What can be changed after saving a solution?

[tricky]

I have been pondering this question for some time now. When I pre-calc a solution for a piece of animation (camera only movement), what things can be changed afterwards that will not cause problems? The following are a list of statements/questions in no particular order. I am not sure which are true/false/rubbish!

eg:
1) I can calculate without glass, then render with glass and it will look ok.

2) I can calculate, then add an object and render - the object should be OK as long as I am happy with just the direct light and shadow that results fits OK with the pre-calc'ed solution - from the sunlight for eaxample

3) I can calculate, then remove an object: there will be a hole in the 'gi' where the object was, but the space behind it will be lit by the direct lights in the scene that weren't stored with the irradiance map.

4) I can calculate with various blurry (non interpolated) materials. At rendertime, I can remove blurry settings and the image will render fine, just with sharp reflections where once there were blurry.

5) I can calculate with a global switch of, say, 2 reflection/refraction. Then at rendertime up this value to, say, 10 and it will render fine.

6) I can calculate a solution and at rendertime, tweak bitmaps in diffuse slots - for instance, swap an oak bitmap for a cherrywood bitmap. The render will look fine, but the 'accurate' colour bounces from the original oak map will not be correctly updated for the redder tones in the cherrywood.

7) I can calculate with a certain setup of materials with certain glossy settings. Say a bit of metal has glossiness set to 0.9. At rendertime, if I change this to 0.75 will it render OK, just a bit more blurry?

Just a monday morning train of thought...

[rpc212]

Tricky I would like to know the answers to your questions too!

[vlado]

1) I can calculate without glass, then render with glass and it will look ok.

This is only partially true. If the glass is reflective, it may reflect regions that were not covered when you calculated the irradiance map. These regions will look wrong in the final rendering.

2) I can calculate, then add an object and render - the object should be OK as long as I am happy with just the direct light and shadow that results fits OK with the pre-calc'ed solution - from the sunlight for example.

Again, this is only partially true. V-Ray will still attempt to use the irradiance map for that object, which may lead to artifacts. However, you can turn off the "Receive GI" option for that object and it should be fine.

3) I can calculate, then remove an object: there will be a hole in the 'gi' where the object was, but the space behind it will be lit by the direct lights in the scene that weren't stored with the irradiance map.

That is correct, yes. However, V-Ray will still attempt to use the irradiance map in the uncovered region, which may lead to some artifacts.

4) I can calculate with various blurry (non interpolated) materials. At rendertime, I can remove blurry settings and the image will render fine, just with sharp reflections where once there were blurry.

This is correct, yes. The other way round (e.g. calculating with sharp reflections but rendering with blurry) is more problemmatic since the blurry reflection expands the part of the scene visible through the reflections, and some parts may not be covered by the sharp reflections. Typically though, this is not a problem.

5) I can calculate with a global switch of, say, 2 reflection/refraction. Then at rendertime up this value to, say, 10 and it will render fine.

Again, this is only partially true. Larger trace depth values may cause parts of the scene that were not visible when the irradiance map was calculated, to become visible in the final rendering and those will look wrong. Typically, this is not a problem though.

6) I can calculate a solution and at rendertime, tweak bitmaps in diffuse slots - for instance, swap an oak bitmap for a cherrywood bitmap. The render will look fine, but the 'accurate' colour bounces from the original oak map will not be correctly updated for the redder tones in the cherrywood.

This is correct, yes. People often use this fact to reduce color bleeding in the final image.

7) I can calculate with a certain setup of materials with certain glossy settings. Say a bit of metal has glossiness set to 0.9. At rendertime, if I change this to 0.75 will it render OK, just a bit more blur

See my reply to 4)

Best regards,
Vlado

[panthon]

Hi!

You can calculate the gi pass with general displacement OFF if u have low height displacement, e.g. displaced grass, with the "don´t render final image" option checked and making sure it´s automatically saving your irradiance map....Your memory usage will decrease amazingly, and rendertimes too. Don´t forget to turn displacement ON again after u have saved your irradiance map. Obviously, the results aren´t as good as making it the right way, but clients won´t notice it anyway...

[percydaman]

1) I can calculate without glass, then render with glass and it will look ok.

ya I made a similiar goof awhile back. Rendered out an irradiance map using an override material, because I didn't want any color bleed. Of course when I rendered the actual animation, everything reflected in the glass that wasn't actually ever in the cameras view, look incredibly bad. man what a wake up call that was. haha

[tricky]

I'm glad for the responses to this. They are awkward questions but of major importance with animation.

It would be good to have a seperate forum for animation related vray things.