How to composite this vray renders?

[alexhuerga]

I'm trying to render a sphere animation inside a box. But, I want to render the box using render to texture to save time because it has still lights, and the moving sphere using GI. I want the box not be affected by anything but the sphere's shadows, and the sphere by anything but the HDRI dome light I'm using. Is this possible?? How to setup this? If I exclude the box from the dome light out loses the sphere shadows, but if I include the box receives the dome light

[Francisco Penaloza]

A little hard to understand what you are trying to achieve. But from what I can guess, I would recommend to render a pass with the box alone, I am imagining the camera stills moves.

 

 

Then apply a material wrapper to the box and check the box Matte surface, that will eliminate the box from being render, but still will use it will show in the reflections and will cast shadows.

Then render the sphere animation and add a Matte Shadow pass, a lighting pass and if you fancy a Dirt pass to fake AO.

Later you will need to comp both passes using After Effects or similar program.

 

 

Now depending on what you are trying to achieve, do you need GI at all??

only using the dome light, you may get a nice image. But if you are going for full realism then GI may be necessary.

[alexhuerga]

Thank you so much! Actually it's a character inside a room, but I explained it with a box and sphere to make it simple. I'm thinking about your name... Do you speak spanish like me? It could simplify this conversation a lot XD

[Francisco Penaloza]

Hi, Yes I do speak Spanish, but as a policy for this community we all speak English so we all can learn from each other.

Otherwise, send me a PM if English is hard for you.

[alexhuerga]

OK bro, thanks. As you can see in the image, the box has a texture with baked lights, because I want it renders very fast. But the sphere is being illuminated by an hdri, because it will move and have bump maps and glossiness. The box represent a complex room (static) with baked textures. And the sphere represents a character moving. The box must not be affected by any light, but it must receive shadows from the sphere. The sphere must receive lights only from the hdri. I imagine that if I use an HDRI taken from a 360° render of the room, I could get good reflections... no? In simply words, I want only to process the character frame by frame, and not to lose time rendering the room.

https://drive.google.com/file/d/1edAziERLxK4cF2yUKeIZcPZq2hdxJtb9/view?usp=sharing

[John Dollus]

you could use the sphere fade for your animated object-

https://docs.chaosgroup.com/display/VRAY4MAX/VRaySphereFade

[Francisco Penaloza]

If it is a person walking in a room or something like that, then there are many ways you can approach that, but think about this.

By the time that it takes you to setup passes and render two times, the background and the character, then composite, try and error. with all that time sometimes it is way faster just render the whole thing with Brute force. The new VRay render quite fast in this method and everything will look great.

 

 

If still you need to do passes, you can do like I mentioned before, render your scene, bake textures then using the material wrapper so your scene capture character shadows but it doesn't render. You can choose also if you wan the scene to occlude your character.

 

 

Other way can be like John mentioned the Sphere fade function. it works great.

 

 

 

A similar way can be the select option in VRay, this one I use it quite often when we have material or objects changes. just render your scene once, then select your character and choose render select only, This is render only your character but still uses scene lights and GI and everything.

 

 

Now the illumination you have it wrong, if your character will be inside the room, then you can't use an exterior HDRI to lit the character, this will look bad.

The character should be illuminated by the same light that it is in the room. or render a 360 of the room and use that to illuminate your character with a dome light.

 

 

 

 

and last but not least.... Have you thought in using Unreal for this?

[alexhuerga]

Yeah, good idea. Thanks!

[alexhuerga]

you could use the sphere fade for your animated object-

https://docs.chaosgroup.com/display/VRAY4MAX/VRaySphereFade

 

Nice! thank you

[alexhuerga]

If it is a person walking in a room or something like that, then there are many ways you can approach that, but think about this.

By the time that it takes you to setup passes and render two times, the background and the character, then composite, try and error. with all that time sometimes it is way faster just render the whole thing with Brute force. The new VRay render quite fast in this method and everything will look great.

 

 

If still you need to do passes, you can do like I mentioned before, render your scene, bake textures then using the material wrapper so your scene capture character shadows but it doesn't render. You can choose also if you wan the scene to occlude your character.

 

 

Other way can be like John mentioned the Sphere fade function. it works great.

 

 

 

A similar way can be the select option in VRay, this one I use it quite often when we have material or objects changes. just render your scene once, then select your character and choose render select only, This is render only your character but still uses scene lights and GI and everything.

 

 

Now the illumination you have it wrong, if your character will be inside the room, then you can't use an exterior HDRI to lit the character, this will look bad.

The character should be illuminated by the same light that it is in the room. or render a 360 of the room and use that to illuminate your character with a dome light.

 

 

 

 

and last but not least.... Have you thought in using Unreal for this?

 

 

Hahaha yeah of course I tried Unreal, and also I've using Blender's realtime Eevee. But I want ultra realistic results, that's why I'm doing it with Vray. I found Blender's Cycles, Redshift and Corona are a little more slow than Vray, what do you think? In my opinion what makes special to a render, is the way the shadows and bumps looks like, and in my experience, Vray gets better results in less time.

You guys gave me very good ideas, I really appreciate it. Thank you!!!