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Poser F.A.Q (Updated: 2015 Aug 18 8:24 pm)


 Subject: Displacement Question

blbarrett opened this issue on Oct 05, 2012 · 25 posts

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  blbarrett () ( posted at 3:28PM Fri, 05 October 2012 · edited on 3:29PM Fri, 05 October 2012

Using Poser Pro 2010 & 2012, I've often noticed that some models specifically Terrain, will show gaps in the mesh at render time... when displacement is used. ( the background shows through or they appear as clear areas in a .png image)

Is there a technique to use when creating, importing or exporting the model to prevent this?

Any other Displacement related ifo is welcome too.

I use 3ds MAX 2010 as my modeling application.

-Brett


  wimvdb () ( posted at 4:02PM Fri, 05 October 2012  · @3996179

Do not use sharp b/w edges, put a small transition in it. If it is too sharp, the render engine goes directly from one height to another leaving nothing in between. This is not always desired, but often you can get away with it if you use a high resolution map.

But I am not sure  if this is the problem you are having


  blbarrett () ( posted at 4:06PM Fri, 05 October 2012  · @3996181

I'll see if i can find an image to show :)


  vilters () ( posted at 4:14PM Fri, 05 October 2012  · @3996186

Look at my tread about LaurieA's teapot :-)

All about displacement driven by diffuse color texture map

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  raven () ( posted at 4:25PM Fri, 05 October 2012  · @3996190

The gaps could also be caused by having the minimum displacement bounds value in the render settings dialog set too low. Try increasing the value and rendering again. ( Page 398/399 of the reference manual explains more about it )



  blbarrett () ( posted at 4:35PM Fri, 05 October 2012  · @3996194

Turns out that what was happening was just a poser / computer glitch.

this Dell of mine does some crazy things from time to time.

I just opened the same scene I was having problems with this morning and I can't dupicate the problem. if it happens again I'll just know to reboot and open the file again, lol

Essentially what was happening is, it was showing every face in the terrain with a small gap, as if the model had been exploded slightly..... so weird, lol

Thanks wimvdb, vilters, and raven.... aside from my original issue I learned a few new things form your suggestions.

I'm good to go :)


  3doutlaw () ( posted at 4:37PM Fri, 05 October 2012  · @3996195

I had gaps in a render at one point, but the folks here pointed out that I was applying "smoothing" to the wrong things, or to the whole scene in the render settings, which causes bad things to happen to sharp edges and corners.

Just in case that was it, and you mistook it for displacement?


  lesbentley () ( posted at 4:38PM Fri, 05 October 2012  · @3996196


 

Displacement displaces the surface along its normal, so if you displace the faces of (for example) a cube outwards, naturally its going to leave gaps. It's the same as if you translated the sides of an unwelded cube.

In Poser no displacement is equal to black in the displacement map, and maximum displacement is white. In this set up you would need to have touching edges as black on the map to stop them coming apart.

You can also set the neutral displacement as mid grey (or any other shade) by adding a math node to the shader (see image above). In this set up, touching edges would need to be mid grey in order to stay together.

The hex value for mid grey is #808080, or in RGB each colour would have a value of 128.


  lesbentley () ( posted at 4:58PM Fri, 05 October 2012  · @3996206


Here is a displacement map I use as a test image to check displacement.


  hborre () ( posted at 6:08PM Fri, 05 October 2012  · @3996219

Also, in the Pro series, if you are using gamma = 2.2 in the render settings and have not set the gamma = 1 in transparency, bump, and displacement maps, the mesh will be altered causing similar results.


  blbarrett () ( posted at 10:11PM Fri, 05 October 2012  · @3996252

Well poser has a default smoothing value of 80, and due to some issues loading some models, I've recently reduced the default amount to 15 - much easier to adjust after loading. I never thought about the smoothing check box in the render settings, I'll take a look there... thanks.

 

Quote - I had gaps in a render at one point, but the folks here pointed out that I was applying "smoothing" to the wrong things, or to the whole scene in the render settings, which causes bad things to happen to sharp edges and corners.

Just in case that was it, and you mistook it for displacement?


  blbarrett () ( posted at 10:12PM Fri, 05 October 2012  · @3996253

lesbentley - Awesome info, I've been linking my diffuse or black and white bump map into the displacement slot... I had no idea the neutral gray was required.

hborre - another gem I was not aware of, I'll take a look at my scene and see if this applies, thanks.


  vilters () ( posted at 4:49AM Sat, 06 October 2012  · @3996283

HOLD !

The neutral gray can only be used if you use the Math_Function node with it to MAKE the gray the neutral displacement.

Poser default is BLACK is no displacement
White is displacement.

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  blbarrett () ( posted at 5:00PM Sat, 06 October 2012  · @3996469

Thanks vilters, I picked up on the math function node.

Still, interested in trying both ways to see which one provides better results, if any.

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  lesbentley () ( posted at 11:04PM Mon, 08 October 2012  · @3997264


Quote - Still, interested in trying both ways to see which one provides better results, if any.

By all means, try it out for yourself.

If you don't use a maths node to set mid grey as nutral displacement, you can only do positive displacement, bumps but not dents. If you only need positive displacement, then that's OK, no need for the maths node. But some times you may want the displacement to go either way, with some parts going out and other parts going in from the default location of the un-dispalaced surface. With no maths node, the lowest point you can get on the surface will be the altitude of the un-displaced surface. With a maths node the surface can go below its default altitude.

In the image above. #1, with no maths node only positive displacement is possible. #2, with maths node, positive and negative diaplacement. #3, same displacement map as #2,  but without maths node results in gaps in cube.


  lesbentley () ( posted at 11:10PM Mon, 08 October 2012  · @3997265

  lesbentley () ( posted at 11:11PM Mon, 08 October 2012  · @3997266

  lesbentley () ( posted at 11:16PM Mon, 08 October 2012  · @3997267


Try this one on a cube to see what hapens at the edges.


  blbarrett () ( posted at 2:10AM Tue, 09 October 2012  · @3997287

Thanks for the nice clean write up on this Les.

Very clear and easy to understand, I'll definately give these maps a try.


  Zev0 () ( posted at 5:21PM Tue, 09 October 2012  · @3997550

Is it better to create a displacement texture that has solid black as Bg or nuetral grey with a math node?

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  lesbentley () ( posted at 10:30PM Tue, 09 October 2012  · @3997659

It depends what you need it to do, sometimes the maths node is extra work that you don't need to do. Neutral grey with a math node is more flexible, because with that set up you can displace the surface in either a positive or negative direction from its default position. Without the maths node, you can only displace the surface in a positive direction.

Black on the map is going to be the the lowest point on the surface (whatever set up you use), and white is going to be the highest point. Without the maths node, any black parts on the map are going to leave the surface in its original position. To make a depression in the surface, you would need to use a colour that was blacker than black, but no colour is blacker than black. That's where the maths node comes in, it "fools" Poser into "thinking" that mid grey on the map is black, and that black on the map is blacker than black.

Not sure if that makes sense, but it's the best explanation I can manage.

If you only need to displace the surface in a positive direction, it's best not to use a maths node. If you want to displace the surface in both positive and negative directions - relative to  its initial location - you need a maths node.


  vilters () ( posted at 5:27AM Wed, 10 October 2012  · @3997735

One extra warning here.

When the figure has a displacement map, it is only calculated at render time.

The cloth room does not "know" that the figure has a displacement map.

The cloth room calculates around the figure object file.

At render time, the displacement map can provoke poking, if the "at render time" calculated dispacement can push through the clothing.

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  Zev0 () ( posted at 5:30AM Wed, 10 October 2012 · edited on 5:30AM Wed, 10 October 2012 · @3997736

Quote - It depends what you need it to do, sometimes the maths node is extra work that you don't need to do. Neutral grey with a math node is more flexible, because with that set up you can displace the surface in either a positive or negative direction from its default position. Without the maths node, you can only displace the surface in a positive direction.

Black on the map is going to be the the lowest point on the surface (whatever set up you use), and white is going to be the highest point. Without the maths node, any black parts on the map are going to leave the surface in its original position. To make a depression in the surface, you would need to use a colour that was blacker than black, but no colour is blacker than black. That's where the maths node comes in, it "fools" Poser into "thinking" that mid grey on the map is black, and that black on the map is blacker than black.

Not sure if that makes sense, but it's the best explanation I can manage.

If you only need to displace the surface in a positive direction, it's best not to use a maths node. If you want to displace the surface in both positive and negative directions - relative to  its initial location - you need a maths node.

 

makes perfect sense..

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  dnstuefloten () ( posted at 11:01AM Wed, 10 October 2012  · @3997819

Wow...lots of fascinating information here! I'll have to start experimenting....

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  blbarrett () ( posted at 11:11AM Wed, 10 October 2012  · @3997820

Quote - #3, same displacement map as #2,  but without maths node results in gaps in cube.

 

lesbentley- this is what was causing the issue I started this thread with.

I opened the scene last night and added the math node...... problem solved

**Thanks to everyone for all the great and helpful responses!
**


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