Hey all,

well the book is off to the publisher and I have had a good long nap so I have some time to get back into this. I'm looking at the pile of questions, threads and emails I have had since the book started to consume my days and nights!

I've decided to start out with a thread covering William Gaylord's particle issue. I will eventually get all these questions answered in one way or another.

I'm wrapping up some of the details for part one of this tut and will post it here as soon as I'm happy with it.

-David

Good to see the book is /has come along (can hardly wait) , and also to see you back on the board,

Michael

Thanks, David! I've really been looking forward to this and I think others will find a lot of value in it as well. Congratulations on getting your book off to the publishers! Look forward to that as well.

Bill Gaylord

Determining Needs



Unlike our previous efforts where we allow A:M to render buffers and then determine what we need to adjust after the final render is complete in the case where we need to split out data that is not possible inside the buffers of our EXR files.

In the case of William's ball person we are looking at particle effects, these particles need to be compositeid to avoid any geometry intersection arrtifacts that might come from a straight render. If you haven't already go ahead and look through William's original thread.

I will be using his data from that thread to generate files and renders to work with.


The goal of rendering particle effects separate is an obvious one: we need particles rendered into a series of images by themselves with an alpha channel (or some other masking method which we may get into later) in addition to that we need a set of images that have the other elements of the render in them (although we could break out each set of elements this will probably be uneccesary in this case.) This means that we need to break our elements up into two separate choreographies. this is important to pay attention to: if we are breraking things up into two separate choreographies we must be aware that this can only happen at the end of the animation process. any changes will not propigate through the split choreograpies and you will need top re-split them if you need to adjust anything. I always recommend leaving everything intact until a shot is 'in the can' so to speak. then and only then would I break out a layer.

Setting up the Choreographies

Once the animation is complete we save the choreography external to the project that it is in, I like to save it with a name like "choreography_master.cho" the master tag reminds me that this is the final animation version of a choreography, this allows me to roll back to the unsplit chor later if I need to. ONce you have your chor saved externally re-embed it in the project this in effect makes two versions of the chor: one master saved externally to the hard drive and a copy of the master embeded in the project. these two are now unrelated and you can make any changes you need to the one embeded in the project without damaging the master.

Now we re-name the chor that we embeded in the project I typically call it something such as "choreography_base" as it will be the base of all compositing efforts. Once that is renamed you can simply import the 'master' choreography. embed it and rename it for each non-buffered layer you need to render. In our case we will only need one additional choreography Let's call it "Choreography_particles" and make 100% sure that it is embeded (A:M has an embed all function that you can use to make sure of this if you like.)

Now each choreography gets changes made to the shortcuts for models inside of it to isolate those elements we need to pull out. ...



We'll cover that in part two, which I will start working on as I drink my coffee!
-David

I'm Following along, Nice tips too, so far..

Michael

Getting the Renders

Ok so the first thing we need to do is to determine: is this enough choreographies, and if so what do we want to appear in the rendered image from each chor?

We have one chor that can hold buffers found only in the EXR file this will include lights and shadows and other surface attributes. this will be fine for the base, what we need to ensure is that there are no particles rendered in this pass. this is a render property that does just that on the camera:



easy as pie. we now render this chor just as we do any other, using EXR will allow us to access buffers later and give us more compositing options, I would render it exactly like I did the Starting Simple project.

Our second chor is a little more complex, what we are looking to isolate here is the particles, we don't want any other aspect of the chor to render at all. we have a couple options on how we can accomplish this, my prefered method will not alter the contents of the chor at all: Start with the uneccesary models which in this case is just Ground and turn their active property to OFF:



now we have just the ball guy and the particles in the scene, we need to make the ball guy invisible so we can just keep the particles. we do this by setting the surface property for transparency on the shortcut in the particles chor to 100%:



now we render this chor in any file type that supports alpha channels. I like to use openEXR just to give more flexability when we composite later. but the only buffer we need will be the Alpha buffer:



but of course we will need to render with Multi-Pass on and Particles Enabled. we can, however turn off shadows and reflections to help speed things along.




Next time: Building the Composite

Sorry this took so long (and when you see how easy this is you really will wonder what the hold-up was!)

Building the Composite

When you have rendered out your project (twice once for the regular stuff once for the particles as we set up earlier) you will have two sets of images something like these:



We start like we would with the Starting Simple composite, simply take the EXR sequences into A:M and build a composite for the diffuse elements of the scene. The resuling comp will look like this in the PWS"



From here we want to layer the particles into the scene. This is easily done... almost too easily done

at the final mix node of the composte bring up the contextual menu and add an Over node:



This node will have two inputs somewhat like a Mix but the second input will be layered over the top of the first. In our case we want to put the particles Over the rest of this comp. THis works because we rendered the particles out with an alpha channel (and made the sphere transparent in the render.) Over uses this alpha channel to mask out parts of a sequence before layering it on top of the rest of the composite. Simple drarg and drop the color alpha channel from the particles render onto the Over node



Now comes the tricky part... no wait... we're done! simply:



Save as animation and call it a night! No really that's it!

Check out the composited animation and give it a whirl!

-David

Thanks, David!! Really appreciate the time you've put in to this. Time for me to put it to practice and do some roasting!

David,
Thanks again for the tut on composite. I must admit I got lost her on the last part were you say at the final mix node of the composite bring up the context menu. Could you tell me the location of this node more spacifily or or draw a circle around this node in the image?
By the way I can not wait for your next book to come out. Do you know what the release date will be yet?