+ // Whether this effect expects its input to come directly from
+ // a texture. If this is true, the framework will not chain the
+ // input from other effects, but will store the results of the
+ // chain to a temporary (RGBA fp16) texture and let this effect
+ // sample directly from that.
+ //
+ // There are two good reasons why you might want to set this:
+ //
+ // 1. You are sampling more than once from the input,
+ // in which case computing all the previous steps might
+ // be more expensive than going to a memory intermediate.
+ // 2. You rely on previous effects, possibly including gamma
+ // expansion, to happen pre-filtering instead of post-filtering.
+ // (This is only relevant if you actually need the filtering; if
+ // you sample on whole input pixels only, it makes no difference.)
+ //
+ // Note that in some cases, you might get post-filtered gamma expansion
+ // even when setting this option. More specifically, if you are the
+ // first effect in the chain, and the GPU is doing sRGB gamma
+ // expansion, it is undefined (from OpenGL's side) whether expansion
+ // happens pre- or post-filtering. For most uses, however,
+ // either will be fine.
+ virtual bool needs_texture_bounce() const { return false; }
+
+ // Whether this effect expects mipmaps or not. If you set this to
+ // true, you will be sampling with bilinear filtering; if not,
+ // you could be sampling with simple linear filtering and no mipmaps
+ // (although there is no guarantee; if a different effect in the chain
+ // needs mipmaps, you will also get them).
+ virtual bool needs_mipmaps() const { return false; }
+
+ // How many inputs this effect will take (a fixed number).
+ // If you have only one input, it will be called INPUT() in GLSL;
+ // if you have several, they will be INPUT1(), INPUT2(), and so on.
+ virtual unsigned num_inputs() const { return 1; }
+
+ // Requests that this effect adds itself to the given effect chain.
+ // For most effects, the default will be fine, but for effects that
+ // consist of multiple passes, it is often useful to replace this
+ // with something that adds completely different things to the chain.
+ virtual void add_self_to_effect_chain(EffectChain *graph, const std::vector<Effect *> &inputs);
+
+ // Outputs one GLSL uniform declaration for each registered parameter
+ // (see below), with the right prefix prepended to each uniform name.
+ // If you do not want this behavior, you can override this function.
+ virtual std::string output_convenience_uniforms() const;
+
+ // Returns the GLSL fragment shader string for this effect.
+ virtual std::string output_fragment_shader() = 0;
+
+ // Set all uniforms the shader needs in the current GL context.
+ // The default implementation sets one uniform per registered parameter.
+ //
+ // <sampler_num> is the first free texture sampler. If you want to use
+ // textures, you can bind a texture to GL_TEXTURE0 + <sampler_num>,
+ // and then increment the number (so that the next effect in the chain
+ // will use a different sampler).
+ //
+ // NOTE: Currently this is also abused a bit to set other GL state
+ // the effect might need.
+ virtual void set_uniforms(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num);
+
+ // Set a parameter; intended to be called from user code.
+ // Neither of these take ownership of the pointer.
+ virtual bool set_int(const std::string&, int value);
+ virtual bool set_float(const std::string &key, float value);
+ virtual bool set_vec2(const std::string &key, const float *values);
+ virtual bool set_vec3(const std::string &key, const float *values);