Pfthb

I'm trying to build a simple y=x curve with -0.5< x <0.5 and z = 0. But for some reason, half of the x points are not rendered. I'm using point primitive to be simple, and not using any index buffer.
I checked that x values are generated correctly and are in the range, but still the positive half (0< x <0.5) is not displayed.

The code is here:
https://github.com/abhimittal664/opengl

I'm not entirely sure, but can it be due to MVP matrices? I tried experimenting with them but no use.

On an additional note, is there some way to debug problems in shader file? I am using visual studio 2017 on intel integrated graphics machine. Looks like visual studio graphics debugger is for directx only. Currently i'm just trying to debug by outputting points with different color to get visual hints.

Thanks

Edit 1:
The y = x function is in the vertex shader. The vertex buffer only has x values, with y,z = 0.

Extracted from the link to your code:

//Vertex buffer definition
struct vertex 
 glm::vec3 position;
 glm::vec3 color;
;

and

void populate_vertex_buffer(vertex* vertices, int n_vertices) {
 ...
 for (int x = 0; x < n_vertices; x++) {
 count = -0.5f + (1.f / n_vertices)*(float)x;
 vertices[x].position = glm::vec3((-0.5f + (1.f / n_vertices)*(float)x), 0, 0);
 vertices[x].color = glm::vec3(0.0, 0.0, 0.0);
 ...

So data in the buffer is XYZRGBXYZRGBXYZRGB...... with Y,Z,R,G,B all = 0)

You tell the driver how to read this buffer:

glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
...
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, (const GLvoid*)offsetof(vertex, color));

Pay attention to the second glVertexAttribPointer. It tells that the second attribute (vc in your VS) starts at position offsetof(vertex, color) and then each color is contiguous to previous (the fifth param = 0). That is good for a buffer data like XYZXYZXYZ......RGBRGBRGBRGB...

I think the read instructions would be

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), NULL);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), 3*sizeof(float);

where the 6 comes from six values XYZRGB between two same attributes.