I seem to be experiencing strange things in COPs, but I am not sure what exactly is happening.

Running VEX based COPs. Specifically Time Filter. Lets say that Time Filter COP is in a COP network sandwiched between two other COPs. If I were to press BYPASS option on Time Filter tile, that COP turns off, as its suppoused to. Now if I were to turn BYPASS off, the VEX runs but the RESULT of the COP is no longer affected by Time Filter COP. Weird right. If I delete that tile and replace it with a fresh Time Filter COP, everything works fine, untill I turn bypass option On and OFF again. In other words the Time Filter COP, once it is ignored, stays ignored. Perhaps its my machine, Athlon 1100 Ghz with 1gb if ram, but Time Filter COP renders very slowly. Other COPs render very fast by comparssion. To proccess 640X400 24bit frame takes Time Filter (5 & 1 setting) over two minutes.

Now what is the procedure for making COP network to work incrementally. That is so its caches the result of COP tiles, so when a new tile is added, only its effect is computed, as if the previous result is already cooked.

Thank you
David Rindner

I have to admit that I find the cops very slow. Considering how fast all the other aspects of Houdini are I was suprised to find using a mono tile and a blend tile to be less than interactive.. I do lot of after effects and combustion and I think that their cacheing systems must be way more advanced… I did like the fact that there is a cache sop. That way the end user can manage cacheing… Hopefully SESI will include a cache cop or is there one already… Also I would have thought that the compositor would have worked in 3d-space almost all modern composting tools are 2.5 d now. I was kind of expecting that from SESI.. Oh well I guess I won't throw out After Effects and Combustion upgrade offers just yet..

Perhaps HALO by itself may or may not have 2.5d capabilities as I understand them in AE5, but in Master I consider COPs to be 3d as they are integrated with rest of Houdini. You just have to pipe output of COP network into VEX or SHOP and map them into planes, which hang in 3D space.

For example. Say you have a photo of skyline, and wish to have a snaking particle stream, snaking inbetween the buildings. Heres how I would approach the shot, given what I know of Hoiudini.

After Photoshoping the photo to achive the dramatic lighting effect, I would construct a projection model.

Set up the image as COP and pipe it into Camera view as backround.
Using cam view as guide construct simple outlines (closed polygons)for each building, and place the polygon outlines in 3d space to approximate the spatial (depth) position of the building.

Merge SOP all those polygon outlines into single geometry.

Apply flat UV projection from Camera's position.

Make a SHOP that uses the cityscape image as diffuse and luminance maps. Apply the shader to the cityscape geometry. No lights are needed to light this scene as image is self illuminating. Thats your compositing layer #1.

Now I would create a curve path that I want the particle stream to take through the city.

In Particles, set up POPs to send stream of particles (light instances) along the path. Position POP provides nice way to define trajectory of particles with its Path option.

Pre-render the particle path using the cityscape geometry as alpha occluder.

Render the city-scape by itself w/o particles. The cool thing with projection models, is that camera can be animated a little bit providing true 3d cues with parralaxing. Only a small amount of movement is allowed as to much will reveal that cityscape is a bunch of flat polygons.

Now bring both passes into COP network, and apply various filters.

Composite render the final sequence.

Dave Rindner

You might want to check the compositor cache size under Edit > Preferences. The default value in Houdini Master is only 10 Mb which is hardly useful for real compositing.