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too_many_stars

C++ Shader help

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Hello Everyone,

I am having an issue getting my shaders to work. Here is what I have. This is the rendering function.

glUseProgram( program_id );

GLfloat v[6] = { 0.0f , 0.0f , 1.0f , 1.0f , 1.0f, 0.0f };
GLuint vbo_id = 0;
glGenBuffers( 1 , &vbo_id);
glBindBuffer( GL_ARRAY_BUFFER , vbo_id);
glBufferData( GL_ARRAY_BUFFER , sizeof(v) , v , GL_STATIC_DRAW);


glEnableVertexAttribArray( 0 );
glBindBuffer( GL_ARRAY_BUFFER , vbo_id );

glVertexAttribPointer( 0 , 2 , GL_FLOAT, GL_FALSE , 0 , 0 );
glDrawArrays( GL_TRIANGLES , 0 , 3 );



glBindBuffer( GL_ARRAY_BUFFER , 0 );
glDisableVertexAttribArray(0);

And the vertex shader

#version 330

in vec2 vertex_position;
//layout( location = 0 ) in vec2 vertex_position;
void main(){
		
	gl_Position.xy = vertex_position * 1.2;
	gl_Position.z = 0;
	gl_Position.w = 1;
}

The fragment shader

#version 330



void main(){
	
	gl_FragColor = vec4(1.0,0.0,0.0,1.0);

}

I did not post the compiling , linking and attribute adding code because it appears to work. For example, if I make a syntax error in one the shaders, it get a warning. Or if there's a linker problem for example.

My issue is that I do get a triangle to show up on the screen, but no matter what I do to the vertex or fragment shaders (for example changing the color or size ) it has no effect with what I see on the screen.

In essence, there appears to be no communication between the shaders and glew.

My frustration is further compounded by the fact that I was able to get this working before on the same laptop.

If anyone has any ideas on what could be wrong with my incredibly simple program, please let me know.

Thanks,

 

Mike

 

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You shouldn't call 

glGenBuffers( 1 , &vbo_id);

in the rendering function, because it creates a new buffer object, causing performance and memory issues.

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I dont think that your matrix transform is correct, you should pass a matrix to the shader instead of creating your own one. I might be wrong but it seems as if your Triangle is behind the 'camera'

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gl_FragColor has been deprecated since GLSL 130; use an out vec4 instead.  Your GLSL compilation should be giving you an error for this.

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