How to add dirt to a glass shader?

Question

I am rendering an image of a grotty old looking light-bulb. I can make a decent clear glass material, but, not a perfect one.

I simply cannot get the dirt textures to overlay properly.

How can I add dirt to my glass shader without ruining the glass material underneath it.

There is also an emission shader on the filament inside the bulb.

I tried looking for tutorial but they are all based on non transparent materials.

It would be helpful if you added more information on what you have tried so far so far. Add images of your current settings and anything that would help us help you — , Jun 03 '16 at 14:39
related:http://blender.stackexchange.com/questions/9310/light-bulb-filaments-brightness-and-internal-reflections-in-cycles — , Jun 03 '16 at 14:41
also related: http://blender.stackexchange.com/questions/32166/adding-surface-scratches and http://blender.stackexchange.com/questions/15642/how-to-apply-a-material-e-g-dirt-over-an-object-that-already-has-multiple-mat — , Jun 03 '16 at 14:42
also related: http://blender.stackexchange.com/questions/32494/how-to-make-dirty-looking-object/33054#33054 and http://blender.stackexchange.com/questions/51814/how-can-i-create-a-glass-globe-with-a-sandblasted-effect — , Jun 03 '16 at 16:01

score 5 · Answer 1 · edited Jun 03 '16 at 17:07

You can try adding a scratches map to your glass material. A quick Google search for "scratch bump map" can lead to some good results.

For the nodes, I would suggest two Glass BSDF shaders, one with 0 roughness and one with 0.4 roughness, run into a Mix Shader (0.4 Roughness one in top shader input). Use the image as a fac in the Mix Shader. You can add a Bright/Contrast node between the Image Texture and the Mix Shader. Adjust the Bright: value to affect the roughness.

Unfortunately, I can't post screenshots right now.

How to add dirt to a glass shader?

1 Answers1