为什么仅当我在 SDL2 中设置非零 alpha 大小时才获得 sRGB 帧缓冲区？
Why do I get an sRGB framebuffer only when I'm setting a non-zero alpha size in SDL2?
我正在尝试按照 this guide 并参考 SDL2 文档以了解如何在默认帧缓冲区上启用 SRGB 支持，以正确的伽玛方式渲染典型的 OpenGL 颜色三角形。
这是我编写的绘制三角形的代码：
#include <SDL.h>
// Header file generated with glLoadGen
#include "gl_core_3_3.h"
#include <cstdlib>
void sdl_loop(SDL_Window* window);
static const char* const vertexSource = R"(
#version 330
in vec2 position;
in vec3 color;
out vec3 vs_color;
void main()
{
gl_Position = vec4(position, 0.0, 1.0);
vs_color = color;
}
)";
static const char* const fragmentSource = R"(
#version 330
in vec3 vs_color;
out vec4 fragColor;
void main()
{
fragColor = vec4(vs_color, 1.0);
}
)";
static const float vertices[] = {
// X Y R G B
-0.9f, -0.9f, 1.0f, 0.0f, 0.0f,
0.9f, -0.9f, 0.0f, 1.0f, 0.0f,
0.0f, 0.9f, 0.0f, 0.0f, 1.0f,
};
static const unsigned short indices[] = { 0, 1, 2 };
void sdl_loop(SDL_Window* window)
{
glClearColor(0.0f, 0.1f, 0.2f, 1.0f);
glEnable(GL_FRAMEBUFFER_SRGB);
auto program = glCreateProgram();
auto vertexShader = glCreateShader(GL_VERTEX_SHADER);
auto fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(vertexShader, 1, &vertexSource, nullptr);
glShaderSource(fragmentShader, 1, &fragmentSource, nullptr);
glCompileShader(vertexShader);
glCompileShader(fragmentShader);
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glBindFragDataLocation(program, 0, "fragColor");
glLinkProgram(program);
glDetachShader(program, vertexShader);
glDetachShader(program, fragmentShader);
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
auto positionAttr = glGetAttribLocation(program, "position");
auto colorAttr = glGetAttribLocation(program, "color");
unsigned vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
unsigned vertexBuffer;
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
unsigned indexBuffer;
glGenBuffers(1, &indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
size_t stride = 5 * sizeof(float);
size_t offset = 0;
glEnableVertexAttribArray(positionAttr);
glVertexAttribPointer(positionAttr, 2, GL_FLOAT, false, stride, (void*) offset);
offset += 2 * sizeof(float);
glEnableVertexAttribArray(colorAttr);
glVertexAttribPointer(colorAttr, 3, GL_FLOAT, false, stride, (void*) offset);
offset += 3 * sizeof(float);
glUseProgram(program);
SDL_Event evt;
for (;;) {
while (SDL_PollEvent(&evt)) {
if (evt.type == SDL_QUIT) {
goto out;
}
}
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_SHORT, nullptr);
SDL_GL_SwapWindow(window);
}
out:
glDeleteProgram(program);
glDeleteBuffers(1, &vertexBuffer);
glDeleteBuffers(1, &indexBuffer);
glDeleteVertexArrays(1, &vao);
}
int main()
{
if (SDL_Init(SDL_INIT_EVERYTHING) < 0) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"Couldn't initialize SDL: %s", SDL_GetError());
SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
"Couldn't initialize SDL", SDL_GetError(), nullptr);
return EXIT_FAILURE;
}
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 8);
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
// Commenting this line out doesn't give you an sRGB framebuffer on Intel GPUs
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
SDL_GL_SetAttribute(SDL_GL_FRAMEBUFFER_SRGB_CAPABLE, 1);
auto* window = SDL_CreateWindow("Hello OpenGL 3!",
SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
800, 600,
SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL);
if (window == nullptr) {
SDL_LogError(
SDL_LOG_CATEGORY_APPLICATION,
"Couldn't initialize SDL window: %s", SDL_GetError());
SDL_ShowSimpleMessageBox(
SDL_MESSAGEBOX_ERROR,
"Couldn't create SDL window", SDL_GetError(), nullptr);
return EXIT_FAILURE;
}
auto context = SDL_GL_CreateContext(window);
SDL_GL_MakeCurrent(window, context);
SDL_GL_SetSwapInterval(1);
ogl_LoadFunctions();
sdl_loop(window);
SDL_GL_DeleteContext(context);
SDL_DestroyWindow(window);
SDL_Quit();
return EXIT_SUCCESS;
}
我 运行 使用 Ubuntu 16.04（使用 HWE 驱动程序），我使用的机器同时具有 Intel HD 4000 GPU 和带 Optimus 的专用 nvidia GPU。理论上，我应该得到一个 sRGB 帧缓冲器。但是，仅当 运行 在 nvidia GPU 下或使用 ApiTrace 时，我才获得 sRGB 帧缓冲区。如果我在 Intel GPU 下 运行，如果我使用 SDL2 指定非零 alpha 大小，我只会得到一个 sRGB 帧缓冲区。如果我为 alpha 指定一个零大小（或根本不指定一个），我将得到一个线性帧缓冲区。
这是我的示例在 运行 在 nvidia GPU（以及具有非零 alpha 位大小的 Intel GPU）下的样子：
这是 运行 在 Intel GPU 下使用零 alpha 位大小（sRGB 不正确）时的样子：
这就是我使用 ApiTrace 得到的结果：
我也 运行 glxinfo -t 据我所知，即使设置了零 alpha 位，我也应该获得 sRGB 支持（编辑：那是不是这样。glxinfo 的输出应该在 sRGB 列中显示 ses，但由于某些原因并没有发生）：
40 GLX Visuals
Vis Vis Visual Trans buff lev render DB ste r g b a s aux dep ste accum buffer MS MS
ID Depth Type parent size el type reo sz sz sz sz flt rgb buf th ncl r g b a num bufs caveats
--------------------------------------------------------------------------------------------------------------------
0x 21 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 22 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x b7 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x b8 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x b9 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x ba 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x bb 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x bc 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x bd 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x be 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x bf 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x c0 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x c1 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x c2 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x c3 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x c4 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x c5 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x c6 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x c7 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x c8 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
0x c9 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x ca 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x cb 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x cc 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x cd 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x ce 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x cf 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x d0 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x d1 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x d2 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x d3 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x d4 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x d5 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x d6 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x d7 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x d8 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x d9 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x da 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x db 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
0x 76 32 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
64 GLXFBConfigs:
Vis Vis Visual Trans buff lev render DB ste r g b a s aux dep ste accum buffer MS MS
ID Depth Type parent size el type reo sz sz sz sz flt rgb buf th ncl r g b a num bufs caveats
--------------------------------------------------------------------------------------------------------------------
0x 77 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 78 0 TrueColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 79 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 7a 0 TrueColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 7b 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 7c 0 TrueColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 7d 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 7e 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 7f 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 80 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 81 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x 82 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x 83 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x 84 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x 85 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 86 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 16 16 16 0 0 0 Slow
0x 87 32 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 88 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x 89 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x 8a 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x 8b 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 4 1 None
0x 8c 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 8 1 None
0x 8d 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 4 1 None
0x 8e 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 8 1 None
0x 8f 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x 90 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x 91 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x 92 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x 93 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x 94 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x 95 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x 96 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
0x 97 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 98 0 DirectColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 99 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 9a 0 DirectColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 9b 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 9c 0 DirectColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 9d 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 9e 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 9f 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x a0 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x a1 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x a2 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x a3 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x a4 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x a5 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x a6 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 16 16 16 0 0 0 Slow
0x a7 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x a8 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x a9 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x aa 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x ab 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 4 1 None
0x ac 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 8 1 None
0x ad 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 4 1 None
0x ae 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 8 1 None
0x af 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x b0 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x b1 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x b2 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x b3 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x b4 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x b5 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x b6 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
在那种情况下，为什么我没有获得 sRGB 帧缓冲区？我是否遇到了英特尔驱动程序错误？
显然罪魁祸首是 Intel Mesa 驱动程序中的 this bug（感谢 SO 用户 genpfault 在 freedesktop bugzilla 中找到它）。
我正在尝试按照 this guide 并参考 SDL2 文档以了解如何在默认帧缓冲区上启用 SRGB 支持，以正确的伽玛方式渲染典型的 OpenGL 颜色三角形。
这是我编写的绘制三角形的代码：
#include <SDL.h>
// Header file generated with glLoadGen
#include "gl_core_3_3.h"
#include <cstdlib>
void sdl_loop(SDL_Window* window);
static const char* const vertexSource = R"(
#version 330
in vec2 position;
in vec3 color;
out vec3 vs_color;
void main()
{
gl_Position = vec4(position, 0.0, 1.0);
vs_color = color;
}
)";
static const char* const fragmentSource = R"(
#version 330
in vec3 vs_color;
out vec4 fragColor;
void main()
{
fragColor = vec4(vs_color, 1.0);
}
)";
static const float vertices[] = {
// X Y R G B
-0.9f, -0.9f, 1.0f, 0.0f, 0.0f,
0.9f, -0.9f, 0.0f, 1.0f, 0.0f,
0.0f, 0.9f, 0.0f, 0.0f, 1.0f,
};
static const unsigned short indices[] = { 0, 1, 2 };
void sdl_loop(SDL_Window* window)
{
glClearColor(0.0f, 0.1f, 0.2f, 1.0f);
glEnable(GL_FRAMEBUFFER_SRGB);
auto program = glCreateProgram();
auto vertexShader = glCreateShader(GL_VERTEX_SHADER);
auto fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(vertexShader, 1, &vertexSource, nullptr);
glShaderSource(fragmentShader, 1, &fragmentSource, nullptr);
glCompileShader(vertexShader);
glCompileShader(fragmentShader);
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glBindFragDataLocation(program, 0, "fragColor");
glLinkProgram(program);
glDetachShader(program, vertexShader);
glDetachShader(program, fragmentShader);
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
auto positionAttr = glGetAttribLocation(program, "position");
auto colorAttr = glGetAttribLocation(program, "color");
unsigned vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
unsigned vertexBuffer;
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
unsigned indexBuffer;
glGenBuffers(1, &indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
size_t stride = 5 * sizeof(float);
size_t offset = 0;
glEnableVertexAttribArray(positionAttr);
glVertexAttribPointer(positionAttr, 2, GL_FLOAT, false, stride, (void*) offset);
offset += 2 * sizeof(float);
glEnableVertexAttribArray(colorAttr);
glVertexAttribPointer(colorAttr, 3, GL_FLOAT, false, stride, (void*) offset);
offset += 3 * sizeof(float);
glUseProgram(program);
SDL_Event evt;
for (;;) {
while (SDL_PollEvent(&evt)) {
if (evt.type == SDL_QUIT) {
goto out;
}
}
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_SHORT, nullptr);
SDL_GL_SwapWindow(window);
}
out:
glDeleteProgram(program);
glDeleteBuffers(1, &vertexBuffer);
glDeleteBuffers(1, &indexBuffer);
glDeleteVertexArrays(1, &vao);
}
int main()
{
if (SDL_Init(SDL_INIT_EVERYTHING) < 0) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"Couldn't initialize SDL: %s", SDL_GetError());
SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
"Couldn't initialize SDL", SDL_GetError(), nullptr);
return EXIT_FAILURE;
}
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 8);
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
// Commenting this line out doesn't give you an sRGB framebuffer on Intel GPUs
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
SDL_GL_SetAttribute(SDL_GL_FRAMEBUFFER_SRGB_CAPABLE, 1);
auto* window = SDL_CreateWindow("Hello OpenGL 3!",
SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
800, 600,
SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL);
if (window == nullptr) {
SDL_LogError(
SDL_LOG_CATEGORY_APPLICATION,
"Couldn't initialize SDL window: %s", SDL_GetError());
SDL_ShowSimpleMessageBox(
SDL_MESSAGEBOX_ERROR,
"Couldn't create SDL window", SDL_GetError(), nullptr);
return EXIT_FAILURE;
}
auto context = SDL_GL_CreateContext(window);
SDL_GL_MakeCurrent(window, context);
SDL_GL_SetSwapInterval(1);
ogl_LoadFunctions();
sdl_loop(window);
SDL_GL_DeleteContext(context);
SDL_DestroyWindow(window);
SDL_Quit();
return EXIT_SUCCESS;
}
我 运行 使用 Ubuntu 16.04（使用 HWE 驱动程序），我使用的机器同时具有 Intel HD 4000 GPU 和带 Optimus 的专用 nvidia GPU。理论上，我应该得到一个 sRGB 帧缓冲器。但是，仅当 运行 在 nvidia GPU 下或使用 ApiTrace 时，我才获得 sRGB 帧缓冲区。如果我在 Intel GPU 下 运行，如果我使用 SDL2 指定非零 alpha 大小，我只会得到一个 sRGB 帧缓冲区。如果我为 alpha 指定一个零大小（或根本不指定一个），我将得到一个线性帧缓冲区。
这是我的示例在 运行 在 nvidia GPU（以及具有非零 alpha 位大小的 Intel GPU）下的样子：
这是 运行 在 Intel GPU 下使用零 alpha 位大小（sRGB 不正确）时的样子：
这就是我使用 ApiTrace 得到的结果：
我也 运行 glxinfo -t 据我所知，即使设置了零 alpha 位，我也应该获得 sRGB 支持（编辑：那是不是这样。glxinfo 的输出应该在 sRGB 列中显示 ses，但由于某些原因并没有发生）：
40 GLX Visuals
Vis Vis Visual Trans buff lev render DB ste r g b a s aux dep ste accum buffer MS MS
ID Depth Type parent size el type reo sz sz sz sz flt rgb buf th ncl r g b a num bufs caveats
--------------------------------------------------------------------------------------------------------------------
0x 21 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 22 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x b7 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x b8 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x b9 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x ba 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x bb 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x bc 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x bd 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x be 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x bf 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x c0 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x c1 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x c2 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x c3 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x c4 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x c5 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x c6 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x c7 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x c8 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
0x c9 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x ca 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x cb 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x cc 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x cd 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x ce 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x cf 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x d0 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x d1 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x d2 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x d3 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x d4 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x d5 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x d6 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x d7 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x d8 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x d9 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x da 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x db 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
0x 76 32 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
64 GLXFBConfigs:
Vis Vis Visual Trans buff lev render DB ste r g b a s aux dep ste accum buffer MS MS
ID Depth Type parent size el type reo sz sz sz sz flt rgb buf th ncl r g b a num bufs caveats
--------------------------------------------------------------------------------------------------------------------
0x 77 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 78 0 TrueColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 79 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 7a 0 TrueColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 7b 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 7c 0 TrueColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 7d 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 7e 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 7f 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 80 24 TrueColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 81 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x 82 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x 83 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x 84 24 TrueColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x 85 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 86 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 16 16 16 0 0 0 Slow
0x 87 32 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x 88 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x 89 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x 8a 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x 8b 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 4 1 None
0x 8c 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 8 1 None
0x 8d 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 4 1 None
0x 8e 0 TrueColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 8 1 None
0x 8f 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x 90 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x 91 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x 92 24 TrueColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x 93 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x 94 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x 95 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x 96 24 TrueColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
0x 97 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 98 0 DirectColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 0 0 0 0 0 0 0 0 None
0x 99 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 9a 0 DirectColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x 9b 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 9c 0 DirectColor 0 16 0 rgba 0 0 5 6 5 0 . . 0 24 8 0 0 0 0 0 0 None
0x 9d 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 9e 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 0 0 0 0 0 0 0 0 None
0x 9f 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x a0 24 DirectColor 0 32 0 rgba 0 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x a1 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x a2 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 0 0 0 0 0 0 0 0 None
0x a3 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x a4 24 DirectColor 0 24 0 rgba 0 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x a5 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 0 0 None
0x a6 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 16 16 16 0 0 0 Slow
0x a7 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 0 0 None
0x a8 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 16 16 16 16 0 0 Slow
0x a9 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 0 0 None
0x aa 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 16 16 16 0 0 0 Slow
0x ab 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 4 1 None
0x ac 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 0 0 0 0 0 0 8 1 None
0x ad 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 4 1 None
0x ae 0 DirectColor 0 16 0 rgba 1 0 5 6 5 0 . . 0 16 0 0 0 0 0 8 1 None
0x af 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 4 1 None
0x b0 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 0 0 0 0 0 0 8 1 None
0x b1 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 4 1 None
0x b2 24 DirectColor 0 32 0 rgba 1 0 8 8 8 8 . . 0 24 8 0 0 0 0 8 1 None
0x b3 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 4 1 None
0x b4 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 0 0 0 0 0 0 8 1 None
0x b5 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 4 1 None
0x b6 24 DirectColor 0 24 0 rgba 1 0 8 8 8 0 . . 0 24 8 0 0 0 0 8 1 None
在那种情况下，为什么我没有获得 sRGB 帧缓冲区？我是否遇到了英特尔驱动程序错误？
显然罪魁祸首是 Intel Mesa 驱动程序中的 this bug（感谢 SO 用户 genpfault 在 freedesktop bugzilla 中找到它）。