Object animation cheat

[podlovics]

A small tutorial of how to reduce prepass rendering time to half/third/fourth/fifth of the original prepass calculation in case of object animation

I was very pissed with one client who wanted a built-in closet's door open in an archviz animation while going around in the house.
I had to render prepass for each 400 frames while the doors slowly opened. I was wondering if I could just use every 2nd or even every 5th frame to render the prepass and interpolate between them for the final animation.
So I made a test. In the attached movie you can see the animated cube in 2 versions.
In the Every2nd.mp4 every 2nd Anim Prepass frame was rendered: pre_0000, pre_0002, pre_0004, etc. Then I used IrfanView's (a very good image viewing program) Batch Rename function to rename every prepass file to one higher number. So pre_0000 became pre_0001, pre_0002 became pre_0003, etc.
This way I had the prepass files for every frame, although every odd number was the same as the one before.
Then I used the Anim render function in vray, set the Interpolated frames to 3 and I got this result.
http://download.podlovics.hu/tutorial/Every2nd.mp4

I went even further, rendered the prepass for every 5th frame, converted pre_0000 to pre_0001, pre_0002, pre_0003, pre_0004 and so on and rendered the cube with this setup too. In this case I set the Interpolated samples to 5 in the Anim render.
The result is here:
http://download.podlovics.hu/tutorial/Every5th.mp4

The result was still ok, although it had some flickering already. However if the animation movement is slow you can use higher values, especially if you have dark surfaces, where diffuse lights are not that strong, anyway.

I hope it was clear.
Tamas

[stefan]

yes thats a nice trick.

in vray 1.2.1 we have a very nice new function in that regard, where you can override GI per material to use brute force instead of IR.

so if only few things animate(like cars on a street, moving doors and windows, etc) you can set the influenced materials to use BR, all the rest can still take a baked simple flythrough animation GI. this makes great new work flows possible, which all use the super fast multiframe incremental method:-)

cheers
stefan

[zoppo]

very clever and very interesting. thanks.

[STRAT]

yes, the vray gi is very flexible and worth experimenting any ideas you have.

for instance, in our animation in the link here - http://vimeo.com/8718427?hd=1 the building of the bridge bit at around 30 seconds (completely flicker free in HD) was standard ir/lc camera animation, purely because this kind of 'progressive' animation lent itself perfectly to it. if your object animation leaves no residuals from frame to frame then there's no reason why normal camera animation techniques wont be completely flicker free.

[podlovics]

BTW if anyone cares to see the final animation it can be downloaded from here:
http://download.podlovics.hu/zimits/
I recomment Save target as... since it is a non-streaming mp4 file, 170MB
The opening of the doors was rendered before I figured out my new cheat and there is some flicker, but I just did not want to re-render those 400 frames because of this.
Tamas

[Diegoto]

yes thats a nice trick.

in vray 1.2.1 we have a very nice new function in that regard, where you can override GI per material to use brute force instead of IR.



Stefan, could you tell me the steps to do what are saying?

Thanks!

Diego

[stefan]

deactivate "use irradiance map" in the material you want to render brute force, all objects using such materials will render brute force.

also using detail ehencement is using brute force, for corners and details then.
both very handy to get best of both worlds, brute force detail and IR speed and cleanness.

[Diegoto]

Very interesting!

I noticed "use irradiance map" is only in the diffuse channels and not the whole material. Is there any other channel that I should check?

Thanks!

Diego

[stefan]

it affects the whole object who has this material applied, no need for each channel.
its only in diffuse as this is the "base" channel.