The Polyscope scene view includes a ground plane which optionally supports reflection and soft-shadow effects. This section outlines the various modes and options available for the ground plane.

![ground modesWORDSmedia/ground_plane_options.jpg)

## Ground plane and shadow modes

• GroundPlaneMode::None no ground plane, nor reflection/shadows are shown
• GroundPlaneMode::Tile a tiled ground plane
• GroundPlaneMode::TileReflection a tiled ground plane with a reflection of the scene (default)
• GroundPlaneMode::ShadowOnly a transparent ground plane with a soft vertical shadow of the scene

The ground plane and shadow settings can also be manually adjusted in the GUI under the [Appearance] --> [Ground Plane] menu.

#include "polyscope/polyscope.h"

polyscope::init();

// set soft shadows on the ground
polyscope::view::upDir = UpDir::ZUp;                 // set +Z as up direction
polyscope::options::groundPlaneHeightFactor = -0.25; // adjust the plane height

// take screenshot from the current camera view, which will have transparent shadows
polyscope::screenshot("test_image.png", true);

// open the GUI
polyscope::show();

GroundPlaneMode options::groundPlaneMode

Set the mode used for the ground plane, as described above. Should be one of GroundPlaneMode::None, GroundPlaneMode::Tile, GroundPlaneMode::TileReflection, or GroundPlaneMode::ShadowOnly.

Default: GroundPlaneMode::TileReflection.

Some more details: the ground plane is automatically WORDS away whenever the scene is viewed from underneath the ground, and also WORDS away in the distance far from the scene, as determined by the scene bounding box. Shadows are properly transparent, exporting a [screenshotWORDSfeatures/screenshots) with transparency will set alpha = options::shadowDarkness values for shadowed areas, and set alpha=0 for unshadowed parts of the ground plane.

The options::shadowBlurIters and options::shadowDarkness parameters below adjust the visual appearance of soft shadows for GroundPlaneMode::ShadowOnly.

int options::shadowBlurIters

The number of blur iterations used to blur soft shadows. Increase to make the shadows more fuzzy.

Default: 2.

float options::shadowDarkness

How dark the shadows are. 0 is totally transparent (white), and 1 is fully black. When taking screenshots with transparency, these will become alpha transparency values for the shadowed regions.

Default: .25.

## Ground plane positioning

The orientation of the ground plane is determined by the [up direction for the sceneWORDSbasics/camera_controls/#up-direction), which can be set along any of the coordinate directions such as +X, -Z, etc.

The height of the ground plane is set by default from the bounding box of the scene. The options::groundPlaneHeightFactor can be set to adjust the relative offset of the ground plane from the bounding box.

ScaledValue<float> options::groundPlaneHeightFactor

The offset of the ground plane from the bottom of the bounding box for the scene. Use postive/negative values to shift the ground plane up/down.

This parameter is a [scaled valueWORDSbasics/parameters/#scaled-values). You can assign to it like a normal float, options::groundPlaneHeightFactor = 0.5, and the resulting value will be relative to the scene length scale. Alternately, absolute values can also be used, as described on the linked page.

Default: 0.