[vtk-developers] GLSL Shader on a vtkActor (VTK 6.1 and Qt 5.2.1)
carlinhos
carlinhosmp87 at gmail.com
Wed Jul 30 09:40:52 EDT 2014
Hello Joachim!
I did it, it was the right way to do it :). Thank you so much for your
explanation.
I resume the steps for everyone:
0- Create a shader file with the function *propFuncFS**(Fragment shader)*
* or **propFuncVS(Vertex shader).*
1- Load the shader from disk.
2- Create a vtkShader2 and set the source code.
3- Create a vtkShaderProgram2 and initialize it (DO NOT BUILD THE PROGRAM).
4- Add the shader to the program.
5- Obtain the actor vtkOpenGLProperty and set the program
6- Set the shading on.
Code:
> *QFile fragmentFile(QStringLiteral("C:/myfragmentshader"));*
> * fragmentFile.open(QIODevice::ReadOnly);*
> * auto fragmentBytes = fragmentFile.readAll();*
> * fragmentFile.close();** QString fragmentShaderSource(fragmentBytes);*
>
> * //The GLSL binded program*
> * vtkSmartPointer<vtkShaderProgram2> program =
> vtkSmartPointer<vtkShaderProgram2>::New();*
> * // Prepare the fragment shader*
> * vtkSmartPointer<vtkShader2> shader = vtkSmartPointer<vtkShader2>::New();*
> * shader->SetType(VTK_SHADER_TYPE_FRAGMENT);**
> shader->SetSourceCode(fragmentShaderSource.toStdString().c_str());*
> * program->GetShaders()->AddItem(shader);*
>
> * vtkSmartPointer<vtkOpenGLProperty> openGLproperty =
> static_cast<vtkOpenGLProperty*>(gemActor->GetProperty());*
> * openGLproperty->SetPropProgram(program);** openGLproperty->ShadingOn();*
Shader (simple shader to paint all fragments red):
* #version 110*
>
> * void propFuncFS(void)*
> * {*
> * gl_FragColor = (255,0,0,1);** }*
Thanks again and have a nice day! =)
2014-07-29 21:48 GMT+02:00 Carlos Martinez <carlinhosmp87 at gmail.com>:
> Joachim,
>
> Thank you so much for the explanation, I tried something similar but
> building the shaders instead of not doing it (if I remember well).
> Tomorrow i will try it and I will tell you the results!!
>
> Carlos.
>
>
>
>
> 2014-07-29 15:14 GMT+02:00 Joachim Pouderoux [via VTK] <
> ml-node+s1045678n5728004h64 at n5.nabble.com>:
>
>> Carlos
>>
>> Ok actually I was wrong. My patch works but it is not how this is
>> supposed to happen.
>> Basically, VTK will merge 2 different shader source code to define each
>> type of shader (vertex, fragment etc.).
>> A first source will come from the shader code that can be attached to the
>> renderer shaders.
>> If it not exist, the default is a main function that will call
>> propFuncVS()/propFuncFS() etc - depending the shader type.
>> The second source will come from the shader code that can be attached to
>> the actor's property.
>> If it not exist, the default behaviour is to define that propFuncVS/FS
>> functions.
>> Both source codes will be appended before being compiled by the
>> openGlProperty.
>>
>> So basically if you do not define a renderer shader program, you simply
>> have to provide a shader codes to your property that defines propFuncVS/FS
>> functions instead of usual main() functions.
>> Also do not build your shader program (program->Build()) in your code as
>> it will fail because the main() functions are not provided. Remember they
>> will be added later automatically before compilation by OpenGLProperty.
>>
>> Hope it is clear and it helps!
>>
>> Best,
>>
>>
>>
>> *Joachim Pouderoux*
>>
>> *PhD, Technical Expert*
>> *Kitware SAS <http://www.kitware.fr>*
>>
>>
>>
>> 2014-07-29 14:55 GMT+02:00 Joachim Pouderoux <[hidden email]
>> <http://user/SendEmail.jtp?type=node&node=5728004&i=0>>:
>>
>>> Actually it seems like there is a bug in vtkOpenGLProperty.cxx that I
>>> might have fixed. I will make a patch soon.
>>> In the meanwhile try to change those lines:
>>>
>>>
>>> needDefaultMainVS = !progHasVertex
>>> && propProg->HasVertexShaders();
>>> needDefaultMainFS = !progHasFragment
>>> && propProg->HasFragmentShaders();
>>>
>>> by
>>>
>>> needDefaultMainVS = !progHasVertex
>>> && !propProg->HasVertexShaders();
>>> needDefaultMainFS = !progHasFragment
>>> && !propProg->HasFragmentShaders();
>>>
>>> With that fixed, the steps you defined should now work as no second
>>> main() will be added to both shader code.
>>>
>>> Joachim
>>>
>>> *Joachim Pouderoux*
>>>
>>> *PhD, Technical Expert*
>>> *Kitware SAS <http://www.kitware.fr>*
>>>
>>>
>>>
>>> 2014-07-18 11:03 GMT+02:00 carlinhos <[hidden email]
>>> <http://user/SendEmail.jtp?type=node&node=5728004&i=1>>:
>>>
>>> Hello Xiaoming,
>>>>
>>>> I created a new vtkOpenGLProperty and set it to the actor, anyways i
>>>> tried to cast the vtkProperty obtained by the a vtkActor::GetProperty(),
>>>> because vtkProperty is an abstract class. I tried so many things to make it
>>>> work but i didn't manage to do it. Also i tried to use vtkOpenGLActors
>>>> instead of vtkActors but it also didn't work.
>>>>
>>>> Carlos.
>>>>
>>>>
>>>> 2014-07-18 9:46 GMT+02:00 xiaoming [via VTK] <[hidden email]
>>>> <http://user/SendEmail.jtp?type=node&node=5727905&i=0>>:
>>>>
>>>>> i'm sorry but i see that vtkActor::GetProperty() returns a pointer to
>>>>> the vtkProperty not vtkOpenGLProperty,which has a member of
>>>>> SetPropProgram,i 'm just confused with the 7th step,would you bother to
>>>>> tell me sth about that ,thanks in advance.
>>>>> Quote:
>>>>> < 7- Put ShadingOn to the property and SetPropProgram with the
>>>>> vtkShaderProgram2 build before (The vtkShaderProgram on debug has only
>>>>> the
>>>>> 2 shaders I put in).>
>>>>>
>>>>>
>>>>>
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