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Schnulla

OpenGL OpenGL 3.2 Core Profile - First Triangle

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Hi,

I can see my first "OpenGL 3.2 core profile triangle"
but somehow it disappears when adding perspective.

Here is my code... not much so I hope someone can help me...
Back-face culling and depth test are disabled.

#version 150 core

uniform mat4 ModelViewProjectionMatrix;

in vec3 in_Position;

void main(void)
{
gl_Position= ModelViewProjectionMatrix * vec4(in_Position, 1.0);
}




#version 150 core

out vec4 out_Color;

void main(void)
{
out_Color = vec4(1.0, 0.0, 0.0, 1.0);
}





// setup projection matrix

ProjectionMatrix= glm::mat4(1.0f);
ProjectionMatrix*= glm::perspective(45.0f, 1024.0f / 768.0f, 0.1f, 200.0f);


// setup modelview matrix (look down the negative z-axis)

ModelViewMatrix= glm::mat4(1.0f);
ModelViewMatrix*= glm::lookAt(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 0.0f, -1.0f), glm::vec3(0.0f, 1.0f, 0.0f));


// create and upload modelviewprojection matrix

ModelViewProjectionMatrix= ProjectionMatrix * ModelViewMatrix;
glUniformMatrix4fv(glGetUniformLocation(m_handle, "ModelViewProjectionMatrix"), 1, false, glm::value_ptr(ModelViewProjectionMatrix));


// setup triangle using VBO and VAO

float* vert = new float[9];

vert[0] = 0.0; vert[1] = 1.0; vert[2]= -10.0;
vert[3] =-1.0; vert[4] =-1.0; vert[5]= -10.0;
vert[6] = 1.0; vert[7] =-1.0; vert[8]= -10.0;

unsigned int m_vaoID;

glGenVertexArrays(1, &m_vaoID);
glBindVertexArray(m_vaoID);

glGenBuffers(1, &m_vboID);
glBindBuffer(GL_ARRAY_BUFFER, m_vboID);
glBufferData(GL_ARRAY_BUFFER, 9 * sizeof(GLfloat), vert, GL_STATIC_DRAW);
glVertexAttribPointer((GLuint)ATTRIBUTE_LOCATION_WORLDVERTEX, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(ATTRIBUTE_LOCATION_WORLDVERTEX);


// render

glDrawArrays(GL_TRIANGLES, 0, 3);


// cleanup

glBindVertexArray(0);

delete[] vert;

glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glDeleteBuffers(1, &m_vboID);

glDeleteVertexArrays(1, &m_vaoID);





I can see this triangle when I apply the
following changes to the code above:

glUniformMatrix4fv(glGetUniformLocation(m_handle, "ModelViewProjectionMatrix"), 1, false, glm::value_ptr(glm::mat4(1.0f)/*ModelViewProjectionMatrix*/));

vert[0] = 0.0; vert[1] = 1.0; vert[2]= -1.0;
vert[3] =-1.0; vert[4] =-1.0; vert[5]= -1.0;
vert[6] = 1.0; vert[7] =-1.0; vert[8]= -1.0;





So basically I upload an identity (no projection) matrix for the
modelviewprojection matrix and display the triangle at z == -1.0f
instead of -10.0f.

Where is my mistake? I can't get the triangle to work
with perspective. I'm really stuck :(

Help is very appreciated!

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I have tried your codes and got expected results in both two cases. So I think there is no mistake. What's your development environment? Mine is openSUSE 11.2 with GTX260+.

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- Windows 7 x64
- Radeon HD 5850

And I use Visual Studio 2010 Ultimate to code my stuff in.

edit: sorry forgot to say thanks for your effort! :)

[Edited by - Schnulla on July 20, 2010 9:08:24 AM]

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I just found the problem. While converting stuff from OpenGL 1.X to 3.2
I had to comment out some old code in a utility class to avoid that
glGetError throws errors. Unfortunately in this code also some arrays
were allocated. Later there was a write operation on these arrays
(which I forgot to comment out too) that now wrote into undefined
memory locations overwriting my glm matrices. I don't know why
this did not crash my application. I figured this out by putting
the matrix calculations directly in front of the glDrawElements
command. So yes nothing is wrong with the code above and thanks
god I finally found the problem. Also thanks for your effort!


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