SDL2 + OpenGL programming, ES2 Linux4.2.5 mesa11.0.4, Intel integrated graphics, GDB debugging found glGetUniformLocation returns 1, window screen, how to do? If direct delete uniform variable relevant code can show normal triangle, GLSL code is write wrong?
I'm learning to use OpenGL ES

 
#include  
#include  
#include  

Void changemvp (GLfloat MVP [16]); 

Int main (int arg c, char * * argv) {
SDL_Init (SDL_INIT_VIDEO); 

SDL_GL_SetAttribute (SDL_GL_CONTEXT_PROFILE_MASK SDL_GL_CONTEXT_PROFILE_ES); 
SDL_GL_SetAttribute (SDL_GL_CONTEXT_MAJOR_VERSION, 2); 
SDL_GL_SetAttribute (SDL_GL_CONTEXT_MINOR_VERSION, 1); 
SDL_GL_SetAttribute (SDL_GL_RED_SIZE, 8); 
SDL_GL_SetAttribute (SDL_GL_GREEN_SIZE, 8); 
SDL_GL_SetAttribute (SDL_GL_BLUE_SIZE, 8); 
SDL_GL_SetAttribute (SDL_GL_DOUBLEBUFFER, 1); 

SDL_DisplayMode dm; 
SDL_GetDesktopDisplayMode (0, & amp; Dm); 

SDL_Window * win=SDL_CreateWindow (" Hello ", 0, 0, dm, w, dm, h, SDL_WINDOW_OPENGL); 
SDL_GLContext GLC=SDL_GL_CreateContext (win); 

Const GLchar * vShaderStr=
"The attribute vec4 vPosition;" 
"The attribute vec4 vColor;" 
"Uniform mat4 MVP" 
"Varying vec4 v_color;" 
"Void main () 
""{" 
Gl_Position=MVP * vPosition; "" 
"V_color=vColor;" 
"} "; 

Const GLchar * fShaderStr=
"Precision mediump float;" 
"Varying vec4 v_color;" 
"Void main () 
""{" 
"Gl_FragColor=v_color;" 
"} "; 

GLuint vertexShader; 
GLuint fragmentShader; 
GLuint programObject; 

VertexShader=glCreateShader (GL_VERTEX_SHADER); 
FragmentShader=glCreateShader (GL_FRAGMENT_SHADER); 

GlShaderSource (vertexShader, 1, & amp; VShaderStr, NULL); 
GlShaderSource (fragmentShader, 1, & amp; FShaderStr, NULL); 
GlCompileShader (vertexShader); 
GlCompileShader (fragmentShader); 

ProgramObject=glCreateProgram (); 

GlAttachShader (programObject vertexShader); 
GlAttachShader (programObject fragmentShader); 

GlLinkProgram (programObject); 
GlDeleteShader (vertexShader); 
GlDeleteShader (fragmentShader); 

GlUseProgram (programObject); 

GlClearColor (0.0 f, f, 0.0 0.0 f, 0.0 f); 
GlClear (GL_COLOR_BUFFER_BIT); 
GlViewport (0, 0, dm. W, dm, h); 


GLfloat vVertices []={0.5 0.0 f, f, f 0.0, 0.67 f, f 0.4, 0.47 f, 
1.0 f to 0.5 f to 0.0 f to 1.0 f to 0.4 f to 0.97 f, 
0.5 f to 0.5 f, 0.0 f, f 0.0, 0.4 f, 0.57 f 
}; 
# define stride 6 
# define vPosition_offset 0 
# define vPosition_size 3 
# define vColor_offset 3 
# define vPosition_size 3 

GLfloat MVP [16]={1,0,0,0, 
0,1,0,0, 
0,0,1,0, 
0,0,0,1 
}; 
GlBindAttribLocation (programObject, 0, "vPosition"); 
GlBindAttribLocation (programObject, 1, "vColor"); 
GlVertexAttribPointer (0, vPosition_size, GL_FLOAT, GL_FALSE, stride * sizeof (float), vVertices + vPosition_offset); 
GlVertexAttribPointer (1, vPosition_size, GL_FLOAT, GL_FALSE, stride * sizeof (float), vVertices + vColor_offset); 
Int mvploc=glGetUniformLocation (programObject, "MVP"); 
GlUniformMatrix4fv (mvploc, 1, GL_FALSE, MVP); 
GlEnableVertexAttribArray (0); 
GlEnableVertexAttribArray (1); 
GlDrawArrays (GL_TRIANGLES, 0, 3); 
SDL_GL_SwapWindow (win); 


SDL_Event e; 
While (1) {
Int r=SDL_PollEvent (& amp; E); 
if(! R) continue; 
If (e. ype==SDL_KEYDOWN) goto the quit; 
If (e. ype==SDL_MOUSEMOTION) {
Changemvp (MVP); 
} 
} 

The quit: 
SDL_GL_DeleteContext (GLC); 
SDL_DestroyWindow (win); 
SDL_Quit (); 
} 

Void changemvp (GLfloat MVP [16]) {
} 

CodePudding user response:

If you declare a variable is not used, then glGetUniformLocation return value is always 1