Optimize VAO/VBO usage for minimal state changes.

[movit] / effect_chain.cpp

diff --git a/effect_chain.cpp b/effect_chain.cpp
index 385a87b9f458bd4ed417de9737f709475d0a214a..b0d4aafbac71dc9a2864c0941ddf01cfc10c8bd0 100644 (file)
--- a/effect_chain.cpp
+++ b/effect_chain.cpp
@@ -51,6 +51,14 @@ EffectChain::EffectChain(float aspect_nom, float aspect_denom, ResourcePool *res
        } else {
                owns_resource_pool = false;
        }
+
+       // Generate a VBO with some data in (shared position and texture coordinate data).
+       float vertices[] = {
+               0.0f, 2.0f,
+               0.0f, 0.0f,
+               2.0f, 0.0f
+       };
+       vbo = generate_vbo(2, GL_FLOAT, sizeof(vertices), vertices);
 }
 
 EffectChain::~EffectChain()
@@ -66,6 +74,8 @@ EffectChain::~EffectChain()
        if (owns_resource_pool) {
                delete resource_pool;
        }
+       glDeleteBuffers(1, &vbo);
+       check_error();
 }
 
 Input *EffectChain::add_input(Input *input)
@@ -448,6 +458,14 @@ void EffectChain::compile_glsl_program(Phase *phase)
        }
 
        phase->glsl_program_num = resource_pool->compile_glsl_program(vert_shader, frag_shader, frag_shader_outputs);
+       GLint position_attribute_index = glGetAttribLocation(phase->glsl_program_num, "position");
+       GLint texcoord_attribute_index = glGetAttribLocation(phase->glsl_program_num, "texcoord");
+       if (position_attribute_index != -1) {
+               phase->attribute_indexes.insert(position_attribute_index);
+       }
+       if (texcoord_attribute_index != -1) {
+               phase->attribute_indexes.insert(texcoord_attribute_index);
+       }
 
        // Collect the resulting location numbers for each uniform.
        collect_uniform_locations(phase->glsl_program_num, &phase->uniforms_sampler2d);
@@ -1699,6 +1717,17 @@ void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height
        glDepthMask(GL_FALSE);
        check_error();
 
+       // Generate a VAO that will be used during the entire execution,
+       // and bind the VBO, since it contains all the data.
+       GLuint vao;
+       glGenVertexArrays(1, &vao);
+       check_error();
+       glBindVertexArray(vao);
+       check_error();
+       glBindBuffer(GL_ARRAY_BUFFER, vbo);
+       check_error();
+       set<GLint> bound_attribute_indices;
+
        set<Phase *> generated_mipmaps;
 
        // We choose the simplest option of having one texture per output,
@@ -1723,12 +1752,19 @@ void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height
                                CHECK(dither_effect->set_int("output_height", height));
                        }
                }
-               execute_phase(phase, phase_num == phases.size() - 1, &output_textures, &generated_mipmaps);
+               execute_phase(phase, phase_num == phases.size() - 1, &bound_attribute_indices, &output_textures, &generated_mipmaps);
                if (do_phase_timing) {
                        glEndQuery(GL_TIME_ELAPSED);
                }
        }
 
+       for (set<GLint>::iterator attr_it = bound_attribute_indices.begin();
+            attr_it != bound_attribute_indices.end();
+            ++attr_it) {
+               glDisableVertexAttribArray(*attr_it);
+               check_error();
+       }
+
        for (map<Phase *, GLuint>::const_iterator texture_it = output_textures.begin();
             texture_it != output_textures.end();
             ++texture_it) {
@@ -1740,6 +1776,13 @@ void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height
        glUseProgram(0);
        check_error();
 
+       glBindBuffer(GL_ARRAY_BUFFER, 0);
+       check_error();
+       glBindVertexArray(0);
+       check_error();
+       glDeleteVertexArrays(1, &vao);
+       check_error();
+
        if (do_phase_timing) {
                // Get back the timer queries.
                for (unsigned phase_num = 0; phase_num < phases.size(); ++phase_num) {
@@ -1792,7 +1835,10 @@ void EffectChain::print_phase_timing()
        printf("Total:   %5.1f ms\n", total_time_ms);
 }
 
-void EffectChain::execute_phase(Phase *phase, bool last_phase, map<Phase *, GLuint> *output_textures, set<Phase *> *generated_mipmaps)
+void EffectChain::execute_phase(Phase *phase, bool last_phase,
+                                set<GLint> *bound_attribute_indices,
+                                map<Phase *, GLuint> *output_textures,
+                                set<Phase *> *generated_mipmaps)
 {
        GLuint fbo = 0;
 
@@ -1853,27 +1899,33 @@ void EffectChain::execute_phase(Phase *phase, bool last_phase, map<Phase *, GLui
        // from there.
        setup_uniforms(phase);
 
-       // Now draw!
-       float vertices[] = {
-               0.0f, 2.0f,
-               0.0f, 0.0f,
-               2.0f, 0.0f
-       };
-
-       GLuint vao;
-       glGenVertexArrays(1, &vao);
-       check_error();
-       glBindVertexArray(vao);
-       check_error();
+       // Clean up old attributes if they are no longer needed.
+       for (set<GLint>::iterator attr_it = bound_attribute_indices->begin();
+            attr_it != bound_attribute_indices->end(); ) {
+               if (phase->attribute_indexes.count(*attr_it) == 0) {
+                       glDisableVertexAttribArray(*attr_it);
+                       check_error();
+                       bound_attribute_indices->erase(attr_it++);
+               } else {
+                       ++attr_it;
+               }
+       }
 
-       GLuint position_vbo = fill_vertex_attribute(glsl_program_num, "position", 2, GL_FLOAT, sizeof(vertices), vertices);
-       GLuint texcoord_vbo = fill_vertex_attribute(glsl_program_num, "texcoord", 2, GL_FLOAT, sizeof(vertices), vertices);  // Same as vertices.
+       // Set up the new attributes, if needed.
+       for (set<GLint>::iterator attr_it = phase->attribute_indexes.begin();
+            attr_it != phase->attribute_indexes.end();
+            ++attr_it) {
+               if (bound_attribute_indices->count(*attr_it) == 0) {
+                       glEnableVertexAttribArray(*attr_it);
+                       check_error();
+                       glVertexAttribPointer(*attr_it, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
+                       check_error();
+                       bound_attribute_indices->insert(*attr_it);
+               }
+       }
 
        glDrawArrays(GL_TRIANGLES, 0, 3);
        check_error();
-
-       cleanup_vertex_attribute(glsl_program_num, "position", position_vbo);
-       cleanup_vertex_attribute(glsl_program_num, "texcoord", texcoord_vbo);
        
        glUseProgram(0);
        check_error();
@@ -1886,9 +1938,6 @@ void EffectChain::execute_phase(Phase *phase, bool last_phase, map<Phase *, GLui
        if (!last_phase) {
                resource_pool->release_fbo(fbo);
        }
-
-       glDeleteVertexArrays(1, &vao);
-       check_error();
 }
 
 void EffectChain::setup_uniforms(Phase *phase)