Spread Value for Octane Area Lights

[philcoffman]

I was following along with this video tutorial by Bryan Coleman and even though he uses Redshift I was able to replicate his steps easily enough in Octane, except for one specific one (video linked to this moment in his process). At the 19:16 timestamp in his tutorial he uses a long, super thin Redshift area light to simulate a scan line across his scene. In Redshift he has the option to adjust the spread of the light which helps him tighten in the angle of light thus achieving a tight, thin line of light...like a laser line. I dug around in Octane and even asked Bryan if he knew of a way to achieve the same effect in Octane but came up empty. I figured I'd reach out here to see if anyone knows of a solution to accomplish the same effect.

I did find a similar way of doing this effect in Octane via this video tutorial, and it's okay, but it's not exactly the same nor does it look as good (especially up close).

I'd love a spread slider in Octane as it seems super helpful even if it's not physically accurate. Anyway, hope someone has some ideas. Thanks in advance!

[james_conkle]

Yes please!! It’s super helpful in redshift. I know in Octane there’s barn doors for one of the light types but it’s totally not the same.

[Hurricane046]

Yep. This would be THE feature for area lights.

[philcoffman]

Glad to see others are also interested in this ability for lights.

[pxlntwrk]

Hi,
I think that we can achieve a very similar result with Octane,
by constraining the distribution by a texture (osl or other), and a perspective projection.

[philcoffman]

Hi,
I think that we can achieve a very similar result with Octane,
by constraining the distribution by a texture (osl or other), and a perspective projection.

Thank you pxlntwrk for taking the time to try this, your approach is fascinating. I'm trying to replicate it now but am unable to get the same result you did (I'm still new to all of this):
- is the image you're using for the distribution of the blackbody a simple square with a white line down the middle?
- you mention perspective projection, are there any specific settings you enable under the Texture Projection? When I set it to perspective I don't have a noticeable result.
- I'm assuming you applied this material to a long, skinny plane object?

I'm going to play around with my scene further. Happy to share what I have if it helps figure out what I'm doing wrong.

[philcoffman]

I think I finally got something working using pxlntwrk's approach. I think I just had my scene set up wrong. Using an Area Light I added a black image with a white stripe into the Distribution and set the projection to Perspective with the border mode set to Black. I then made the OctaneLight super long and skinny (2000cm x 0.01cm in my scene) and started to get much closer to my desired result. Here's a quick render.

[james_conkle]

Awesome results! A few steps to setup though... are you able to control the spread this way or does it just create this scan line effect?

[nejck]

Afaik even before OSL you could control the spread with light blockers off to the side of your lights - pretty much replicating certain real life setups. With OSL you can recreate that with even more control but I do agree with you folks, having this ability be built in would be extremely useful. Whenever I use other renderers I really enjoy having the ability to control the spread without having to mess with textures, UV transforms or physical blockers. I really can't stress it enough, I'd +10 this feature if I could

[philcoffman]

Afaik even before OSL you could control the spread with light blockers off to the side of your lights - pretty much replicating certain real life setups. With OSL you can recreate that with even more control but I do agree with you folks, having this ability be built in would be extremely useful. Whenever I use other renderers I really enjoy having the ability to control the spread without having to mess with textures, UV transforms or physical blockers. I really can't stress it enough, I'd +10 this feature if I could

I need to take a look at OSL, I've never used that method before. I originally tried light blockers off to the side but in my experiments it was still hard to get a nice, tight light line. Also, I had to be careful with where my light blockers were positioned so they didn't intersect the geometry so it's not an elegant solution, not nearly as nice as Redshift's spread slider. Having something like that built in would be so much easier and produce the best results.