Donnerstag, 26. November 2009

Perlin Noise Terrain Raycasting

Here a first trial to raycast perlin noise on the fly for achieving volumetric terrain rendering. In the demo, a 128^3 sized random volume data is used as a base for the scenes on the screenshots above.

By optimizing the empty-space skipping, it is possible to raycast reasonably large outdoor scenes at interactive framerates (20-40 fps) on a Nvidia GTX 260 GPU. The advantage of this kind of landscapes is, that they are extremely easy to handle and also that they are very memory friendly ( its just 128^3 rgba voxels = 8 MB of data ). Also can the performance easily adjusted for older graphics cards depending on the empty-space skipping configuration.

The Demo can be downloaded here: Perlin_Noise_Raycasting.zip Controls are w,s,a,d.

Kommentare:

  1. And how many option in empty-space skipping?

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  2. What do you mean by option?

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  3. >>Also can the performance easily adjusted for older graphics cards depending on the empty-space skipping configuration

    what algo do you use?
    any space skipping example?

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  4. The algo is very similar to what is described here: http://medvis.vrvis.at/projects/gpuraycast
    Depending on the stepwidth you can increase the speed.

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  5. Is this using SVO? Awesome demo btw!

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  6. Thanks!
    This time its not SVO - its basic raycasting through volume data, without any hierarchy.

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  7. Hi, I get this error:

    please wait - creating volume texture
    CG ERROR : The compile returned an error.
    (83) : warning C7011: implicit cast from "float4" to "float3"
    (83) : warning C7011: implicit cast from "float4" to "float3"
    (105) : warning C7012: not unrolling loop that executes 450 times since maximum
    loop unroll count is 256
    (105) : warning C7012: not unrolling loop that executes 450 times since maximum
    loop unroll count is 256
    (105) : warning C7012: not unrolling loop that executes 450 times since maximum
    loop unroll count is 256
    (105) : error C5013: profile does not support "for" statements
    (97) : error C5053: profile does not support "break" statements
    (104) : error C5053: profile does not support "break" statements
    165 lines, 9 warnings, 3 errors.


    Maybe you specified the profile incorrectly or something. This is on a ATI Radeon 5770, latest driver.

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  8. Hm.. I didnt try it yet on ATI. Seems ATI and NVidia always have compatibility problems.

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  9. Hi, I get this error on my GeForce-8500:

    please wait - creating volume texture
    CG ERROR : The compile returned an error.
    (83) : warning C7011: implicit cast from "float4" to "float3"
    (83) : warning C7011: implicit cast from "float4" to "float3"
    (105) : warning C7012: not unrolling loop that executes 450 times since maximum
    loop unroll count is 256
    (105) : warning C7012: not unrolling loop that executes 450 times since maximum
    loop unroll count is 256
    (105) : warning C7012: not unrolling loop that executes 450 times since maximum
    loop unroll count is 256

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  10. Just came across this, amazing demo's. Completely entranced. Have you worked on it at all since 2009? Do you have any plans for it?

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  11. Hi, Interesting demo. Just wanted to ask u two things:
    1) What is the stepsize that u use here and how many bisection refinement steps do u use here?
    1) I notice artifacts esp at the edges of the isosurface. These are evident when u approacha a structure. I experience this issue in isosurface raycasting do u think there is a solution for this?

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  12. The step size is dynamic and is reduced near the surface. Afterwards a binary search for hitpoint refinement is performed. The edges are due to trilinear sampling. Cubic sampling does not have this problem.

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