Hey all,

Having recently stumbled upon sprite-based rendering I am quite surprised to find that the technique is not used more widely (and more frequently) in films. The brilliant results that WETA achieved by using the combination of real life footage on sprites for the fire and smoke that emits from the Balrog, and the more recent work done by MPC on the ‘Sunshine’ cloud sequences, are a clear indication that the technique can be very successful.

It seems quite strange that such a versatile tool is not more prominent in today's industry.

Have any of you used sprites in projects?
If you have, what did you find to be negative or positive aspects in using them?
Why do you think that more people don't use sprites?

Any feedback would be greatly appreciated.

Thanks everyone, have a great day!

srgb

Yes those sprite rendering techniques are good for full shots, but not as for close up shots.
So in many studios, they will prefer to comp the real footage in stead of dealing with sprites or particle generations, otherwise if there is a hard camera movements and can't use real footage, best way to integrate fluid simulation.
I have used fluids for quite a long time, and trust me you can really achive nice results, but fluid simulations is quite time consuming.
There is a saying, for beauty you have to pay!

sprites are definately good for crowds … a big client changed their mind at the extreme last minute for a commercial (a day and a half) and I had to replace my whole scripted cached-mesh crowd with live-action green screen crowd (using sprites).

Luckily there was a feature in PFlow (max) to do an animated sprite crowd pretty easily but the cost on the render time was HUGE. The scene would barely open on a 64-bit monster machine and would crash all the render-farm computers.

I doubt this would have even been an issue in Houdini though since the particle features are a little more main-stream (heck-they even call them sprites in Houdini), and it's instanced at render-time I believe.

The key with the sprite crowd was definately to use planes etc for the closer stuff so you could have more control over the foreground. After about 3-rows back the repetition and flat-ness are almost unnoticable.

I use a lot of sprites. In my web page I have a totorial about doing a meteor with sprites in Houdini ( www.miguelperezsenent.com [miguelperezsenent.com] )
I think sprites are really great, I've recently used them with VEX procedural textures to create snow
http://forums.odforce.net/index.php?showtopic=5306 [forums.odforce.net]
and a tornado http://forums.odforce.net/index.php?act=ST&f=37&t=5251&st=0#entry35398 [forums.odforce.net]

With deep shadows the render is very fast and they look like volumetrics.

Hi Miguel, you have created some amazing pieces of work! As the forerunning individual in sprite-based rendering that I have encountered in the Sidefx forum so far, I was wondering if you be so kind as to provide me with a few of your personal opinions?

You seem to have a very sound knowledge of Houdini's VOPs level. Do you think that the ability to create high quality, fully CG sprite-based renders for volumetric smoke, snow, fire (i.e. not using any live-action footage for texturing as WETA did for the Balrog) is dependant on having a very good understanding of VOPs (and expressions)?

The reason I ask is because I completed your very thorough ‘Meteor’ tutorial and achieved some really nice results, but without a better understanding of VOPs and expressions on my part, I don't feel that I would be able to create the high standard of work that you have produced.

Do you have any advice for new Houdini users who are interested in pursuing the use of sprites in their work? Should they perhaps focus on the other areas first (such as VOPs and expressions) to gain a clearer understanding of the power that sprites can give you?

And, what do you think are the limitations of sprites with regards to being used as a tool for visual effects shots in films?

Thanks you for your time, and the inspiration that you provide to all of us.

Regards,

srgb

PS. Would you mind if I showed sections of your tutorial work (i.e. your excellent productions) on the website that I am creating for my Masters Student Research Project? You will be credited within the site and a link will be provided to your home page (if its ok with you)?

I'm glad you like my works, profcondor. Of course I don't mind if you put my tutorial in any place, it's an honor

The knowledge of VOPs is just to create the shaders properly, and the shader you have done reading my tutorial is exactly the same I've used in the snow and tornado scenes, only changing some values. I don't create a new shader for each scene, sometimes I improve it.
Vop shader works very well for smoke and things like that. To create realistic fire the better approach is to use live action footages, I did some tests a while ago and it works perfectly with Houdini.
Of course to start creating sprites you need a little experience with VOPs if you are going to create procedural shaders.

The main limitation of the sprites is that they are not volumetrics, You can't create all the thinks you could create with volumetrics, and the light setup sometimes requires tricks to give te volume sensation.

Miguel

“It seems quite strange that such a versatile tool is not more prominent in today's industry.”


hmm that's news to me..

Im pretty sure sprites are used whenever they can be used because of the economy, but there are alot of drawbacks which big time film aficianado's wont tollorate, such as rim lighting, and depth, meaning inside not volumey edge, but actually through the inside, especially when it hits comp.

I like sprites well enough, but my opinion is it's best suited for video games. To create a real nice looking volumetric effect, you should start with a real volume. IMO

-P

Thanks for the information Phenom. When I said, “It seems quite strange that such a versatile tool is not more prominent in today's industry”, I was basing this statement on the information, or rather, the lack thereof regarding sprites that I came across in my online search sessions. I found it rather hard to find articles in which the people involved with special fx shots for films ever mentioned sprites. I guess the fault lies in my presumption. I have just received an email from a very helpful gentleman in Australia who echoes the very things that you have pointed out. I am here to learn, so thank you for the insight.

When you mention ‘economy’ are you referring to render time?

Regards,

srgb

level of details should also be concerned, sprite can be any thing you can imagine,
trees, building, soldiers…, when it's too far away to have details, a sprite may save
you a lot of time.

prof. I apologize if I came off curt. Im on hour number 70 and will be working sat and sun also (mom thinks Im a jerk too ;-] ). So it's not you, it's me, and really im glad to help.

by economy I mean many things, yes render time is one of the main time savers, as is the intuitive results sprites yield. Burning through half-rez tests is a boon to an fx artist, with a volumetric renderer your voxel rez will often dictate the results, making half-vox-rez sims can be, at times, useless.

the big problem with a true volumetric renderer is the technical difficulties of art directing, and iterating through versions, and if your using a 3rd party renderer, integration can be hell, but the results are often worth the time and effort invested.


-P

Hi Miguel,

I've been going through your tutorial on procedural sprites using Houdini 9 and have come to a stopping point because of interface changes.

The geometry render tab seems to have changed a bit since the tutorial.
Could you give a pointer as to where to go from the SHADING, LIGHTNING AND RENDERING section?

Thanks!

MiguelPerez
I use a lot of sprites. In my web page I have a totorial about doing a meteor with sprites in Houdini ( www.miguelperezsenent.com [miguelperezsenent.com] )
I think sprites are really great, I've recently used them with VEX procedural textures to create snow
http://forums.odforce.net/index.php?showtopic=5306 [forums.odforce.net]
and a tornado http://forums.odforce.net/index.php?act=ST&f=37&t=5251&st=0#entry35398 [forums.odforce.net]

With deep shadows the render is very fast and they look like volumetrics.

Hi Miguel,

I've been going through your tutorial on procedural sprites using Houdini 9 and have come to a stopping point because of interface changes.

The geometry render tab seems to have changed a bit since the tutorial.
Could you give a pointer as to where to go from the SHADING, LIGHTNING AND RENDERING section?

Thanks!

MiguelPerez
I use a lot of sprites. In my web page I have a totorial about doing a meteor with sprites in Houdini ( www.miguelperezsenent.com [miguelperezsenent.com] )
I think sprites are really great, I've recently used them with VEX procedural textures to create snow
http://forums.odforce.net/index.php?showtopic=5306 [forums.odforce.net]
and a tornado http://forums.odforce.net/index.php?act=ST&f=37&t=5251&st=0#entry35398 [forums.odforce.net]

With deep shadows the render is very fast and they look like volumetrics.

Hi
as far as I know sprites are very widely used!
We just finished over 50 shots of clouds based on sprites for
Fred Clause.
I was responsible for cloud modeling development , and now I am ready for vacation and new job.
One thing I didnt try though and maybe someone did is to normal map sprite card to get better volume shadowing results?
regards
z

frogspasm_deux
Hi Miguel,

I've been going through your tutorial on procedural sprites using Houdini 9 and have come to a stopping point because of interface changes.

The geometry render tab seems to have changed a bit since the tutorial.
Could you give a pointer as to where to go from the SHADING, LIGHTNING AND RENDERING section?

Thanks!

Hi frogspasm. I have not tried to render sprites in H9 yet, so I don't really know how to do it.
But I think the way is using the shader called mantra procedural: sprites, or something like that.
Let me know if you do it!