Procedural modelling in Houdini based on Function Representation

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5.3 Morph<strong>in</strong>g Figure 5.4: Animation graph of the truck animation 5.3 Morph<strong>in</strong>g The fact that objects are mathematical functions allows us to <strong>in</strong>terpolate between these functions. For the user, all that is needed is to connect two objects us<strong>in</strong>g a metamorphosis node. Figure 5.5 shows an example of metamorphosis of two objects with different topologies. Figure 5.5: Metamorphosis of simple 3D character to a screw 31
5.4 Limitations 5.4 Limitations All of the functionality the FRep API offers is still not <strong>in</strong>tegrated at this stage. However, the project has been designed with extendability <strong>in</strong> m<strong>in</strong>d. There is a list of known issues and limitations to the current system: • The node type is currently determ<strong>in</strong>ed by compar<strong>in</strong>g node names (e.g. frep_bend). Therefore, if the node is renamed, the tree traversal algorithm ceases to recognise it. However, suffixes can still be added (i.e. frep_bend_arm will work). To solve this, nodes would have to be identified by their class type which would be one of the first issues to fix <strong>in</strong> a potential future version. • The polygonisation can not be canceled us<strong>in</strong>g the escape key like it is good practice <strong>in</strong> Houd<strong>in</strong>i. This has to do with the fact that Houd<strong>in</strong>i’s <strong>in</strong>terrupt has to be placed with<strong>in</strong> the loop of a critical operation. S<strong>in</strong>ce the polygonisation is part of the FRep API, this is not possible. • When animat<strong>in</strong>g FRep attributes, like alpha <strong>in</strong> the metamorph node, the nodes are not refreshed. The current work around is to set two keyframes to an attribute of any other Houd<strong>in</strong>i native node <strong>in</strong> the network (even if it is not chang<strong>in</strong>g values). The reason might lie <strong>in</strong> the evaluation of animatable attributes <strong>in</strong> custom nodes, but needs further <strong>in</strong>vestigation. • There can only be one FRep base node per network, so it is not possible to feed a f<strong>in</strong>al FRep node back <strong>in</strong>to another one. This behaviour is correct, but an appropriate error message should be displayed. • Bypass<strong>in</strong>g a node currently has no effect on the system. The solution would be to query this flag for every node dur<strong>in</strong>g tree traversal and simply ignore bypassed nodes (cont<strong>in</strong>ue the execution of the recursive function). Some open questions rema<strong>in</strong> <strong>in</strong> terms of deploy<strong>in</strong>g the project to other platforms. One of the downsides of us<strong>in</strong>g the HDK rather than Python, is the requirement for the plug<strong>in</strong> to be recompiled on every platform us<strong>in</strong>g the same compiler Houd<strong>in</strong>i was compiled with. 32
Page 1 and 2: Procedural <strong
Page 3 and 4: Contents Abstract Table of Contents
Page 5 and 6: List of Figures 2.1 Example of a bo
Page 7 and 8: Acknowledgements I would like to ex
Page 9 and 10: Chapter 2 Previous work There are d
Page 11 and 12: 2.2 The Function Representation (FR
Page 13 and 14: 3.1 FRep API Figure 3.1: Full struc
Page 15 and 16: 3.1 FRep API Figure 3.3: FRep tree
Page 17 and 18: 3.2 Houdini Develo
Page 19 and 20: 3.2 Houdini Develo
Page 21 and 22: Chapter 4 Design and implementation
Page 23 and 24: 4.2 Development environment 4.2 Dev
Page 25 and 26: 4.3 Using the FRep
Page 27 and 28: 4.4 Procedural fun
Page 37: 5.2 Animation Figure 5.2: Pengu<str
Page 41 and 42: 6.2 Future work 6.2 Future work In

Procedural modelling in Houdini based on Function Representation

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