# How to set custom shader with VTK 8.1(C++)
**URL:** https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122
**Category:** Support
**Created:** [January 8, 2025, 5:52am UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122 "2025-01-08T05:52:37Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@1078586743](https://discourse.vtk.org/u/1078586743)
#### Post date: [January 8, 2025, 5:52am UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/1 "2025-01-08T05:52:37Z")
Hi,everyone
How can i set custom shader with VTK8.1?
I know it’s probably using vtkShaderProgram,but i can’t find any example.
Could you please provide insights for achieving this? Your guidance would be greatly appreciated.
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### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [January 8, 2025, 10:32pm UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/2 "2025-01-08T22:32:07Z")
Hello,
To set shaders for your mapper in VTK 8.1, please take a look at [Rendering/OpenGL2/Testing/Cxx/TestUserShader.cxx · v8.1.0 · VTK / VTK · GitLab](https://gitlab.kitware.com/vtk/vtk/-/blob/v8.1.0/Rendering/OpenGL2/Testing/Cxx/TestUserShader.cxx) and [Rendering/OpenGL2/Testing/Cxx/TestUserShader2.cxx · v8.1.0 · VTK / VTK · GitLab](https://gitlab.kitware.com/vtk/vtk/-/blob/v8.1.0/Rendering/OpenGL2/Testing/Cxx/TestUserShader2.cxx) .
best,
PC
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### Author:  [@1078586743](https://discourse.vtk.org/u/1078586743)
#### Post date: [January 9, 2025, 2:08am UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/3 "2025-01-09T02:08:23Z")
Thanks for your reply.
I can’t find the method of `AddShaderReplacement`,but i will try SetVertexShaderCode and SetFragmentShaderCode.
Hope it works.
Thanks again for your help
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### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [January 9, 2025, 11:19am UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/4 "2025-01-09T11:19:50Z")
Hello,
`AddShaderReplacement()` belongs to the `vtkOpenGLShaderProperty` class, which was introduced in VTK 9.
best,
PC
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### Author:  [@1078586743](https://discourse.vtk.org/u/1078586743)
#### Post date: [January 10, 2025, 3:38am UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/5 "2025-01-10T03:38:36Z")
Hello,
Thanks for your reply.
I use AddVertexShaderReplacement and AddFragmentShaderReplacement in VTK(9.3.0), which can work well.But while replaced with SetFragmentShaderCode and SetVertexShaderCode, if i set opacity and get closer to the model, it will be low FPS.
In NVIDIA Nsight Graphics, i find this:
glClear() and Draw many times, could you tell me what’s wrong with it.
It will have the same issue in VTK(8.1.0).
Any reply would be greatly appreciated
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### Author:  [@1078586743](https://discourse.vtk.org/u/1078586743)
#### Post date: [January 10, 2025, 6:33am UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/6 "2025-01-10T06:33:45Z")
Sorry,i found this was a Depthpeeling problem, I did not set the reference in the shader
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### Author:  [@1078586743](https://discourse.vtk.org/u/1078586743)
#### Post date: [January 10, 2025, 6:37am UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/7 "2025-01-10T06:37:59Z")
How do I set the uniform attribute in VTK(8.1.0).
The method of SetUniform is only found in vtkShaderProgram, but i don’t know how to use vtkShaderProgram.No other method related to ShaderProgram was found.
Any reply would be greatly appreciated
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### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [March 6, 2025, 1:46pm UTC](https://discourse.vtk.org/t/how-to-set-custom-shader-with-vtk-8-1-c/15122/8 "2025-03-06T13:46:20Z")
Hello,
Sorry for the late reply. Examples of usage of `vtkShaderProgram::SetUniform*(...)` can be found in the example codes shared further above:
best,
PC