+/*
+ * This is a faster approximation
+ */
+GLfloat
+_swrast_compute_lambda(GLfloat dsdx, GLfloat dsdy, GLfloat dtdx, GLfloat dtdy,
+ GLfloat dqdx, GLfloat dqdy, GLfloat texW, GLfloat texH,
+ GLfloat s, GLfloat t, GLfloat q, GLfloat invQ)
+{
+ GLfloat dsdx2 = (s + dsdx) / (q + dqdx) - s * invQ;
+ GLfloat dtdx2 = (t + dtdx) / (q + dqdx) - t * invQ;
+ GLfloat dsdy2 = (s + dsdy) / (q + dqdy) - s * invQ;
+ GLfloat dtdy2 = (t + dtdy) / (q + dqdy) - t * invQ;
+ GLfloat maxU, maxV, rho, lambda;
+ dsdx2 = FABSF(dsdx2);
+ dsdy2 = FABSF(dsdy2);
+ dtdx2 = FABSF(dtdx2);
+ dtdy2 = FABSF(dtdy2);
+ maxU = MAX2(dsdx2, dsdy2) * texW;
+ maxV = MAX2(dtdx2, dtdy2) * texH;
+ rho = MAX2(maxU, maxV);
+ lambda = LOG2(rho);
+ return lambda;
+}
+
+
+/**
+ * Fill in the span.texcoords array from the interpolation values.
+ * Note: in the places where we divide by Q (or mult by invQ) we're
+ * really doing two things: perspective correction and texcoord
+ * projection. Remember, for texcoord (s,t,r,q) we need to index
+ * texels with (s/q, t/q, r/q).
+ * If we're using a fragment program, we never do the division
+ * for texcoord projection. That's done by the TXP instruction
+ * or user-written code.
+ */