[movit] / effect.h

#ifndef _MOVIT_EFFECT_H
#define _MOVIT_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 <epoxy/gl.h>
#include <assert.h>
#include <stddef.h>
#include <map>
#include <string>
#include <vector>
#include <Eigen/Core>

#include "defs.h"

namespace movit {

class EffectChain;
class Node;

// Can alias on a float[2].
struct Point2D {
        Point2D() {}
        Point2D(float x, float y)
                : x(x), y(y) {}

        float x, y;
};

// Can alias on a float[3].
struct RGBTriplet {
        RGBTriplet() {}
        RGBTriplet(float r, float g, float b)
                : r(r), g(g), b(b) {}

        float r, g, b;
};

// Can alias on a float[4].
struct RGBATuple {
        RGBATuple() {}
        RGBATuple(float r, float g, float b, float a)
                : r(r), g(g), b(b), a(a) {}

        float r, g, b, a;
};

// Represents a registered uniform.
template<class T>
struct Uniform {
        std::string name;  // Without prefix.
        const T *value;  // Owner by the effect.
        size_t num_values;  // Number of elements; for arrays only. _Not_ the vector length.
        std::string prefix;  // Filled in only after phases have been constructed.
        GLint location;  // Filled in only after phases have been constructed. -1 if no location.
};

class Effect {
public:
        virtual ~Effect() {}

        // An identifier for this type of effect, mostly used for debug output
        // (but some special names, like "ColorspaceConversionEffect", holds special
        // meaning). Same as the class name is fine.
        virtual std::string effect_type_id() const = 0;

        // 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_texture_bounce(), 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, but you can set it to false
        // if you process each channel independently, equally _and_
        // in a linear fashion.
        virtual bool needs_srgb_primaries() const { return true; }

        // How this effect handles alpha, ie. what it outputs in its
        // alpha channel. The choices are basically blank (alpha is always 1.0),
        // premultiplied and postmultiplied.
        //
        // Premultiplied alpha is when the alpha value has been be multiplied
        // into the three color components, so e.g. 100% red at 50% alpha
        // would be (0.5, 0.0, 0.0, 0.5) instead of (1.0, 0.0, 0.0, 0.5)
        // as it is stored in most image formats (postmultiplied alpha).
        // The multiplication is taken to have happened in linear light.
        // This is the most natural format for processing, and the default in
        // most of Movit (just like linear light is).
        //
        // If you set INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA or
        // INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK, all of your inputs
        // (if any) are guaranteed to also be in premultiplied alpha.
        // Otherwise, you can get postmultiplied or premultiplied alpha;
        // you won't know. If you have multiple inputs, you will get the same
        // (pre- or postmultiplied) for all inputs, although most likely,
        // you will want to combine them in a premultiplied fashion anyway
        // in that case.
        enum AlphaHandling {
                // Always outputs blank alpha (ie. alpha=1.0). Only appropriate
                // for inputs that do not output an alpha channel.
                // Blank alpha is special in that it can be treated as both
                // pre- and postmultiplied.
                OUTPUT_BLANK_ALPHA,

                // Always outputs postmultiplied alpha. Only appropriate for inputs.
                OUTPUT_POSTMULTIPLIED_ALPHA,

                // Always outputs premultiplied alpha. As noted above,
                // you will then also get all inputs in premultiplied alpha.
                // If you set this, you should also set needs_linear_light().
                INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA,

                // Like INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA, but also guarantees
                // that if you get blank alpha in, you also keep blank alpha out.
                // This is a somewhat weaker guarantee than DONT_CARE_ALPHA_TYPE,
                // but is still useful in many situations, and appropriate when
                // e.g. you don't touch alpha at all.
                //
                // Does not make sense for inputs.
                INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK,

                // Keeps the type of alpha (premultiplied, postmultiplied, blank)
                // unchanged from input to output. Usually appropriate if you
                // process all color channels in a linear fashion, do not change
                // alpha, and do not produce any new pixels that have alpha != 1.0.
                //
                // Does not make sense for inputs.
                DONT_CARE_ALPHA_TYPE,
        };
        virtual AlphaHandling alpha_handling() const { return INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA; }

        // 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 1:1 between pixels and texels, 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.
        enum MipmapRequirements {
                // If chosen, you will be sampling with bilinear filtering,
                // ie. the closest mipmap will be chosen, and then there will be
                // bilinear interpolation inside it (GL_LINEAR_MIPMAP_NEAREST).
                NEEDS_MIPMAPS,

                // Whether the effect doesn't really care whether input textures
                // are with or without mipmaps. You could get the same effect
                // as NEEDS_MIPMAPS or CANNOT_ACCEPT_MIPMAPS; normally, you won't
                // get them, but if a different effect in the same phase needs mipmaps,
                // you will also get them.
                DOES_NOT_NEED_MIPMAPS,

                // The opposite of NEEDS_MIPMAPS; you will always be sampling from
                // the most detailed mip level (GL_LINEAR). Effects with NEEDS_MIPMAPS
                // and CANNOT_ACCEPT_MIPMAPS can not coexist within the same phase;
                // such phases will be split.
                //
                // This is the only choice that makes sense for a compute shader,
                // given that it doesn't have screen-space derivatives and thus
                // always will sample the most detailed mip level.
                CANNOT_ACCEPT_MIPMAPS,
        };
        virtual MipmapRequirements needs_mipmaps() const {
                if (is_compute_shader()) {
                        return CANNOT_ACCEPT_MIPMAPS;
                } else {
                        return DOES_NOT_NEED_MIPMAPS;
                }
        }

        // Whether there is a direct correspondence between input and output
        // texels. Specifically, the effect must not:
        //
        //   1. Try to sample in the border (ie., outside the 0.0 to 1.0 area).
        //   2. Try to sample between texels.
        //   3. Sample with an x- or y-derivative different from -1 or 1.
        //      (This also means needs_mipmaps() and one_to_one_sampling()
        //      together would make no sense.)
        //
        // The most common case for this would be an effect that has an exact
        // 1:1-correspondence between input and output texels, e.g. SaturationEffect.
        // However, more creative things, like mirroring/flipping or padding,
        // would also be allowed.
        //
        // The primary gain from setting this is that you can sample directly
        // from an effect that changes output size (see changes_output_size() below),
        // without going through a bounce texture. It won't work for effects that
        // set sets_virtual_output_size(), though.
        //
        // Does not make a lot of sense together with needs_texture_bounce().
        // Cannot be set for compute shaders.
        virtual bool one_to_one_sampling() const { return strong_one_to_one_sampling(); }

        // Similar in use to one_to_one_sampling(), but even stricter:
        // The effect must not use texture coordinate in any way beyond
        // giving it unmodified to its (single) input. This allows it to
        // also be used after a compute shader, in the same phase.
        //
        // An effect that it strong one-to-one must also be one-to-one.
        virtual bool strong_one_to_one_sampling() const { return false; }

        // Whether this effect wants to output to a different size than
        // its input(s) (see inform_input_size(), below). See also
        // sets_virtual_output_size() below.
        virtual bool changes_output_size() const { return false; }

        // Whether your get_output_size() function (see below) intends to ever set
        // virtual_width different from width, or similar for height.
        // It does not make sense to set this to true if changes_output_size() is false.
        virtual bool sets_virtual_output_size() const { return changes_output_size(); }

        // Whether this effect is effectively sampling from a a single texture.
        // If so, it will override needs_texture_bounce(); however, there are also
        // two demands it needs to fulfill:
        //
        //  1. It needs to be an Input, ie. num_inputs() == 0.
        //  2. It needs to allocate exactly one sampler in set_gl_state(),
        //     and allow dependent effects to change that sampler state.
        virtual bool is_single_texture() const { return false; }

        // If set, this effect should never be bounced to an output, even if a
        // dependent effect demands texture bounce.
        //
        // Note that setting this can invoke undefined behavior, up to and including crashing,
        // so you should only use it if you have deep understanding of your entire chain
        // and Movit's processing of it. The most likely use case is if you have an input
        // that's cheap to compute but not a single texture (e.g. YCbCrInput), and want
        // to run a ResampleEffect directly from it. Normally, this would require a bounce,
        // but it's faster not to. (However, also note that in this case, effective texel
        // subpixel precision will be too optimistic, since chroma is already subsampled.)
        //
        // Has no effect if is_single_texture() is set.
        virtual bool override_disable_bounce() const { return false; }

        // If changes_output_size() is true, you must implement this to tell
        // the framework what output size you want. Also, you can set a
        // virtual width/height, which is the size the next effect (if any)
        // will _think_ your data is in. This is primarily useful if you are
        // relying on getting OpenGL's bilinear resizing for free; otherwise,
        // your virtual_width/virtual_height should be the same as width/height.
        //
        // Note that it is explicitly allowed to change width and height
        // from frame to frame; EffectChain will reallocate textures as needed.
        virtual void get_output_size(unsigned *width, unsigned *height,
                                     unsigned *virtual_width, unsigned *virtual_height) const {
                assert(false);
        }

        // Whether this effect uses a compute shader instead of a regular fragment shader.
        // Compute shaders are more flexible in that they can have multiple outputs
        // for each invocation and also communicate between instances (by using shared
        // memory within each group), but are not universally supported. The typical
        // pattern would be to check movit_compute_shaders_supported and rewrite the
        // graph to use a compute shader effect instead of a regular effect if it is
        // available, in order to get better performance. Since compute shaders can reuse
        // loads (again typically through shared memory), using needs_texture_bounce()
        // is usually not needed, although it is allowed; the best candidates for compute
        // shaders are typically those that sample many times from their input
        // but can reuse those loads across neighboring instances.
        //
        // Compute shaders commonly work with unnormalized texture coordinates
        // (where coordinates are integers [0..W) and [0..H)), whereas the rest
        // of Movit, including any inputs you may want to sample from, works
        // with normalized coordinates ([0..1)). Movit gives you uniforms
        // PREFIX(inv_output_size) and PREFIX(output_texcoord_adjust) that you
        // can use to transform unnormalized to normalized, as well as a macro
        // NORMALIZE_TEXTURE_COORDS(vec2) that does it for you.
        //
        // Since compute shaders have flexible output, it is difficult to chain other
        // effects after them in the same phase, and thus, they will always be last.
        // (This limitation may be lifted for the special case of one-to-one effects
        // in the future.) Furthermore, they cannot write to the framebuffer, just to
        // textures, so Movit may have to insert an extra phase just to do the output
        // from a texture to the screen in some cases. However, this is transparent
        // to both the effect and the user.
        virtual bool is_compute_shader() const { return false; }

        // For a compute shader (see the previous member function), what dimensions
        // it should be invoked over. Called every frame, before uniforms are set
        // (so you are allowed to update uniforms based from this call).
        virtual void get_compute_dimensions(unsigned output_width, unsigned output_height,
                                            unsigned *x, unsigned *y, unsigned *z) const {
                *x = output_width;
                *y = output_height;
                *z = 1;
        }

        // Tells the effect the resolution of each of its input.
        // This will be called every frame, and always before get_output_size(),
        // so you can change your output size based on the input if so desired.
        //
        // Note that in some cases, an input might not have a single well-defined
        // resolution (for instance if you fade between two inputs with
        // different resolutions). In this case, you will get width=0 and height=0
        // for that input. If you cannot handle that, you will need to set
        // needs_texture_bounce() to true, which will force a render to a single
        // given resolution before you get the input.
        virtual void inform_input_size(unsigned input_num, unsigned width, unsigned height) {}

        // 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; }

        // Inform the effect that it has been just added to the EffectChain.
        // The primary use for this is to store the ResourcePool uesd by
        // the chain; for modifications to it, rewrite_graph() below
        // is probably a better fit.
        virtual void inform_added(EffectChain *chain) {}

        // Let the effect rewrite the effect chain as it sees fit.
        // Most effects won't need to do this, but this is very useful
        // if you have an effect that consists of multiple sub-effects
        // (for instance, two passes). The effect is given to its own
        // pointer, and it can add new ones (by using add_node()
        // and connect_node()) as it sees fit. This is called at
        // EffectChain::finalize() time, when the entire graph is known,
        // in the order that the effects were originally added.
        //
        // Note that if the effect wants to take itself entirely out
        // of the chain, it must set “disabled” to true and then disconnect
        // itself from all other effects.
        virtual void rewrite_graph(EffectChain *graph, Node *self) {}

        // Returns the GLSL fragment shader string for this effect.
        virtual std::string output_fragment_shader() = 0;

        // Set all OpenGL state that this effect needs before rendering.
        // The default implementation sets one uniform per registered parameter,
        // but no other state.
        //
        // <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).
        virtual void set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num);

        // If you set any special OpenGL state in set_gl_state(), you can clear it
        // after rendering here. The default implementation does nothing.
        virtual void clear_gl_state();

        // 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 &key, int value) MUST_CHECK_RESULT;
        virtual bool set_ivec2(const std::string &key, const int *values) MUST_CHECK_RESULT;
        virtual bool set_float(const std::string &key, float value) MUST_CHECK_RESULT;
        virtual bool set_vec2(const std::string &key, const float *values) MUST_CHECK_RESULT;
        virtual bool set_vec3(const std::string &key, const float *values) MUST_CHECK_RESULT;
        virtual bool set_vec4(const std::string &key, const float *values) MUST_CHECK_RESULT;

protected:
        // 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). It will also
        // register a uniform of the same name (plus an arbitrary prefix
        // which you can access using the PREFIX macro) that you can access.
        //
        // Neither of these take ownership of the pointer.

        // These correspond directly to int/float/vec2/vec3/vec4 in GLSL.
        void register_int(const std::string &key, int *value);
        void register_ivec2(const std::string &key, int *values);
        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);
        void register_vec4(const std::string &key, float *values);

        // Register uniforms, such that they will automatically be set
        // before the shader runs. This is more efficient than set_uniform_*
        // in effect_util.h, because it doesn't need to do name lookups
        // every time. Also, in the future, it will use uniform buffer objects
        // (UBOs) if available to reduce the number of calls into the driver.
        //
        // May not be called after output_fragment_shader() has returned.
        // The pointer must be valid for the entire lifetime of the Effect,
        // since the value is pulled from it each execution. The value is
        // guaranteed to be read after set_gl_state() for the effect has
        // returned, so you can safely update its value from there.
        //
        // Note that this will also declare the uniform in the shader for you,
        // so you should not do that yourself. (This is so it can be part of
        // the right uniform block.) However, it is probably a good idea to
        // have a commented-out declaration so that it is easier to see the
        // type and thus understand the shader on its own.
        //
        // Calling register_* will automatically imply register_uniform_*,
        // except for register_int as noted above.
        void register_uniform_sampler2d(const std::string &key, const int *value);
        void register_uniform_bool(const std::string &key, const bool *value);
        void register_uniform_int(const std::string &key, const int *value);
        void register_uniform_ivec2(const std::string &key, const int *values);
        void register_uniform_float(const std::string &key, const float *value);
        void register_uniform_vec2(const std::string &key, const float *values);
        void register_uniform_vec3(const std::string &key, const float *values);
        void register_uniform_vec4(const std::string &key, const float *values);
        void register_uniform_float_array(const std::string &key, const float *values, size_t num_values);
        void register_uniform_vec2_array(const std::string &key, const float *values, size_t num_values);
        void register_uniform_vec3_array(const std::string &key, const float *values, size_t num_values);
        void register_uniform_vec4_array(const std::string &key, const float *values, size_t num_values);
        void register_uniform_mat3(const std::string &key, const Eigen::Matrix3d *matrix);

private:
        std::map<std::string, int *> params_int;
        std::map<std::string, int *> params_ivec2;
        std::map<std::string, float *> params_float;
        std::map<std::string, float *> params_vec2;
        std::map<std::string, float *> params_vec3;
        std::map<std::string, float *> params_vec4;

        // Picked out by EffectChain during finalization.
        std::vector<Uniform<int>> uniforms_image2d;
        std::vector<Uniform<int>> uniforms_sampler2d;
        std::vector<Uniform<bool>> uniforms_bool;
        std::vector<Uniform<int>> uniforms_int;
        std::vector<Uniform<int>> uniforms_ivec2;
        std::vector<Uniform<float>> uniforms_float;
        std::vector<Uniform<float>> uniforms_vec2;
        std::vector<Uniform<float>> uniforms_vec3;
        std::vector<Uniform<float>> uniforms_vec4;
        std::vector<Uniform<float>> uniforms_float_array;
        std::vector<Uniform<float>> uniforms_vec2_array;
        std::vector<Uniform<float>> uniforms_vec3_array;
        std::vector<Uniform<float>> uniforms_vec4_array;
        std::vector<Uniform<Eigen::Matrix3d>> uniforms_mat3;
        friend class EffectChain;
};

}  // namespace movit

#endif // !defined(_MOVIT_EFFECT_H)