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OuncleJulien

Float hell

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Hey guys, I''m ~75% done with my first BSP tree! I currently only have one problem- For some reason when I use the D3DXPlaneDotCoord function and I pass it a vertex that *lies on the plane* it''ll return -0.00000f or 0.00000f, which when compared to 0.0f with the equality operator it will return false. I thought it might have been the function so I wrote my own which frustratingly enough returns the same result. I use this function to determine which side of the plane the vertices of a face are on so I can send it to the left or right as needed. Without being able to compare the dot product I can''t determine which side a face should goto. Does anyone know why this is occurring or how I can detect/fix it properly?

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It''s generally a bad idea to compare floating point numbers with the equality operator. Floating point numbers are not exact.

Instead, make sure the absolute value of their difference is below a certain threshhold, which is commonly referred to as "epsilon". 1e-5 is a pretty good epsilon value for many common uses, but you may want to change it if your numbers are very low or high.


"Sneftel is correct, if rather vulgar." --Flarelocke

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