Re: [osg-users] TBN Matrix for Normal Mapping - OSG and GLSL

[Robert Osfield]

Hi Rômulo,

On 8 November 2017 at 21:46, Rômulo Cerqueira
 wrote:
> thanks for your replies. I will have a look on osg::TangentSpaceVisitor, 
> however I have a question: I will have in my OSG scene a lot of objects 
> with/without normal mapping. How can I handle different normal textures using 
> the same osg::TangentSpaceVisitor?

To tailor the behavior to suit your scene graph usage case you could
subclass from the TengentSapceVisitor and add your own checks for
traversal.

Robert.
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Re: [osg-users] TBN Matrix for Normal Mapping - OSG and GLSL

[Rômulo Cerqueira]

Hi Jordi and Sebastian,

thanks for your replies. I will have a look on osg::TangentSpaceVisitor, 
however I have a question: I will have in my OSG scene a lot of objects 
with/without normal mapping. How can I handle different normal textures using 
the same osg::TangentSpaceVisitor?

... 

Thank you!

Cheers,
Rômulo

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Re: [osg-users] TBN Matrix for Normal Mapping - OSG and GLSL

[Jordi Torres]

Ouch bad link:

https://github.com/openscenegraph/OpenSceneGraph/blob/master/src/osgPlugins/gles/TangentSpaceVisitor.cpp#L46

this one is the right one!

2017-11-08 9:19 GMT+01:00 Jordi Torres :

> Hi Romulo,
>
> You can use TangentSpaceGenerator to get the values of the T B and N. Here
> you have a code example: https://github.com/sketchfab/osg/blob/
> 5d35b2a2d55e92b4c736ea5edcd9eeedf9ea6786/src/osgPlugins/
> gles/TangentSpaceVisitor.cpp#L46
>
> Cheers.
>
> 2017-11-07 21:48 GMT+01:00 Rômulo Cerqueira :
>
>> Hi,
>>
>> I have used normal mapping using GLSL and OSG for my application (an
>> imaging sonar simulation) and I got problems by calculating the TBN matrix
>> on shaders. The normal vectors contain lower resolution on border in
>> comparison with the center of image.
>>
>> Follows my vertex code:
>>
>> Code:
>>
>> #version 130
>>
>> out vec3 pos;
>> out vec3 normal;
>> out mat3 TBN;
>>
>> void main() {
>> pos = (gl_ModelViewMatrix * gl_Vertex).xyz;
>> normal = gl_NormalMatrix * gl_Normal.xyz;
>>
>> vec3 n = normalize(normal);
>> vec3 t = normalize(cross(normal, vec3(-1,0,0)));
>> vec3 b = cross(t, n) + cross(n, t);
>> TBN = transpose(mat3(t,b,n));
>>
>> gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
>> gl_TexCoord[0] = gl_MultiTexCoord0;
>> }
>>
>>
>>
>>
>> Part of my fragment code:
>>
>> Code:
>>
>> #version 130
>>
>> in vec3 pos;
>> in vec3 normal;
>> in mat3 TBN;
>> uniform sampler2D normalTexture;
>>
>> void main() {
>> vec3 newNormal = (texture2D(normalTexture, gl_TexCoord[0].st).rgb *
>> 2.0 - 1) * TBN;
>> newNormal = normalize(newNormal);
>> ...
>> }
>>
>>
>>
>>
>> The resulting figure is attached.
>>
>> How can I calculate the TBN matrix to compute the normal mapping properly?
>>
>> Thanks in advance,
>>
>>
>> ...
>>
>> Thank you!
>>
>> Cheers,
>> Rômulo[/img]
>>
>> --
>> Read this topic online here:
>> http://forum.openscenegraph.org/viewtopic.php?p=72324#72324
>>
>>
>>
>>
>> Attachments:
>> http://forum.openscenegraph.org//files/screenshot_from_2017_
>> 11_06_23_00_48_832.png
>>
>>
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>>
>
>
>
> --
> Jordi Torres
>
>
>


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Re: [osg-users] TBN Matrix for Normal Mapping - OSG and GLSL

[Jordi Torres]

Hi Romulo,

You can use TangentSpaceGenerator to get the values of the T B and N. Here
you have a code example:
https://github.com/sketchfab/osg/blob/5d35b2a2d55e92b4c736ea5edcd9eeedf9ea6786/src/osgPlugins/gles/TangentSpaceVisitor.cpp#L46

Cheers.

2017-11-07 21:48 GMT+01:00 Rômulo Cerqueira :

> Hi,
>
> I have used normal mapping using GLSL and OSG for my application (an
> imaging sonar simulation) and I got problems by calculating the TBN matrix
> on shaders. The normal vectors contain lower resolution on border in
> comparison with the center of image.
>
> Follows my vertex code:
>
> Code:
>
> #version 130
>
> out vec3 pos;
> out vec3 normal;
> out mat3 TBN;
>
> void main() {
> pos = (gl_ModelViewMatrix * gl_Vertex).xyz;
> normal = gl_NormalMatrix * gl_Normal.xyz;
>
> vec3 n = normalize(normal);
> vec3 t = normalize(cross(normal, vec3(-1,0,0)));
> vec3 b = cross(t, n) + cross(n, t);
> TBN = transpose(mat3(t,b,n));
>
> gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
> gl_TexCoord[0] = gl_MultiTexCoord0;
> }
>
>
>
>
> Part of my fragment code:
>
> Code:
>
> #version 130
>
> in vec3 pos;
> in vec3 normal;
> in mat3 TBN;
> uniform sampler2D normalTexture;
>
> void main() {
> vec3 newNormal = (texture2D(normalTexture, gl_TexCoord[0].st).rgb *
> 2.0 - 1) * TBN;
> newNormal = normalize(newNormal);
> ...
> }
>
>
>
>
> The resulting figure is attached.
>
> How can I calculate the TBN matrix to compute the normal mapping properly?
>
> Thanks in advance,
>
>
> ...
>
> Thank you!
>
> Cheers,
> Rômulo[/img]
>
> --
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=72324#72324
>
>
>
>
> Attachments:
> http://forum.openscenegraph.org//files/screenshot_from_
> 2017_11_06_23_00_48_832.png
>
>
> ___
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Re: [osg-users] TBN Matrix for Normal Mapping - OSG and GLSL

[Sebastian Messerschmidt]

Hi Rômulo,


Hi,

I have used normal mapping using GLSL and OSG for my application (an imaging 
sonar simulation) and I got problems by calculating the TBN matrix on shaders. 
The normal vectors contain lower resolution on border in comparison with the 
center of image.


You cannot get a valid Co-TangentSpace by taking only the normal into 
account considering arbitrary geometries. There are multiple ways to 
tackle this however:
First is to calculate the mesh's tangentspace beforehand and pass the 
tangent and binormal via vertex attributes.
See the osgUtil::TangentSpaceGenerator (example in the osg::CookBook 
AFAIK).


Second one is to calculate it in the view-space. Beware of dragons, 
since the precision will be awful for big coordinates:


http://www.thetenthplanet.de/archives/1180

hth
Sebastian



Follows my vertex code:

Code:

#version 130

out vec3 pos;
out vec3 normal;
out mat3 TBN;

void main() {
 pos = (gl_ModelViewMatrix * gl_Vertex).xyz;
 normal = gl_NormalMatrix * gl_Normal.xyz;

 vec3 n = normalize(normal);
 vec3 t = normalize(cross(normal, vec3(-1,0,0)));
 vec3 b = cross(t, n) + cross(n, t);
 TBN = transpose(mat3(t,b,n));

 gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
 gl_TexCoord[0] = gl_MultiTexCoord0;
}




Part of my fragment code:

Code:

#version 130

in vec3 pos;
in vec3 normal;
in mat3 TBN;
uniform sampler2D normalTexture;

void main() {
 vec3 newNormal = (texture2D(normalTexture, gl_TexCoord[0].st).rgb * 2.0 - 
1) * TBN;
 newNormal = normalize(newNormal);
...
}




The resulting figure is attached.

How can I calculate the TBN matrix to compute the normal mapping properly?

Thanks in advance,


...

Thank you!

Cheers,
Rômulo[/img]

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Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=72324#72324




Attachments:
http://forum.openscenegraph.org//files/screenshot_from_2017_11_06_23_00_48_832.png


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[osg-users] TBN Matrix for Normal Mapping - OSG and GLSL

[Rômulo Cerqueira]

Hi,

I have used normal mapping using GLSL and OSG for my application (an imaging 
sonar simulation) and I got problems by calculating the TBN matrix on shaders. 
The normal vectors contain lower resolution on border in comparison with the 
center of image.

Follows my vertex code:

Code:

#version 130

out vec3 pos;
out vec3 normal;
out mat3 TBN;

void main() {
pos = (gl_ModelViewMatrix * gl_Vertex).xyz;
normal = gl_NormalMatrix * gl_Normal.xyz;

vec3 n = normalize(normal); 
vec3 t = normalize(cross(normal, vec3(-1,0,0)));
vec3 b = cross(t, n) + cross(n, t); 
TBN = transpose(mat3(t,b,n));

gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
gl_TexCoord[0] = gl_MultiTexCoord0;
}




Part of my fragment code:

Code:

#version 130

in vec3 pos;
in vec3 normal;
in mat3 TBN;
uniform sampler2D normalTexture;

void main() {
vec3 newNormal = (texture2D(normalTexture, gl_TexCoord[0].st).rgb * 2.0 - 
1) * TBN;
newNormal = normalize(newNormal);
...
}




The resulting figure is attached.

How can I calculate the TBN matrix to compute the normal mapping properly?

Thanks in advance,


... 

Thank you!

Cheers,
Rômulo[/img]

--
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=72324#72324




Attachments: 
http://forum.openscenegraph.org//files/screenshot_from_2017_11_06_23_00_48_832.png


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