Hi all,

I’m having problems with drawing the outlines of a camera frustum. Basically, I’m not seeing any lines drawn at all and I don’t really have a clue why it’s not drawing them.

My shader compiles fine and has no errors (verified with cgc). I also bind the single attribute to the shader on creation.

For my algebraics, I’m using the GLM library.

Rougly, the relevant code is as follows:

I have a class Frustum with following members:

GLuint m_vertexBuffer;

GLuint m_indexBuffer;

std::vector<glm::vec3> m_vertices;

std::vector<GLuint> m_indices;

The vectors and buffers are initialised with following code, (where m_nearClip and m_farClip are arrays of glm::vec3):

//The near clip plane

m_vertices.push_back(m_nearClip[0]);

m_vertices.push_back(m_nearClip[1]);

m_vertices.push_back(m_nearClip[2]);

m_vertices.push_back(m_nearClip[3]);

m_indices.push_back(0);m_indices.push_back(1);m_indices.push_back(1);m_indices.push_back(2);m_indices.push_back(2);m_indices.push_back(3);m_indices.push_back(3);m_indices.push_back(0); //indices

//The far clip plane

m_vertices.push_back(m_farClip[0]);

m_vertices.push_back(m_farClip[1]);

m_vertices.push_back(m_farClip[2]);

m_vertices.push_back(m_farClip[3]);

int i = 4;

m_indices.push_back(i+0);m_indices.push_back(i+1);m_indices.push_back(i+1);m_indices.push_back(i+2);m_indices.push_back(i+2);m_indices.push_back(i+3);m_indices.push_back(i+3);m_indices.push_back(i+0); //indices

//Edges between

m_indices.push_back(0);m_indices.push_back(i+0);m_indices.push_back(1);m_indices.push_back(i+1);m_indices.push_back(2);m_indices.push_back(i+2);m_indices.push_back(3);m_indices.push_back(i+3);

```
glGenBuffers(1, &m_vertexBuffer); //Generate a buffer for the vertices
glBindBuffer(GL_ARRAY_BUFFER, m_vertexBuffer); //Bind the vertex buffer
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::vec3)*m_vertices.size(), &m_vertices[0], GL_STATIC_DRAW);
glGenBuffers(1, &m_indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint) * m_indices.size(), &m_indices[0], GL_STATIC_DRAW);
```

m_vertices and m_indices get filled in as I’d expect them to be, so I don’t really think there’s an issue here, but perhaps I’m overlooking something

Now, the render method is essentially this (sendUniform is a verified method I use, I know it succesfully sends in uniforms to the binded shader, I also debugged and modelview and projectionMatrix are as expected):

getShader()->bindShader();

getShader()->sendUniform4x4(“modelview_matrix”, modelviewMatrix);

getShader()->sendUniform4x4(“projection_matrix”, projectionMatrix);

```
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, m_vertexBuffer);
glVertexAttribPointer((GLint)0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_indexBuffer);
glDrawElements(GL_LINES, m_indices.size(), GL_UNSIGNED_INT, 0);
glDisableVertexAttribArray(0);
```

That’s it for relevant code. Here come the simple shaders!

Now, my vertex shader looks like this:

#version 130

uniform mat4 projection_matrix;

uniform mat4 modelview_matrix;

layout (location = 0) in vec3 a_Vertex;

void main(void)

{

vec4 pos = modelview_matrix * vec4(a_Vertex, 1.0);

gl_Position = projection_matrix * pos;

}

And my fragment shader is as follows, it’s just supposed to render my lines in red:

#version 330

layout(location = 0) out vec4 outColor;

void main(void) {

outColor = vec4(1.0, 0.0, 0.0, 1.0);

}

I appreciate any help given very much!

Thanks and kind regards,

Lodeman