# Enabling self-occlusion shadows wrt. Image-based skybox lighting
**URL:** https://discourse.vtk.org/t/enabling-self-occlusion-shadows-wrt-image-based-skybox-lighting/4358
**Category:** Support
**Created:** [October 6, 2020, 8:37am UTC](https://discourse.vtk.org/t/enabling-self-occlusion-shadows-wrt-image-based-skybox-lighting/4358 "2020-10-06T08:37:24Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Chopian](https://discourse.vtk.org/u/Chopian)
#### Post date: [October 6, 2020, 8:37am UTC](https://discourse.vtk.org/t/enabling-self-occlusion-shadows-wrt-image-based-skybox-lighting/4358/1 "2020-10-06T08:37:24Z")
I want to illuminate a triangle mesh (from an .stl file) using only imagebased skybox lighting. When rendering an object, it appears that no shadows are cast from self occlusion. Eg. lighting a cylinder from a 45 degree angle wrt. the symmetry axis leads to a rendering where the inside of the cylinder have the same amount of illumination where realistically the light should only be able to light a part of the inside while the rest is in shadow.
Is it possible to enable casting of shadows?
Perhaps I should add that I have not computed normals or tangents for the imported .stl mesh. Is this neccesary?
Below is a codesnippet showing the setup of the vtkRenderer:
renderer-\>RemoveAllLights();
renderer-\>SetTwoSidedLighting(false);
renderer-\>SetLightFollowCamera(false);
renderer-\>SetAutomaticLightCreation(false);
renderer-\>UseImageBasedLightingOn();
renderer-\>SetEnvironmentTexture(cubemap);
renderer-\>SetBackground(colors-\>GetColor3d(“BkgColor”).GetData());
renderer-\>AddActor(actor);
auto skyboxActor = vtkSmartPointer::New();
skyboxActor-\>SetTexture(skybox);
renderer-\>AddActor(skyboxActor);
---
### Author:  [@fraseyboo](https://discourse.vtk.org/u/fraseyboo)
#### Post date: [October 6, 2020, 7:49pm UTC](https://discourse.vtk.org/t/enabling-self-occlusion-shadows-wrt-image-based-skybox-lighting/4358/2 "2020-10-06T19:49:56Z")
I think that if you want to render proper shadows you’ll need to add the proper passes into your rendering pipeline, vtkSSAOPass will add in ambient occlusion to a scene and I’ve used it fine but I’m not sure if it’ll work with external lights or with color. There’s also vtkShadowMapPass that supports colored lighting however I don’t know how advanced it is.
I’ve included a function to add in SSAO, it might be useful. You should have a look at the other passes VTK can utilise.
```
def add_SSAO(ren):
bounds = np.asarray(ren.ComputeVisiblePropBounds())
b_r = np.linalg.norm([bounds[1] - bounds[0], bounds[3] - bounds[2], bounds[5] - bounds[4]])
occlusion_radius = b_r * 0.1 # tune to your preference
occlusion_bias = 0.04 # not actually sure what this does
passes = vtk.vtkRenderPassCollection()
passes.AddItem(vtk.vtkRenderStepsPass())
seq = vtk.vtkSequencePass()
seq.SetPasses(passes)
ssao = vtk.vtkSSAOPass()
ssao.SetRadius(occlusion_radius)
ssao.SetDelegatePass(seq)
ssao.SetBias(occlusion_bias)
ssao.SetBlur(True)
ssao.SetKernelSize(256) # if this is too low the AO is inaccurate
fxaaP = vtk.vtkOpenGLFXAAPass() # Anti-Aliasing isn't included in the default
fxaaP.SetDelegatePass(ssao)
ren.SetPass(fxaaP)
ren.SetUseDepthPeeling(True)
ren.SetOcclusionRatio(0.1)
ren.SetMaximumNumberOfPeels(100)
return ren
```
---
### Author:  [@Chopian](https://discourse.vtk.org/u/Chopian)
#### Post date: [October 15, 2020, 12:08pm UTC](https://discourse.vtk.org/t/enabling-self-occlusion-shadows-wrt-image-based-skybox-lighting/4358/3 "2020-10-15T12:08:10Z")
I think you are correct that I need the correct render passes. I have implemented the vtkShadowMapPass and I get self occluding shadows from vtkLights, however there is no occlusion from the environment lighting.
---
### Author:  [@Michael](https://discourse.vtk.org/u/Michael)
#### Post date: [October 16, 2020, 8:20am UTC](https://discourse.vtk.org/t/enabling-self-occlusion-shadows-wrt-image-based-skybox-lighting/4358/4 "2020-10-16T08:20:06Z")
Environment lighting is not used in the vtkShadowMapPass.
If you have a static scene, the best result can be achieved using baked lighting textures (you need to use an external software for this) and use it in VTK (with the ORM texture)