// Output a GLSL 3x3 matrix declaration.
std::string output_glsl_mat3(const std::string &name, const Eigen::Matrix3d &m);
+// Calculate where to sample, and with what weight, if one wants to use
+// the GPU's bilinear hardware to sample w1 * x[0] + w2 * x[1].
+//
+// Note that since the GPU might have limited precision in its linear
+// interpolation, the effective weights might be different from the ones you
+// asked for. sum_sq_error, if not NULL, will contain the sum of the
+// (estimated) squared errors of the two weights.
+void combine_two_samples(float w1, float w2, float *offset, float *total_weight, float *sum_sq_error);
+
#ifdef NDEBUG
#define check_error()
#else
#define check_error() { int err = glGetError(); if (err != GL_NO_ERROR) { printf("GL error 0x%x at %s:%d\n", err, __FILE__, __LINE__); exit(1); } }
#endif
+#ifdef __GNUC__
+#define MUST_CHECK_RESULT __attribute__((warn_unused_result))
+#else
+#define MUST_CHECK_RESULT
+#endif
+
+// CHECK() is like assert(), but retains any side effects no matter the compilation mode.
+#ifdef NDEBUG
+#define CHECK(x) (void)(x)
+#else
+#define CHECK(x) do { bool ok = x; if (!ok) { fprintf(stderr, "%s:%d: %s: Assertion `%s' failed.\n", __FILE__, __LINE__, __PRETTY_FUNCTION__, #x); abort(); } } while (false)
+#endif
+
#endif // !defined(_UTIL_H)