Smoke and Fire

Everything is rendered and composited and unless there are some hidden compositing issues I am almost ready to press the final composite button ;o) The last thing that I'm tweaking is the smoke and fire on the sofa. The start of it is great, but it's not working when the emitter on the sofa is scaled. I've just switched from having 1 emitter on the sofa to having 3 and it looks good in the render region. I also removed the collision that I had set up to the sofa geometry, I'm hoping that this is what was causing the fire to take so long to render.

Anyway, here goes to launching the smoke and fire renders and hoping that will be it!

Fire crashing

hmm this is the second time I've had trouble rendering a fire particle pass (using sprites). Rendering from the command line would render 2 or 3 frames and then the window would close. Rendering interactively would crash XSI. The first time this happened a few months ago I changed the sprite (just by duplicating it and changing its name). Today changing the sprite didn't solve the issue. Today's solution was to duplicate the entire PType (I have 2 emitters that were using the same Ptype). I saved the PType preset and applied it to the second emitter. The color animation on the Ptype didn't get saved :o( so I copied the animation from the original ptype to the duplicate. The pass is now rendering more than 2 frames again from the command line.

clouds, emitters and partitions

Although it is possible to have more than one emitter per particle cloud, it might not be a good idea if you need to separate the emitters into different passes. It is the cloud that matters in the partition, so even if an emitter is not in the partition the emission from it may still appear in the render because the cloud that it belongs to is in the partition.

Why re-using a ptype may not give the same color results as the original

Remember that lighting affects the look of your particles, so if you are reusing a ptype with different lighting, it may look completely different. If you are doing this in the same scene and the emission is just not in the same position as the original, you can add an exclusive light to that particle cloud so that it can look the same as the other, but the rest of your scene won't be affected by the additional light.

animate particle color at frame 1 if you're using age% as the animation reference

This is probably obvious if you think about it, but since I just spent a couple of hours trying to figure out why my particles were rendering grey and not the animated colors I had set, I figure it's worth blogging. If you are using age% animation reference for the particle color, make sure the colors are animated at frame 1. Otherwise depending on what frame you are animating the emission at you may only get the last color of color animation.

more smoking

The volume shader didn't work out on the moose's moving cigarette... it looks great on a static object but looks strange on a moving object. I've reverted back to using particles. I've got a decent looking smoke emitting from the cigarette ash, using the beam type for the shape. I've added a vortex (child of the ash) to give the stream a bit of variety. It doesn't look convincing on a static frame but it does look pretty good in movement.

For the exhaling smoke, I've setup events to billow the smoke and have gravity, turbulence and vortex affecting the particles.

smokin

Lately, I've been spending most of my smoking moose time working on the smoke effects. Currently focusing on making the moose smoke his cigarette. I've analyzed cigarette smoking videos and films (from getty images and from some DVDs I have .. Ryan has some good examples of cigarette smoke). When smoking a cigarette there are 3 different types of smoke:

1. the smoke that rises from the tip (end) of the cigarette as it burns
2. the smoke that rises from the filter of the cigarette after an inhalation (most likely this is the smoke that has been pulled through the cigarette but didn't get inhaled)
3. the smoke that the smoker blows out

For now, I'm ignoring the 2nd type of smoke and just focus on the first and last .. if I hadn't have analyzed the video footage, I'm not sure I would have seen this 2nd type.

I started experimenting with XSI particles and then adding effects in the fx tree. This could work well if I could pin the start of the particles to the end of the cigarette (in theory this is possible using the tracker, but I'm using XSI 4.2 and the fxtree tracker crashes XSI... This is fixed in 5.0 but I'm a bit weary of upgrading at this point in production).

Currently I'm experimenting with the volume shader for cigarette smoke. You can get a good head start on this by using Holger Schonberger's preset downloadable from http://www.edharriss.com/shaders/shaders.htm. A small tip about using the volume shader technique - the smoke rises straight up until it hits the center of the object - so to control when the turbulence starts in the smoke, edit the center of the object.

For the exhaling of the smoke, I'm currently experimenting with the smoke explosion particleop.