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How to use caustics while rendering in Redshift
In order to add caustics to your scene you need at least one object to cast caustics, one to reflect them and a light to emit caustic photons.
*** Also, make sure bucket rendering mode is on in the render view or you won't be able to see any caustics ***
Select the object you'd like to emit caustics from and the objects that will reflect those caustics.
Add a Redshift Object Tag to each of them.
Click the RS object tag for the object that will cast caustics - Select the Visibility Tab - check the override option - In the bottom right under the global illumination parameters select the "Cast Caustic Photons" box
Click the RS object tag for the object that will reflect caustics -Select the Visibility Tab - check the override option - The "Receives Caustic Photons" option will be on by default.
Select the lights in your scene that you would like to affect the caustics - go to the Photon tab and under the Caustic parameters select the "Emit Caustic Photons" check box.
Increase the "Number of Photons to Emit" parameter a lot... like a lot a lot. The default value is 100,000 - you probably won't get decent results until your over 10,000,000 photons.
Open up the Redshift Render Settings and make sure the "advanced settings are turned on". Deselect automatic sampling and adjust your samples min and max to be more appropriate for your scene. My default is usually min 4, max 512. Select the reflection, refraction and light overrides increase each of these to 2048 to give those areas of your render more samples to work with.
Turn on the picture viewer and see how your caustics are looking. You can also preview them in the redshift render view with bucket mode on as I mentioned earlier but I want to see our render in full resolution.
If you're already using a large # of photons like I suggested but you're seeing a lot of tiny dots making up your caustics, you can go to your RS render settings, select the Caustics tab, and increase the blur radius. Move it upwards in small increments until your caustics appear smooth. If you increase it too much you're caustics will begin to blur and lose their detail.
You can always go back to the "number of photons to emit" parameter in your light and increase it even more to get better quality caustics but this will continue to increase your render times.
As you can see adding more photons and adding a small amount of blur radius to our settings really helped clean up the render.
Lastly you can also increase the "intensity multiplier" to brighten your caustics. This won't make the quality of the caustics better in any way, it will only make them brighter which is sometimes helpful when your balancing the levels of your lighting throughout your scene.
28 окт 2021
