Animating a moving sun

[CEJ1976]

Hi,

 

I have a few shots from an animation I am working on, where I have a stationary camera, but the sun is animated.

 

I was just wondering what methods people have used to achieve this in the past in terms of Light Cache calculation and Irr map calculations.

 

What's the most time effective way for a nice flicker free sequence? (using Vray)

 

Cheers.

[John Dollus]

for that situation, I usually, save out the LC to a file first and then pre calc the IR map at every 10-15 frames.

Depending on your scene, you could also just render a direct light pass of the sun and composite the result over a bg plate but that requires a bit more finesse.

[Corey Beaulieu]

I am likely wrong, but I don't believe you can use IRR/LC in this situation. Maybe you could get away with the animation pre-pass method, but any pre-calc is going to be wrong. Light cache stores an average light value for the geometry of each pixels in your image. To get this to acknowledge change over time, you are going to need to render it Brute force with LC on single frame.

[CEJ1976]

Thanks for the ideas fellas.

 

I found this post from a few years back, seems to make sense and I think I will give it a go, just though I would share it with you - it was posted by Brian Kitts:

 

Re: Vray Timelapse / different times of day

 

I've done some testing with this as I'm going to be doing an animation coming up where we are doing the same thing of timelapsing day to night.

 

I leave the lightcache set to single frame, 800 subdivs, then run the irradiance in animation(prepass) mode for every frame, that way the lightcache info gets saved into the irradiance map (remember the light cache info is used to approximate the irradiance map at calculation time).

 

Then after you have the irr precalced go back and render the animation with Lightcache still set to single frame, and the irradiance set to animation(render). Right now Im using the blending set to 2 frames for the IRR map.

 

Seems to be working pretty well. You get the speed advantage having the lightcache calc, even though it's running at every frame,it's alot quicker than using brute force for your secondary light bounces. Then frame blending of the animation irr map smooths the GI changing throughout.

[salvador]

I did one some time ago but I had to discard it because it didn't come out clean and the time was drawing near. I'll certainly try to clear some time to test according to Ciaran Ryan's approach.

[John Dollus]

Yes, the post you included is the method i was trying to describe though every 2 frames seems too much but it does depend upon your rate of change and total frame count.

[off the cuffe]

Do what John suggested, as I have done this before with good results. Render a single frame with hi gi settings, save the image as a 32 bit image. Then turn off gi altogether and apply a an override texture of black to the whole scene or just save out the direct igniting channel. Then do some post production with the saved channels.

[CEJ1976]

Thanks.

 

I went with the prepass option which has worked out perfectly and the end result is completely smoothe. the prepass did not take too long too calculate as I set it off across my render farm.

 

I highly recommend this option, and the 2 frame blending mode was perfect.

 

Cheers.