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  • Volume Clearity

    Hey,

    I have made LDM of DICOM files.

    After rendering it, i m getting lot of noise in the volume. please have a look on the screen shots.
    image1.jpg

    image2.jpg
    how can i remove this noise. is it require filtering? how can i do this?

    One screen is without volumeQuality light and 2nd is with light, can i change the intensity of light. As there is not API to change the light intensity in the VolumeRenderingQuality node.

    I have also tried to on the VolumeRender Node light. but it is having no effect.

    Please suggest.

    Vishal..

  • #2
    Re: Volume Clarity

    I have made LDM of DICOM files.
    After rendering it, i m getting lot of noise in the volume. please have a look on the screen shots.
    how can i remove this noise. is it require filtering? how can i do this?
    Hi Vishal,
    I guess you're talking about the "terrace" effect visible in these screen shots (thanks for including those, by the way, they're very helpful). What you're seeing is the edges of the texture mapped polygons drawn to render the volume. It's yet another kind of aliasing, a rendering artifact caused by too low a sampling rate. Two things you can try:
    • Increase the number of "slices" (polygons) used to render the volume. See the fields numSlicesControl and numSlices in SoVolumeRender. Drawing more slices effectively increases the sampling rate and can be critical to image quality, especially if your data set is very small in one dimension (e.g. 512 x 512 x 32).
    • Enable "jittering". This is analogous to enabling anti-aliasing for polygonal geometry. The edges of the "slices" are slightly blurred to remove the sharp edges you're seeing now. See the jittering field in SoVolumeRenderingQuality.

    Note that you can experiment with most of these settings by loading your data set in the VolRend example/demo program provided with VolumeViz.
    One screen is without volumeQuality light and 2nd is with light, can i change the intensity of light. As there is not API to change the light intensity in the VolumeRenderingQuality node.

    I have also tried to on the VolumeRender Node light. but it is having no effect.
    Yes, you can change all the usual properties of the light. When you enable lighting using the SoVolumeRenderingQuality node, VolumeViz uses the first directional light node found in the scene graph to illuminate the volume. If your application doesn't specifically create any lights, then this will normally be the "headlight" created by the viewer class. You can get a pointer to this light and modify it (see SoWinViewer getHeadlight), but usually it's better to explicitly create a directional light node. This node allows you to control the direction, color, intensity, etc. See SoDirectionalLight.

    We don't recommend using the lighting field in the SoVolumeRender node. This is an older feature that enables a "static" lighting computation done on the CPU. SoVolumeRenderingQuality enables dynamic lighting computed on the GPU with various high quality options (see section 20.3.5.3 of the Open Inventor User's Guide).

    Regards,
    Mike
    Last edited by mikeheck; December 23rd, 2008, 05:50 AM. Reason: forgot title

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    • #3
      Volume Clarity

      Dear Mike,

      I tired all those attributes, it really increases the clearity. if i changed the numSlices from 200 to 1024, but its speed went damn slow. Is there any other setting to optimize the performance? my Laptop RAM size is 4GB.

      Regards,
      Vishal

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      • #4
        Volume rendering performance

        Originally posted by vishal.sharma View Post
        I tired all those attributes, it really increases the clearity. if i changed the numSlices from 200 to 1024, but its speed went damn slow. Is there any other setting to optimize the performance? my Laptop RAM size is 4GB.
        Hi Vishal,

        Yes, there are multiple parameters that affect volume rendering performance. There is a nice summary in section 20.5.2 of the Open Inventor Users Guide (included in the SDK install as a PDF file).

        Some of these parameters improve performance in general when rendering a large volume or rendering with many slices. Another important technique is automatic reduction of image quality when interacting with the scene (e.g. moving the camera).

        Regards,
        Mike

        Comment


        • #5
          Hey Mike,

          I have just added a SoVolumeRenderingQuality Node in my Scene Graph having


          volQuality = new SoVolumeRenderingQuality();
          volQuality->lighting.setValue(TRUE);
          volQuality->preIntegrated.setValue(TRUE);


          After that i m getting one error, please check the screen shot

          VolumeQuality_Error.JPG

          Please suggest, how can i solve this problem.

          Thanks...

          Comment


          • #6
            Re: Error message

            Hi,

            There is always the possibility of a bug, so you should probably report this problem to the Hotline. Please include basic context including: OIV version, OS, compiler, etc.

            On the other hand, we use SoVolumeRenderingQuality all the time, so there probably isn't anything fundamentally broken. Here are a few things to check for more clues:

            1. Scroll back to the beginning of the error messages to see if there is something different, e.g. OIV couldn't find one of the predefined shader files.

            2. Set the following environment variable to get more details about the GLSL linking problem:
            OIV_GLSL_DEBUG

            Mike

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