Hi There

How do I render out my fluid sim in front of an image so the fluid sees the image?
Guessing it's thru compositing somehow but I can't figure it out and I can't find a tutorial that goes through this?

Any advice much appreciated.

cheers
Nigel.

Yes it involves compositing.

First render out your fluid simulation to a series of images. If this is anything but games industry standard is to render to OpenEXR or .exr as the extension. For games, it will most likely be .gif these days.

Once the sequence of frames is rendered, in Houdini go to /img/comp1 and add two File COPs. the first File COP will fetch your sequence. The second File COP loads in the background image. Then append an Over COP and using MiddleMouseButton on the two input tabs to the Over COP. You will see that the left input tab is Foreground and the right input tab is Background.

Wire the sequence in to the left Foreground input and the background image in to the right input or Background of the Over COP.

To render out the final composted sequence, append a ROP File Output COP to the Over and give a good name to the file and render out the final sequence.

Pretty straight forward.


To cover the basics, you can display your background image in the viewport when working on the scene by referencing the background image through the camera. Camera has the parameter to reference the background image. Then use the display option to turn the display of the background image on and off.

Hi Jeff

Thanks, yeah got that ta.
Tho If I'm supplying the fluid sim onward to a compositor I should just be leaving it against black?

cheers
Nigel.