C4D .obj to Houdini.

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Joined: June 2020

I am new to Houdini, making the transition from Cinema 4D, when I export a .obj file to Houdini the file inside Houdini is extremely big so I have to scale it dow, when working with the Pyro FX Houdini creates another instance of the imported .obj file and I had encountered several issues, can someone please explain e the proper procedure to export .obj´s files in order to use them correctly inside Houdini?.

Thanks in advance.
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Joined: Oct. 2016

obj is a file format that “thinks” in unitless values, meaning, there is no fixed “scale” for an OBJ. Within your pipeline, you will usually define your scale anyway (e.g. “1 = 1 m” in the civilized world) and there is no fixed rule for what this unit is.

Some applications are having problems with floating-point accuracy and therefor prefer large values (a human being there would be 180 units in size - which you COULD read as cm, but, see above, that's not defined). If you export from such an application or if your scene scale is huge (simply look at the VALUES you are exporting!), any application that uses - for example - SI as a unit scale will probably import the model over-sized.

If you want to work with grids/volumes/VDB etc, you probably want to keep values within reasonable measures. Again, mainly because of floating-point limitations. Depending on which system you use (libraries etc), you will have a “sweet spot” of values (Bullet for example prefers a value range between 1 and 10 for the most part). Read: You will most likely have to scale on import and export anyway, so setting up a proper pipeline unit makes a lot of sense.

Marc Albrecht
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