VrayDistanceTex Slowdown and issue

[trixian]

The other day I was playing around with the cloud setup from Platige's film mentioned here on the forum, with the bakes vertex colours etc.
After setting this up, I found it really hard to get the scattered "puffs" on the surface to look any good, and at one point thought I'd try to use VRayDistanceTex to make a mask from the cloud shape and out some units.
2 things happened:

1. The distanceTex makes max hang for several seconds every time I try to adjust it, or any map it is connected to (composite in this case). It even makes my max interface disappear and flash white when it comes back.
2. Rendering the clouds with the distanceTex piped into the opacity forces the puffs to become additively blended for some reason.

Supplying the file for people to test, as I have no idea if this is just a problem on my machine or if others experience it.

Download the max-file here

[trixian]

Oh....forgot. This is vanilla VRay v.2.40.04 on 3dsmax Design 2014.

[tashko.zashev]

Hi Christian,

Regarding point one, this is something that we need to improve and already added to our "to do" list. We need to make the Distance text evaluation in the material editor faster.
About point two, did you try with Multiple color by opacity checked?

Here is the result i get in my test:

[mcnamex]

composite will always be slower than any shader..(in mat editor) esp in multisub context

[trixian]

Mcnamex: Slow as is making the UI hang for several seconds? This has never been a problem with any of my materials before using VRayDistanceTex.
It seems to me like the DistanceTex node is evaluating the geometry included in its list-box for every object it contains. As these two "clouds" are pretty dense meshes, it seems Max hangs significantly more than when testing with, say a sphere.

The main issue here Tashko, as you can see in your image, is that the blending of the planes is additive on top of the base cloud shape. This does not happen if you pipe any other map into the opacity lot, including VRayDirt. In addition, when rendering it as additive, it seems to slow the rendering down a lot, as you can see if you pipe a gradient ramp into the opacity slot and render.
Why is the blending being calculated as additive for the DistanceTex?

[tashko.zashev]

Hi,

Actually i don't see any differences when i replace the existing composite map with the Dirt one. Maybe i miss something in this setup.
Do you have an image that shows the requested render result?

Everything works as expected in my tests.



Rendered with 2.40.04/ Max 2014

[vlado]

It seems to me like the DistanceTex node is evaluating the geometry included in its list-box for every object it contains.

This is exactly what happens. We definitely need to improve it.

Best regards,
Vladao

[trixian]

Good to get this confirmed, though a rather strange implementation I must say.

What about the blending issue? Is it the VRayLightMtl that default forces additive blending?
Checking multiply colour by opacity removes the additive blending, but also multiplies the geometry that overlaps the base shape so you get the strange darkening.
I get the expected blending while using the regular VRayMlt, though with a black diffuse and the vertexcolor map plugged into the self illumination slot, like the image under.
Please excuse the ultra tacky look

[trixian]

This kinda veered away from the original issue obviously, now that I got it working (sort of).
I'm thinking the use of the distanceTex is not the best in this example, as the result is now some sort of furry cloud. Not really getting the wispyness on the edges I was looking for.
Also, I was hoping on deriving a work flow that was a lot more streamlined and flexible, for use with animated base shapes with scattered planes on them, but the baking and projecting kinda defeats this approach.

While fiddling around with this setup, I started wondering if it would be feasible with a new map/material type for vray, where lighting/shading is sampled from the underlying object (cloud shape in this case), and blends it self into it, like I'm doing now with Baked vertex colours on the cloud shape, projected into the plates vertices via a projection modifier.
If Vray could just "shade" the base cloud shape like regular rendering (should be really fast), the plates would then be lit like the base in a dynamic/procedural manner when used in an animated scene.
Not sure if this brain fart is clear or needs further elaboration.