From: Steinar H. Gunderson Date: Wed, 3 Oct 2012 15:37:18 +0000 (+0200) Subject: Comment the Effect class. X-Git-Tag: 1.0~402 X-Git-Url: https://git.sesse.net/?p=movit;a=commitdiff_plain;h=b77dca09201f3373c5466d695338e1e29406072b Comment the Effect class. --- diff --git a/effect.h b/effect.h index eb3313a..f495867 100644 --- a/effect.h +++ b/effect.h @@ -1,6 +1,15 @@ #ifndef _EFFECT_H #define _EFFECT_H 1 +// Effect is the base class for every effect. It basically represents a single +// GLSL function, with an optional set of user-settable parameters. +// +// A note on naming: Since all effects run in the same GLSL namespace, +// you can't use any name you want for global variables (e.g. uniforms). +// The framework assigns a prefix to you which will be unique for each +// effect instance; use the macro PREFIX() around your identifiers to +// automatically prepend that prefix. + #include #include #include @@ -34,31 +43,104 @@ void set_uniform_vec4_array(GLuint glsl_program_num, const std::string &prefix, class Effect { public: + // Whether this effects expects its input (and output) to be in + // linear gamma, ie. without an applied gamma curve. Most effects + // will want this, although the ones that never actually look at + // the pixels, e.g. mirror, won't need to care, and can set this + // to false. If so, the input gamma will be undefined. + // + // Also see the note on needs_many_samples(), below. virtual bool needs_linear_light() const { return true; } + + // Whether this effect expects its input to be in the sRGB + // color space, ie. use the sRGB/Rec. 709 RGB primaries. + // (If not, it would typically come in as some slightly different + // set of RGB primaries; you would currently not get YCbCr + // or something similar). + // + // Again, most effects will want this. virtual bool needs_srgb_primaries() const { return true; } + + // Whether this effect expects to be sampling many times from + // its input. 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. + // + // Note that if you do _not_ set this, and do not sample on + // whole pixels (ie. you request linear filtering), it is undefined + // whether that filtering happen in linear gamma or not. + // It _could_ be (for instance in the case where the input is sRGB + // and your GPU applies gamma expansion before filtering), but you + // have no such guarantee. For most uses, however, this will be fine. virtual bool needs_many_samples() 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; } + + // 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(std::vector *chain) { chain->push_back(this); } + // 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. + // + // is the first free texture sampler. If you want to use + // textures, you can bind a texture to GL_TEXTURE0 + , + // 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); - // Neither of these take ownership. + // 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); protected: - // Neither of these take ownership. + // Register a parameter. Whenever set_*() is called with the same key, + // it will update the value in the given pointer (typically a pointer + // to some private member variable in your effect). + // + // Neither of these take ownership of the pointer. + + // int is special since GLSL pre-1.30 doesn't have integer uniforms. + // Thus, ints that you register will _not_ be converted to GLSL uniforms. void register_int(const std::string &key, int *value); + + // These correspond directly to float/vec2/vec3 in GLSL. void register_float(const std::string &key, float *value); void register_vec2(const std::string &key, float *values); void register_vec3(const std::string &key, float *values); + + // This will register a 1D texture, which will be bound to a sampler + // when your GLSL code runs (so it corresponds 1:1 to a sampler2D uniform + // in GLSL). + // + // Note that if you change the contents of , you will need to + // call invalidate_1d_texture() to have the picture re-uploaded on the + // next frame. This is in contrast to all the other parameters, which are + // set anew every frame. void register_1d_texture(const std::string &key, float *values, size_t size); void invalidate_1d_texture(const std::string &key);