[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 <jtorresfabra at gmail.com>:

> 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 <romulogcerqueira at gmail.com>:
>
>> 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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>> osg-users at lists.openscenegraph.org
>> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>>
>
>
>
> --
> Jordi Torres
>
>
>


-- 
Jordi Torres
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