It's all about mirror and empty space

[~nature~]

Hi guys,

Nice day!

I have two issues need your help,

- Is there a way to concentrate rendering only on some specific object? I mean when there is a single object in the empty space, the black empty space consume considerable rendering time which is not necessary.

I found I could use crop function of the camera, but this is obvious a dirty solution because I need to animate it to follow the object or it becomes tricky when I only need to render the object in the mirror, did I miss some point?

-Is there a way to render the object in the mirror with the original passes, I mean I need to extract the refraction and reflection passes of the original object in the mirror, which in normal cases mantra will not maintain the passes of the object when you actually render the mirror geometry.

Any suggestion would be helpful to me,

Thanks very much,

Kind regards.

[dennis.albus]

As for concentrating rendering on a specific object you could try using the micropolygon hider instead of the raytracing hider.

You could also calculate your crop regions by converting your object to NDC space and use the min and max bounds of that for the crop regions. Be warned though, this is dodgy as it tells you it generates an infinite loop when you try to move your camera while the expressions are active. This however only happens for viewport navigation. For rendering it might be wise to bake your values in chops first and check the result to prevent possible hiccups.

To get your original passes I think you have to render each element separately to get it inside your reflection.

-dennis

ndc.hip

Edited November 14, 2012 by dennis.weil

[~nature~]

Hi Dennis,

Thanks for your help and the hip file, it's helpful, and in this case will it only work for single object, how about multiple objects?

for the second question, If I render each element separately, would the energy conservation rule get broken? and I am a little bit confused while dividing the PBR rendering layer manually.

Edited November 14, 2012 by ~nature~

[dennis.albus]

For several objects you could just merge them all into one single object and use that.

I would just manually ensure energy conservation. All your intensities added up may not exceed 1 (diff+refl+sss+...+emission<=1). This way you should be safe.

[~nature~]

Thanks dennis, what I meant is while there're several objects in the scene, the crop version only calculate the objects as a whole, there would be some empty space between objects,if the two objects for example is far away from each other. Or maybe in this case, we can only render out the objects separately and combine them together

cheers,

best regards

[dennis.albus]

Ah, now I get it. I guess the only thing you could do in that case is use the micropolygon hider which is faster with empty space. To speed this up with a raytrace hider we would need something like the adaptive dmc sampler in vray (which I would really like to see in mantra because it would speed up a lot of things).