Package com.openinventor.inventor.nodes

Class SoShadowGroup

  • All Implemented Interfaces:
    SafeDisposable
    public class SoShadowGroup
extends SoGroup
    Shadow casting group node. This group node performs real-time shadow casting. Because shadows depends on a lot of OpenInventor elements, it is recommended to put children of this group under a SoSeparator in order to have a cache. Each shape within this group will be included in the shadow casting computation. A shape may cast a shadow on other shapes or on itself (self-shadowing), and/or may be shadowed by other shapes within the group. The current shadow style is used to determine if shapes cast a shadow and/or can be shadowed (see SoShadowStyle).

    This class defines a single shadowing method. The method field allows for future shadowing methods to be added.

    • VARIANCE_SHADOW_MAP : This mode allows to display soft shadows. The smoothFactor field can be used to increase or decrease the softness. Aliasing won't be displayed, but on large scenes shadows will progressively fade away. Increasing quality will reduce this problem. Only the last on state directional light is used during rendering, other lights are ignored.

      Shaders
      Only the VARIANCE_SHADOW_MAP method is available with shaders (custom or internal). In order to use shadows with user defined GLSL shaders (SoShaderProgram or SoVolumeShader), the following functions must be used in the shader programs.
      In the vertex shader:

      • void OivSetupShadowVertex(): Must be called in the vertex shader.

      In the fragment shader:

      • float OivComputeShadow(): Returns a scalar in [0-1]. 0 means fragment is fully shadowed, 1 means no shadow. Should be used to modify the fragment color.
      • void OivGenerateShadowMap(): Must be called during the shadowmap pass in order to create the shadowmap. During this pass, the shader must not write to gl_FragColor. Use the uniform OivShadowPass to know when the shadowmap is being computed.

      The following uniform is available in vertex and fragment shaders:

      • uniform bool OivShadowPass: Is true if the shadowmap is currently being rendered

      The following code can be used as a skeleton for a GLSL shader that works with shadows: 

       // The vertex shader:
 void OivSetupShadowVertex();
 void main()
 {
   ..userCode..
   //Needed for shadowing
   OivSetupShadowVertex();
 }
 
 // The fragment shader:
 //If true we are in shadowmap generation pass
 uniform bool OivShadowPass;
 
 void OivGenerateShadowMap();
 float OivComputeShadow();
 void main()
 {
   if ( !OivShadowPass ) {
     ..compute fragment color here..
     // Define the final color
     gl_FragColor.xyz = fragColor.xyz * OivComputeShadow();
     gl_FragColor.w = fragColor.w;
   }
   else {
     // Output the shadowmap during the shadow map pass
     OivGenerateShadowMap();
   }
 }

      Transparency:
      Transparent objects are treated as follows, depending on the transparency type:

      • NO_SORT: Transparent objects cast a shadow and are shadowed but the shadow intensity doesn't depend on the transparency value (the same shadow is displayed for full transparent shapes and opaque shapes).
      • OPAQUE_FIRST, SORTED_OBJECT and SORTED_PIXEL: Same as previous case for VARIANCE_SHADOW_MAP.

      Texture units:
      In VARIANCE_SHADOW_MAP mode, this node reserves texture unit OIV_SHADOW_TEXTURE_UNIT0 for its rendering (see SoPreferences to set these). If this value is not set the application can specify which texture units OpenInventor should automatically use by setting environment variables (see SoPreferences). The texture units between OIV_FIRST_RESERVED_TEXTURE_UNIT and OIV_FIRST_RESERVED_TEXTURE_UNIT + SoShaderProgram.getNumReservedTextures() -1 inclusive are reserved for internal OpenInventor use. If OIV_FIRST_RESERVED_TEXTURE_UNIT is not set, its default value is SoFragmentShader.getMaxTextureImageUnit()-SoShaderProgram.getNumReservedTextures(). Note: The value returned by SoShaderProgram.getNumReservedTextures() may change between OpenInventor versions. The total number of available texture units depends on the graphics hardware.

      Hardware requirements:
      The Shadow and Depth Texture OpenGL extensions (standard in OpenGL 1.4) are used if they are available and generally improve performance.
      In order to increase quality and performance of the shadows, OpenGL PBuffers are used. PBuffers are a limited resource on some systems. Set OIV_PBUFFER_ENABLE to 0 to disallow use of PBuffers.

      A DirectX 10 graphics board is needed to support VARIANCE_SHADOW_MAP.

      Use the isSupported() static method to determine if the current graphics board supports shadowing.

      Limitations

      Notes:

      • Geometry cannot receive shadows if lighting is disabled.
        For example if an SoLightModel node sets the lighting model to BASE_COLOR.
      • Geometry cannot receive shadows if a texture is applied using the DECAL or REPLACE models.

      File format/default:

      ShadowGroup {

        isActive true
        isShapesBefore false
        intensity 0.5
        precision 0.5
        quality 0.5
        shadowCachingEnabled true
        visibilityRadius 1.0
        visibilityFlag LONGEST_BBOX_EDGE_FACTOR
        smoothFactor 1
        minVariance 1e-5
        method VARIANCE_SHADOW_MAP
        lightBleedingReduction 0.01
      }

    See Also:
    SoShadowStyle

    • Field Detail

      • intensity

        public final SoSFFloat intensity
        Specifies the intensity of the shadow. 0 = lowest intensity (the shadow is invisible), 1 = highest intensity (the shadow is solid black).

      • precision

        public final SoSFFloat precision
        Specifies the precision of the shadow. 0 = lowest precision, 1 = highest precision. With lower precisions, some parts of the scene may be unlit where they should be lit, or vice versa. Increasing the precision will reduce performance.

        NOTE: If your graphics driver does not support the required OpenGL extensions, you may see low precision results even when this field is set to the highest precision.

      • quality

        public final SoSFFloat quality
        Specifies the quality of the shadow. The texture used for shadowmap rendering will be of size 2*quality*ViewportSize. Increasing the quality will reduce performance and increase memory consumption.

      • shadowCachingEnabled

        public final SoSFBool shadowCachingEnabled
        Indicates if a cache should be used for computing the shadows. Using a cache will improve rendering performance if the lights of your scene and your scene under this group node do not change.

      • smoothFactor

        public final SoSFInt32 smoothFactor
        Set the smoothness of shadows. Higher values give smoother shadows. Default is 1.

        Since:
        Open Inventor 8.1

      • minVariance

        public final SoSFFloat minVariance
        Increasing this value will decrease possible self-shadowing artifacts but will make shadows fade away. The default value is safe for most scenes. Increasing the quality field is also preferable before tweaking this value. A special case is for SoVolumeRender node which has a minimum of 0.001 or IVVR_SHADOW_MIN_VARIANCE if set. Default is 1e-5 and range is [0-1].

        Since:
        Open Inventor 8.1

      • lightBleedingReduction

        public final SoSFFloat lightBleedingReduction
        In some cases, a halo may appear around shadows intersecting each other. Increasing this value will decrease this effect. Default value is safe for most scenes. Default is 0.01 and range is [0-1].

        Since:
        Open Inventor 8.1

    • Constructor Detail

      • SoShadowGroup

        public SoShadowGroup()
        Default constructor.

      • SoShadowGroup

        public SoShadowGroup​(int nChildren)
        Constructor that takes approximate number of children.

    • Method Detail

      • isSupported

        public static boolean isSupported()
        Calls isSupported(SoShadowGroup.ShadowingMethods.valueOf( SoShadowGroup.ShadowingMethods.VARIANCE_SHADOW_MAP.getValue() )).

      • isSupported

        public static boolean isSupported​(SoShadowGroup.ShadowingMethods method)
        Indicates if shadow casting is supported by your graphic board. When using a debug build of Open Inventor, some "no context available" warning messages may be generated. You can ignore them or see SoGLExtension for an example of using SoGLContext to avoid them.