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Asked: 2026-05-10T18:32:59+00:00

I am using Direct3D to display a number of I-sections used in steel construction.

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I am using Direct3D to display a number of I-sections used in steel construction. There could be hundreds of instances of these I-sections all over my scene.

I could do this two ways:

I-Sections

Using method A, I have fewer surfaces. However, with backface culling turned on, the surfaces will be visible from only one side. If backface culling is turned off, then the flanges (horizontal plates) and web (vertical plate) may be rendered in the wrong order.

Method B seems correct (and I could keep backface culling turned on), but in my model the thickness of plates in the I-section is of no importance and I would like to avoid having to create a separate triangle strip for each side of the plates.

Is there a better solution? Is there a way to switch off backface culling for only certain calls of DrawIndexedPrimitives? I would also like a platform-neutral answer to this, if there is one.

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1 Answer

  1. First off, backface culling doesn’t have anything to do with the order in which objects are rendered. Other than that, I’d go for approach B for no particular reason other than that it’ll probably look better. Also this object probably isn’t more than a hand full of triangles; having hundreds in a scene shouldn’t be an issue. If it is, try looking into hardware instancing.

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