V-Ray Curvature

[david.anastacio]

What is up with the curvature node? Doesn't seem to be working very well at the moment.

Trying to use on some simple geo gives mixed results.

Geo setup with a default dirt:


Not the result I expected. Plus the size difference in the boxes seems to give different result on the curvature.


With a more complex geometry and with default settings. Fiddling with the setting can't really get the desired result too.


Same geometry in 3dsMax and default curvature settings. Far from perfect also, but at least is getting somewhere.


And this is a result of a "Labs Measure Curvature", more of what I expect to see happening out of a curvature attribute.


So, is the V-Ray curvature node working correctly? Is there anything that can be done to improve its results?

Best,
David.

[fixeighted]

I get (in Max) a similar result to the bottom image, using curvature as a mask, if that is any use.

[ronald_a]

isn't the curvature node scene size dependent? this would explain not getting the same results with the same settings from max.

and don't get me wrong, curvature is somewhat weird to setup for some reason and the results are not always what one would expect when tweaking the parameter (at least from what I found out when working with it).

[david.anastacio]

isn't the curvature node scene size dependent? this would explain not getting the same results with the same settings from max.

and don't get me wrong, curvature is somewhat weird to setup for some reason and the results are not always what one would expect when tweaking the parameter (at least from what I found out when working with it).

Yeah, this is not working at all. Did some more testing and compared the results to the mantra and arnold curvatures and out of the box these other render engines do what you expect right away.

Example on Arnold and V-Ray, both set at a 0.01 radius.


With V-Ray I kind of could get something by setting the scale to 0.01 and the radius to 1.0 (which makes no sense), and this messes up the possibility to use radius maps for varying the width of the edges.


Also the threshold is not working. And this is necessary to avoid issues with thin objects.


The same in Arnold working as expected.


Gosho.Genchev, can we get the curvature node fixed please, plus would be great to get convex and concave options in it.

Best,
David.

[chakarov]

I'll take a look at it.

[david.anastacio]

I'll take a look at it.

Thanks chakarov, let me know when you have something

[david.anastacio]

Hi, any update on this chakarov ?

[chakarov]

Hi david.anastacio , here is what I figured out:
"Radius" label is wrong - should be "sample spread"
Scale - distance from surface along normal at current point, where sample rays will be spawn
Sample Spread /currently wrongly named Radius / - a multiplier for sample rays distribution.
actual spread = Scale * Sample Spread
Trace Distance - multiplier for max distance ray travels after which it is killed
actual max trace distance = Trace Distance * Scale * Sample Spread

here is an video example to explain everything
green line - normal at given point
green point - point along this normal where sample rays are spawn
yellow lines - rays distribution
red dots - points where rays hit surface

today we will have a meeting and will discus how to simplify the UI of curvature node

[sirio76]

today we will have a meeting and will discus how to simplify the UI of curvature node

May I ask if this meeting will be only about Vray for Houdini version? because also on Cinema4D we have hard time using the curvature shader, most time I end up using the Vray dirt shader but is not the same..
Thanks for the video and all the description!

[chakarov]

Yes it was only for V-Ray for Houdini. But I guess Curvature in Cinema4D works the same way, so you could use the info above.

[sirio76]

Thanks! I'll perform some more tests using your information

[david.anastacio]

Hi david.anastacio , here is what I figured out:
"Radius" label is wrong - should be "sample spread"
Scale - distance from surface along normal at current point, where sample rays will be spawn
Sample Spread /currently wrongly named Radius / - a multiplier for sample rays distribution.
actual spread = Scale * Sample Spread
Trace Distance - multiplier for max distance ray travels after which it is killed
actual max trace distance = Trace Distance * Scale * Sample Spread

here is an video example to explain everything
green line - normal at given point
green point - point along this normal where sample rays are spawn
yellow lines - rays distribution
red dots - points where rays hit surface

today we will have a meeting and will discus how to simplify the UI of curvature node

Hi chakarov, thanks for looking into this.

This seams quite over complicated, plus the current labels used make you think they do a completely different thing.
The Arnold curvature shader is quite intuitive to use, and uses less parameters to control the effect.

- Radius - size/spread of the effect around a shaded point. And with theoption to add a map as input (The radius of the sphere around the shading point within which the curvature will be estimated. Smaller values show finer details, while larger values give a smoother result.)
- Spread = sample spread (Lower values of spread will shoot rays more vertically with respect to the surface, and the default value of 1 means that rays are shot in all directions. This acts as a threshold to remove unwanted small variations of the curvature.)
- Threshold = threshold (Consider only curvature above this normalized angle, with (0, 1) mapping to (0°, 180°)
- Trace Distance = No need or extrapolate from the radius.
- Scale = No need
- Color Min/Max, and bias are not necessary, we can just post-process the curvature with a set range, gamma, or a curve.
- And a self inclusion/exclusion would be great to have too.

Best,
David

[blackcrownvisuals]

Right now Vray_Curvature is really hard to get your head around, Don't think of a more straight forward node.
Any plan to fix this ? Any modern shading graph uses Curvature nowadays.

Best,
Tanguy

[anthony_kyriazis]

Am having huge issues with the curvature node, i am trying to use it to drive a mix and when i have a render region and try to change the settings of the node in hope of developing a look it crashes vray all the time... i have 2 x rtx 3090's and using the latest houdini nightly...

[bdancer]

Any chance for a hip file? Crash could be not only related to the VOP nodes setup...