Field Concept and Dependency Graphs

3 Recap: Scene Graphs hierarchical representation of the elements of a scene (and their properties) to be rendered the field concept defines every node of the scene graph being a field container simplified scene graph for a motorcycle 3 The Field Concept and Dependency Graphs

4 Recap: Scene Graphs hierarchical representation of the elements of a scene (and their properties) to be rendered the field concept defines every node of the scene graph being a field container simplified scene graph for a motorcycle But what does that mean? 4 The Field Concept and Dependency Graphs

5 Definitions field more complex form of an attribute represents object state information input and output fields easy serialization and distribution 5 The Field Concept and Dependency Graphs

6 Examples Fields avango SFBool SFInt SFFloat [ ] SFMatrix4 SFVec3 SFVec4 [ ] avango.gua 6 The Field Concept and Dependency Graphs

7 Definitions field container collection of fields method called when one field changes 7 The Field Concept and Dependency Graphs

8 Definitions field container collection of fields method called when one field changes example: class Increment(avango.script.Script): Increment Input : SFInt Output : SFInt Input = avango.sfint() Output = avango.sfint() def evaluate(self): self.output.value = self.input.value The Field Concept and Dependency Graphs

9 Definitions method Input : SFInt Output : SFInt def evaluate(self): self.output.value = self.input.value + 1 a field container s method executes max. three steps in the following order 9 The Field Concept and Dependency Graphs

10 Definitions method Input : SFInt Output : SFInt def evaluate(self): self.output.value = self.input.value + 1 a field container s method executes max. three steps in the following order read values from local input fields 10 The Field Concept and Dependency Graphs

11 Definitions method Input : SFInt Output : SFInt def evaluate(self): self.output.value = self.input.value + 1 a field container s method executes max. three steps in the following order read values from local input fields calculate new values derived from the read values 11 The Field Concept and Dependency Graphs

12 Definitions method Input : SFInt Output : SFInt def evaluate(self): self.output.value = self.input.value + 1 a field container s method executes max. three steps in the following order read values from local input fields calculate new values derived from the read values write the results to the output fields 12 The Field Concept and Dependency Graphs

13 Definitions method Input : SFInt Output : SFInt def evaluate(self): self.output.value = self.input.value + 1 a field container s method executes max. three steps in the following order read values from local input fields calculate new values derived from the read values write the results to the output fields to increase reuse, no external data should be accessed 13 The Field Concept and Dependency Graphs

14 Examples Fields SFBool SFInt SFFloat [ ] avango SFMatrix4 SFVec3 SFVec4 [ ] avango.gua Field Containers avango.gua TransformNode GeometryNode PointLightNode Classes derived from avango.script.script 14 The Field Concept and Dependency Graphs

15 Implementing a field container class Container(avango.script.Script): 15 The Field Concept and Dependency Graphs

16 Implementing a field container class Container(avango.script.Script): #declaration of fields, e.g. sf_mat = avango.gua.sfmatrix4() 16 The Field Concept and Dependency Graphs

17 Implementing a field container class Container(avango.script.Script): #declaration of fields, e.g. sf_mat = avango.gua.sfmatrix4() def init (self): self.super(container). init () 17 The Field Concept and Dependency Graphs

18 Implementing a field container class Container(avango.script.Script): #declaration of fields, e.g. sf_mat = avango.gua.sfmatrix4() def init (self): self.super(container). init () def my_constructor(parameter1, PARAMETER2, ): #initialize variables, parameters, etc. 18 The Field Concept and Dependency Graphs

19 Implementing a field container class Container(avango.script.Script): #declaration of fields, e.g. sf_mat = avango.gua.sfmatrix4() def init (self): self.super(container). init () def my_constructor(parameter1, PARAMETER2, ): #initialize variables, parameters, etc. def evaluate(self): #perform update when fields change 19 The Field Concept and Dependency Graphs

20 Evaluation policies class Container(avango.script.Script): #declaration of fields, e.g. sf_mat = avango.gua.sfmatrix4() def init (self): self.super(container). init () def my_constructor(parameter1, PARAMETER2, ): #initialize variables, parameters, etc. def evaluate(self): #perform update when fields change 20 The Field Concept and Dependency Graphs

21 Evaluation policies called when at least one of the fields changes 21 The Field Concept and Dependency Graphs

22 Evaluation policies class Container(avango.script.Script): #declaration of fields, e.g. sf_mat = avango.gua.sfmatrix4() def init (self): self.super(container). init () self.always_evaluate(true) def my_constructor(parameter1, PARAMETER2, ): #initialize variables, parameters, etc. def evaluate(self): #perform update every frame 22 The Field Concept and Dependency Graphs

23 Evaluation policies called when at least one of the fields changes self.always_evaluate(true) forces evaluation every frame regardless of field changes 23 The Field Concept and Dependency Graphs

24 Evaluation policies class Container(avango.script.Script): #declaration of fields, e.g. sf_mat = avango.gua.sfmatrix4() def init (self): self.super(container). init () def my_constructor(parameter1, PARAMETER2, ): #initialize variables, parameters, def sf_mat_changed(self): #perform update when sf_mat changed 24 The Field Concept and Dependency Graphs

25 Evaluation policies called when at least one of the fields changes self.always_evaluate(true) forces evaluation every frame regardless of field only evaluated when SFFoo changes function name can vary 25 The Field Concept and Dependency Graphs

26 Dependencies sometimes it is the case that an output field of one field container forms the input of another one (e.g. sensors) 26 The Field Concept and Dependency Graphs

27 Dependencies sometimes it is the case that an output field of one field container forms the input of another one (e.g. sensors) field connections: the value of a field is copied into another one after evaluation Node A Input : type Output : type Dependency Field connection Node B Input : type Output : type 27 The Field Concept and Dependency Graphs

28 Dependencies sometimes it is the case that an output field of one field container forms the input of another one (e.g. sensors) field connections: the value of a field is copied into another one after evaluation Node A Input : type Output : type Dependency Field connection Node B Input : type Output : type b.input.connect_from(a.output) 28 The Field Concept and Dependency Graphs

29 Dependencies problem: if node B is evaluated before node A, the input of B is not specified Node A Input : type Output : type evaluatedependency() Node B Input : type Output : type evaluatedependency() 29 The Field Concept and Dependency Graphs

30 Dependencies problem: if node B is evaluated before node A, the input of B is not specified Node A Input : type Output : type evaluatedependency() Node B Input : type Output : type evaluatedependency() solution: evaluatedependency() method is called on all unevaluated field containers recursively calls same method on all dependent field containers then calls on itself returns when recognizing a loop (warning message) 30 The Field Concept and Dependency Graphs

31 Feedback propagation although evaluatedependency() checks and ignores cyclic dependencies, they are sometimes unavoidable 31 The Field Concept and Dependency Graphs

32 Feedback propagation although evaluatedependency() checks and ignores cyclic dependencies, they are sometimes unavoidable let s suppose we want to move a figure in a virtual environment using an input device (e.g. joystick) 32 The Field Concept and Dependency Graphs

33 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 33 The Field Concept and Dependency Graphs

34 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 34 The Field Concept and Dependency Graphs

35 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 Combining the last and relative transformation matrix in one 35 The Field Concept and Dependency Graphs

36 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 GroundFollowing sf_mat : SFMatrix4 sf_corrected_mat : SFMatrix4 Combining the last and relative transformation matrix in one 36 The Field Concept and Dependency Graphs

37 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 GroundFollowing sf_mat : SFMatrix4 sf_corrected_mat : SFMatrix4 Combining the last and relative transformation matrix in one Corrects the transformation matrix with respect to collisions 37 The Field Concept and Dependency Graphs

38 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 GroundFollowing sf_mat : SFMatrix4 sf_corrected_mat : SFMatrix4 Combining the last and relative transformation matrix in one Corrects the transformation matrix with respect to collisions 38 The Field Concept and Dependency Graphs

39 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 GroundFollowing sf_mat : SFMatrix4 sf_corrected_mat : SFMatrix4 Combining the last and relative transformation matrix in one Corrects the transformation matrix with respect to collisions problem: the output of GroundFollowing is required as an input in the next frame to be rendered 39 The Field Concept and Dependency Graphs

40 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 GroundFollowing sf_mat : SFMatrix4 sf_corrected_mat : SFMatrix4 solution: weak field connection 40 The Field Concept and Dependency Graphs

41 Feedback propagation KeyboardInput sf_move_left : SFBool sf_move_right : SFBool sf_jump : SFBool sf_move_vec : SFVec3 Accumulator sf_move_vec : SFVec3 sf_mat : SFMatrix4 GroundFollowing sf_mat : SFMatrix4 sf_corrected_mat : SFMatrix4 solution: weak field connection is ignored during dependency evaluation the corresponding value however is propagated in the next frame accum.sf_mat.connect_weak_from(gf.sf_corrected_mat) 41 The Field Concept and Dependency Graphs

42 Transform nodes in the scenegraph Node TransformNode Name : SFString Parent : SFNode Children : MFNode Transform : SFMatrix4 WorldTransform : SFMatrix4 42 The Field Concept and Dependency Graphs

43 Summary every node of the scene graph and classes derived from avango.script.script are called field container 43 The Field Concept and Dependency Graphs

44 Summary every node of the scene graph and classes derived from avango.script.script are called field container state of a field container is defined by state of the fields easy serialization easy network distribution within AVANGO 44 The Field Concept and Dependency Graphs

45 Summary every node of the scene graph and classes derived from avango.script.script are called field container state of a field container is defined by state of the fields easy serialization easy network distribution within AVANGO within a field container, no external data is accessed dependencies are realized with field connections loose coupling between field container instances easily reusable ( component-based design) 45 The Field Concept and Dependency Graphs

46 Summary every node of the scene graph and classes derived from avango.script.script are called field container state of a field container is defined by state of the fields easy serialization easy network distribution within AVANGO within a field container, no external data is accessed dependencies are realized with field connections loose coupling between field container instances easily reusable ( component-based design) feedback propagation using weak field connections 46 The Field Concept and Dependency Graphs

47 References Kuck, R., Wind, J., Riege, K., Bogen, M.: Improving the AVANGO VR/AR Framework Lessons Learned, Paper from the 5th GI VR/AR workshop, 2008 Fröhlich, B., Bernstein, A.C.: Avango Virtual Reality Framework, Virtual Reality lecture, 2011 Avango: Autodesk Maya Documentation: Guacamole simple example (VR Cluster): /opt/avango/master/examples/simple_example 47 The Field Concept and Dependency Graphs

48 The End Thank you for your attention! In your next assignment, you will build your first own dependency graph. Have fun 48 The Field Concept and Dependency Graphs