Enum to specify whether DrawBrushPreview previews the source render texture or the destination render texture of a PaintContext.
| SourceRenderTexture | Specifies that TerrainPaintUtilityEditor.DrawBrushPreview uses the source render texture of the PaintContext. |
| DestinationRenderTexture | Specifies that TerrainPaintUtilityEditor.DrawBrushPreview uses the destination render texture of the PaintContext. |