OTOY Forums

Hi everyone,

Just bought myself a gtx580 as I was desperate to try Octane Render, and so far I'm really impressed. I've only had it for about 2 days so I'm only
just on that first bit of the learning curve and I'm sure it's about to shoot up! I have a few questions that have arisen since playing with my first
scene in Octane, hopefully you guys can help me with this, I've searched through the forums and also watched all of the youtube tutorials to try
to find the answers, but I'm still not 100% on some things. Hopeully this will help improve my renders as well as my knowledge of Octane.

Firstly I have no idea how add a falloff to reflections. There's an IOR setting on the specular material, but no Index Of Reflection on the glossy material.
My understanding of physically based materials is that pretty much everything unless is metal or a mirror has some kind of falloff dependant on viewing
angle. How do I apply this to my materials? It seems to me that the wall at the back of my render is far too shiny on the almost perpendicular face.
I know I could turn the overal specularity down, but surely I should be able to keep this specularity at sharper angles?

Secondly, the lamp on the left... I used a specular material with a coloured absorbtion, lowered the transmission and made the refractions rougher to
simulate the SSS. I'm happy with this, but I had to lower the rayepsilon to as low as possible for it to not render with artifacts. This is no doubt due
to the fact that my lamp shade model is almost paper thin. Is there a better workflow for this? I guess I could just make the lamp shade thicker, but
in real life it would be very thin. What are the downsides of using such a low rayepsilon (the manual says to leave it as default).

My main concern is with the sharpness of the image. The attached image rendered really quickely, about 50 mins to complete the 16k samples, I know
I could bump this value up and the render would take longer, but I'm not convinced it will give me the sharpness I'm looking for. I've used a filter size
of 1.2 but the detail in the fabric is still very blurry. I guess I could just render at a massive resolution and then shrink the image back down, but surely
there's a way of getting the detail in there at the right resolution from the start?

This may be related to the last point, but how does anti-aliasing work in Octane? There are the sub sampling options above the node window, but these
seem to do nothing when I change between them.

Looking forward to your comments, feel free to criticise the image too, I'm not too fussed on the artistic aspect of it (but also comments welcome), it was
just a test scene thrown together to work out how to use Octane and how I might include it into my workflow for a typical job.

Mike

The SSS and the IOR in glossy materials have just arrived with the new built 2.55, download it and try again with the scene if you want, btw nice render.

cool thanks, I just had a look on the download forum, it says the current release is 2.52 which is the one that i've got installed. Have I missed the download link for 2.55 or have I missed where the SSS and index of reflection sliders are in 2.52? Thanks again, glad you like the render

Rico_uk wrote:This may be related to the last point, but how does anti-aliasing work in Octane? There are the sub sampling options above the node window, but these
seem to do nothing when I change between them.

the "subsampling" buttons for the viewport have a quite misleading name. their only purpose is to lower the rendering resolution every time the rendering is restarted by 2 or 4. say you move the camera the initial image is there in half or quarter the time; though noiser it could help having better interactivity esp. for camera transforms.

denoising is controlled via the "filtersize" setting in the rendering kernel. also you need to look at the hotpixel removal setting in the imager node. 1 means "not hp removal", whereas lower values remove more hot pixels - and blur/smear the image of course.

if the lighting is not problematic (like high contrast inside shots and/or lots of light sources) you can increase sharpness by lowering the filtersize substantially and setting hp removal to 1.

edit: 2.55 is a beta "test" release (a beta-beta) so you need to look here: http://www.refractivesoftware.com/forum ... m.php?f=33

the latest built is always in the release candidate forum http://www.refractivesoftware.com/forum ... 37&start=0 and you didn't miss those options on 2.52, they are new to 2.55

brilliant thanks guys, thanks for the links and the explanations about subsampling. I've attached a render where I've reduced the filter size and and also rendered at double the resolution before shrinking down. I've also played a bit more with the lighting (included an ies on the metal lamp) although I think from an artistic point of view this lamp is now too bright. I've played with the shaders some more, I haven't installed that latest release yet, but am I right in thinking that the falloff is related to the specular level, and not something I have to set seperatly? I guess this will become clearer after I install the latest version and try the new IOR feature on glossy materials.

If any one has any pointers as to how this image could be improved (from a rendering point of view) I'd really appreciate it. It's not going to be the nicest image ever, it's just a test scene to see how nice I can make a simple setup with very basic lighting.

Thanks again for all the help so far, I think it's already made the image look infinitely cleaner and much nicer.

I like your work. Btw bump on the floor is inverted.

This i think you will find interesting.You can improve the edging artifacts of the window blends using this approach. You can improve the rendering speed with using higher res images then de-noising technics+hotpixel removal and scaling down 2x or even 4x times if your Vram allows it instead of waiting for a perfectly clean image...
http://www.refractivesoftware.com/forum ... f=21&t=878
Also the bump on the floor appears inverted.

Yes the bump definately looks inverted to me too, I had wondered about that but thought nothing else of it as the bump texture looks correct to me, it's white where the surface should appear raised, and black in the grooves between the planks, or does Octane use inverted maps? I've also applied this as a float image, is this the correct procedure? I'll try inverting the texture too, but I would have thought that bump maps would be the same as with other renderers?

Thanks again for comments and links, all very useful. I'm really loving this renderer seems very very powerful with nice results that don't need a lot of post.

Take a look at the pdf that comes with Octane. If you use greyscale images for bump maps (simple bumps not normal maps) then you should use Float Texture not Float Image. It will correctly understand the image as grey scale and save a lot of Vram if that does not work there is always invert tick that you can press. Float image is used with Normal maps and diffuse textures.