This addon can produce high-quality caustics from sun and point lights at a quality that would only be achievable with other render engines like Lux-Render. As the name suggests it achieves this by computing the caustics beforehand and baking it into a texture. This comes with all the advantages and disadvantages of baked lighting.

Watch the full Tutorial:

How does it Work?

The addon places a camera on the position of your light source. Then it uses an emission shader to display the UV coordinates on your baking target. It now renders an image from the light source's viewpoint with a single sample. It can see the UV coordinates reflected and refracted in the object it is looking at. Because of specialized shaders, there is no shift in color or brightness so each pixel now contains the coordinate where a lightray would hit the baking target. The addon now takes all of these coordinates and adds a little bit of light to a new texture at the corresponding pixel. For color it renders a second pass, only analyzing how the color changes on the path.

What makes it better than blenders' own shadow caustic solution?

• as the name suggests, blenders' shadow caustics only work in the object's shadow. Any area not in the shadow will not receive any caustics. with this addon, the caustics will appear on all objects you are baking on.

• blenders shadow caustics ignore normal or bump maps. With this addon, you can use them to add surface detail that translates very well to the resulting caustics.

• blenders shadow caustics don't use the volume absorption shader, which is irreplaceable when making colored glass. With this addon, the volume absorption shader is fully supported.

• blenders shadow caustics only do refractive caustics. With this addon, you can do both reflective and refractive caustics.

• blenders shadow caustics only work on curved surfaces. With this addon, there are no such limitations.

What are the limitations of this method?

• It only works with sun and point lights.
• It assumes all lights are infinitely small points. (The result of this is extremely sharp caustics. To combat this you can either blur the texture or increase the roughness of the material)
• It only bakes the defuse Part of the light as the specular part is dependent on the camera angle.

FAQ

Why is my bake completely Black?

Two things could have happened.

• One of your receiver or contributor objects doesn't have a Material applied to it. The addon manipulates the Material of the object during the baking process. Without a Material, this step won't work. (I will add a warning for this case in future releases)
• The texture might appear black because the values are too low to be visible. When you are not using the Bake Energy option the brightness of the light will not be baked in, so the values can be extremely low.