我对GLSL文档中缺乏明确性以及不同版本中允许，弃用和推荐的内容感到沮丧。
我有一堆片段着色器，我正在用GLSL 1.3版编写。他们工作，但有一个我怀疑可能会出现的神秘错误，因为我没有指定任何顶点着色器，而是依靠已弃用的gl_TexCoord[i]变量来获取纹理数据。无论如何，我确实希望以标准和推荐的方式做事。
所以我要问的是：顶点着色器的正确，最小的例子是什么，除了在GLSL 1.3中复制关于顶点定位和纹理坐标插值的固定管道功能之外什么都不做，我该怎么做读取片段着色器中的纹理坐标？
我现在的尝试看起来像这样：
// Vertex shader
#version 130
out vec2 texCoord;
void main()
{
gl_Position = vec4(gl_Vertex.xy, 0.0, 1.0);
texCoord = 0.5 * gl_Position.xy + vec2(0.5, 0.5);
}
//Fragment shader
#version 130
in vec2 texCoord;
uniform sampler2D tex;
out vec4 outColor;
void main() {
outColor = texture2D(tex, texCoord.xy);
}
但这并没有给出与简单地省略顶点着色器并用gl_TexCoord[0]替换texCoord相同的结果（事实上，在我的测试中我根本没有输出数据）。最重要的是，我的司机抱怨gl_Vertex也被弃用了！
那么，有人可以提供符合标准的推荐示例，以便如何简单地完成固定管道在GLSL＆gt; = 1.3中的作用吗？如果推荐的方式在1.3以上的版本之间有所不同，我会很感激的例子，如果可能的话也会证明这一点。
如果重要 - 我希望它不重要 - 我的视口设置如下（F＃，但代码应该是不言自明的）：
GL.Viewport(base.ClientRectangle.X, base.ClientRectangle.Y, base.ClientRectangle.Width, base.ClientRectangle.Height)
let ratio = (float base.ClientRectangle.Height) / (float base.ClientRectangle.Width)
GL.MatrixMode(MatrixMode.Projection)
GL.Ortho(-0.5, 0.5, ratio/2.0, -ratio/2.0, -10., 10.)
GL.MatrixMode(MatrixMode.Modelview)
答案 0 :(得分：5)
所以我要问的是：顶点着色器的最小例子是什么，除了复制固定管道功能（...）之外什么都不做？
没有静态GLSL着色器源将复制固定功能管道是“一个尺寸，错误，着色器适合所有”的方式。许多固定功能管道设置（如使用 glTexEnvi 完成转换为不同的着色器代码。
无论如何，您的着色器代码毫无意义。 gl_Vertex传输顶点位置（转换前），除非您想模拟纹理坐标生成，否则不会产生纹理坐标。
OpenGL-2的完全工作，最小GLSL示例，使用GLFW进行上下文和窗口创建，使用GLEW进行扩展加载。
#include <stdlib.h>
#include <stdio.h>
#include <GL/glew.h>
#include <GL/glfw.h>
static void pushModelview()
{
GLenum prev_matrix_mode;
glGetIntegerv(GL_MATRIX_MODE, &prev_matrix_mode);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glMatrixMode(prev_matrix_mode);
}
static void popModelview()
{
GLenum prev_matrix_mode;
glGetIntegerv(GL_MATRIX_MODE, &prev_matrix_mode);
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(prev_matrix_mode);
}
static const GLchar *vertex_shader_source =
"#version 120\n"
"void main()"
"{"
" gl_Position = gl_ProjectionMatrix * gl_ModelViewMatrix * gl_Vertex;"
" gl_TexCoord[0] = gl_MultiTexCoord0;"
" gl_FrontColor = gl_Color;"
" gl_BackColor = gl_Color;"
"}\0";
GLuint shaderVertex = 0;
static const GLchar *fragment_shader_source =
"#version 120\n"
"uniform sampler2D texCMYK;"
"uniform sampler2D texRGB;"
"void main()"
"{"
" gl_FragColor = -texture2D(texCMYK, gl_TexCoord[0].st) + texture2D(texRGB, gl_TexCoord[0].st);"
"}\0";
GLuint shaderFragment = 0;
GLuint shaderProgram = 0;
#define TEX_CMYK_WIDTH 2
#define TEX_CMYK_HEIGHT 2
GLubyte textureDataCMYK[TEX_CMYK_WIDTH * TEX_CMYK_HEIGHT][3] = {
{0x00, 0xff, 0xff}, {0xff, 0x00, 0xff},
{0xff, 0xff, 0x00}, {0x00, 0x00, 0x00}
};
GLuint texCMYK = 0;
#define TEX_RGB_WIDTH 2
#define TEX_RGB_HEIGHT 2
GLubyte textureDataRGB[TEX_RGB_WIDTH * TEX_RGB_HEIGHT][3] = {
{0x00, 0x00, 0xff}, {0xff, 0xff, 0xff},
{0xff, 0x00, 0x00}, {0x00, 0xff, 0x00}
};
GLuint texRGB = 0;
GLfloat cube_vertices[][8] = {
/* X Y Z Nx Ny Nz S T */
{-1.0, -1.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0}, // 0
{ 1.0, -1.0, 1.0, 0.0, 0.0, 1.0, 1.0, 0.0}, // 1
{ 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 1.0, 1.0}, // 2
{-1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0}, // 3
{ 1.0, -1.0, -1.0, 0.0, 0.0, -1.0, 0.0, 0.0},
{-1.0, -1.0, -1.0, 0.0, 0.0, -1.0, 1.0, 0.0},
{-1.0, 1.0, -1.0, 0.0, 0.0, -1.0, 1.0, 1.0},
{ 1.0, 1.0, -1.0, 0.0, 0.0, -1.0, 0.0, 1.0},
{-1.0, -1.0, 1.0, -1.0, 0.0, 0.0, 0.0, 0.0},
{-1.0, -1.0, -1.0, -1.0, 0.0, 0.0, 1.0, 0.0},
{-1.0, 1.0, -1.0, -1.0, 0.0, 0.0, 1.0, 1.0},
{-1.0, 1.0, 1.0, -1.0, 0.0, 0.0, 0.0, 1.0},
{ 1.0, -1.0, -1.0, 1.0, 0.0, 0.0, 0.0, 0.0},
{ 1.0, -1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0},
{ 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 1.0},
{ 1.0, 1.0, -1.0, 1.0, 0.0, 0.0, 0.0, 1.0},
{ 1.0, -1.0, -1.0, 0.0, -1.0, 0.0, 0.0, 0.0},
{-1.0, -1.0, -1.0, 0.0, -1.0, 0.0, 1.0, 0.0},
{-1.0, -1.0, 1.0, 0.0, -1.0, 0.0, 1.0, 1.0},
{ 1.0, -1.0, 1.0, 0.0, -1.0, 0.0, 0.0, 1.0},
{-1.0, 1.0, 1.0, 0.0, 1.0, 0.0, 0.0, 0.0},
{ 1.0, 1.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0},
{ 1.0, 1.0, -1.0, 0.0, 1.0, 0.0, 1.0, 1.0},
{-1.0, 1.0, -1.0, 0.0, 1.0, 0.0, 0.0, 1.0},
};
static void draw_cube(void)
{
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glVertexPointer(3, GL_FLOAT, sizeof(GLfloat) * 8, &cube_vertices[0][0]);
glNormalPointer(GL_FLOAT, sizeof(GLfloat) * 8, &cube_vertices[0][3]);
glTexCoordPointer(2, GL_FLOAT, sizeof(GLfloat) * 8, &cube_vertices[0][6]);
glDrawArrays(GL_QUADS, 0, 24);
}
static void bind_sampler_to_unit_with_texture(GLchar const * const sampler_name, GLuint texture_unit, GLuint texture)
{
glActiveTexture(GL_TEXTURE0 + texture_unit);
glBindTexture(GL_TEXTURE_2D, texture);
GLuint loc_sampler = glGetUniformLocation(shaderProgram, sampler_name);
glUniform1i(loc_sampler, texture_unit);
}
static void display(double T)
{
int window_width, window_height;
glfwGetWindowSize(&window_width, &window_height);
if( !window_width || !window_height )
return;
const float window_aspect = (float)window_width / (float)window_height;
glDisable(GL_SCISSOR_TEST);
glClearColor(0.5, 0.5, 0.7, 1.0);
glClearDepth(1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glViewport(0, 0, window_width, window_height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-window_aspect, window_aspect, -1, 1, 1, 100);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0, 0, -5);
pushModelview();
glRotatef(T * 0.1 * 180, 0., 1., 0.);
glRotatef(T * 0.1 * 60, 1., 0., 0.);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glUseProgram(shaderProgram);
bind_sampler_to_unit_with_texture("texCMYK", 0, texCMYK);
bind_sampler_to_unit_with_texture("texRGB", 1, texRGB);
draw_cube();
popModelview();
glfwSwapBuffers();
}
static int open_window(void)
{
#if 0
glfwWindowHint(GLFW_OPENGL_VERSION_MAJOR, 2);
glfwWindowHint(GLFW_OPENGL_VERSION_MINOR, 0);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);
#endif
if( glfwOpenWindow(0, 0, /* default size */
8, 8, 8, /* 8 bits per channel */
8, 24, 8, /* 8 alpha, 24 depth, 8 stencil */
GLFW_WINDOW) != GL_TRUE ) {
fputs("Could not open window.\n", stderr);
return 0;
}
if( glewInit() != GLEW_OK ) {
fputs("Could not initialize extensions.\n", stderr);
return 0;
}
return 1;
}
static int check_extensions(void)
{
if( !GLEW_ARB_vertex_shader ||
!GLEW_ARB_fragment_shader ) {
fputs("Required OpenGL functionality not supported by system.\n", stderr);
return 0;
}
return 1;
}
static int check_shader_compilation(GLuint shader)
{
GLint n;
glGetShaderiv(shader, GL_COMPILE_STATUS, &n);
if( n == GL_FALSE ) {
GLchar *info_log;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &n);
info_log = malloc(n);
glGetShaderInfoLog(shader, n, &n, info_log);
fprintf(stderr, "Shader compilation failed: %*s\n", n, info_log);
free(info_log);
return 0;
}
return 1;
}
static int init_resources(void)
{
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glGenTextures(1, &texCMYK);
glBindTexture(GL_TEXTURE_2D, texCMYK);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, TEX_CMYK_WIDTH, TEX_CMYK_HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, textureDataCMYK);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glGenTextures(1, &texRGB);
glBindTexture(GL_TEXTURE_2D, texRGB);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, TEX_RGB_WIDTH, TEX_RGB_HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, textureDataRGB);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
shaderVertex = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(shaderVertex, 1, (const GLchar**)&vertex_shader_source, NULL);
glCompileShader(shaderVertex);
if( !check_shader_compilation(shaderVertex) )
return 0;
shaderFragment = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(shaderFragment, 1, (const GLchar**)&fragment_shader_source, NULL);
glCompileShader(shaderFragment);
if( !check_shader_compilation(shaderFragment) )
return 0;
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, shaderVertex);
glAttachShader(shaderProgram, shaderFragment);
glLinkProgram(shaderProgram);
return 1;
}
static void main_loop(void)
{
glfwSetTime(0);
while( glfwGetWindowParam(GLFW_OPENED) == GL_TRUE ) {
display(glfwGetTime());
}
}
int main(int argc, char *argv[])
{
if( glfwInit() != GL_TRUE ) {
fputs("Could not initialize framework.\n", stderr);
return -1;
}
if( !open_window() )
return -1;
if( !check_extensions() )
return -1;
if( !init_resources() )
return -1;
main_loop();
glfwTerminate();
return 0;
}