+// A class that caches FBOs that render to a given set of textures.
+// It never frees anything, so it is only suitable for rendering to
+// the same (small) set of textures over and over again.
+template<size_t num_elements>
+class PersistentFBOSet {
+public:
+ void render_to(const array<GLuint, num_elements> &textures);
+
+ // Convenience wrappers.
+ void render_to(GLuint texture0, enable_if<num_elements == 1> * = nullptr) {
+ render_to({{texture0}});
+ }
+
+ void render_to(GLuint texture0, GLuint texture1, enable_if<num_elements == 2> * = nullptr) {
+ render_to({{texture0, texture1}});
+ }
+
+ void render_to(GLuint texture0, GLuint texture1, GLuint texture2, enable_if<num_elements == 3> * = nullptr) {
+ render_to({{texture0, texture1, texture2}});
+ }
+
+ void render_to(GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3, enable_if<num_elements == 4> * = nullptr) {
+ render_to({{texture0, texture1, texture2, texture3}});
+ }
+
+private:
+ // TODO: Delete these on destruction.
+ map<array<GLuint, num_elements>, GLuint> fbos;
+};
+
+template<size_t num_elements>
+void PersistentFBOSet<num_elements>::render_to(const array<GLuint, num_elements> &textures)
+{
+ auto it = fbos.find(textures);
+ if (it != fbos.end()) {
+ glBindFramebuffer(GL_FRAMEBUFFER, it->second);
+ return;
+ }
+
+ GLuint fbo;
+ glCreateFramebuffers(1, &fbo);
+ GLenum bufs[num_elements];
+ for (size_t i = 0; i < num_elements; ++i) {
+ glNamedFramebufferTexture(fbo, GL_COLOR_ATTACHMENT0 + i, textures[i], 0);
+ bufs[i] = GL_COLOR_ATTACHMENT0 + i;
+ }
+ glNamedFramebufferDrawBuffers(fbo, num_elements, bufs);
+
+ fbos[textures] = fbo;
+ glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+}
+