OTOY Forums

Hi guys, how can I create the illusion of cloud shadows using light from the sky either via the sun or some other trickery.

This is close but its not in octane - https://www.youtube.com/watch?v=uaog4aL7AhM
This too at 18mins - https://www.youtube.com/watch?v=MiiPhAPu2SI

They both have the idea but is there a way I can achieve this in modo with octane?

Thanks

Hi - I think if you Create Octane Emitter on the Area Light, then assign the gobo image to the Distribution you will be on the right track. Then you need to plugin an Octane Perspective Projection into the Distribution image Projection pin. Then the tricky bit is setting the projection transform. I couldn't work it out - but I suspect it is something similar to http://poserphysics.blogspot.com.au/201 ... r-for.html

Paul

Edit to the above - I got a close result between Octane and Modo if I set the Area Light to be very small, set the power very high to compensate. I then set the Octane Perspective Rotate to that of the Modo Area Light.

Paul

I'm trying unsuccessfully to get this to work. It's simple in Modo, just setting the image to front projection. But I can only get an image to display in reflections in Octane by using implicit UV. It's not affecting the distribution at all with any of the Modo projection options. I tried setting up an emitter on the area light but could not get any results there either.

I had a look at that first video and created it for modo using an area light.

I then replicated the look in Octane using a separate area light (because it needs different settings/connections).

Octane (left), modo (right) The Octane version has a texture plugged into the distribution pin, with a linear projection set to object space. The transform controls the size of the gobo projection. The size of the area light controls how soft/blurry the projection is, so I made the area light small (1%)

I have attached an LXO

Problem with current gobo feature in Octane is that it needs additional light source to works so we have double lightened areas. This cause overexposure effect on surfaces. Solution is to have simple invisible to camera polygon with gobo texture in opacity channel.

SSmolak wrote:Problem with current gobo feature in Octane is that it needs additional light source to works so we have double lightened areas.

I'm only using 1 light

Thanks so much for posting this. I almost had the setup correct before. Couple of things I noticed. I could not see the linear projection in the projection types, had to add via the schematic search. In Octane the tiny area light is resulting in very hard shadows compared to Modo.

rubberchicken wrote:I could not see the linear projection in the projection types

Ah sorry, it's actually called "XYZ to UVW projection", but modo still uses the old "Linear projection" name in several places.

rubberchicken wrote:In Octane the tiny area light is resulting in very hard shadows compared to Modo.

I'm not seeing an obvious way to control this separately in Octane. I'll have to try a few things out, but you may have to create a gobo polygon to place in front of the light as SSmolak mentioned.