shadowCatcherPlane causes lighting artifacts

[mnaehrig]

Pathtracing with shadowCatcherPlane enabled affects lighting in an unexpected way.

shadowCatcherPlane enabled (0, 0, 1, 0):

shadowCatcherPlane disabled:

The scene contains just a single ambient light.

[johguenther]

I tried to reproduce the scene (simple geometry, single ambient light which is either visible, or using a background color), with current devel, looks good:

Are there other (transparent?) objects in the scene?

[mnaehrig]

Hi Johannes,
many thanks for your support! There are no transparent objects in the scene. Also tried with current devel now, but the effect is still there. Finally I added a shadow plane option to ospExamples:

static bool renderShadowPlane = false;
if (ImGui::Checkbox("renderShadowPlane", &renderShadowPlane)) {
  if (renderShadowPlane) {
    renderer->setParam("shadowCatcherPlane", vec4f(0, 0, 1, 1));
    addObjectToCommit(renderer->handle());
  } else {
    renderer->setParam("shadowCatcherPlane", vec4f(0, 0, 0, 0));
    addObjectToCommit(renderer->handle());
  }
}

With scene "planes" there is a noticable effect directly above the shadow plane: