This is a follow up of the Frosted glass tutorial that I posted last week, here on cgdigest. If you havenâ€™t already read that one, I strongly suggest you do that before going through this one.
If you went through that tutorial, youâ€™ve most probably noticed that the rendering times, when you activate blurred reflections and refractions are considerably high.
However, if you are not rendering an animation and the final product is a still rendering, there is another way around it; this is what Iâ€™m trying to explain in this tutorial.
The first thing that you need to do is to start with material settings suitable for clear glass, with no blurred reflections of refractions. Duplicate the material, rename it, and make it a vray material wrapper, with the base material being the clear glass.
Change the alpha contribution parameter to â€œ-1â€ and keep the rest untouched.
Now select the polygons like in the image bellow and assign the new material only to this selection.
In case you are wondering why you didnâ€™t assign the new material, the answer is simple; we will going to tweak this in post processing in order to add blur reflection and reflection, but we need to keep the edges sharp.
Render a high resolution rendering, and save the result as a tiff with alpha channel.
Open the rendering in photoshop.
Click on â€œselectâ€, â€œload selectionâ€, â€œalpha 1â€, than invert the selection.
At this point you have the material selected and you can start tweaking it.
In order to have blurred reflections and refractions, click on filters, blur, and choose Gaussian blur.
One of the advantages of using this method is that you can adjust the amount of blur that you need in your image dynamically, without having to render the scene again.
Also, you have more control on the color simply by adjusting the color balance.
Bellow are 3 examples that I managed to do in a few seconds using this method (if I had to do it directly in 3d, I would have had to render each one separately):
As you can see these images are already similar to the renderings done directly in 3d.
You can take them even further by using filters like glass (tiny lens, canvas or blocks) or any other filter that fit your needs..
As I said previously, this method of creating frosted glass with photoshop has a lot of advantages; however it has some disadvantages as well. Besides not working for animations, you can not control the amount of blur for reflections and refractions separately.
Depending on what are your requirements you can choose either of the methods shown above.
If there is something you don’t understand, feel free to ask!