-#ifndef _UTIL_H
-#define _UTIL_H 1
+#ifndef _MOVIT_UTIL_H
+#define _MOVIT_UTIL_H 1
+// Various utilities.
+
+#include <epoxy/gl.h>
#include <stdio.h>
#include <stdlib.h>
-
+#include <Eigen/Core>
#include <string>
-#include <GL/gl.h>
-
#define BUFFER_OFFSET(i) ((char *)NULL + (i))
-// assumes h in [0, 2pi> or [-pi, pi>
+namespace movit {
+
+// Converts a HSV color to RGB. Assumes h in [0, 2pi> or [-pi, pi>
void hsv2rgb(float h, float s, float v, float *r, float *g, float *b);
-// Column major (same as OpenGL).
-typedef double Matrix3x3[9];
+// Converts a HSV color to RGB, but keeps luminance constant
+// (ie. color luminance is as if S=0).
+void hsv2rgb_normalized(float h, float s, float v, float *r, float *g, float *b);
+// Read a file from disk and return its contents.
+// Dies if the file does not exist.
std::string read_file(const std::string &filename);
+
+// Compile the given GLSL shader (typically a vertex or fragment shader)
+// and return the object number.
GLuint compile_shader(const std::string &shader_src, GLenum type);
-void multiply_3x3_matrices(const Matrix3x3 a, const Matrix3x3 b, Matrix3x3 result);
-void invert_3x3_matrix(const Matrix3x3 m, Matrix3x3 result);
-void print_3x3_matrix(const Matrix3x3 m);
+
+// Print a 3x3 matrix to standard output. Useful for debugging.
+void print_3x3_matrix(const Eigen::Matrix3d &m);
+
+// Output a GLSL 3x3 matrix declaration.
+std::string output_glsl_mat3(const std::string &name, const Eigen::Matrix3d &m);
+
+// Calculate a / b, rounding up. Does not handle overflow correctly.
+unsigned div_round_up(unsigned a, unsigned b);
+
+// 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);
+
+// Create a VBO with the given data, and bind it to the vertex attribute
+// with name <attribute_name>. Returns the VBO number.
+GLuint fill_vertex_attribute(GLuint glsl_program_num, const std::string &attribute_name, GLint size, GLenum type, GLsizeiptr data_size, const GLvoid *data);
+
+// Clean up after fill_vertex_attribute().
+void cleanup_vertex_attribute(GLuint glsl_program_num, const std::string &attribute_name, GLuint vbo);
+
+// If v is not already a power of two, return the first higher power of two.
+unsigned next_power_of_two(unsigned v);
+
+// Get a pointer that represents the current OpenGL context, in a cross-platform way.
+// This is not intended for anything but identification (ie., so you can associate
+// different FBOs with different contexts); you should probably not try to cast it
+// back into anything you intend to pass into OpenGL.
+void *get_gl_context_identifier();
+
+} // namespace movit
#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); } }
+#define check_error() { int err = glGetError(); if (err != GL_NO_ERROR) { printf("GL error 0x%x at %s:%d\n", err, __FILE__, __LINE__); abort(); } }
+#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)
+#endif // !defined(_MOVIT_UTIL_H)
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