void InitSegments()

in unity/Assets/PostProcessingV2/Runtime/Utils/HableCurve.cs [121:226]
65 lines of code
1 McCabe index (conditional complexity)

        void InitSegments(DirectParams srcParams)
        {
            var paramsCopy = srcParams;

            whitePoint = srcParams.W;
            inverseWhitePoint = 1f / srcParams.W;

            // normalize params to 1.0 range
            paramsCopy.W = 1f;
            paramsCopy.x0 /= srcParams.W;
            paramsCopy.x1 /= srcParams.W;
            paramsCopy.overshootX = srcParams.overshootX / srcParams.W;

            float toeM = 0f;
            float shoulderM = 0f;
            {
                float m, b;
                AsSlopeIntercept(out m, out b, paramsCopy.x0, paramsCopy.x1, paramsCopy.y0, paramsCopy.y1);

                float g = srcParams.gamma;

                // Base function of linear section plus gamma is
                // y = (mx+b)^g
                //
                // which we can rewrite as
                // y = exp(g*ln(m) + g*ln(x+b/m))
                //
                // and our evaluation function is (skipping the if parts):
                /*
                    float x0 = (x - offsetX) * scaleX;
                    y0 = exp(m_lnA + m_B*log(x0));
                    return y0*scaleY + m_offsetY;
                */

                var midSegment = segments[1];
                midSegment.offsetX = -(b / m);
                midSegment.offsetY = 0f;
                midSegment.scaleX = 1f;
                midSegment.scaleY = 1f;
                midSegment.lnA = g * Mathf.Log(m);
                midSegment.B = g;

                toeM = EvalDerivativeLinearGamma(m, b, g, paramsCopy.x0);
                shoulderM = EvalDerivativeLinearGamma(m, b, g, paramsCopy.x1);

                // apply gamma to endpoints
                paramsCopy.y0 = Mathf.Max(1e-5f, Mathf.Pow(paramsCopy.y0, paramsCopy.gamma));
                paramsCopy.y1 = Mathf.Max(1e-5f, Mathf.Pow(paramsCopy.y1, paramsCopy.gamma));

                paramsCopy.overshootY = Mathf.Pow(1f + paramsCopy.overshootY, paramsCopy.gamma) - 1f;
            }

            this.x0 = paramsCopy.x0;
            this.x1 = paramsCopy.x1;

            // Toe section
            {
                var toeSegment = segments[0];
                toeSegment.offsetX = 0;
                toeSegment.offsetY = 0f;
                toeSegment.scaleX = 1f;
                toeSegment.scaleY = 1f;

                float lnA, B;
                SolveAB(out lnA, out B, paramsCopy.x0, paramsCopy.y0, toeM);
                toeSegment.lnA = lnA;
                toeSegment.B = B;
            }

            // Shoulder section
            {
                // Use the simple version that is usually too flat 
                var shoulderSegment = segments[2];

                float x0 = (1f + paramsCopy.overshootX) - paramsCopy.x1;
                float y0 = (1f + paramsCopy.overshootY) - paramsCopy.y1;

                float lnA, B;
                SolveAB(out lnA, out B, x0, y0, shoulderM);

                shoulderSegment.offsetX = (1f + paramsCopy.overshootX);
                shoulderSegment.offsetY = (1f + paramsCopy.overshootY);

                shoulderSegment.scaleX = -1f;
                shoulderSegment.scaleY = -1f;
                shoulderSegment.lnA = lnA;
                shoulderSegment.B = B;
            }

            // Normalize so that we hit 1.0 at our white point. We wouldn't have do this if we 
            // skipped the overshoot part.
            {
                // Evaluate shoulder at the end of the curve
                float scale = segments[2].Eval(1f);
                float invScale = 1f / scale;

                segments[0].offsetY *= invScale;
                segments[0].scaleY *= invScale;

                segments[1].offsetY *= invScale;
                segments[1].scaleY *= invScale;

                segments[2].offsetY *= invScale;
                segments[2].scaleY *= invScale;
            }
        }