Gobo in Vray

[Dentzz]

I'm trying to use an area light to get this effect with a texture.

This has a lot of different names gobo/stencil/cookie/pattern/etc, and typing in gobo vray didn't find any results. Anyone know what this is called in vray/how you can do this in vray for modo?

[vladimir.nedev]

Can you attach this scene ?
I think the most correct way to do this would be to add a plane in front of the light with a texture for its opacity/transparency.
Isn't that how this effect is done in real life ?

Greetings,
Vladimir Nedev

[Dentzz]

Can you attach this scene ?
I think the most correct way to do this would be to add a plane in front of the light with a texture for its opacity/transparency.
Isn't that how this effect is done in real life ?

Here is a scene I included the stencil in the image folder but took out the HDR.
http://1drv.ms/1WPMuML

In real life you are correct you would put it in front of the light either being held away from the light or as an attachment on the light.
The closer the light source is to the object being lit the sharper the shadows the further the distance the less sharp the shadows . Also the the more like a point light the source is the more defined the shadows.

In modo you attach an image file to the light in the shading tab. In the texture locator for that image you set the projection type to be Front Projection and the Projection camera to either be the light itself or what I assume most people do is create a camera to be the projector and position the light and the pattern as separate elements.

[vladimir.nedev]

In the texture locator for that image you set the projection type to be Front Projection and the Projection camera to either be the light itself or what I assume most people do is create a camera to be the projector and position the light and the pattern as separate elements.

Currently, in V-Ray for MODO, the Front projection mapping works correctly only when the Projection camera is the current render camera. I need to fix this eventually.

But for area lights (rectangle/ellipse/dome) the texture will always be applied on the light itself, and not as a projection on the geometry that is being lit.
Users actually complained initially that the texture was acting as a gobo (which is what MODO does)
http://forums.chaosgroup.com/showthr...highlight=gobo
There are some explanations in that thread how the textures are applied to area lights.

For the point lights, V-Ray will also apply the texture on the lit objects, and not the light itself (like MODO does), but you can't use the Front projection mapping yet.

Edit : Just change the type of your light from Area to Directional, and you will see that V-Ray will do something similar to MODO, but the projection will be from the render camera, which is what needs to be fixed.

Greetings,
Vladimir Nedev

[Dentzz]

Changing it to a directional light works minus being able to choose the projection camera.



Now I guess the new question would be what would be needed to get volumetrics/god rays to work.


Looking at the earlier thread I could see it being incredibly annoying if that was not what someone was trying to do and it would always default to the render camera which means you could never place things correctly either. Maybe in the future whenever you are able to get projection camera decisions to work it might make sense to add the ability to not ignore front projection, projection types?

[vladimir.nedev]

Now I guess the new question would be what would be needed to get volumetrics/god rays to work.

The simple volumetrics that MODO has are not exported to V-Ray. The only solution for now would be to use a "V-Ray Environment Fog" object. It has a "Lights" list in case you want it to affect only some lights in the scene.

Looking at the earlier thread I could see it being incredibly annoying if that was not what someone was trying to do and it would always default to the render camera which means you could never place things correctly either. Maybe in the future whenever you are able to get projection camera decisions to work it might make sense to add the ability to not ignore front projection, projection types?

For area lights, V-Ray can be told to either apply the texture on the light itself, or project it on the lit surface. In MODO you have only the "Light color" effect, so the user can't specify between the two.
The initial problem was that I was telling V-Ray to project the texture on the lit surface, and not to apply it on the light itself.

When you add a texture to any type of light in MODO, it gets created with a Texture locator set to "Front projection". And I think most people using V-Ray will want the texture to be applied on the light itself (if it's an area light).
So I won't be changing this behavior for Area lights. It's better to create actual stencil geometry anyway.

Greetings,
Vladimir Nedev

[Dentzz]

The simple volumetrics that MODO has are not exported to V-Ray. The only solution for now would be to use a "V-Ray Environment Fog" object. It has a "Lights" list in case you want it to affect only some lights in the scene.

Okay was able to get some images with environment fog.
Had some questions on using fog, where do you apply textures on a gizmo, is it on the object that is a gizmo or on the environment fog?
Fog doesn't seem to be semi transparent with respect to an alpha channel. I tried playing around adjusting settings but the fog always seems to kill any background from appearing, if I turn affect background off it kills any rays that would pass over the background. Is there any setting that I need to adjust to make something that could be composited later?
Also it doesn't seem to work for GPU rendering is this modo-vray gpu or vray gpu doesn't yet handle it?

For area lights, V-Ray can be told to either apply the texture on the light itself, or project it on the lit surface. In MODO you have only the "Light color" effect, so the user can't specify between the two.
The initial problem was that I was telling V-Ray to project the texture on the lit surface, and not to apply it on the light itself.

When you add a texture to any type of light in MODO, it gets created with a Texture locator set to "Front projection". And I think most people using V-Ray will want the texture to be applied on the light itself (if it's an area light).
So I won't be changing this behavior for Area lights.

I think I am a little conflicted on that one. While I agree that for everyone the default behavior is wanting to attach something to the light itself and not projecting something on the lit surface. I also like how the object now fills automatically the full light without any adjustment. It still makes me a little nervous to lock any of the lights in a way that you are not able to change the projection type. Being able to adjust the size, transform the position and falloff seems like something that gets locked out by having it always exist in an implicit UV space as well as losing the ability to see similar results from lighting behavior with how modo would work. For the situation I wrote about creating a pattern I think I will be able to do everything I need to do with a either a spot light or a directional light. Not really sure how other people use this so either might be good to keep it how you have it or might be better to stick with how modo does it.

It's better to create actual stencil geometry anyway.

If you mean actually creating geo vs doing a quick 2d photo/Photoshop paint job I totally disagree.

[vladimir.nedev]

Had some questions on using fog, where do you apply textures on a gizmo, is it on the object that is a gizmo or on the environment fog?

It's not possible to apply textures per gizmo. If you want different textures, you can create several Environment fog items with different textures and have each use a separate set of gizmos.
In Max/Maya you can have a per-gizmo fade-out radius and per-gizmo lights, but only that. This is not in MODO yet.

Fog doesn't seem to be semi transparent with respect to an alpha channel. I tried playing around adjusting settings but the fog always seems to kill any background from appearing, if I turn affect background off it kills any rays that would pass over the background. Is there any setting that I need to adjust to make something that could be composited later?

Without a gizmo, the fog is infinite, and the background is infinitely away, so the fog will hide it completely. If you modify the camera to look up(from inside the fog), you will see that the alpha is semi-transparent at the horizon.
Use a gizmo, if you want to see the background behind the fog.

Also it doesn't seem to work for GPU rendering is this modo-vray gpu or vray gpu doesn't yet handle it?

No support in RT GPU yet as far as I know. This is not V-Ray for MODO specific.

Being able to adjust the size, transform the position and falloff seems like something that gets locked out by having it always exist in an implicit UV space

You can still adjust the horizontal/vertical wrap, horizontal/vertical repeat, UV rotation and UV offset. You just need to switch the Projection type to UV map, so MODO will allow you to modify these channels.
It's as if the Area light is a rectangle with an UV map that goes from 0,0 in one corner to 1,1 in the opposite.

For the situation I wrote about creating a pattern I think I will be able to do everything I need to do with a either a spot light or a directional light. Not really sure how other people use this so either might be good to keep it how you have it or might be better to stick with how modo does it.

I couldn't get MODO to apply the texture on the actual light, no matter what Projection type I tried. So it is needed to deviate from MODO's behavior in this case.
If more people require projection on the lit surface, I can add it as some kind of option to the V-Ray Light tab.

If you mean actually creating geo vs doing a quick 2d photo/Photoshop paint job I totally disagree.

I meant creating a plane with a material that has a transparency/opacity texture set to the stencil image that you otherwise apply on the light.
But I am no artist, so I may be wrong.

Greetings,
Vladimir Nedev

[Dentzz]

It's not possible to apply textures per gizmo. If you want different textures, you can create several Environment fog items with different textures and have each use a separate set of gizmos.
In Max/Maya you can have a per-gizmo fade-out radius and per-gizmo lights, but only that. This is not in MODO yet.

So on the environment fog? I wasn't having much luck getting textures to work with the fog at least using the vvol Fog Density(map) though may easily have had the wrong values on the textures to see anything.

You can still adjust the horizontal/vertical wrap, horizontal/vertical repeat, UV rotation and UV offset. You just need to switch the Projection type to UV map, so MODO will allow you to modify these channels.
It's as if the Area light is a rectangle with an UV map that goes from 0,0 in one corner to 1,1 in the opposite.

I couldn't get MODO to apply the texture on the actual light, no matter what Projection type I tried. So it is needed to deviate from MODO's behavior in this case.
If more people require projection on the lit surface, I can add it as some kind of option to the V-Ray Light tab.

Okay that works, I really have no idea if it is something that other people would need and really is not that super important. When the projection camera can work not using the render camera it will be much easier to understand what is able to work and not. Mostly with modo things often work in multiple ways and it is hard for me to exactly know how systems interact so sometimes worried if adding a plug in if parts don't work what impact that might have on other parts of the chain. But generally hate for you to add any unneeded complexity since people will want to just add something to the light or add extra buttons that no one uses/needs. Why I was mostly saying to look back at it maybe after other parts are functioning as they are supposed to be.

I meant creating a plane with a material that has a transparency/opacity texture set to the stencil image that you otherwise apply on the light.
But I am no artist, so I may be wrong.

Your not wrong, that would be the correct way to do things but typically adding an opacity/alpha in a card and having a light further back it would interact with would add to rendertime and now lining things up becomes more finicky. Probably at some point someone will make more artist friendly controls to just be some sliders that could control the sharpness of the shadows by adjusting the card depth but for now seems easier and faster to just make the adjustments in photoshop.

Same thing what I think Disney paper wrote about doing with volumetrics https://disney-animation.s3.amazonaw...ogrammable.pdfjust looking to get benefits of a realistic way things should work but sometimes have more control to make it "movie" real and not real world.

[vladimir.nedev]

So on the environment fog? I wasn't having much luck getting textures to work with the fog at least using the vvol Fog Density(map) though may easily have had the wrong values on the textures to see anything.

I am attaching two scenes - one for the environment fog as an atmosphere, and one as volume material. In both cases a Bercon noise texture is used to drive the Fog Density.
Notice that I have increased the "Low" parameter of the bercon noise to 0.7, so there are more well defined "puffs" in the result.

env_fog_textures.zip

Greetings,
Vladimir Nedev

[Dentzz]

Thank you, now I understand I wasn't doing it the same way either as a volume material or with the environment fog in how I was connecting the textures. In just rendering your scene I was getting little black triangles any idea what that might be?

[vladimir.nedev]

Thank you, now I understand I wasn't doing it the same way either as a volume material or with the environment fog in how I was connecting the textures. In just rendering your scene I was getting little black triangles any idea what that might be? [ATTACH=CONFIG]25808[/ATTACH]

It seems they are shading errors in the environment fog, we should look into that.
I had some black pixels, but they were much smaller. I thought they were caused by the Fixed image sampler with 1 subdiv that I was using.

Did you increase the AA filter size or change anything else in the scene to get this result ?

Greetings,
Vladimir Nedev

[Dentzz]

Didn't change AA filter size but I did change the sampler. Not 100% sure which one I uploaded that picture from but taking a guess I think adaptive had the biggest dots.

[vladimir.nedev]

Thank you, now I understand I wasn't doing it the same way either as a volume material or with the environment fog in how I was connecting the textures. In just rendering your scene I was getting little black triangles any idea what that might be? [ATTACH=CONFIG]25808[/ATTACH]

The black dots are actually NaN (not a number) pixels that were created after some divisions by zero in the V-Ray Bercon Noise texture. The environment fog code wasn't the culprit.
The problem is fixed in the official 3.01.02 build, as well as the latest nightly builds.

Greetings,
Vladimir Nedev

[Dentzz]

Interesting that it was the noise texture that was the problem.