vehicle animation render tips

[jasonazure]

Hi,

I'm currently producing some test renders for a well known car manufacturer, and I need to get a few pointers from anyone more experienced.

Initially, I had to produce some really high quality interior renders, so I used an HDRI environment image and vray portal lights shining in through all the windows to get a 'non-blotchy' render using IR/LC. This worked very well and all was good.

I have more recently been asked to produce a render starting inside the front of the car (high quality still required), but then I need to move the camera outside to see the whole car (in a real 3D environment - not HDRI image (apart from the sky)) and then into the back of the car with the doors opening and closing as required! Using a real environment as opposed to just an image has meant that one side of the car, facing a building, is being lit primarily via light bouncing off of the building and the interior render of the car is getting pretty blotchy regardless of light portals or anything else!

Is there any way to get better quality GI lighting inside the car in this scenario, or is there a possible cheat where I can produce a 360 HDRI render of the environment and shine this in through the windows via the portal lights to get more light information into the inside of the car?

Any suggestions would be appreciated!

[joconnell]

Probably turn off the glass to casting shadows so it isn't blocking your GI calculation - unless you've got tinted windows it'll probably be very close to doing a really cleanly sampled render with it calculating the windows fully. Render yourself some multimattes so you can darken the inside of the car after you've pulled through the glass.

[jasonazure]

Sorry! Forgot to mention that I've made the glass invisible to the GI. The GI calcs just see a car with holes where the windows are!

[joconnell]

And turned off to shadows too?

The IRmap / LC combination kind of falls down here if your light source is the bounce of a bounce - you're into using the Light cache here rather than the IRmap. The irmap is only used for the very first bounce of your gi so you might be getting some of this into the car but the majority of the illumination is likely coming from bounces that are being calculated by the light cache. Light cache is designed for filling out soft, airy volumes of light rather than producing very sharp results. It's brilliant for making interiors a lot lighter but most of them are made of flat white walls instead of detailed things. What might be worth a look is doing a render with irmap and no secondary bounce at all, then having a look at your global illumination render element to see how much you're getting from the first bounce of light and whether it's blotchy or not, secondly doing a render with your primary and secondary GI set to light cache to see the results of that. If the IRmap on it's own doesn't provide much light in the GI element then you may be getting a lot from your secondary bounces of GI which is the less detailed light cache. Might be worth your while trying to go to Brute force for primary and secondary to get sharper detail if it's the GI causing the issues.

[super gnu]

id point out that the imap is used for the first bounce *from the camera into the scene* since the light calculations in vray go backwards compared to reality. so it will always be the imap you are seeing.

id say its more likely to be the imap causing the blotchies than anythng else. (assuming your LC is decent enough, and you dont have any bad geometry in your scene)

however the simple answer to your question is dont use imap for animation. BF/LC or if you are really stuck, BF/BF are the way to go for anything with animated geometry.

rendertimes will go up significantly, but your setup headaches will disappear.