Topics

1

[Max] I need help! / Red glass problem strikes again!

« on: 2015-02-07, 10:35:21 »

The CoronaLight inside is absolutely white, (inside the red transparent LED glass).

I need it to be white in the center, as on reference pic above.

Why is it pink, and why is Green value -2? And how can I fix it?

P.S. It's solved by making the red glass not so red. But I need it red. There's something weird with the color math...

2

[Max] General Discussion / What does Absorption color lightness mean?

« on: 2015-01-13, 14:14:31 »

Absorption has two parameters - color and thickness distance.

Physical absorption has a graph for all spectrum distance (usually displayed in cm^-1).
Example:


So there are different wavelengths = different hues & maybe "saturation" (closer to white = all wavelengths).

But there is no value, lightness, brightness on these graphs!

Because we set the "value" by Distance.

So why do we need another value parameter in color?

So what I mean - absorption should react to Hue & Saturation, but should ignore the Lightness.

Because now I don't know what should I set the Lightness to - it reacts similar to saturation, but when it's dark - the material is getting black faster (which can be done by decreasing the distance).

Why should we have another meaningless parameter? Maybe we should simplify this?

I don't ask for a CoronaSpectral material (althought that would be very nice to have!) - but let's at least follow common logic.

3

[Max] Resolved Bugs / Interactive rendering window aspect ratio

« on: 2015-01-13, 14:03:12 »

I have this problem:


How do I make interactive to render the whole image, not only part?

4

[Max] Tutorials & Guides / Corona Webinar by Polymax - Translated into English!

« on: 2014-12-26, 17:40:49 »

Hi guys!

Finally I had time to do my translation for Corona Webinar by Polymax:

He describes the basics of interior rendering, render settings & materials setup.

Hope it'll be interesting for you!

5

[Max] I need help! / White dots on glossy glass + HDR

« on: 2014-12-24, 17:08:14 »

There are bright dots on glass with 0.6 reflection glossy. The dots only appear if I enable refraction.

The scene is a simple sphere on black plane + HDR.



20 minutes, 200+ passes, the dots don't disappear.

Here you can download the scene (or create one yourself):
https://www.dropbox.com/s/sblsxb55azz219z/refraction_dots.max?dl=0

Here is a HDRi:
https://www.dropbox.com/s/113sm77dh9asya2/04-28_Night_C1.hdr?dl=0

The build is latest 21 Dec, the settings are all Default.

Am I doing something wrong?

6

Gallery / Audi Accessories

« on: 2014-11-05, 14:08:09 »

Audi Accessories rendering.

Here are the wireframes & stuff:
https://www.behance.net/gallery/21062115/Audi-Accessories-render

7

[Max] General Discussion / IES + Glass = Noise

« on: 2014-10-29, 12:02:01 »

I don't know if I should post it here, or in Bugs section... But let me describe the problem.

Everyone knows that IES lights give much noise in Corona now. And the noise is un-even, clear in front, and noise on sides as you can see:


But what's more problematic is that the noise increases dramatically if IES is hitting glass:


Or even more glass => even more noise:


Guys here faced this problem on a museum render, with high glass boxes everywhere. IESes there are helly noisy after hours!

What can be done? Any advice?

8

Work in Progress/Tests / Vicnaum's Test corner

« on: 2014-09-20, 18:43:53 »

Here I'll be posting my little tests renders, which I don't dare to put into the main gallery :)

9

Gallery / Ocean

« on: 2014-09-11, 21:38:24 »

Ocean rendering test in Corona

https://www.behance.net/gallery/19703265/Ocean

10

[Max] Resolved Feature Requests / Exposure slider instead of Level in Diffuse slot

« on: 2014-09-07, 18:53:17 »

Hello guys!

There is no intuitive way in 3dsmax to change the texture exposure, which is sad - because this action is needed 99% of time when working with textures in Albedo-correct way. Most textures are photographed with the wrong exposure, have reflection lighting in them, so they need to be tuned down a bit (or up!).

There are numerous ways of altering the texture brightness:
1) Level slider
2) Map % slider (with black color in the color slot)
3) Output Level inside bitmap map
4) RGB Level inside bitmap map
5) Gain in ColorCorrect map
6) .......
7) ...etc,etc,etc

But NONE of them tunes the exposure. They all tune brightness, so when you make the texture darker - it also looses saturation and contrast => becomes more faded & grayish.

To see what I mean by that - just open any texture in Photoshop, and apply Exposure in "Camera Raw..." filter.
Then open the same texture in 3dsmax and try any of the above ways to achieve the same - and you'll see the difference between the real exposure, and 3ds max ways instantly.

Also - it's also much harder to rise the texture exposure, than darken it. So the Exposure slider which can do -/+ to texture in the CORRECT way - will be a great handy tool when rendering objects with photographic textures.

P.S. I could post some screenshots, but I think you should try it yourself to see in your own eyes.

Thanks.

11

[Max] Resolved Bugs / Displacement values >1.0 and <0.0 produce geometry bugs

« on: 2014-09-04, 20:28:40 »

The thread https://forum.corona-renderer.com/index.php?topic=5104 led to this bug:

1) Camera subdivision doesn't take displacement map values >1.0 into account:

Noise Map: Output 10.0, Corona Displacement: 20cm


Noise Map: Output 1.0, Corona Displacement: 200cm


2) Displacement map values lower than 0.0 just cut:

Noise: Output 1.0, RGB Offset: -0.5



And please don't ask why I did that... Some generators (like PhoenixFDOceanTex) can have any values, not limited to 0.0-1.0.
Modifier "Displace" is working correctly with out of range (0.0-1.0) values. Vray is also working correctly with them.

Corona cuts <0, and re-optimises >1.

12

[Max] I need help! / Rendering large (prefferable - infinite) planes with displacement

« on: 2014-09-04, 19:00:34 »

Hello guys!

Here I have my usual crazy-mind problem for you:
How to render large (or infinite) planes with displacement?

VrayPlane doesn't work, we know it. So we're starting with a simple Plane. And a displace map from PhoenixOcean.

1. Creating a huge plane (1x1 km) with 512x512 subdivs + Turbosmooth (1 render iteration) leads to this:

The Infamous poly-smoothing problem (at the bottom).

2. Increasing Turbosmooth to 2 render iterations makes it not much better than above:


3. Increasing plane subdivs to 1000x1000 led to 1 hour of "Building acc. structure", then I was just tired to wait...

4. Here's a plane 300m in size, with 512x512 subdivs and 2 iterations of turbosmooth:

It's seen that further subdivision wouldn't help much in defeating these smoothing-bugs, and just lead to rendertime hell.

So. What's the correct method method to create huge geometry with displace when subdivision is not an option?

Btw, here's a standard Max Displace modifier:


It's not so detailed (sadly), but the bugs are almost gone (only one 'square' is visible on the front).

That proves that something isn't right with "displacement+smoothing bugs", or displacement is using normals from low-poly geometry, or smth... I don't understand this in detail.

Corona version: Aug 3 2014

13

[Max] I need help! / Understanding SSS

« on: 2014-08-11, 12:22:18 »

Hello to the community!

Here's an interesting research of measuring real-world scattering/absorption values:
http://vision.seas.harvard.edu/inverse/




And it has this kind of data in PDF:



The worth of this data is clear, because it's very hard to distinguish realistic values for SSS/Absorption by hand, so it's handy to have something to start with (some "presets" available).

So what I ask for:
Could please someone explain the internal mechanics of Corona values, and how can I convert the provided measured mm^-1 data to corona Absorption/Scattering RGB color + Distance in mm. And Directionality also (but I completely don't understand how to convert their phase functions into directionality)
(First Sigma S is for scattering, second Sigma alpha - is for absorption, in R/G/B, 1/mm values)

14

Gallery / Pixel Pitch

« on: 2014-08-08, 20:10:21 »

Following the trend :)

https://www.behance.net/gallery/18920897/Pixel-Pitch

15

[Max] General Discussion / PBR kinda materials

« on: 2014-06-03, 09:09:39 »

What do you guys think of taking principles of PBR somewhere in future to develop materials in corona?

http://www.marmoset.co/toolbag/learn/pbr-theory
http://www.marmoset.co/toolbag/learn/pbr-practice

Key aspects (for ones who are lazy to read):
1) Diffusion & Reflection linked: More leflection -> Less diffusion
2) Fresnel linked to base reflectivity & gloss
3) Microsurface roughness linked to Reflection
4) Diffusion, Translucency, SSS all linked as representing the same effect
...etc...

That leads us to much simpler system, wich much less parameters, where less errors can be made.

I bet in a couple of years all renders will shift to something like that (comparing how they shifted from simple phong Diffuse/Specular Highlights model 10-15 years ago - to what we have now in vray/corona/etc).

So why don't make that shift earlier?

Btw, the described system can be tried out here (in realtime): http://www.marmoset.co/toolbag/store