What is a epsilon? ( Lights )
Community Forums/Technical Discourse/What is a epsilon? ( Lights )
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| void xLightShadowEpsilons ( Light * light, float epsilon1, float epsilon2 ) Sets epsilon values of light source. Every light sources has 2 epsilon values for shadows rendering. First value is a depth bias (it's needed to compensate inaccuracy of floating-point values), second value is to prevent shadowing of angularly triangles. Epsilons delete some noise from shadows, but can lead to incorrect rejection of a part of shadow. Default values are optimal, but you may need to adjust them for best results. Parameters: light Light source handle epsilon1 First epsilon value (compensates inaccuracy of floating-point values) epsilon2 Second epsilon value (prevents shadowing of angularly triangles), actually it is a cosine of maximum angle of shadowed triangle. |
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| Epsilon is easily and best remembered as 'close enough'. It's used to test for 2 values to be equal but with an allowing bias - the bias is the Epsilon. Due to the difficulty of comparing floating point numbers you use an epsilon value to accept that a value is close enough to another value for the 2 values to be considered equal even when they aren't exactly the same. For eg, a floating point value may never actually reach 0.0, it may be 0.0000012. In this case if you consider anything from -0.0001 to 0.0001 to be a value 'close enough' to zero, then 0.0001 is the epsilon. At the same time - comparing two values: 4.000112 and 4.000134 with an epsilon of 0.0001 will consider the two values to be equal. |
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| When i see the shadows in Hitman absolution and how fast it is on my low end computer, i say hurray to shaders... |
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| From that vague description (cosine of maximum angle, in relation to what? -- but I know it wasn't you who wrote it, Yue), epsilon2 seems to be a bias to avoid terminator shading problems. You probably increase the value of it to help avoid the problem seen on the object on the left:  (Picture taken from some other place unrelated to Xors3D.) |
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