]> git.sesse.net Git - movit/blobdiff - effect_chain.cpp
Add edge information about odd things, such as bounces, resizes and non-standard...
[movit] / effect_chain.cpp
index e728963759a7f85c85c86f29e304a72c7d8f315b..63fcdac68fc8f1a019f179cb664fee243641feb8 100644 (file)
 #include <string.h>
 #include <assert.h>
 
-#include <GL/gl.h>
-#include <GL/glext.h>
+#include <algorithm>
+#include <set>
+#include <stack>
+#include <vector>
 
 #include "util.h"
 #include "effect_chain.h"
 #include "gamma_expansion_effect.h"
 #include "gamma_compression_effect.h"
-#include "lift_gamma_gain_effect.h"
 #include "colorspace_conversion_effect.h"
-#include "sandbox_effect.h"
-#include "saturation_effect.h"
-#include "mirror_effect.h"
-#include "vignette_effect.h"
-#include "blur_effect.h"
+#include "input.h"
+#include "opengl.h"
 
 EffectChain::EffectChain(unsigned width, unsigned height)
-       : width(width), height(height), use_srgb_texture_format(false), finalized(false) {}
+       : width(width),
+         height(height),
+         finalized(false) {}
 
-void EffectChain::add_input(const ImageFormat &format)
+Input *EffectChain::add_input(Input *input)
 {
-       input_format = format;
-       current_color_space = format.color_space;
-       current_gamma_curve = format.gamma_curve;
+       char eff_id[256];
+       sprintf(eff_id, "src_image%u", (unsigned)inputs.size());
+
+       inputs.push_back(input);
+
+       Node *node = new Node;
+       node->effect = input;
+       node->effect_id = eff_id;
+       node->output_color_space = input->get_color_space();
+       node->output_gamma_curve = input->get_gamma_curve();
+
+       nodes.push_back(node);
+       node_map[input] = node;
+
+       return input;
 }
 
 void EffectChain::add_output(const ImageFormat &format)
 {
        output_format = format;
 }
-       
-Effect *instantiate_effect(EffectId effect)
+
+void EffectChain::add_effect_raw(Effect *effect, const std::vector<Effect *> &inputs)
 {
-       switch (effect) {
-       case EFFECT_GAMMA_EXPANSION:
-               return new GammaExpansionEffect();
-       case EFFECT_GAMMA_COMPRESSION:
-               return new GammaCompressionEffect();
-       case EFFECT_COLOR_SPACE_CONVERSION:
-               return new ColorSpaceConversionEffect();
-       case EFFECT_SANDBOX:
-               return new SandboxEffect();
-       case EFFECT_LIFT_GAMMA_GAIN:
-               return new LiftGammaGainEffect();
-       case EFFECT_SATURATION:
-               return new SaturationEffect();
-       case EFFECT_MIRROR:
-               return new MirrorEffect();
-       case EFFECT_VIGNETTE:
-               return new VignetteEffect();
-       case EFFECT_BLUR:
-               return new BlurEffect();
+       char effect_id[256];
+       sprintf(effect_id, "eff%u", (unsigned)nodes.size());
+
+       Node *node = new Node;
+       node->effect = effect;
+       node->effect_id = effect_id;
+
+       assert(inputs.size() == effect->num_inputs());
+       assert(inputs.size() >= 1);
+       for (unsigned i = 0; i < inputs.size(); ++i) {
+               assert(node_map.count(inputs[i]) != 0);
+               node_map[inputs[i]]->outgoing_links.push_back(node);
+               node->incoming_links.push_back(node_map[inputs[i]]);
+               if (i == 0) {
+                       node->output_gamma_curve = node_map[inputs[i]]->output_gamma_curve;
+                       node->output_color_space = node_map[inputs[i]]->output_color_space;
+               } else {
+                       assert(node->output_gamma_curve == node_map[inputs[i]]->output_gamma_curve);
+                       assert(node->output_color_space == node_map[inputs[i]]->output_color_space);
+               }
        }
-       assert(false);
+
+       nodes.push_back(node);
+       node_map[effect] = node;
 }
 
-void EffectChain::normalize_to_linear_gamma()
+void EffectChain::find_all_nonlinear_inputs(Node *node,
+                                            std::vector<Node *> *nonlinear_inputs,
+                                            std::vector<Node *> *intermediates)
 {
-       if (current_gamma_curve == GAMMA_sRGB) {
-               // TODO: check if the extension exists
-               use_srgb_texture_format = true;
+       if (node->output_gamma_curve == GAMMA_LINEAR) {
+               return;
+       }
+       if (node->effect->num_inputs() == 0) {
+               nonlinear_inputs->push_back(node);
        } else {
-               GammaExpansionEffect *gamma_conversion = new GammaExpansionEffect();
-               gamma_conversion->set_int("source_curve", current_gamma_curve);
-               gamma_conversion->add_self_to_effect_chain(&effects);
+               intermediates->push_back(node);
+               assert(node->effect->num_inputs() == node->incoming_links.size());
+               for (unsigned i = 0; i < node->incoming_links.size(); ++i) {
+                       find_all_nonlinear_inputs(node->incoming_links[i], nonlinear_inputs, intermediates);
+               }
        }
-       current_gamma_curve = GAMMA_LINEAR;
 }
 
-void EffectChain::normalize_to_srgb()
+Node *EffectChain::normalize_to_linear_gamma(Node *input)
 {
-       assert(current_gamma_curve == GAMMA_LINEAR);
+       // Find out if all the inputs can be set to deliver sRGB inputs.
+       // If so, we can just ask them to do that instead of inserting a
+       // (possibly expensive) conversion operation.
+       //
+       // NOTE: We assume that effects generally don't mess with the gamma
+       // curve (except GammaCompressionEffect, which should never be
+       // inserted into a chain when this is called), so that we can just
+       // update the output gamma as we go.
+       //
+       // TODO: Setting this flag for one source might confuse a different
+       // part of the pipeline using the same source.
+       std::vector<Node *> nonlinear_inputs;
+       std::vector<Node *> intermediates;
+       find_all_nonlinear_inputs(input, &nonlinear_inputs, &intermediates);
+
+       bool all_ok = true;
+       for (unsigned i = 0; i < nonlinear_inputs.size(); ++i) {
+               Input *input = static_cast<Input *>(nonlinear_inputs[i]->effect);
+               all_ok &= input->can_output_linear_gamma();
+       }
+
+       if (all_ok) {
+               for (unsigned i = 0; i < nonlinear_inputs.size(); ++i) {
+                       bool ok = nonlinear_inputs[i]->effect->set_int("output_linear_gamma", 1);
+                       assert(ok);
+                       nonlinear_inputs[i]->output_gamma_curve = GAMMA_LINEAR;
+               }
+               for (unsigned i = 0; i < intermediates.size(); ++i) {
+                       intermediates[i]->output_gamma_curve = GAMMA_LINEAR;
+               }
+               return input;
+       }
+
+       // OK, that didn't work. Insert a conversion effect.
+       GammaExpansionEffect *gamma_conversion = new GammaExpansionEffect();
+       gamma_conversion->set_int("source_curve", input->output_gamma_curve);
+       std::vector<Effect *> inputs;
+       inputs.push_back(input->effect);
+       gamma_conversion->add_self_to_effect_chain(this, inputs);
+
+       assert(node_map.count(gamma_conversion) != 0);
+       Node *node = node_map[gamma_conversion];
+       node->output_gamma_curve = GAMMA_LINEAR;
+       return node;
+}
+
+Node *EffectChain::normalize_to_srgb(Node *input)
+{
+       assert(input->output_gamma_curve == GAMMA_LINEAR);
        ColorSpaceConversionEffect *colorspace_conversion = new ColorSpaceConversionEffect();
-       colorspace_conversion->set_int("source_space", current_color_space);
+       colorspace_conversion->set_int("source_space", input->output_color_space);
        colorspace_conversion->set_int("destination_space", COLORSPACE_sRGB);
-       colorspace_conversion->add_self_to_effect_chain(&effects);
-       current_color_space = COLORSPACE_sRGB;
+       std::vector<Effect *> inputs;
+       inputs.push_back(input->effect);
+       colorspace_conversion->add_self_to_effect_chain(this, inputs);
+
+       assert(node_map.count(colorspace_conversion) != 0);
+       Node *node = node_map[colorspace_conversion];
+       node->output_color_space = COLORSPACE_sRGB;
+       return node;
 }
 
-Effect *EffectChain::add_effect(EffectId effect_id)
+Effect *EffectChain::add_effect(Effect *effect, const std::vector<Effect *> &inputs)
 {
-       Effect *effect = instantiate_effect(effect_id);
-
-       if (effect->needs_linear_light() && current_gamma_curve != GAMMA_LINEAR) {
-               normalize_to_linear_gamma();
-       }
-
-       if (effect->needs_srgb_primaries() && current_color_space != COLORSPACE_sRGB) {
-               normalize_to_srgb();
+       assert(inputs.size() == effect->num_inputs());
+
+       std::vector<Effect *> normalized_inputs = inputs;
+       for (unsigned i = 0; i < normalized_inputs.size(); ++i) {
+               assert(node_map.count(normalized_inputs[i]) != 0);
+               Node *input = node_map[normalized_inputs[i]];
+               if (effect->needs_linear_light() && input->output_gamma_curve != GAMMA_LINEAR) {
+                       input = normalize_to_linear_gamma(input);
+               }
+               if (effect->needs_srgb_primaries() && input->output_color_space != COLORSPACE_sRGB) {
+                       input = normalize_to_srgb(input);
+               }
+               normalized_inputs[i] = input->effect;
        }
 
-       effect->add_self_to_effect_chain(&effects);
+       effect->add_self_to_effect_chain(this, normalized_inputs);
        return effect;
 }
 
@@ -139,26 +218,70 @@ std::string replace_prefix(const std::string &text, const std::string &prefix)
        return output;
 }
 
-EffectChain::Phase EffectChain::compile_glsl_program(unsigned start_index, unsigned end_index)
+Phase *EffectChain::compile_glsl_program(
+       const std::vector<Node *> &inputs,
+       const std::vector<Node *> &effects)
 {
+       assert(!effects.empty());
+
+       // Deduplicate the inputs.
+       std::vector<Node *> true_inputs = inputs;
+       std::sort(true_inputs.begin(), true_inputs.end());
+       true_inputs.erase(std::unique(true_inputs.begin(), true_inputs.end()), true_inputs.end());
+
        bool input_needs_mipmaps = false;
        std::string frag_shader = read_file("header.frag");
-       for (unsigned i = start_index; i < end_index; ++i) {
-               char effect_id[256];
-               sprintf(effect_id, "eff%d", i);
+
+       // Create functions for all the texture inputs that we need.
+       for (unsigned i = 0; i < true_inputs.size(); ++i) {
+               Node *input = true_inputs[i];
+       
+               frag_shader += std::string("uniform sampler2D tex_") + input->effect_id + ";\n";
+               frag_shader += std::string("vec4 ") + input->effect_id + "(vec2 tc) {\n";
+               frag_shader += "\treturn texture2D(tex_" + input->effect_id + ", tc);\n";
+               frag_shader += "}\n";
+               frag_shader += "\n";
+       }
+
+       for (unsigned i = 0; i < effects.size(); ++i) {
+               Node *node = effects[i];
+
+               if (node->incoming_links.size() == 1) {
+                       frag_shader += std::string("#define INPUT ") + node->incoming_links[0]->effect_id + "\n";
+               } else {
+                       for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
+                               char buf[256];
+                               sprintf(buf, "#define INPUT%d %s\n", j + 1, node->incoming_links[j]->effect_id.c_str());
+                               frag_shader += buf;
+                       }
+               }
        
                frag_shader += "\n";
-               frag_shader += std::string("#define FUNCNAME ") + effect_id + "\n";
-               frag_shader += replace_prefix(effects[i]->output_convenience_uniforms(), effect_id);
-               frag_shader += replace_prefix(effects[i]->output_fragment_shader(), effect_id);
+               frag_shader += std::string("#define FUNCNAME ") + node->effect_id + "\n";
+               frag_shader += replace_prefix(node->effect->output_convenience_uniforms(), node->effect_id);
+               frag_shader += replace_prefix(node->effect->output_fragment_shader(), node->effect_id);
                frag_shader += "#undef PREFIX\n";
                frag_shader += "#undef FUNCNAME\n";
-               frag_shader += "#undef LAST_INPUT\n";
-               frag_shader += std::string("#define LAST_INPUT ") + effect_id + "\n";
+               if (node->incoming_links.size() == 1) {
+                       frag_shader += "#undef INPUT\n";
+               } else {
+                       for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
+                               char buf[256];
+                               sprintf(buf, "#undef INPUT%d\n", j + 1);
+                               frag_shader += buf;
+                       }
+               }
                frag_shader += "\n";
 
-               input_needs_mipmaps |= effects[i]->needs_mipmaps();
+               input_needs_mipmaps |= node->effect->needs_mipmaps();
+       }
+       for (unsigned i = 0; i < effects.size(); ++i) {
+               Node *node = effects[i];
+               if (node->effect->num_inputs() == 0) {
+                       node->effect->set_int("needs_mipmaps", input_needs_mipmaps);
+               }
        }
+       frag_shader += std::string("#define INPUT ") + effects.back()->effect_id + "\n";
        frag_shader.append(read_file("footer.frag"));
        printf("%s\n", frag_shader.c_str());
        
@@ -172,141 +295,313 @@ EffectChain::Phase EffectChain::compile_glsl_program(unsigned start_index, unsig
        glLinkProgram(glsl_program_num);
        check_error();
 
-       Phase phase;
-       phase.glsl_program_num = glsl_program_num;
-       phase.input_needs_mipmaps = input_needs_mipmaps;
-       phase.start = start_index;
-       phase.end = end_index;
+       Phase *phase = new Phase;
+       phase->glsl_program_num = glsl_program_num;
+       phase->input_needs_mipmaps = input_needs_mipmaps;
+       phase->inputs = true_inputs;
+       phase->effects = effects;
 
        return phase;
 }
 
+// Construct GLSL programs, starting at the given effect and following
+// the chain from there. We end a program every time we come to an effect
+// marked as "needs texture bounce", one that is used by multiple other
+// effects, every time an effect wants to change the output size,
+// and of course at the end.
+//
+// We follow a quite simple depth-first search from the output, although
+// without any explicit recursion.
+void EffectChain::construct_glsl_programs(Node *output)
+{
+       // Which effects have already been completed in this phase?
+       // We need to keep track of it, as an effect with multiple outputs
+       // could otherwise be calculate multiple times.
+       std::set<Node *> completed_effects;
+
+       // Effects in the current phase, as well as inputs (outputs from other phases
+       // that we depend on). Note that since we start iterating from the end,
+       // the effect list will be in the reverse order.
+       std::vector<Node *> this_phase_inputs;
+       std::vector<Node *> this_phase_effects;
+
+       // Effects that we have yet to calculate, but that we know should
+       // be in the current phase.
+       std::stack<Node *> effects_todo_this_phase;
+
+       // Effects that we have yet to calculate, but that come from other phases.
+       // We delay these until we have this phase done in its entirety,
+       // at which point we pick any of them and start a new phase from that.
+       std::stack<Node *> effects_todo_other_phases;
+
+       effects_todo_this_phase.push(output);
+
+       for ( ;; ) {  // Termination condition within loop.
+               if (!effects_todo_this_phase.empty()) {
+                       // OK, we have more to do this phase.
+                       Node *node = effects_todo_this_phase.top();
+                       effects_todo_this_phase.pop();
+
+                       // This should currently only happen for effects that are phase outputs,
+                       // and we throw those out separately below.
+                       assert(completed_effects.count(node) == 0);
+
+                       this_phase_effects.push_back(node);
+                       completed_effects.insert(node);
+
+                       // Find all the dependencies of this effect, and add them to the stack.
+                       std::vector<Node *> deps = node->incoming_links;
+                       assert(node->effect->num_inputs() == deps.size());
+                       for (unsigned i = 0; i < deps.size(); ++i) {
+                               bool start_new_phase = false;
+
+                               // FIXME: If we sample directly from a texture, we won't need this.
+                               if (node->effect->needs_texture_bounce()) {
+                                       start_new_phase = true;
+                               }
+
+                               if (deps[i]->outgoing_links.size() > 1 && deps[i]->effect->num_inputs() > 0) {
+                                       // More than one effect uses this as the input,
+                                       // and it is not a texture itself.
+                                       // The easiest thing to do (and probably also the safest
+                                       // performance-wise in most cases) is to bounce it to a texture
+                                       // and then let the next passes read from that.
+                                       start_new_phase = true;
+                               }
+
+                               if (deps[i]->effect->changes_output_size()) {
+                                       start_new_phase = true;
+                               }
+
+                               if (start_new_phase) {
+                                       effects_todo_other_phases.push(deps[i]);
+                                       this_phase_inputs.push_back(deps[i]);
+                               } else {
+                                       effects_todo_this_phase.push(deps[i]);
+                               }
+                       }
+                       continue;
+               }
+
+               // No more effects to do this phase. Take all the ones we have,
+               // and create a GLSL program for it.
+               if (!this_phase_effects.empty()) {
+                       reverse(this_phase_effects.begin(), this_phase_effects.end());
+                       phases.push_back(compile_glsl_program(this_phase_inputs, this_phase_effects));
+                       this_phase_effects.back()->phase = phases.back();
+                       this_phase_inputs.clear();
+                       this_phase_effects.clear();
+               }
+               assert(this_phase_inputs.empty());
+               assert(this_phase_effects.empty());
+
+               // If we have no effects left, exit.
+               if (effects_todo_other_phases.empty()) {
+                       break;
+               }
+
+               Node *node = effects_todo_other_phases.top();
+               effects_todo_other_phases.pop();
+
+               if (completed_effects.count(node) == 0) {
+                       // Start a new phase, calculating from this effect.
+                       effects_todo_this_phase.push(node);
+               }
+       }
+
+       // Finally, since the phases are found from the output but must be executed
+       // from the input(s), reverse them, too.
+       std::reverse(phases.begin(), phases.end());
+}
+
+void EffectChain::output_dot(const char *filename)
+{
+       FILE *fp = fopen(filename, "w");
+       if (fp == NULL) {
+               perror(filename);
+               exit(1);
+       }
+
+       fprintf(fp, "digraph G {\n");
+       for (unsigned i = 0; i < nodes.size(); ++i) {
+               fprintf(fp, "  n%ld [label=\"%s\"];\n", (long)nodes[i], nodes[i]->effect->effect_type_id().c_str());
+               for (unsigned j = 0; j < nodes[i]->outgoing_links.size(); ++j) {
+                       std::vector<std::string> labels;
+
+                       if (nodes[i]->outgoing_links[j]->effect->needs_texture_bounce()) {
+                               labels.push_back("needs_bounce");
+                       }
+                       if (nodes[i]->effect->changes_output_size()) {
+                               labels.push_back("resize");
+                       }
+
+                       switch (nodes[i]->output_color_space) {
+                       case COLORSPACE_REC_709:
+                               labels.push_back("spc[rec709]");
+                               break;
+                       case COLORSPACE_REC_601_525:
+                               labels.push_back("spc[rec601-525]");
+                               break;
+                       case COLORSPACE_REC_601_625:
+                               labels.push_back("spc[rec601-625]");
+                               break;
+                       default:
+                               break;
+                       }
+
+                       switch (nodes[i]->output_gamma_curve) {
+                       case GAMMA_sRGB:
+                               labels.push_back("gamma[sRGB]");
+                               break;
+                       case GAMMA_REC_601:  // and GAMMA_REC_709
+                               labels.push_back("gamma[rec601/709]");
+                               break;
+                       default:
+                               break;
+                       }
+
+                       if (labels.empty()) {
+                               fprintf(fp, "  n%ld -> n%ld;\n", (long)nodes[i], (long)nodes[i]->outgoing_links[j]);
+                       } else {
+                               std::string label = labels[0];
+                               for (unsigned k = 1; k < labels.size(); ++k) {
+                                       label += ", " + labels[k];
+                               }
+                               fprintf(fp, "  n%ld -> n%ld [label=\"%s\"];\n", (long)nodes[i], (long)nodes[i]->outgoing_links[j], label.c_str());
+                       }
+               }
+       }
+       fprintf(fp, "}\n");
+
+       fclose(fp);
+}
+
+void EffectChain::find_output_size(Phase *phase)
+{
+       Node *output_node = phase->effects.back();
+
+       // If the last effect explicitly sets an output size,
+       // use that.
+       if (output_node->effect->changes_output_size()) {
+               output_node->effect->get_output_size(&phase->output_width, &phase->output_height);
+               return;
+       }
+
+       // If not, look at the input phases, if any. We select the largest one
+       // (really assuming they all have the same aspect currently), by pixel count.
+       if (!phase->inputs.empty()) {
+               unsigned best_width = 0, best_height = 0;
+               for (unsigned i = 0; i < phase->inputs.size(); ++i) {
+                       Node *input = phase->inputs[i];
+                       assert(input->phase->output_width != 0);
+                       assert(input->phase->output_height != 0);
+                       if (input->phase->output_width * input->phase->output_height > best_width * best_height) {
+                               best_width = input->phase->output_width;
+                               best_height = input->phase->output_height;
+                       }
+               }
+               assert(best_width != 0);
+               assert(best_height != 0);
+               phase->output_width = best_width;
+               phase->output_height = best_height;
+               return;
+       }
+
+       // OK, no inputs. Just use the global width/height.
+       // TODO: We probably want to use the texture's size eventually.
+       phase->output_width = width;
+       phase->output_height = height;
+}
+
 void EffectChain::finalize()
 {
+       output_dot("final.dot");
+
+       // Find the output effect. This is, simply, one that has no outgoing links.
+       // If there are multiple ones, the graph is malformed (we do not support
+       // multiple outputs right now).
+       std::vector<Node *> output_nodes;
+       for (unsigned i = 0; i < nodes.size(); ++i) {
+               Node *node = nodes[i];
+               if (node->outgoing_links.empty()) {
+                       output_nodes.push_back(node);
+               }
+       }
+       assert(output_nodes.size() == 1);
+       Node *output_node = output_nodes[0];
+
        // Add normalizers to get the output format right.
-       if (current_color_space != output_format.color_space) {
+       if (output_node->output_color_space != output_format.color_space) {
                ColorSpaceConversionEffect *colorspace_conversion = new ColorSpaceConversionEffect();
-               colorspace_conversion->set_int("source_space", current_color_space);
+               colorspace_conversion->set_int("source_space", output_node->output_color_space);
                colorspace_conversion->set_int("destination_space", output_format.color_space);
-               effects.push_back(colorspace_conversion);
-               current_color_space = output_format.color_space;
+               std::vector<Effect *> inputs;
+               inputs.push_back(output_node->effect);
+               colorspace_conversion->add_self_to_effect_chain(this, inputs);
+
+               assert(node_map.count(colorspace_conversion) != 0);
+               output_node = node_map[colorspace_conversion];
+               output_node->output_color_space = output_format.color_space;
        }
-       if (current_gamma_curve != output_format.gamma_curve) {
-               if (current_gamma_curve != GAMMA_LINEAR) {
-                       normalize_to_linear_gamma();
+       if (output_node->output_gamma_curve != output_format.gamma_curve) {
+               if (output_node->output_gamma_curve != GAMMA_LINEAR) {
+                       output_node = normalize_to_linear_gamma(output_node);
                }
-               assert(current_gamma_curve == GAMMA_LINEAR);
                GammaCompressionEffect *gamma_conversion = new GammaCompressionEffect();
                gamma_conversion->set_int("destination_curve", output_format.gamma_curve);
-               effects.push_back(gamma_conversion);
-               current_gamma_curve = output_format.gamma_curve;
-       }
+               std::vector<Effect *> inputs;
+               inputs.push_back(output_node->effect);
+               gamma_conversion->add_self_to_effect_chain(this, inputs);
 
-       // Construct the GLSL programs. We end a program every time we come
-       // to an effect marked as "needs many samples" (ie. "please let me
-       // sample directly from a texture, with no arithmetic in-between"),
-       // and of course at the end.
-       unsigned start = 0;
-       for (unsigned i = 0; i < effects.size(); ++i) {
-               if (effects[i]->needs_many_samples() && i != start) {
-                       phases.push_back(compile_glsl_program(start, i));
-                       start = i;
-               }
+               assert(node_map.count(gamma_conversion) != 0);
+               output_node = node_map[gamma_conversion];
+               output_node->output_gamma_curve = output_format.gamma_curve;
        }
-       phases.push_back(compile_glsl_program(start, effects.size()));
+
+       // Construct all needed GLSL programs, starting at the output.
+       construct_glsl_programs(output_node);
 
        // If we have more than one phase, we need intermediate render-to-texture.
        // Construct an FBO, and then as many textures as we need.
+       // We choose the simplest option of having one texture per output,
+       // since otherwise this turns into an (albeit simple)
+       // register allocation problem.
        if (phases.size() > 1) {
                glGenFramebuffers(1, &fbo);
 
-               unsigned num_textures = std::max<int>(phases.size() - 1, 2);
-               glGenTextures(num_textures, temp_textures);
+               for (unsigned i = 0; i < phases.size() - 1; ++i) {
+                       find_output_size(phases[i]);
 
-               for (unsigned i = 0; i < num_textures; ++i) {
-                       glBindTexture(GL_TEXTURE_2D, temp_textures[i]);
+                       Node *output_node = phases[i]->effects.back();
+                       glGenTextures(1, &output_node->output_texture);
+                       check_error();
+                       glBindTexture(GL_TEXTURE_2D, output_node->output_texture);
                        check_error();
                        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
                        check_error();
                        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
                        check_error();
-                       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F_ARB, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+                       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F_ARB, phases[i]->output_width, phases[i]->output_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
                        check_error();
+
+                       output_node->output_texture_width = phases[i]->output_width;
+                       output_node->output_texture_height = phases[i]->output_height;
                }
        }
-       
-       // Translate the input format to OpenGL's enums.
-       GLenum internal_format;
-       if (use_srgb_texture_format) {
-               internal_format = GL_SRGB8;
-       } else {
-               internal_format = GL_RGBA8;
-       }
-       if (input_format.pixel_format == FORMAT_RGB) {
-               format = GL_RGB;
-               bytes_per_pixel = 3;
-       } else if (input_format.pixel_format == FORMAT_RGBA) {
-               format = GL_RGBA;
-               bytes_per_pixel = 4;
-       } else if (input_format.pixel_format == FORMAT_BGR) {
-               format = GL_BGR;
-               bytes_per_pixel = 3;
-       } else if (input_format.pixel_format == FORMAT_BGRA) {
-               format = GL_BGRA;
-               bytes_per_pixel = 4;
-       } else {
-               assert(false);
+               
+       for (unsigned i = 0; i < inputs.size(); ++i) {
+               inputs[i]->finalize();
        }
 
-       // Create PBO to hold the texture holding the input image, and then the texture itself.
-       glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 2);
-       check_error();
-       glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, width * height * bytes_per_pixel, NULL, GL_STREAM_DRAW);
-       check_error();
-       glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
-       check_error();
+       assert(phases[0]->inputs.empty());
        
-       glGenTextures(1, &source_image_num);
-       check_error();
-       glBindTexture(GL_TEXTURE_2D, source_image_num);
-       check_error();
-       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-       check_error();
-       // Intel/Mesa seems to have a broken glGenerateMipmap() for non-FBO textures, so do it here.
-       glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, phases[0].input_needs_mipmaps ? GL_TRUE : GL_FALSE);
-       check_error();
-       glTexImage2D(GL_TEXTURE_2D, 0, internal_format, width, height, 0, format, GL_UNSIGNED_BYTE, NULL);
-       check_error();
-
        finalized = true;
 }
 
-void EffectChain::render_to_screen(unsigned char *src)
+void EffectChain::render_to_screen()
 {
        assert(finalized);
 
-       // Copy the pixel data into the PBO.
-       glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 2);
-       check_error();
-       void *mapped_pbo = glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY);
-       memcpy(mapped_pbo, src, width * height * bytes_per_pixel);
-       glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
-       check_error();
-
-       // Re-upload the texture from the PBO.
-       glActiveTexture(GL_TEXTURE0);
-       check_error();
-       glBindTexture(GL_TEXTURE_2D, source_image_num);
-       check_error();
-       glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, height, format, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
-       check_error();
-       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-       check_error();
-       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-       check_error();
-       glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
-       check_error();
-
        // Basic state.
        glDisable(GL_BLEND);
        check_error();
@@ -327,88 +622,106 @@ void EffectChain::render_to_screen(unsigned char *src)
                check_error();
        }
 
+       std::set<Node *> generated_mipmaps;
+
        for (unsigned phase = 0; phase < phases.size(); ++phase) {
-               // Set up inputs and outputs for this phase.
-               glActiveTexture(GL_TEXTURE0);
-               if (phase == 0) {
-                       // First phase reads from the input texture (which is already bound).
-               } else {
-                       glBindTexture(GL_TEXTURE_2D, temp_textures[(phase + 1) % 2]);
-                       check_error();
-               }
-               if (phases[phase].input_needs_mipmaps) {
-                       if (phase != 0) {
-                               // For phase 0, it's done further up.
-                               glGenerateMipmap(GL_TEXTURE_2D);
+               // See if the requested output size has changed. If so, we need to recreate
+               // the texture (and before we start setting up inputs).
+               if (phase != phases.size() - 1) {
+                       find_output_size(phases[phase]);
+
+                       Node *output_node = phases[phase]->effects.back();
+
+                       if (output_node->output_texture_width != phases[phase]->output_width ||
+                           output_node->output_texture_height != phases[phase]->output_height) {
+                               glActiveTexture(GL_TEXTURE0);
+                               check_error();
+                               glBindTexture(GL_TEXTURE_2D, output_node->output_texture);
+                               check_error();
+                               glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F_ARB, phases[phase]->output_width, phases[phase]->output_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
                                check_error();
+                               glBindTexture(GL_TEXTURE_2D, 0);
+                               check_error();
+
+                               output_node->output_texture_width = phases[phase]->output_width;
+                               output_node->output_texture_height = phases[phase]->output_height;
                        }
-                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
+               }
+
+               glUseProgram(phases[phase]->glsl_program_num);
+               check_error();
+
+               // Set up RTT inputs for this phase.
+               for (unsigned sampler = 0; sampler < phases[phase]->inputs.size(); ++sampler) {
+                       glActiveTexture(GL_TEXTURE0 + sampler);
+                       Node *input = phases[phase]->inputs[sampler];
+                       glBindTexture(GL_TEXTURE_2D, input->output_texture);
                        check_error();
-               } else {
-                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+                       if (phases[phase]->input_needs_mipmaps) {
+                               if (generated_mipmaps.count(input) == 0) {
+                                       glGenerateMipmap(GL_TEXTURE_2D);
+                                       check_error();
+                                       generated_mipmaps.insert(input);
+                               }
+                               glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
+                               check_error();
+                       } else {
+                               glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+                               check_error();
+                       }
+
+                       std::string texture_name = std::string("tex_") + input->effect_id;
+                       glUniform1i(glGetUniformLocation(phases[phase]->glsl_program_num, texture_name.c_str()), sampler);
                        check_error();
                }
 
+               // And now the output.
                if (phase == phases.size() - 1) {
                        // Last phase goes directly to the screen.
                        glBindFramebuffer(GL_FRAMEBUFFER, 0);
                        check_error();
+                       glViewport(0, 0, width, height);
                } else {
+                       Node *output_node = phases[phase]->effects.back();
                        glFramebufferTexture2D(
                                GL_FRAMEBUFFER,
                                GL_COLOR_ATTACHMENT0,
                                GL_TEXTURE_2D,
-                               temp_textures[phase % 2],
+                               output_node->output_texture,
                                0);
                        check_error();
-               }
-
-               // We have baked an upside-down transform into the quad coordinates,
-               // since the typical graphics program will have the origin at the upper-left,
-               // while OpenGL uses lower-left. In the next ones, however, the origin
-               // is all right, and we need to reverse that.
-               if (phase == 1) {
-                       glTranslatef(0.0f, 1.0f, 0.0f);
-                       glScalef(1.0f, -1.0f, 1.0f);
+                       glViewport(0, 0, phases[phase]->output_width, phases[phase]->output_height);
                }
 
                // Give the required parameters to all the effects.
-               glUseProgram(phases[phase].glsl_program_num);
-               check_error();
-
-               glUniform1i(glGetUniformLocation(phases[phase].glsl_program_num, "input_tex"), 0);
-               check_error();
-
-               unsigned sampler_num = 1;
-               for (unsigned i = phases[phase].start; i < phases[phase].end; ++i) {
-                       char effect_id[256];
-                       sprintf(effect_id, "eff%d", i);
-                       effects[i]->set_uniforms(phases[phase].glsl_program_num, effect_id, &sampler_num);
+               unsigned sampler_num = phases[phase]->inputs.size();
+               for (unsigned i = 0; i < phases[phase]->effects.size(); ++i) {
+                       Node *node = phases[phase]->effects[i];
+                       node->effect->set_gl_state(phases[phase]->glsl_program_num, node->effect_id, &sampler_num);
+                       check_error();
                }
 
                // Now draw!
                glBegin(GL_QUADS);
 
-               glTexCoord2f(0.0f, 1.0f);
+               glTexCoord2f(0.0f, 0.0f);
                glVertex2f(0.0f, 0.0f);
 
-               glTexCoord2f(1.0f, 1.0f);
+               glTexCoord2f(1.0f, 0.0f);
                glVertex2f(1.0f, 0.0f);
 
-               glTexCoord2f(1.0f, 0.0f);
+               glTexCoord2f(1.0f, 1.0f);
                glVertex2f(1.0f, 1.0f);
 
-               glTexCoord2f(0.0f, 0.0f);
+               glTexCoord2f(0.0f, 1.0f);
                glVertex2f(0.0f, 1.0f);
 
                glEnd();
                check_error();
 
-               // HACK
-               glActiveTexture(GL_TEXTURE0);
-               glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
-               check_error();
-               glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1000);
-               check_error();
+               for (unsigned i = 0; i < phases[phase]->effects.size(); ++i) {
+                       Node *node = phases[phase]->effects[i];
+                       node->effect->clear_gl_state();
+               }
        }
 }