Suffix file name to 16-bit EXR ?

[FalconCrest]

I want to know why when exporting 16-bit EXR the following example suffix is added to the file name, g0.514724 but not when exporting 32-bit EXR ?

In this video the author is demostrating to get perfect displacement maps from Mudbox using this suffix that is added to the file name. 

[RobinBall6995]

I believe the suffix is the range or bias of the 16 bit displacement. You don't need a range for 32bit. I've never used it myself though, so could be wrong there.

[FalconCrest]

That is what I originally thought as well, although with 32-bit EXR I still have problems with Maya getting perfect displacement maps. What is the road one must cross to get this sorted out ? 🙂

I was informed of this equation, can anyone make sense of it, it uses the suffix that is appened to the 16-bit EXR displacement maps, although as mentioned 32-bit EXR don't have this equation, how can I get this value from 32-bit EXR displacements ?

The equation and the origin of the equation is very vague, what I want to know is how it is figured out ?

(if you didn't change the name it will now be something like rings5_ringH1_dotH2_g60.exr) and set its alpha offset to minus half the value appended to the map's name (-1(*60/2)=-30) and the alpha offset to the full value (60)

[RobinBall6995]

Well I would guess that 32bit would require a value of 1 or 100%? I'm not familiar with Maya or displacement, but 1 usually means the full value, so I'd start with that.

[FalconCrest]

When exporting a 16-bit EXR the value is appended to the file name, not with 32-bit EXR. I want to know the math behind this because the results are perfect displacement maps and all the other conventional displacement methods are not working successfully 😞

[FalconCrest]

This is extremely frustrating, because 32-bit EXR are a value of 1.0 (-1(1/2)-.5) I put this value into the alpha offset, bloated displacement maps continue. I scoured the internet for videos on displacement, and yes there are many, and yes the videos all show the displacement working, it doesn't appear to be what the videos make out to be, or they are missing details that are crucial.

[RobinBall6995]

I'm afraid not knowing maya or really displacement, I can't help much more. Oglu should be able to help if he's around.

I'd check you don't have gamma correction on that map though. That messes up normal maps and would be the same for other data type maps.

[FalconCrest]

This is extremely frustrating that I can't get displacements to work perfectly, that is my goal. 😞 I never apply a gamma correction on a displacement 🙂

[FalconCrest]

I know I'm getting bloated displacements because of my alpha gain & alpha offset not being correct. How do I accuratly calculate a 32-bit displacement alpha gain and alpha offset, at this moment all I'm doing is trying random values with no progress. I've searched online for the answer, and have made no progress in getting this correct, if you know of a link that will accurately describe how to render perfect displacement maps, or you know how and are willing to share I'm open.

[RobinBall6995]

I tried it on a plane, subdivided and sculpted, then extracted to a 32bit exr from a second plane.

I imported this plane to 3DSMax, assigned the exr map as displacement, didn't set anything (it defaults to 1), made sure the displacement max distance was enough in the Mental Ray settings and hit render. It came out as expected. Looked the same as the sculpted mesh in Mudbox.

Try reproducing this in Maya. No offset or gain. Maybe it will work on a plane but not on your model. Then at least we should know if the setup is right.

The other thing that occurred to me is to check if your model has been scaled at all. If it has either in Maya or Mudbox, that might be causing it.

[FalconCrest]

I created a plane, sculpted on the plane, exported the 32-displacement map, loaded the plane into Maya, applied Geo Approx as well.  I didn't touch Alpha Gain or Alpha Offset, this is the results.

[FalconCrest]

Sorta the wrong image previously, this is the result. 

[ShiqiangBao · Accepted solution]

We don't need the gain value(the suffix) for 32 bit EXR, as we store real accurate displacement value inside the image file. So in Maya you should use default value for alpha gain(1.0) and offset(0.0)

For bitdepth other than 32, we encode the displacement value like this:

Suppose  the displacement value "v_disp" is ranging from -a, to b, and we want to generate an image with values(v_img) ranging from 0.0 to 1.0, with 0.5 as the zero displacement value. We use this equation:

                v_disp

v_img = -------------- + 1/2

             2*max(a, b)

And we store 2*max(a, b) as the suffix gain value "g"

So to decode it in Maya, we use this equation:

v_disp = (v_img - 1/2) * g = v_img * g - 0.5 * g, which means you should put the suffix gain "g" as alpha gain, and -0.5 * "g" as the alpha offset. 

Make sense? It looks your images are no longer avaliable, can you post it again, please?

[FalconCrest]

I'm a little confused on your equation; although I want to understand, once again your equation is for 16-bit EXR, correct ?

[ShiqiangBao]

It's for 16-bit EXR, yes

[FalconCrest]

My issue is with 32-bit EXR, why they are not rendering correctly ?

[ShiqiangBao · Accepted solution]

Can you share me your images and scene files? I can help to take a look.

Thanks,