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Double-buffer the OpenGL VBO

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This should reduce stalling when the OpenGL driver is still
processing the buffer when we're about to upload to it.

Hopefully, this is what was making the OpenGL ES 2.0 renderer so much
slower than the SDLTexture renderer on the Raspberry Pi 3B (SDL uses
*8* buffers). Unfortunately, I don't have access to it right now, so
I can't test this.
This commit is contained in:
Clownacy 2020-01-21 16:43:21 +00:00
parent f8a40318a2
commit 8d92bf2004
1 changed files with 19 additions and 12 deletions
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31
src/Backends/Rendering/OpenGL3.cpp
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@ -17,6 +17,8 @@
#include "../../WindowsWrapper.h" #include "../../WindowsWrapper.h"
#define TOTAL_VBOS 2
typedef enum RenderMode typedef enum RenderMode
{ {
MODE_BLANK, MODE_BLANK,
@ -77,7 +79,7 @@ static GLint program_glyph_subpixel_part2_uniform_colour;
#ifndef USE_OPENGLES2 #ifndef USE_OPENGLES2
static GLuint vertex_array_id; static GLuint vertex_array_id;
#endif #endif
static GLuint vertex_buffer_id; static GLuint vertex_buffer_ids[TOTAL_VBOS];
static GLuint framebuffer_id; static GLuint framebuffer_id;
static VertexBufferSlot *local_vertex_buffer; static VertexBufferSlot *local_vertex_buffer;
@ -358,18 +360,26 @@ static VertexBufferSlot* GetVertexBufferSlot(void)
static void FlushVertexBuffer(void) static void FlushVertexBuffer(void)
{ {
static unsigned long vertex_buffer_size = 0; static unsigned long vertex_buffer_size[TOTAL_VBOS];
static unsigned int current_vertex_buffer = 0;
if (local_vertex_buffer_size > vertex_buffer_size) glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_ids[current_vertex_buffer]);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*)offsetof(Vertex, vertex_coordinate));
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*)offsetof(Vertex, texture_coordinate));
if (local_vertex_buffer_size > vertex_buffer_size[current_vertex_buffer])
{ {
vertex_buffer_size = local_vertex_buffer_size; vertex_buffer_size[current_vertex_buffer] = local_vertex_buffer_size;
glBufferData(GL_ARRAY_BUFFER, vertex_buffer_size * sizeof(VertexBufferSlot), local_vertex_buffer, GL_STREAM_DRAW); glBufferData(GL_ARRAY_BUFFER, vertex_buffer_size[current_vertex_buffer] * sizeof(VertexBufferSlot), local_vertex_buffer, GL_STREAM_DRAW);
} }
else else
{ {
glBufferSubData(GL_ARRAY_BUFFER, 0, current_vertex_buffer_slot * sizeof(VertexBufferSlot), local_vertex_buffer); glBufferSubData(GL_ARRAY_BUFFER, 0, current_vertex_buffer_slot * sizeof(VertexBufferSlot), local_vertex_buffer);
} }
if (++current_vertex_buffer >= TOTAL_VBOS)
current_vertex_buffer = 0;
if (last_render_mode == MODE_DRAW_GLYPH_LCD) if (last_render_mode == MODE_DRAW_GLYPH_LCD)
{ {
// Here we're going to draw with per-component alpha. // Here we're going to draw with per-component alpha.
@ -453,14 +463,11 @@ Backend_Surface* Backend_Init(SDL_Window *p_window)
glBindVertexArray(vertex_array_id); glBindVertexArray(vertex_array_id);
#endif #endif
// Set up Vertex Buffer Object // Set up Vertex Buffer Objects
glGenBuffers(1, &vertex_buffer_id); glGenBuffers(TOTAL_VBOS, vertex_buffer_ids);
glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_id);
// Set up the vertex attributes // Set up the vertex attributes
glEnableVertexAttribArray(1); glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*)offsetof(Vertex, vertex_coordinate));
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*)offsetof(Vertex, texture_coordinate));
// Set up our shaders // Set up our shaders
program_texture = CompileShader(vertex_shader_texture, fragment_shader_texture); program_texture = CompileShader(vertex_shader_texture, fragment_shader_texture);
@ -524,7 +531,7 @@ Backend_Surface* Backend_Init(SDL_Window *p_window)
if (program_texture != 0) if (program_texture != 0)
glDeleteProgram(program_texture); glDeleteProgram(program_texture);
glDeleteBuffers(1, &vertex_buffer_id); glDeleteBuffers(TOTAL_VBOS, vertex_buffer_ids);
#ifndef USE_OPENGLES2 #ifndef USE_OPENGLES2
glDeleteVertexArrays(1, &vertex_array_id); glDeleteVertexArrays(1, &vertex_array_id);
#endif #endif
@ -550,7 +557,7 @@ void Backend_Deinit(void)
glDeleteProgram(program_colour_fill); glDeleteProgram(program_colour_fill);
glDeleteProgram(program_texture_colour_key); glDeleteProgram(program_texture_colour_key);
glDeleteProgram(program_texture); glDeleteProgram(program_texture);
glDeleteBuffers(1, &vertex_buffer_id); glDeleteBuffers(TOTAL_VBOS, vertex_buffer_ids);
#ifndef USE_OPENGLES2 #ifndef USE_OPENGLES2
glDeleteVertexArrays(1, &vertex_array_id); glDeleteVertexArrays(1, &vertex_array_id);
#endif #endif