GPU Caustics 3ds max

[s_gru]

i seem to be getting caustics from the back-side of a disco-ball i have in my scene. i thought they would only be where the light was hitting the ball? the light includes only the ball and nothing else. case shadows is selected and it is invisible. the light diameter and hotspot only encompass the disco-ball.

[s_gru]

here's the top view of the scene. camera is at bottom.

[hermit.crab]

Does it happen with CPU caustics? Is the ball refractive or the groundplane reflective? Is the VRayCaustics any different? Overall, I can't be sure what's happening without the scene.

[s_gru]

in the calc phase of CPU rendering, it appeared to show the caustics all over. i've attached the scene.

[hermit.crab]

Seems odd indeed. Even if you lower the radius of the light to encompass only the front side of the sphere - there are caustics generated from the back. The caustics solver probably utilizes an internal parameter for photon generation. I need to ask the devs how it works.

[hermit.crab]

Update: Disc lights are not yet supported by GPU Caustics - internally a rectangular light will be used instead, so better to switch to Rectangular for an accurate preview. For the backside to not cast caustics, you need to set the light's size so that it is inscribed in the object (not going out of its borders).

[s_gru]

ah! ok thanks!